Conditions

Question 1

A Systematic Approach to Valve Disease

Answer 1

• Define cardiovascular pathology
• Evaluate pathophysiology
  — symptoms - angina, syncope, SOBOE, right heart failure, fatigue
  — investigations - echo, ECG, cardiac MRI, angio/catheterisation
  — assess end organ damage (U+Es, LFTs, INR)
• Pre-operative optimisation - heart failure treatment
• Determine haemodynamic goals
• Anticipate haemodynamic emergencies

Question 2

Achalasia

Answer 2

Disorder of motility of the lower oesophageal sphincter. Impaired peristalsis and failure of the sphincter to relax causes a functional stenosis. Most cases have no known underlying cause.

• Most commonly causes dysphagia, affecting solids more than liquids
• Can cause food bolus impaction and regurgitation
• Chest pain, heart burn
• CXR shows dilated oesophagus with barium swallow - “birds beaking”
• Endoscopy can detect some cases
• Manometry of the oesphagus is gold standard - high resting pressure of LOS, incomplete relaxation on swallowing and absent peristalsis
• Management - myotomy of LOS, pneumatic dilatation, endoscopic injection of botox, calcium channel blockers

Question 3

Acromegaly

Answer 3

Over production of growth hormone from the anterior pituitary.

Pre-operative
* cardiovascular - hypertension, IHD, failure, cardiomyopathy, valve disease, conduction defects
* airway - large jaw/head/tongue, hypertrophy of larynx/trachea, vocal cord thickening, OSA
* neurological - raised ICP, nerve compression syndromes
* endocrine - diabetes, impaired glucose tolerance
* get an ECG +/- echo, consider FNE and CXR

Intra-operative
* large face mask, long blade, consider VL/AFOI/elective trache
* Southwick and Katz grades of airway involvement
* nerve compression - care with protection of vulnerable areas
* issues at extubation > intubation
* extubate awake + sitting if OSA
* somatostatin analogues —> D+V
* bromocriptine — severe postural hypotension

Post-operative
* consider post-op ventilation if sleep apnoea

Question 4

Alcoholic Liver Disease

Answer 4

Pathophysiology
* steatosis - metabolism of ethanol causes accumulation of lipid in liver cells
* alcoholic hepatitis - ethanol metabolism can generate reactive oxygen species and neo-antigens promoting inflammation –> may lead to SIRS and MOF
* prolonged hepatocellular damage generates lyofibrolast-like cells which produce collagen –> fibrosis, hepatocytes are destroyed and liver architecture changes, increased resistance to portal blood flow –> portal hypertension

Extrahepatic Manifestations
* CVS - high CO, low SVR, relative hypovolaemia secondary to vasodilation, cirrhotic cardiomyopathy
* RS - mechanical compression, hepatic hydrothorax, hepatopulmonary syndrome, portopulmonary hypertension
* GI - portal hypertension, SBP
* Renal - acute or chronic renal dysfunction, hepatorenal syndrome
* CNS - hepatic encephalopathy
* Nutrition - malnutrition, muscle wasting, hypoglycaemia, hypoalbuminaemia, impaired wound healing
* Endocrine - adrenal insufficiency, secondary hyperaldosteronism leading to water retention and hyponatraemia
* Haematological - coagulopathy, anaemia, thrombocytopenia, hypofibrinogenaemia

Pre-operative
* MELD/CTP/Mayo/VOCAL-Penn risk scoring
* Thorough preoperative assessment including severity of liver disease, extrahepatic manifestations and any de-compensation
* FBC, LFTs, U+Es, coag, ECG, echo, CPET, ABG, CXR, X match
* ROTEM
* Avoid blood products

Intra-operative
* Full monitoring + invasive monitoring, consider CVC
* Large bore IV access
* Risk of aspiration on induction
* Anticipate fluid shifts, consider CO monitoring
* Consider HAS if large volume of ascites drained
* Prophylactic antibiotics
* Monitor BM
* Careful choice of medication due to altered drug metabolism and decreased synthesis of plasma binding proteins - reduced dose propofol, atracurium/cis, short acting opioids preferred
* Multimodal analgesia (give paracetamol at decreased dose), avoid NSAIDs, regional analgesia

Post-operative
* HDU/ITU
* Keep warm
* Monitor for encephalopathy
* VTE prophylaxis on an individual basis
* Caution with sedatives and analgesia
* Laxatives
* Monitor renal function
* Maintain BM
* Treat sepsis aggressibly with broad spectrum antibiotics

Question 5

Anaesthesia for Premature Infants

Answer 5

A - small and short airway, neutral positioning of head for airway patency
B - RDS, consider oxygen requirement, restrict pressures used, look at CXR
C - ?PDA and right to left shunt, measure and maintain BP, HR dependent cardiac output
D - avoid big swings in PaCO2, risk of IVH/PVL with hypotension
E - “eyes” - avoid high O2 (retinopathy of prematurity)
F - “fluids” - sodium losers, consider post op feeding
G - glucose
H - hypothermia and haematocrit

Question 6

Aortic Dissection

Answer 6

Rare but potentially fatal even resulting in separation of the layers of the tunica media by ingress of blood, producing a false lumen with variable proximal and distal extension.

Classification
Stanford Type A - involves the ascending aorta but may extend into the arch and descending aorta - require surgery
Stanford Type B - involves the descending aorta only - best managed consevatively with medical treatment

Risk Factors
* males
* aged 50-70
* long standing arterial hypertension - advanced age, smoking, dyslipidaemia, cocaine/crack
* connective tissue disorders
* hereditary vascular diseases
* vascular inflammation
* aortic aneurysm
* deceleration trauma
* pregnancy
* iatrogenic

Management
* ABC
* Oxygen
* Close monitoring, detailed history and examination
* ECG, IV access + bloods
* Analgesia
* Careful IV fluid
* BP titration to 110-120 systolic (beta blockage)
* image
* transfer to specialist unit as indicated

Surgical management
* standard anaesthetic principals for cardiac surgery
* adequate peripheral IV access
* cautious fluid management
* antihypertensive therapy
* left radial arterial monitoring
* continuous TOE monitoring
* CVC

Question 7

Aortic Regurgitation

Answer 7

Causes
— primary - rheumatic heart disease, degenerative, infective endocarditis, traumatic rupture
— secondary - type A aortic dissection, connective tissue disease (Marfan’s), AV prolapse

Pathophysiology
— raised LVEDV (volume overload)
— grossly dilated LV (most of SV returning to ventricle)
— quick diastolic run off (limited coronary perfusion)

Symptoms
— acute - tachycardia, pulmonary oedema, cardiogenic shock
— chronic - asymptomatic, exertional breathlessness, angina less common
— look for renal failure

Management
— medical therapy - treat hypertension and heart failure
— surgical - TAVI/AVR

Anaesthetic Goals - “Fast and Loose”
— full preload (adequate circulating volume)
— HR 80-100 (adequate diastolic filling
— sinus rhythm (atrial contribution to CO)
— maintain contractility (needs adequate SV)
— reduce afterload (reduces regurgitation) —> usually tolerate neuraxial well

Aortic Regurgitation in Pregnancy
— usually well tolerated, provided there is no significant LV dysfunction
— many improve symptomatically during pregnancy

Delivery
— early epidural
— avoid increased SVR

Question 8

Aortic Stenosis

Answer 8

Causes
- valvular/supravalvular/subvalvular
- acquired (degenerative/rheumatic) vs congenital (unicuspid/bicuspid valve)

Pathophysiology
- LV hypertrophy - stiff LV/diastolic dysfunction
- fixed CO - impacts on coronary flow
- myocardial oxygen supply/demand imbalance
- increased end diastolic pressure, increased systolic pressure, preserved stroke volume

Symptoms
- angina
- syncope
- breathlessness
- slow rising pulse, ejection systolic murmur

Investigations
- ECG - LVH
- echo
- cardiac MRI

Anaesthetic Considerations
* Identify severity of disease and high risk markers - angina, syncope, CHF
* At increased risk of perioperative cardiovascular complications (MI, CHF, arrhythmias)
* Fixed LVOT obstruction with limited ability to increase cardiac output
* Hypertrophied LV with diastolic dysfunction
* Altered myocardial oxygen supply/demand
* Systolic dysfunction occurs late in disease
* Associated complications - coronary artery disease, other valvular disease, pulmonary hypertension, sudden cardiac death/malignant arrhythmia, potentially ineffective CPR, anaemia/bleeding risk (acquired von Willebrand syndrome, mucosal/GI angiodysplasia)
* Consider valvuloplasty/cardiology and cardiac surgery consult prior to semi-urgent/elective procedures
* Management of medications

Anaesthetic Goals - “Slow and tight”
* full preload (ensure adequate circulating volume)
* rate low normal HR 60-80 (fixed CO state, maximise diastolic filling and coronary perfusion)
* sinus rhythm (needs atrial contribution to CO)
* maintain contractility (fixed CO state - prone to subendocardial ischaemia)
* maintain/mildly increased afterload (support coronary perfusion) - avoid neuraxial
* avoid hypotension - invasive BP monitoring, vasopressors
* avoid myocardial ischaemia - avoid tachycardia, maintain diastolic BP
* maintain LV filling - sinus rhythm, maintain preload
* maintain contractility - avoid cardiac depressants (e.g. Propofol)

Aortic Stenosis and Pregnancy
* if asymptomatic prior to pregnancy, usually tolerate uneventfully
* hyper dynamic circulation in pregnancy usually —> overestimation of severity
* tolerate tachycardia, hypovolaemia + systemic vasodilatation poorly
* for delivery
— GA/LSCS
— carefully titrated regional blocks for vaginal delivery/LSCS
— invasive BP monitoring
— aggressive use of vasopressors

Question 9

Autistic Spectrum Disorder

Answer 9

• occurs in 1-2%+ of children
• lifelong neuro developmental difference
• characterised by functional impairment in social communication, restricted interests and repetitive behaviours
• difficulty with social communications, interaction and imagination
• abnormalities in sensory processing - hypersensitivity to touch, taste, vision or sound
• difficulty coping when out of routine or with new experiences
• challenges with executive functioning
• wide spectrum of possible difficulties from non verbal, fully dependent to “highly functioning” individuals
• may have low, normal or high intelligence
• increasing recognition of autistic spectrum conditions, especially in females where traditionally it has been considered a predominantly male condition
• high incidence of co-occurring psychiatric disorders
• association with metabolic and syndromic conditions in children

Issues for Anaesthesia
* difficulty in communication
* may dislike being touched or examined
* may not tolerate PO pre-med or LA cream
* difficulty being out of routine
* previous negative experiences of hospital setting
* can be disruptive and agitated
* distress may be demonstrated through challenging behaviours
* lack of knowledge and adaptation by staff

Management
* Flexible, holistic approach with advanced notification for all involved
* Flexible admissions process and individualised care
* Autism Passport
* Do as much as possible pre-admission to stream line
* First/only case, minimise disruption to routine
* Clarify specific issues
* Presence of familiar objects/communication aids
* Avoid triggers where known
* Admit and recover in a single quiet room
* Premedication with clonidine/midazolam/ketamine if needed
* Review previous anaesthetic charts
* Involve child in plan for anaesthesia if possible

Question 10

Chronic Spinal Cord injury with Autonomic Dysreflexia

Answer 10

Impact of CSCI:
* Autonomic dysreflexia is a medical emergency characterized by severe hypertension, which can be brought on by a wide range of stimuli below the level of the lesion (above T6 most commonly, but can occur as low as T10)
– pounding headache, flushing, sweating, nasal congestion above injury level
– pallor, chills, goosebumps below injury level
– BP >200/100 or 20-40mmHg higher than normal
– can lead to raised ICP and cardiac complications
– stimulated by bladder and bowel distension, local infection
– thought to a result of a disorganised sympathetic response to stimuli below the level of the lesion, failed higher input to stimulation with exaggerated responses by spinal circuits and activation of the ANS below the level of the lesion
– can occur within weeks or injury but usually >1yr
* Arrhythmias - high cervical lesions - vagal hypersensitivity leading to bradyarrhythmias (usually resolves within 5 weeks of injury, some need PPM)
* CVS - increased risk due to lack of physical activity, reduced muscle mass and development of metabolic syndromes
* Diabetes
* Impaired thermoregulation, especially with high lesions
* Risk of VTE for first 3 months and perioperatively
* Reduced blood volume, anaemia
* Prone to postural hypotension and pooling of blood in lower limbs
* IV access often difficult - atrophic, hyperaesthetic skin with reduced cutaenous blood flow
* Altered respiratory mechanics - degree of ventilatory dysfunction dependent on level and completeness of lesion
– VC increased in supine position due to abdominal wall paralysis
– lesions above C3 - complete dependent on mechanical ventilation
– C3-C5 - variable dependence on ventilatory support
– C6-C8 - may require intermittent noninvasive ventilatory support due to paralysis of intercostals and abdominal wall muscles, impaired cough and poor mobilisation of lung secretions
– thoracic injuries - inefficient cough but little respiratory compromise
* Often restrictive ventilatory defect with reduced ERV, TLC and FRC
* Reduced lung and chest wall compliance with cervical lesions
* Tracheostomy or previous (tracheomalacia/tracheal stenosis)
* Spasticity and contractures - may lead to difficult patient positioning and surgery
* Osteoporosis
* Extrajunctional ACh receptors
* Spinal fixation
* Pressure ulcers - poor nutrition, muscle atrophy, altered blood flow to dermis
* Chronic pain
* Psychological complications
* Delayed gastric emptying
* Gallstones
* Neurogenic bladder
* High prevalence of nosocomial bacterial colonisation

Preoperative
* thorough anaesthetic history and examination
* FBC, U+Es, LFTs
* ?ABG/CXR/spirometry
* routine swabs, review of cultures
* ECH +/- echo
* check for level and completeness of injury
* thorough airway assessment

Intraoperative
* consideration to patient preference, level and completeness of lesion relative to operative site, previous anaesthetic management, presence of autonomic dysreflexia and spasticity
* emergency access to drugs for management of ADR
* may not need anaesthesia for procedures below the level of lesion but need anaesthetist on standby - full monitoring and caution regarding sedation
* regional anaesthesia - safe and effective for abolishing ADR and spasms
– low dose spinal, may be challenging to site
– difficult to assess effectiveness and level of block - change from spasticity to flaccid paralysis, height difficult to assess, loss of Babinski reflex
– cautious with brachial plexus blocks due to risk of causing PTX
* GA - generally lower doses of induction agents needed, sympathetic response to hypotension often absent, low threshold for awake intubation, caution with sux (safe if injury >6 months)
* Maintenance with volatile or TIVA - adequate depth
* Opioid sparing techniques
* Consider invasive monitoring/CO monitoring for major surgery with large fluid shifts
* Caution with positioning and thermoregulation
* Fully reversed before extubation, may required a period of NIV
* Recover patients with C spine injuries in supine position to aid ventilation

Acute management of ADR
* Check BP
* Sit the patient up
* Empty catheter bag, check not blocked, consider replacing (using lubricant containing lidocaine)
* Consider cathetrising if bladder distended and unable to PU
* Investigate for faecal mass in recturm
* Give 1-2 GTN tablets sublingual or 10mg nifedipine sublingual
* Repeat dose after 20 minutes if persisting symptoms
* IV hypotensive may be required e.g. hydralazine
* Identify and treat cause of ADR

Question 11

C-Spine Injury

Answer 11

Mechanism of injury
* abnormal flexion, extension, rotaion and compression
* hyperflexion –> compression of anterior aspects of vertebral bodies and distraction of posterior ligament complex
– chance fractures (horizontal fractures)
– tear drop fractures
– rupture of posterior ligament
– odontoid peg #s
* flexion and rotation (most common mechanism)
– disruption of posterior ligament complex and posterior column
– # of facet joints, lamina, TPs and veterbral bodies
– dislocation of facet joints
– avulsion of spinous processes
– tearing of intervetebral ligaments
* hyperextension
– damages the anterior column
– anteror # of vertebral body
– crush injury to posterior aspect of vertebral body
– Hangman’s fracture
* rotation
– injury to posterior ligament complexes, often unstable
– may result in facet joint dislocation
* compression - wedge #s

Younger children (<8yrs)
* children have relatively larger heads, ligaments and joint capsules are more lax, facet joints are more horizontal and vertebral bodies are wedge shaped
* pseudosubluxation injuries
* spinal cord injury without radiological abnormality

Management
* C-spine immobilisation - manual inline stabilisation for any interventions - remove as soon as it is safe and practicable after trauma
* Various criteria available to clear C-spine in conscious and co-operative patients
* Imaging - plain C-spine X-rays (3 views), CT, MRI

Question 12

Carcinoid Syndrome

Answer 12

Rare and slow growing neuroendocrine tumours. Generally arise from enterochromaffin cells that contain numerous neurosecretory granules, containing physiologically active substances (serotonin, histamine, dopamine, prostaglandins, bradykinin, substance P).

Carcinoid Syndrome - only occurs in around 10% of patients with carcinoid tumours as most of the active substances secreted by gut tumours pass through the portal circulation and are metabolised by the liver.

Presentation
* Majority are clinically silent - may be found incidentally or due to mass effect
* Carcinoid syndrome - typically intermittent symptoms of flushing, abdominal pain, diarrhoea, lacrimation, rhinorrhea, wheeze.

Investigations
* 5HIAA levels
* Serum chromagraffin A
* CT/MRI
* Bronch if lung disease

Management
* Surgical resection, chemotherapy, biotherapy, radiotherapy
* Somatostatin analogues - ocreotide

Anaesthetic Management
* Identify possible complications e.g. carcinoid syndrome, heart failure, dehydration, electrolyte abnormalities, obstruction
* Minimise risk of carcinoid crisis
* Preoperative - full anaesthetic assessment, CVS examination for signs of right heart failure or valvular disease
* FBC, U+Es, LFTs, X match
* ECG, CXR, echo
* Octreotide infusion pre-operatively
* Intraoperative - invasive monitoring
* Thoracic epidural
* Cardiostable induction and maintenance, avoid histamine releasing agents
* Cautious use of phenylephrine due to unpredictable response to vasopressors
* Titrated doses of octreotide intraoperatively
* Careful management of fluid balance
* Postoperative - HDU, monitoring, continue octreotide

Question 13

Cardiomyopathy

Answer 13

A myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease, and congenital heart disease sufficient to cause the observed myocardial abnormality.

Classification
* DCM - dilated cardiomyopathy - disease of the myocardium characterized by impaired systolic function and dilation of the left and right ventricles
* HCM - hypertrophic cardiomyopathy - primary cardiac muscle hypertrophy of the left ventricle in the absence of other structural or functional abnormality
* RCM - restrictive cardiomyopathy - impairment of ventricular diastolic function due to fibrotic or infiltrative changes in the myocardium and/or subendocardium
* ARVC - arrhythmogenic right ventricle cardiomyopathy - structural abnormalities and cardiac dysfunction or the right (+/- left) ventricle
* Unclassified
* Peripartum cardiomyopathy

DCM
* major cause of heart failure and arrhythmia in young adults
* progressive enlargement or one or both ventricles to the stage that the interaction between actin and myosin filaments becomes inefficient leading to a reduction in stroke volume and systolic impairment
* 2/3rds are idiopathic, may be familial, post infective or present as part of another disease process (many possibilities)
* Features - depend on degree of systolic dysfunction from asymptomatic to signs and symptoms of heart failure and arrhythmias, embolic events and sudden death
* Diagnosis - history, examination, bloods, CXR, ECG, echo +/- stress test
* Management - control symptoms and prevent progression and complications
– ACEI/ARB, BB, aldosterone inhibitors, anticoagulants
– non medical management of advanced heart failure
* Perioperative care
– avoid myocardial depression
– maintain adequate preload and prevent increases in afterload
– avoid tachycardia
– prevent sudden hypotension by careful titration of anaesthetic agents
– neuraxial reduces afterload and improves CO but hypotension must be prevented to avoid myocardial hypoperfusion
– invasive monitoring +/- TOE/ODM

RCM
* impairment of ventricular diastolic function due to fibrotic of infiltrative changes in the myocardium and or subendocaridum
* normal or near normal systolic function in the early stages
* can be primary (idiopathic) or secondary (amyloid, sarcoid, haemochromatosis, IHD, HTN, valvular disease)
* features - biventricular failure, evidence of fluid overload
* diagnosis - echo, endomyocardial biopsy, CT, cardiac MRI
* managment - lower ventricular filling pressure without affecting CO
– beta blockers + calcium channel blockers
– diuretics for symptomatic relief
– maintain SR
– PPM/ICD in patients with advanced conducting system dysfunction
* perioperative aims
– maintain adequate preload
– maintain SVR
– maintain SR
– use anaesthetic agent with minimal cardiovascular effect
* invasive BP monitoring and TOE but high risk of morbidity and mortality

ARVC
* arrhythmogenic right ventricle cardiomyopathy - structural abnormalities and cardiac dysfunction or the right (+/- left) ventricle
* 1:5000 healthy young people, seen in up to 20% of all causes of sudden death in young people
* complex genetic condition
* involvement of ryanodine receptor gene
* adipose and fibrous tissues replace myocardial cells, forming re-entry electrical circuits
* phase 1 - concealed disease - patients with some structural abnormality of the myocardium in whom sudden cardiac death can be the first presentation
* phase 2 - overt disease - established structural abnormality of the myocardium with arrhythmias and syncope
* phase 3 - end-stage disease - severe structural changes, ventricular dilatation and RV systolic dysfunction
* myocardial biopsy, cardiac MRI with gadolinium enhancement
* management - prevent or reduce risk of arrhythmia
– ICD
– sotalol, verapamil, amiodarone
– EP study/catheter ablation
– heart transplantation

Peripartum Cardiomyopathy
* 1 in 10,000 pregnancies
* During 3rd trimester or up to 6 months postpartum
* Exclude other causes of acute heart failure
* Risk factors - pre-eclampsia, tocolytic therapy, obesity, advanced age, viral infection, multiple pregnancies
* High mortality due to pulmonary oedema and systemic embolization
* Anaesthetic management
– fluid management
– avoiding myocardial depression
– CSE can probide less haemodynamic instability

Question 14

CKD

Answer 14

An abnormality of kidney structure or function that lasts more than 3 months. Only becomes evident when fewer than 40% of nephrons are functioning.

Aetiology
* comorbidities - vascular disease, hypertension, T2DM
* intrinsic renal disease - glomerulonephritis, AKI, interstitial nephritis, nephropathies (infective, obstructive, refluex)
* genetic - polycystic kidney disease, alport syndrome, fabry disease, cystinosis
* metabolic - hypercalcaemia, hyperPTH causing nephrocalcinosis, oxalosis
* systemic disease - amyloidosis
* autoimmune - Goodpasture syndrome, scleroderma, IgA vasculitis, SLE
* neoplasm - myeloma, renal tumour
* toxins - lead
* drug related - NSAID use nephropathy, calcineurin inhibitors, chemotherapeutic agents
* other - HUS, gout, obstructive uropathy

KDIGO classification
G1 - G5 - by GFR categories
A1-A3 - by persistent albuminuria categories

Manifestations
* metabolic - hyperkalaemia, metabolic acidosis, hyperphosphataemia, hypocalcaemia, hypermagnesaemia, hyperuricaemia, hypoalbuminaemia
* fluid management - salt and water retention
* CVS - hypertension, IHD, LVH from chronic volume overload, pericarditis from severe uraemia
* RS - pulmonary oedema, pleural effusions, restrictive pulmonary dysfunction, reduced FRC, increased VQ mismatch
* haematological - reduced epo –> anaemia, increased risk of VTE
* GI - dehydration, poor nutritional intake, autonomic neuropathy leading to delayed gastric emptying
* CNS - myoclonus, asterixis, chorea, uraemic encephalopathy, seizures, autonomic neuropathy
* endocrine - secondary hyperparathyroidism, bond demineralisation and risk of #s, phosphate retention, decreased sensitivity to insulin

Pharmacokinetics
* gastroparesis - impaired absorption
* fluid overload –> small bowel oedema –> impaired absorption
* altered drug ionisation due to increase in gastric pH from gastric urease
* reduced protein binding of acidic drugs
* increase in Vd due to fluid retention for hydrophilic drugs
* CYP450 activity may be altered in the context of severe CKD
* accumulation of renally excreted drugs, non renal clearance of many drugs also reduced

Anaesthesia
Pre-operative
* aetiology of CKD
* severity of renal impairment (clinical and biochemical)
* fluid status, dru weight, ability to produce urine
* RRT - modality, last session, volume removed
* drug history e.g. steroid immunosuppression
* presence of AV fistula?
* FBC, U+Es, coag +/- CXR, ECG =?- echo

Intra-operative
* consider invasive monitoring
* consider CVC due to poor peripheral access
* care to preserve AV fistulae and protect potential fistula sites
* UO monitoring
* consider RSI (modified)
* avoid nephrotoxics
* regional anaesthesia (with BP support)
* careful fluid balance
* maintain renal perfusion pressure (patients pre-op baseline)

Post-operative
* careful fluid balance
* consider prolonged supplemental oxygen therapy
* may need dialysing
* vulnerable to sedating effects

Question 15

Congenital Syndromes causing difficult airways/intubation

Answer 15

Hypoplastic mandible (micrognathia) –> difficult intubation
* Pierre Robin sequence - Migrognathia; glossoptosis (backward displacement of tongue); cleft palate
* Treacher Collins syndrome - bilateral malar and mandibular hypoplasia; airway obstruction at rest
* Goldenhar syndrome - Asymmetrical malar; maxillary and mandibulary hypoplasia; hemifacial microsomia
* Noonan Syndrome –> webbed neck, micrognathia, short height, congenital heart disease, skeletal malformations

Midface hypoplasia –> difficult BMV
* Apert Syndrome - midface hypoplasia; possible choanal stenosis; progressive calcification of cervical spine
* Crouzon Syndrome - Midface hypoplasia; maxillary hypoplasia
* Pfeiffer Syndrome - Midface hypoplasia

Macroglossia –> difficult BMV and difficult intubation
* Mucopolysaccharidoses (Hunter’s and Hurler’s syndrome) - accumulation of mucopolysaccarides in various tissues, including airway; short, immobile neck; cervical instability
* Beckwith-Wiedemann syndrome - macroglossia
* Down’s syndrome
* Achondroplasia

Question 16

COPD

Answer 16

Chronic and progressive inflammatory condition resulting in expiratory airflow limitation. Affects central and peripheral airways, lung parenchyma, and pulmonary vasculature. Leads to poorly reversible narrowing of the airways due to inflammation, remodelling of airway smooth muscle, increased numbers of goblet cells and mucus secreting glands, and pulmonary vasculature changes resulting in pulmonary hypertension.

Pre-operative
* full history, focus on exercise tolerance, frequency of exacerbations, most recent antibiotics/steroids, hospital admissions, ICU admissions and co-morbidities
* ECG, routine preoperative bloods, consider spirometry
* Functional assessment
* Nutritional status
* Respiratory examination
* Smoking cessation advice
* Pre-op physio if copious sputum
* Pulmonary rehabilitation?

Intraoperative
* regional techniques preferable, especially for post operative analgesia
* consider invasive monitoring
* ventilation - prolonged expiratory time, caution with PEEP (due to intrinsic PEEP), slow RR
* treat bronchospasm
* steroid cover
* beneficial effect of sevo
* cautious administration of oxygen
* ensure fully reversed prior to extubation

Post-operative
* respiratory support
* chest physio
* mobilisation
* effective analgesia

Question 17

Cushings

Answer 17

Excess plasma cortisol, loss of diurnal variation
Hypernatraemia, raised bicarbonate, raised blood sugar, hypokalaemia, hypocalcaemia, ACTH may be increased or decreased

Pre-operative
* ECG (high voltage QRS, inverted T waves)
* Hypertension (usually poorly controlled)
* OSA+ reflux common (give PPI)
* often diabetic/impaired glucose tolerance
* often obese with difficult veins
* excess body fat with abnormal distribution may lead to difficult airway (buffalo hump, central obesity, moon face)

Intra-operative
* blood sugar management
* consideration re: airway management
* very careful positioning - increased risk of pressure sores and fractures

Question 18

Cyanotic Heart Diseases

Answer 18

Any congenital heart defect that occurs due to deoxygenated blood bypassing the lungs and entering the systemic circulation.

• Tetralogy of fallot
• Total anomalous pulmonary venous connection
• Hypoplastic left heart syndrome
• Transposition of the great arteries
• Truncus arteriosus (persistent)
• Tricuspid atresia
• Interrupted aortic arch
• Pulmonary atresia
• Pulmonary stenosis (critical)
• Eisenmenger syndrome (revesal of shunt due to pulmonary hypertension)

Chronic cyanosis affects most organ systems. The main problems relating to anaesthesia and surgery are polycythaemia and coagulopathy. Dehydration, fever and IDA increase these risks.

Management depends on:
* physiology - compensated, decompensated
* lesion
* risk category
* type of surgery
* location of hospital
* avoid air bubbles in lines if hole between atria
* avoid high inspired O2 to minimise L–>R shunt

Question 19

Dementia

Answer 19

Pre-operative
* high risk patients, manage in MDT
* optimise comorbidities
* rationalise drug regimes
* check social situation and discharge plan
* consent/capacity (may need IMCA)

Intra-operative
* minimise dose of anaesthesia given
* consider depth of anaesthesia monitoring
* avoid benzos (risk of delirium)
* consider drug interactions
— central acting anticholinesterases interact with NMBAs + can cause bradycardias
— memantine can increase anticholinergic effects (avoid ketamine)
— antipsychotics can increase vasodilatation/hypotension
* maintain physiological homeostasis

Post-operative
* dementia friendly ward environment - well lit, signs, clocks
* regional analgesia, caution with opioids - consider visual pain scales
* delirium management - individualised approach
— normalised physiology
— safe environment
— non-pharmacological means first
— pharmacological - single agent, lowest dose, shortest duration (haloperidol, benzos if ETOH/Parkinsons)

Question 20

Diabetes Insipidus

Answer 20

• Loss of the effect of ADH on the collecting ducts of the kidneys, resulting in loss of free water.
• Can be central or nephrogenic
• Central - causes that impair synthesis, transport or release of ADH
• Nephrogenic - receptor, or downstream, unresponsiveness to circulating ADH

Diagnosis
* plasma hyperosmolality
* hypernatraemia
* polyuria
* low urine osmolality
* water deprivation test
* investigate for underlying cause

Central DI
Acquired - transphenoidal surgery, traumatic brain injury
idiopathic, autoimmune, tumours, hypoxic brain injury, brain stem death, profound hyponatraemia, radiotherapy, inflammatory conditions, infections, vascular disease)
Congenital - autosomal dominant mutation in ADH production, Wolfram syndrome

Management
1) treat hypernatraemia - replace previous hours UO with an appropriate fluid, avoid a fall in Na by more than 0.5mml/hr
2) address deficit in total body H2O - dehydration and hypovolaemia - isotonic saline
3) supplement ADH (DDAVP)
4) consider associated anterior pituitary dysfunction
5) treat underlying cause
* manage in critical care environment
* monitor Na+ frequently

Nephrogenic Diabetes Insipidus
Acquired
* drug induced - lithium, antibiotics, antivirals, antifungals, antineoplastic drugs
* renal diseases, obstructive nephropathy
* prolonged metabolic imbalances e.g. hypercalcaemia
* idiopathic
Congenital - hereditary X-linked recessive

Management
1) treat hypernatraemia
2) address fluid deficit
2) treat underlying cause
3) hydrochlorthiazide and amiloride
4) restrict dietary salt and protein

Question 21

Down Syndrome

Answer 21

• Trisomy 21

Features (of relevance)
* General - low birth weight, obesity, short stature
* Respiratory - OSA, subglottic and tracheal stenosis, LRTI
* Craniofacial - macroglossia, oropharyngeal hypotonia, micrognathia, short neck, adenotonsillar hypertrophy
* CVS - Congenital heart disease, pulmonary hypertension, valvular heart disease
* CNS - neonatal hypotonia, intellectual impairment, Alzheimers, epilepsy, postoperative agitation
* Spinal - atlanto-axial instability, atlanto-occipital instability, cervical spondylitis
* GI - GORD, gastrointestinal atresias
* Endocrine, hypothyroidism
* Immune system dysfunction

Question 22

Epilepsy

Answer 22

Pre-operative
* optimise seizure management
* identity those most at risk of perioperative seizures - increased risk if on several anti-epileptic drugs with recent or uncontrolled fits
* confirm current seizure control, consider neuro review +/- levels of anti epileptics
* current treatment including diet, nerve stimulation
* associated comorbidities
* social situation, driving license status

Intra-operative
* timing
* take AEDs
* avoid long fasts
* clear perioperative plan
*regional anaesthesia is safe
* maintain normal physiology
* propofol/benzos, volatiles, opioids, analgesics are safe to use
* caution with ketamine, etomidate, enflurane, tramadol, meperidine and dopamine antagonists
* NMBAs - avoid sux in status, use peripheral nerve stimulators if on enzyme inducing AEDs

Post-operative
* restore physiological normality
* clear plan re: AEDs - consider alternate routes if longer disruption, discuss with neuro if required
* double check interactions if prescribing
* consider other causes of seizures but manage as per standard status epilepticus

Question 23

Fixed Cardiac Output States

Answer 23

Fixed cardiac output - the stroke volume cannot increase
* Aortic stenosis (severe)
* Mitral stenosis

Priorities
* maintain adequate pre-load (volume)
* maintain SVR
* maintain sinus rhythm
* low-normal HR - treat tachycardia aggressively
* caution with neuraxial due to drop in SVR

Question 24

Haemorrhagic Shock

Answer 24

ATLS Classification of Classes
* Class I - up to 750ml (15% of volume in a 70kg adult)
— HR <100, BP normal, pulse pressure normal or raised
— RR 14-20
— UO >30ml/hr
— CNS slightly anxious
* Class II - 750-1500ml (15-30%)
— HR 100-120, BP normal, pulse pressure decreased
— RR 20-30
— UO 20-30ml/hr
— CNS mildly anxious
* Class III - 1500-2000ml (30-40%)
— HR 120-140, BP decreased, pulse pressure decreased
— RR 30-40
— UO 5-15ml/hr
— CNS anxious, confused
* Class IV - >2000ml (>40%)
— HR >140, BP low, pulse pressure decreased
— RR >35
— UO negligible
— CNS confused, lethargic

Question 25

HOCM

Answer 25

Primary cardiac muscle hypertrophy of the left ventricle in the absence of other structural or functional abnormality.
70% of HCM develop obstruction.

Aetiology
* autosomal dominant
* variable genetic expressivity, 11 gene mutations identified which encode cardiac muscle sarcomere
* hypertrophy may be asymmetrical, concentric, midventricular or apical and can involve the right ventricle
* leads to diastolic impairment of the left ventricle
* extracellular fibrosis –> increasing hypertrophy, ventricular stiffness, shape distortion, further diastolic impairment
* systolic function remains normal with high EF until latter stages

Categories
* non-obstructive
* labile
* obstructive at rest

Features
* majority asymptomatic
* angina, heart failure, sudden death
* AF
* thromboembolic events
* dynamic LVOTO
* echo, ECG and cardiac MRI helpful

Management
* beta blockade if heart failure - improve LV filing due to prolonged diastolic time
* amiodarone for SVT/VT
* ICD
* invasive treatment - alcohol septal ablation, surgical myectomy

Perioperative care
* optimise medical therapy
* careful fluid status management
* aims
– adequate preload and afterload
– maintain SVR
– avoid sympathetic activation
– reduce contractility
– avoid tachycardia, maintain sinus rhythm
– IV fluid bolus and phenylephrine are preferred first line for hypotension in presence of LVOTO
* GA preferred, regional only with extreme cautiou
* Inotropes with extreme caution (avoid adrenaline in arrests)
* GA, invasive monitoring + TOE

Question 26

Hydrocephalus

Answer 26

Pre-operative
* standard anaesthetic history and examination
* ask re: ICP e.g. seizure activity, decreased GCS
* neurological examination
* ?part of syndrome (especially in paeds)
* consideration re: location of post op care

Intra-operative
* monitoring dependent on patient and procedure
* no absolute contraindication to spinal anaesthesia though often avoided due to concern re: shunt contamination/CNS infection
* laparoscopic surgery is possible - aim to observe CSF flow from distal end of VP shunt at the beginning, during and at the end of procedure, minimise duration and pressure of pneumoperitoneum
* aim to maintain normal physiology

Post-operative
* standard recovery and post op care with addition of neuro obs
* multimodal analgesia

Question 27

ICU Acquired Weakness/Critical illness polyneuropathy

Answer 27

• Occurs in around 50% of all adults on general ICU for more than one week, especially with sepsis
• Clinically detected weakness in critically ill patients in whom there is no plausible aetiology other than critical illness
• Subdivided into critical illness polyneuropathy, critical illness myopathy and critical illness neuromyopathy (considerable overlap between divisions)
• Axonal degeneration of fibres associated with muscle wasting. Demyelination occurs during hypermetabolic states as adipose tissue is sources for glucose

Risk Factors
* severe systemic inflammation, septic shock
* MOF
* prolonged mechanical ventilation/bed rest
* poor glycaemic control
* longer duration of illness
* drugs - corticosteroids, NMBA, aminoglycosides
* possible risk factors - female, age, severity of illness on admission, renal therapy, parenteral nutrition, vasopressors

Diagnosis
1. Weakness after the onset of critical illness
2. Generalised weakness including the proximal and distal muscles, symmetrical and flaccid (CN usually preserved), flaccid quadriplegia, hyporeflexia, muscular atrophy - deep pain produces grimacing with little limb movement, diaphragmatic involvement common
3. Other causes of weakness have been excluded
4. AND one of the following
— low muscle power score on testing of 12 muscles
— dependence on mechanical ventilation
— abnormal sensation (if possible to test)
— autonomic function is normal
Consider MEPs/SSEPs/EMG, muscle and nerve biopsy, CPK if uncertainty over diagnosis.
EMG - normal nerve conduction velocity, slight increase in latency but decreased sensory nerve and motor nerve action potentials, repetitive stimulation gives normal response. Sensory APs may be normal if just myopathy
Muscle biopsy - acute necrotising myopathy, thick filament myopathy and non-necrotising cachetic myopathy

Clinical Consequences
* difficulty weaning from mechanical ventilation
* increased ICU and hospital stay
* increased mortality
* persistent severe disability in survivors
* possible hyperkalaemia cardiac arrest with suxamethonium

Prevention
* care with NMBA, steroids, aminoglycosides
* address risk factors
* sedation holds daily
* reduce total amount of sedation
* enteral nutrition
* early mobilisation

Other causes of muscle weakness
* electrolyte abnormalities
* cachetic myopathy - severe systemic illness, diffuse muscle loss, catabolism, starvation
* drugs - steroids, prolonged action of NMBA in liver and renal failure
* disease states - MG, GBS, peripheral neuropathy, cervical cord pathology, endocrine disorders (Addisons, Cushings)
* critical illness polyneuropathy/myopathy
* damage to anterior horn cells in spinal cord - ischaemia from cardiac arrest, aortic surgery

Question 28

Immune Checkpoint Inhibitors

Answer 28

Immune check point inhibitors are a type of immunotherapy use for cancer treatment that acts to “switch off” a natural protector within our immune system - usually targets a specific protein

Pre-operative
* detailed history and any complications from checkpoint inhibitors
* basic bloods, TFTs, HbA1c, cortisol, ACTH, BNP, troponins
* ECG +/- TTE, CXR/CT, 6MWT, SpO2, spirometry

Intra-operative
* steroid replacement +/- rescue if crisis suspected
* monitor BMs and treat hyperglycaemia
* consider invasive monitoring
* cautious fluid management
* lung protective ventilation strategies

Organ toxicities with greatest potential for perioperative complications
* hypophysitis —> multiple endocrine failure
* hypopituitarism
* hypo/hyperthyroidism
* pneumonitis
* hepatitis
* adrenal insufficiency
* myocarditis
* enterocolitis
* myasthenia gravis

Question 29

Intrauterine Death

Answer 29

Incidence - 3.9 per 1000

Causes
* No specific cause found in 50%
* Causes can be multiple
* Maternal causes - pre-eclampsia, chorioamnionitis, abruption, APH, maternal disease e.g. DM
* Fetal causes - cord prolapse, congenital malformations, congenital fetal infections

Management
* Full history and examination
* Sensitive approach
* FBC, U+Es, coag, Xmatch, blood cultures
* ECG
* Analgesic options - simple analgesia, PCA morphine, epidural analgesia

Question 30

Ischaemic Heart Disease

Answer 30

Pre-operative
* thorough assessment of disease - history, examination, relevant investigations
* risk assessment
* consider medications - usually omit ACE/ARB, consider DAPT duration
* consider pre-medication for anxiolysis

Intra-operative
* maintain adequate myocardial oxygen delivery and minimise any increase in demand
* aim relatively low HR
* maintain sinus rhythm
* “cardio-stable” anaesthetic technique
* ECG in CM5 formation
* keep BP within 20% of normal
* cautious fluid management
* consider arterial line

Post-operative
* supplement O2 for 72hrs
* generous analgesia

Question 31

Long QT Syndrome

>450 in M, >460 in F

Answer 31

Long QT syndrome is caused by malfunction of cardiac ion channels, thereby impairing ventricular repolarisation. This predisposes to the development of polymorphic VT.

Causes:
* Congenital - mutations in the genes encoding for cardiac ion channels
– Jervell and Lange-Nielsen Syndrome - autosomal recessive, concomitant sensorineural hearing loss
– Romano-Ward Syndrome - autosomal dominant
– multiple gene mutations have been identified
* Acquired - malfunction of the ion channels is caused by drugs or metabolic abnormalities
– drugs - sotalol, amiodarone, macrolides, quinolones, droperidol, chlorpromazine, fluoxetine, fluconazole, class I antiarrhythmics, methadone
– electrolyte abnormalities e.g. hypoK, hypoMg, hypoCa
– severe starvation including anorexia nervosa
– neurological injury e.g. after SAH
– hypothermia

Triggers of Torsades (QTc >500)
* SNS stimulation - pain, nausea, emotional stress, loud noise
* Bradycardia, tachycardia, hypertension, hypoxaemia, hypercapnia
* Electrolyte disturbances
* QT prolonging medications (as above)
* Congenital long QT - avoid beta-agonists, ketamine

Management
* Torsades - Mg 25-50mg/kg (2g) IV, repeated +/- infusion, keep K+ >4.5, consider overdrive transvenous pacing, defib + CPR per ALS if needed
* Anaesthesia -
– pre-operatively: continue beta blocker, check ECG, liaise with cardiology, check (+ correct) Mg, K, Ca, discontinue QT prolonging drugs, consider full invasive monitoring and application of defib pads, may have ICD
– intra-operatively: avoid pressor response to intubation, avoid high intrathoracic pressures, avoid hypothermia, maintain normocarbia, avoid ketamine, avoid reversal of neuromuscular block if feasible (or use roc/sugammadex), pre-load and use phenylephrine if neuraxial technique
– post-operatively: prolonged ECG monitoring, adequate analgesia, nurse in a calm and quiet environment

Question 32

Malignant Hyperthermia

RYR1 gene on chromosome 19

Answer 32

Potentially lethal reaction that occurs in response to particular medications used during GA, among those who are susceptible. Exposure to triggering agents (certain volatiles or sux) can lead to development of MH. Susceptibility can occur due to at least 6 genetic mutations - the most comon one being of the RYR1 gene on chromosome 19. This leads to lowered activation and heightened deactivation of RYR1 receptors, resulting in excess calcium release.

Associated conditions - central core disease, multiminicore myopathy, congential myopathy with cores and rods, centronuclear myopathy, congenital fibre type disproportion, KDS, periodic paralysis, nemaline rod myopathy, Native American myopathy, idiopathic hyperCKemia

Early signs - rise in ETCO2, tachycardia, tachypnoea, mixed acidosis, masseter spasm/trismus, suddent cardiac arrest due to hyperkalaemia
Later signs - hyperthermia, muscle rigidity, myoglobinuria, arrhythmias, cardiac arrest

Management
* Call for help and inform theatre team
* Aim to abandon or finish surgery asap
* Call for MH treatment pack and cardiac arrest trolley
* Maintain anaesthesia with TIVA, NMBA with non-depolarising drug
* Eliminate trigger drug - activated charcoal filters on both limbs of breathing circuit
* Give dantrolene - 2.5mg/kg IV bolus, repeat 1mg/kg every 5 minutes until ETCO2 <6 and temp <38.5
* Begin active cooling - apply ice, use cold IV fluids, consider cold peritoneal lavage, other cooling methods
* Additional monitoring - invasive BP, CVC, core and peripheral temp, UO
* Check ABG, U+Es, glucose, FBC, coagulation, urinary pH, CK
* Seek and treat complications
– metabolic acidosis - hyperventilate, sodium bicarb
– hyperkalaemia - sodium bicarb, glucose/insulin, calcium
– myoglobinuria - forced alkaline duiresis
– DIC - FFB, fibrinogen, platelets
– tachyarrhythmias - amiodarone, beta blockers
– compartment syndrome - surgical decompression
* Avoid calcium channel blockers!
* Continue ventilation and plan admission to critical care
* Ensure plan exists to counsel patient and family and refer to Leeds MH unit.

Differential diagnosis - NMS, thyroid storm, anaphylaxis, phaeochromocytoma, drug toxicity

Question 33

Maternal Obesity in Pregnancy

Answer 33

Maternal:
* increased risk of perinatal death
* increased risk of VTE
* increased risk of gestational diabetes
* increased risk of pre-eclampsia
* increased risk of PPH
* increased risk of need for assisted vaginal delivery or C-section
* increased risk of wound infections

Fetal:
* increased risk of miscarriage
* increased risk of still birth
* increased risk of fetal distress
* increased risk of preterm birth
* increased risk of meconium aspiration
* increased risk of low APGAR and admission to NICU

Anatomical and pathophysiological factors
* Airway - increased incidence of failed/difficult intubation (1 in 3, reduced apnoea time, large breast tissue, airway dimensions)
* Respiratory - reduced FRC, VQ mismatch, hypoxia compared to non obese, OSA, pulmonary hypertension/cor pulmonale
* CVS - hypertension, IHD, CCF, less able to cope with CVS changes in pregnancy/labour, exacerbated aortocaval compression
* GI - hiatus hernia, increased is of aspiration
* Practical - equipment, staff training, IV access, regional techniques (difficulty in inserting, respite rate, monitoring, pressure care, DVT prophylaxis, manual handling, weight limits

Epidurals
* increased s/c fat makes identification of landmarks difficult
* unable to adopt ideal position for insertion
* cephalad spread more likely ?secondary to increased intracranial-abdominal pressure
* more likely to fail to site and need respite
* increased incidence of dural puncture (but ?decreased PDPH)

Question 34

Meningitis and Encephalitis

Answer 34

Bacterial meningitis - inflammation of the meninges, particularly the pia and arachnoid mater, associated with the invasion of bacteria into the subarachnoid space.
Viral meningitis - usually less severe and progresses more slowly than bacterial meningitis

Presentation
* fever
* headache
* neck stiffness
* altered mental status
* focal neurological deficits - CN palsies, aphasia, hemiparesis, seizures, coma
* rash - Neisseria meningitidis

Organisms
* Strep pneumoniae
* Neisseria meningitidis (adolescents)
* Listeria monocytogenes (>60s)
* Staphylococcus aureus
* Previously - haemophilus influenza
* Enterovirus, HSV2, VZV (females age 20-40)

Management
* ABCs
* Sepsis 6
* Antibiotic therapy within 1hr - cefotaxime (+/- amoxicillin) + aciclovir + dexamethasone (for bacterial meningitis)
* Diagnostic interventions - LP, contrast CT/MRI

Encephalitis - inflammation of the brain - can be infectious, post-infectious or autoimmune.

Prsentation
* fever
* headache
* altered mental state
* focal neurological signs
* seizures
* GI and respiratory symptoms

Organisms
* HSV1
* VZV
* Enterovirus
* M. tuberculosis

Management
* ABCs
* CSF sampling and neuroimaging, ideally prior to treatment
* Treatment within 6hrs of clinical suspicion of encephalitis
* Aciclovir IV

Question 35

Mitral Regurgitation

Answer 35

Causes
— Type I - normal leaflet motion e.g. annular dilatation, dilated cardiomyopathy
— Type II - excessive leaflet motion e.g. prolapse
— Type III - restricted leaflet motion e.g. rheumatic heart disease, radiation
— Primary - degenerative including Marfan’s, EDS, rheumatic, IE, acute MR (ruptured papillary muscles)
— Secondary - IHD, cardiomyopathy
— acute vs chronic

Pathophysiology
— volume overloaded LV, hyper dynamic
— dilated LA (+/- AF) - much of CO returning to LA rather than aorta
— late pulmonary hypertension

Symptoms
— fatigue
— exertional SOB
— signs - pan systolic murmur (loudest at apex), 3rd heart sound, pulmonary oedema, raised JVP, displaced apex

CXR - cardiomegaly, LA and LV enlarged, pulmonary congestion

ECG - acute ischaemia, broad P waves, LVH, RVH, RBBB

Echo - 2D and colour Doppler

Management
— decrease afterload (vasodilators, IABP)
— decrease filling pressures (diuretics, nitrates)
— heart failure management
— repair vs replacement (open vs minimally invasive

Anaesthetic Goals - “Full, fast and forward”
— full preload
— maintain HR (increase in acute MR)
— sinus rhythm
— maintain contractility may need additional support in acute MR
— maintain afterload (mild decrease in chronic MR)
— avoid increase in PVR
— neuraxial anaesthesia is well tolerated
— use vasopressors with caution

Mitral Regurgitation in Pregnancy
— well tolerated (as long as LV function preserved)
— if symptomatic or LV failure - risk of decompensation
— diuretics to decrease fluid overload
—delivery - early epidural + assisted 2nd stage, avoid increased SVR

Question 36

Mitral Stenosis

Answer 36

Causes
— congenital - cor triatum
— acquired - rheumatic (inflammation, fibrosis and calcification), degenerative, IE, inflammatory (SLE/sarcoid), malignancy, iatrogenic

Pathophysiology
— rising left atrial pressure —> dilatation —> increased pressure on pulmonary vasculature
— limited blood reaching left ventricle - fixed CO

Symptoms
— fatigue, exertional breathlessness, malar flush
— right heart failure - increased JVP, ascites, pedal oedema
— if symptomatic of AF or pulmonary hypertension, likely to need percutaneous valvotomy prior to definitive surgery

Signs
— mid diastolic murmur
— irregularly irregular pulse
— pulmonary and peripheral oedema
— raised JVP

CXR - pulmonary congestion, LA enlargement + pulmonary arteries
ECG - AF, bifid P waves, RVH, TWI
Echo - MV area, gradient, pulmonary arterial pressure, LA size

Management
— rate + rhythm control (Beta blockers, calcium channel blockers)
— diuretics + long acting nitrates
— anti-coagulation
— percutaneous valvuloplasty/open MVR

Anaesthetic Goals - “Slow and Tight”
— adequate pre-load (not too full) - need raised left atrial pressure
— rate 60-80 (adequate diastolic filling)
— sinus rhythm (atrial contribution to CO)
— maintain contractility (need adequate SV)
— maintain afterload
— avoid increases in pulmonary vascular resistance (avoid hypoxia, hypercarbia, pain)
— use neuraxial anaesthesia with caution due to decreased SVR

Mitral Stenosis in Pregnancy
— poorly tolerate
— may be first presentation of symptoms
— pulmonary artery pressures worsen
— mod-sev MS —> 2nd/3rd trimester decompensation
— medical management - beta blockade, diuretics, anticoagulation
— surgical management - percutaneous mitral valvuloplasty
— delivery - control HR and rhythm, maintain afterload, cautious IVI, early epidural, assisted 2nd stage, if NYHA 3/4 —> elective LSCS
— post delivery - HDU, avoid ergometrine, cautious synto

Question 37

Multiple Sclerosis

Answer 37

Pre-operative
* clarify and document neurological function
* detailed neurological examination
* confirm drug history + any impact drugs may have
* consider pulmonary function tests
* clarify any bulbar palsy

Intra-operative
* GA or regional
* central neuraxial blockade can be used with caution (use minimal dose)
* avoid sux due to increased K+
* caution and reduce doses for non-depolarising NMBAs if severely disabled
* careful cardiovascular monitoring - autonomic instability —> marked hypotensive response to drugs and sensitivity to hypovolaemia
* avoid pyrexia and hypothermia

Post-operative
* consider HDU

Question 38

Myaesthenia Gravis

Answer 38

Autoimmune disruption of various components of the neuromuscular junction, including binding of autoantibodies to the acetylcholine receptor, leading to muscular weakness with easy fatiguability.

• thymoma in 15% - benign tumour of thymus, involved in T cell maturation
• can occur as an adverse effect of novel cancer immunotherapies, including immune checkpoint inhibitors
• ocular symptoms commonly first to appear
• weakness more marked in proximal muscles with no wasting/fasciculations and normal tone, sensation and refleces
• can cause speech or swallowing impairment/bulbar symptoms and SOB
• diagnosis - physical and neurological examination, Tensilon test, bloods for Ach/MuSK antibodies, EMG, imaging, spirometry
• management - thymectomy, monoclonal antibodies, anticholinesterase medications for symptom relief, immunosuppressive drugs, plasmapharesis and IVIG

Drugs can aggravate MG
* antibiotics - aminoglycosides, macrolides, clindamycin, quinolones
* cardiac medications - beta blockers, calcium channel blockers, magnesium
* gabapentin
* very sensitive to NMBAs, use small titrated doses with neuromuscular monitoring, avoid reversal if possible due to increased risk of cholinergic crisis (use standard dose if required)

Anaesthetic Goals
* avoid exacerbation of muscle weakness
* preserve respiratory function

Pre-operative
* MDT approach including neurologist
* optimum control of MG prior to elective surgery
* AM surgery when muscle function is at its best
* thorough anaesthetic assessment, including review for bulbar symptoms, respiratory impact and history of myaesthenic crisis, any associated autoimmune disease, current and planned drug therapy
* continue anticholinesterases, anticholinergics and glucocorticoids
* FBC, U+Es, LFTs, TFTs, 12 lead ECG, imaging of any thymoma, FVC
* discussion re: potential need for postoperative ventilation

Intra-operative
* sedation with short acting agents can be used with caution
* local and regional anaesthesia may be used - amide LAs rather than esters due to potential impairment of metabolism of ester LAs
* caution with neuracial/brachial plexus blocks in those with significant respiratory of bulbar weakness
* careful periop management for GA
* respond unpredictably to NMBDs and reversal - avoid where possible (TIVA with remi), use roc/sugammadex with quantitative monitoring if needed
* spontaneous ventilation with pressure support for short procedures
* mechanical ventilation for longer procedures
* consider invasive monitoring
* maintain normotherma and adequate fluid balance
* multimodal analgesia

Post-operative
* dependent on surgery performed, anaesthetic technique etc
* multimodal analgesia
* may be suitable for day surgery
* may need enhanced post op monitoring

Question 39

Myotonic Dystrophy

Answer 39

Autosomal dominant

Pre-operative
* MDT approach with specialist input
* CVS - conduction defects, CCF, cardiomyopathy
* R/S - aspiration/LRTI, restrictive lung disease, poor cough, central + obstructive sleep apnoea, weak respiratory muscles
* CNS - low IQ, cataracts, myotonia (sux/cold)
* GI/other - reflux, T2DM, hypothyroid, adrenal abnormalities

Intra-operative
* consider PPI/prokinetics/RSI
* consider awake arterial line
* avoid NMBA, use neuromuscular monitoring
* avoid sux
* avoid hypothermia/shivering
* cautious use of induction agents/opioids
* multimodal analgesia
* monitor BMs
* reverse fully with sugammadex
* ensure defib available

Post-operative
* early extubation if safe
* physio
* consider enhanced level of post-op care

Question 40

Neurofibromatosis

Answer 40

NF1 - peripheral
* Autosomal dominant
* NF1 gene on chromosome 17
* Loss of production or reduced function of neurofibromin
* Cafe au lait spots, acillary or inguinal freckling, Lisch nodules, neurofibromas. Associated with learning disabilities, scoliosis, epilepsy, cardiomyopathy, phaeochromocytoma, pulmonary fibrosis, apical bullae and cysts, renal artery stenosis

NF2 - central
* Autosomal dominant
* NF2 gene on chromsome 22
* NF2 gene produces schwannomin - a cell membrane related protein that acts as a tumour suppressor
* Neurologic lesions (especially bilateral acoustic neuromas), eye lesions especially cataracts, skin lesions

Both forms have neural tumours - central and peripheral neurofibromas, meningiomas, astrocytomas, gliomas, ependymomas, neuromas

CXR signs
* often none
* fibrosis
* chest wall and pulmonary neurofibromas
* paraspinal masses
* rib notching
* “ribbon ribs” - ribs look twisted
* kyphoscoliosis

Question 41

Neuromuscular Disorders

Answer 41

Categorised by site of abnormality
* Muscle e.g. muscular dystrophies, myotonic dystrophy
* Neuromuscular junction e.g. myasthenia
* Peripheral myelinated nerves e.g. Guillain Barre Syndrome, Charcot-Marie-Tooth
* Anterior Horn Cell e.g. ALS, SMA
* Spinal cord e.g cord injury
* Brain stem/cerebellum/optic nerves/cord e.g. MS

Pre-operative
* precise diagnosis
* MDT approach with specialist input
* airway/CVS/RS/autonomic involvement
* document specific function/neurology
* investigations - consider lung function/echo

Intra-operative
* temperature management
* RA my have advantages but careful consideration needed
* increased sensitivity to opioids
* caution with NMBAs - monitor closely

Post-operative
* complications
— rhabdomyolysis
— autonomic dysfunction
— myotonic contractures
— cardiac and respiratory complications
— MH - hypokalaemic periodic paralysis/central core disease
* early extubation, physio

Question 42

Parkinson’s Disease

Answer 42

Pre-operative
* MDT approach including Parkinson’s specialist
* confirm drug regime
* consider systemic effects and co-morbidities
* social situation and safe discharge plan
* increased peri-operative morbidity and mortality

Intra-operative
* minimise interruption to drugs - ensure taken preoperatively
* consider alternate routes/drugs if prolonged starvation (apomorphine IV - needs challenge beforehand, rotigotine patches)
* benefits of regional anaesthesia
* maintain physiological homeostasis
* risk of monitoring artefact, including from deep brain stimulation
* increased airway risks
* deep brain stimulation - check pre- and post-op (like PPM) and use bipolar diathermy
* caution with atropine, halothane, high dose fent/alt, avoid direct acting sympathomimetics if on MAOBIs, avoid DA antagonists, risk of serotonin syndrome with seligiline

Post-operative
* minimise disruption to drugs - most are enteral only - seek specialist advice
* early detection and management of complications
* analgesic plan (?difficulty operating PCA)

Question 43

Patients who Refuse Blood

Answer 43

Pre-operative
* Check Hb at least 6/52 beforehand and optimise Hb (Fe/EPO)
* Confirm acceptability of products/processes
* Consider paediatric blood bottles for sampling
* MDT discussion +/- Hospital Liaison Committee
* Thorough consent process and documentation

Intra-operative
* Consider acute normovolaemic haemodilution
* Maintain physiologic homeostasis
* Consider hypotensive anaesthesia
* Cell salvage
* TXA
* Use of POCT for coagulation
* Surgical techniques - senior surgeon, tourniquets, minimally invasive, haemostatic agents, electrocautery, topic vasoconstrictors
* Regional anaesthesia

Post-operative
* Comprehensive verbal and written handover
* Minimise ongoing blood loss
* Promote haemostasis
* Correct coagulation defects (as permitted)
* Post-op cell salvage?
* Optimise O2 delivery and consumption
* Consider IV iron/EPO

Question 44

Patients with Cardiac Implanted Electrical Devices

Answer 44

Pre-operative
* Identify device, ensure clarity re: reason for insertion, type of device, recent device check etc
* Confirm functioning and position of device
* Consider need for de-activation (device + surgery dependent) or re-programming

Intra-operative
* Ongoing ECG monitoring
* Consider application of defib pads
* Limit diathermy/electrocautery to short, low energy bursts, ideally using bipolar
* Ensure diathermy pad (if required) positioned so current does not flow through heart/device
* if detectable pacemaker inhibition occurs - inform surgeons and discontinue/minimise cause
* ICDs —> monitor only mode
* PPM (if pacemaker dependent) —> fixed pacing

Post-operative
* continuous ECG monitoring until device returned to normal functioning
* consider need for interrogation of device

Question 45

Patients with Neurosurgical Implants

Answer 45

Pre-operative
* shunts - check pre-op GCS, document any focal neurological deficits, check pupil size and reactivity, consider access point for invasive lines
* VP shunt - any signs of intra-abdominal infection? Risk of adhesions
* VA shunt - signs of pulmonary hypertension, avoid IJ/subclavian lines
* V-pleural shunt - seek advice before draining effusion, IPPV may cause shunt blockage post-op physio is vital to minimise risk of LRTI or atelectasis
* L-P shunt - risk of meningitis, avoid kinking or pressure on shunt, avoid hypotension
* intracranial stents - confirm plan re: DAPT, determine when/why/location of insertion and risks of occlusion
* neurostimulator devices incl. vagal nerve stimulators, deep brain stimulators, spinal cord stimulators, intrathecal baclofen pumps
— confirm type and location of device, date of implantation and last check, current status in terms of symptom control, programmability, severity of symptoms when off, current medications
— avoid electrocautery, use bipolar > mono polar
— USS guided blocks, neuraxial may be possible with spinal cord stimulators

Question 46

Pericarditis

Inflammation in the pericardium

Answer 46

Causes
* viral (coxsackie)
* post infarction
* uraemia
* connective tissue disease
* malignancy (metastatic: lung > breast > leukaemia and lymphoma > melanoma)
* TB
* rheumatic fever
* bacterial - staph, Hib
* radiation
* autoimmune
* vasculitis

Features
* Chest pain (worse on inspiration, lying flat and movement, radiating to trapezius ridge)
* SOB
* Fever
* O/E - fever, pericardial rub, tachypnoea, tachycardia

Investigations
* ECG - diffuse ST elevation with PR depression initially
* Elevated cardiac enzymes
* CXR if tamponade suspected
* Echo

Management
* Oxygen
* Telemetry
* Rule out life threatening causes of chest pain
* NSAIDs
* Pericardiocentesis for tamponade
* Antibiotics if infectious
* Cardiology and cardiothoracic opinion if indicated

Question 47

Phaeochromocytoma

Answer 47

Catecholamine secreting tumour of the adrenal medulla. May be extra-adrenal, malignant, bilateral, familial and found in normotensive patients.
Half are diagnosed incidentally on abdominal imaging.

Causes
* MEN2A/MEN2B
* Neurofibromatosis
* Von Hippel Lindau
* Majority sporadic

Features
* triad - headache, palpitations and sweating
* paroxysmal hypertension
* non-specific symptoms including anxiety, lethargy, weight loss, hyperglycaemia, tremor

Investigations
* urinary catecholamines, metanephrines, VMA
* plasma catecholamines (risk of transient stress response to venesection)
* false positives - recent exercise, dietary factors, renal impairment, common medications e.g. NRI, MAOI, sympathomimetics, paracetamol)
* radiological - abdominal CT/MRI or MIBG

Pre-operative preparation
* Arterial pressure control - pre-operative alpha blockade (phenoxybenzamine/doxazosin) +/- calcium channel blocker - started ~2 weeks pre-op
— non selective irreversible alpha-adrenergic antagonist - permanently alkylates alpha receptors, preventing clinical response to catecholamine release (phenoxybenzamine 10mg)
— selective alpha 1 receptor antagonists - intraoperative control of BP less good (doxazosin)
* Reversal of chronic circulating volume depletion - high sodium diet and fluid intake
* HR and arrhythmia control - selective b1 antagonists (after complete alpha-blockade achieved due to risk of hypertensive crisis otherwise)
* Assessment and optimisation of myocardial function - perform ECG and echo - diastolic dysfunction common and cardiomyopathies
* Reversal of glucose and electrolyte distrubances (e.g. renal impairment, hypercalacemia, hyperglycaemia)

Adequate optimisation (no consensus)
* ECG free of ST/T wave changes
* Arterial pressure consistently <130/88

Intraoperative management
* Premed - anxiolytic, DVT prophylaxis, stop beta blockers evening before surgery
* Invasive monitoring prior to induction - full monitoring including temp, UO
* Consider CVC after induction for vasoactive infusions
* No evidence for CO monitoring
* Laparoscopic - transabdominal/retroperitoneal, lateral position? table break?
* Laparotomy - epidural
* Avoid drug-induced catecholamine release (des, ketamine, drugs causing histamine release, sux, dopamine antagonists, drugs inhibiting catecholamine reuptake e.g. ephedrine)
* Avoid catecholamine release induced by anaesthetic or surgical manouevres (avoid pressor response to intubation)
– magnesium
– remifentanil
* Minimise haemodynamic responses to surgical handling
– phentolamine? sodium nitroprusside?
– GTN/esmolol
* Treat episodes of hypotension, particularly after tumour devascularisation (exacerbated by down regulation of alpha receptors and persistence of preoperative alpha receptor blockade)
– noradrenaline + vasopressin
– fluid resuscitation

Postoperative management
* HDU
* Usually extubatable
* Monitor for hypoglycaemia
* Treat hypertension/hypotension
* Analgesia
* Steroid replacement if bilateral adrenalectomy

Question 48

Porphyria

Answer 48

• Incidence 1:10-20000
• F>M
• Most types autosomal dominant
• Group of disorders related to deficient heme synthesis
• Defective synthesis of porphyrin molecules (found in Hb and CYP450 enzymes)
• Malfunction of certain enzymes in the 8-step synthesis pathway leads to each type
• Commonest type is Acute Intermittent Porphyria - caused by deficiency of porphobilinogen deaminase
• Symptoms
• pain (abdomen, limbs), muscle weakness (proximal, upper limbs), nausea and vomiting, constipation, CNS disturbance (poor concentration and memory, confusion, hallucinations, convulsions), autonomic dysfunction (hypertension, tachycardia), electrolyte disturbance
• Triggers
• smoking, hormonal variations, dieting, starvation, excess alcohol, drugs, stress, infections, pain

Unsafe Drugs
* phenytoin, sulphonamides, statins, carbamazepine, hormonal treatments and contraception, valproate, etomidate, aminophylline, barbiturates, ?pentazocine, ?diclofenac

Management of Acute Porphyric Crisis
* IV fluid with close monitoring of electrolytes
* Correct electrolyte abnormalities
* Analgesia - regional, opioids, ibuprofen
* Enteral nutrition where possible, parenteral if significant GI disturbance - aim for 200kcal of carbohydrate per 24hrs
* IV haem preparations e.g. IV haem arginate if neuropathy present but repeated haem infusions can lead to chronic hepatic inflammation due to iron accunulation
* Beta blockers if hypertension and tachycardia are not resolving
* Treat seizures with benzos or phenothiazines

Anaesthetics in Porphyria
* Ensure effective pre-and post operative analgesia to minimise stress and pain from procedure
* Ensure any resulting infection is treated aggressively (careful consideration of choice of antibiotic)
* Avoid pre and post-opeartive starvation fasting - IV dextrose infusions
* Most agents used in anaesthesia are safe
* Avoid ketamine, etomidate and thiopental

Question 49

Pulmonary Hypertension

Answer 49

Mean PA pressure >/= 25mmHg (on heart catheterisation/PA catheter)
* Group 1 - PAH/idiopathic
* Group 2 - left heart disease
* Group 3 - lung disease/chronic hypoxia
* Group 4 - pulmonary thromboembolism
* Group 5 - miscellaneous e.g. haematological, metabolic, systemic

Pre-operative
* ECG - RV strain, right axis deviation, p-pulmonale, RBBB
* underlying pathology - pre-optimisation of pulmonary hypertension
* echo, BNP, 6MWT, CPET

Intra-operative
* actual technique less important than it’s execution
* invasive monitoring +/- PA catheter/TOE/CO monitor
* obtund response to laryngoscopy
* avoid increase in PVR
* maintain normal HR
* avoid decreased venous return/SVR
* avoid myocardial depression
* clear plan for managing PH crisis/PAH meds

Post-operative
* PACU/HDU/ICU (48-72hrs)
* analgesia

Question 50

Raised ICP

Answer 50

Normal ICP - the pressure exerted by brain tissue and CSF within the cranium. Normal range is 5-15mmHg.
Pressures above 20mmHg usually represent the threshold to treat raised ICP —> focal ischaemia. If ICP >50mmHg = global ischaemia

ICP wave is pulsatile
* cardiac component - correlation with arterial pulsation resulting in 3 peaks P1>P2>P3
— P1 = percussion = arterial pulsation
— P2 = tidal = intracranial compliance
— P3 = dichrotic = aortic vale closure
* respiratory component - correlation with changes in intrathoracic pressure with respiration
* Lundberg waves
— A waves - square wave plateaus up to 50mmHg lasting 5-10 minutes = always pathological, suggestive of herniation
— B waves - variable spikes in ICP at 30-120s intervals = cerebral vasospasm
— C waves - oscillations that occur 4-8x per minute = benign phenomena
* as ICP increases and the brain becomes less compliant, the ICP pressure waveform changes P1<P2>P3</P2>

Early
* headache
* vomiting (without nausea)
* seizures
* focal neurology e.g. ocular palsies (unilateral ptosis, 3rd/6th nerve palsies)
* papilloedema

Late
* hypertension
* bradycardia
* widened pulse pressure
* agitation
* decreased GCS
* motor changes - hemiparesis
* Cheyne Stokes breathing
* apnoea
* ipsilateral progressing to bilateral pupillary dilatation
* decorticate progressing to decerebrate posturing

Measuring ICP
* Indications include TBI, hydrocephalus, stroke, encephalopathy
* EVD (intermittent measurement as also used for drainage of CSF), risk of infection
* “Bolt” - pressure transducer placed in the brain parenchyma, measures local ICP rather than global
* Subdural pressure transducer

Management of ICP>22 for 5 minutes
1. Tier 1 medical management
* deepening of sedation
* maintain CPP 60-70mmHg
* drainage of CSF through an EVD
* neuromuscular paralysis
* optimisation of ventilation to a PaCO2 of 4.5-5.0
* head up position
* CT scan to exclude a new intracranial space occupying lesion
2. Tier 2 management
* hyperventilation to PaCO2 of 4.0-4.5
* osmotherapy
— mannitol 0.25-2g/kg over 30-60 minutes (can be repeated 1-2 times after 4-8hrs)
— hypertonic saline 3% 3-5ml/kg over 10-20 minutes (~250-500ml bolus)
* CT scan to exclude a new intracranial SOL
3. Tier 3 management
* large decompressive craniotomy
* barbiturate coma with continuous EEG monitoring, aiming to achieve 50% burst suppression

Question 51

Rheumatic Fever

Answer 51

• Pathogenesis and immune mechanisms are not fully understood
• Caused by group A beta-haemolytic streptococci
• Affects joints, skin, heart and nervous system
• Thought to be the result of hypersensitivity reaction caused by cross-reacting antibodies, leading to infiltration of heart valves by T cells
• Risk factors - overcrowding, poor hygiene, lack of access to medical services, immunocompromise, comorbid
• Symptoms appear 1-5 weeks after a sore throat, diagnosis based on Jones criteria
  – Polyarthritis - flitting and migratory
  – Carditis - pancarditis, mitral stenosis, congestive cardiac failure
  – Chorea, particularly in females aged 7-12
  – Subcutaneous nodules
  – Erythema marginatum/annulare
  – Fever
  – Raised ESR/CRP
• Management = penicillin, bed rest, NSAIDs

Question 52

Right Ventricular Failure

Answer 52

Caused by RV infarction, OSA, ARDS, PE, mitral disease, congenital heart disease

Pre-operative
* thorough pre-op assessment and risk assessment
* recent echo, heart catheterisation?
* pulmonary function tests, ABG, LFTs
* consider anxiolytics pre-med (but avoid decreased RR)
* plan re: pulmonary vasodilatation (consider pre-op)

Intra-operative
* enhanced monitoring
* avoid hypoventilation, hypoxia, atelectasis, high ventilating pressures, hypercarbia
* general + regional can be used
* care re: depth of anaesthesia + analgesia
* keep warm
* avoid desflurane/nitrous oxide
* maintain sinus rhythm
* avoid increase or decrease in HR
* avoid decreased preload
* avoid increased PVR or decreased SVR
* preserve contractility

Postoperative
* HDU/ICU
* analgesia

Question 53

Serotonin Syndrome

Answer 53

Potentially life threatening drug interaction caused by excessive serotonergic activity in the CNS. It can arise from therapeutic drug use, drug interactions or intentional OD of medications that affect the serotonergic system.

Typically self limiting and resolves with cessation of the drug.

Drugs implicated
* serotonin metabolism - MAOIs, drugs with MAO inhibition activity (e.g. linezolid, methylene blue, linexolid)
* enhanced release of serotonin - MDMA, cocaine, pheylpiperidine opoiods, tramadol, oxycodone
* serotonin reuptake inhibition - SSRIs, SNRIs, TCAs, SARIs, ondanstron, phenylpiperidine opoiods, tramadol
* direct serotonin agonist - triptans, ergot alkaloids

Features
* Hunter’s Criteria for serotonin syndrome
* Altered mental state - confusion
* Neuromuscular irritation - myoclonus, hyperreflexia, tremor
* Autonomic hyperactivity - diaphoresis, shivering, fever
* Patient with current or previous exposure to a triggering agent
* No laboratory or imaging tests specific to SS - metabolic acidosis, abnormal LFTs, increased Cr and leucocytosis. May have raised CK if rhabdo is present.

Differential diagnoses include MH, NMS, anticholinergic syndrome, opioid toxicity.

Management
* Mild - closely monitor in HDU, discontinue serotonergic agents, supportive treatment,
* Management of agitation and anxiety - benzodiazepines
* Management of autonomic instability - IV fluids, direct acting sympathomimetic agents (e.g. phenylephrine, noradrenaline) for hypotension, esmolol/GTN for hypertension and tachycardia
* Topical cooling –> sedation, ventilation, NMBA (non depolarising) –> reduce muscle activity (NB. paracetamol ineffective as hyperthermia mostly mediated by muscle hyperactivity)
* Cyproheptadine - H1 receptor antagonist can provide symptomatic relief
* Consider dexmedetomidine for sedation/anxiolysis

Question 54

SIADH

Syndrome of Inappropriate ADH Secretion

Answer 54

Hyponatraemia due to an increase in concentration of ADH inappropraite to the current osmotic or volume status.

Diagnostic criteria:
1. hypotonic hyponatraemia
2. urine osmolality greater than plasma osmolality (concentrated urine despite hypotonic blood)
3. raised urinary sodium
4. normal renal, hepatic, cardiac, pituitary, adrenal and thyroid function
5. euvolaemia (absence of hypotension, hypovolaemia, oedema)
6. correction by water restriction

Causes
* major surgery - abdominal, thoracic, transsphenoidal (6-7 days)
* ADH prduction by tumours - lung, adenoCa, leukaemia, lymphoma, thymoma
* Drugs - antidepressants, psychotropics, anaesthetic drugs, ADH analogues, chemotherapy, various others
* CNS disorders - SOL, trauma, infection, SAH, porphyria, SLE
* Hormone deficiency - hypothyroid, adrenal insufficiency
* Others - GBS, HIV, hereditary, GCA, idiopathic
* Pulmonary - pneumonia, TB, lung abscess

Management
* fluid restrict
* incremental increase in Na if indicated (max 10-12 per 24hrs to avoid central pontine myelinolysis aka osmotic demyelination syndrome)
* medications to decrease ADH secretion - demeclocycline, lovaptan/conivaptan

Question 55

Diseases of Red Blood Cells

Answer 55

Red cell distruction
* haemoglobinopathies e.g. SCD
* enzymopathy e.g. G6PD
* autoimmune
* membrane disorder e.g. hereditary spherocytosis, elliptocytosis, ovalocytosis, stomatocytosis

Disorders in red cell production
* thalassaemias
* myelodysplasia
* aplastic anaemia

Sickle Cell Disease
* genetic disorder of haemoglobin
* substitution mutation on chromosome 11
* structural abnormality of the beta-globin chain resulting in the production of abnormal haemoglobin which is biochemically unstable
* causes sickling of red cells in hypoxic conditions (SpO2 85% in homozygous, <40% in heterozygous) as it precipitates out of solution
* leads to clumping of sickled cells, which activate coagulation pathways and can lead to infarction –> vaso-occlusive crises
* hyposplenism, reduced cell-mediated immunity, increased risk of infection
* risk of acute anaemia from haemolytic crises or acute splenic sequestration
* aplastic crisis causes acute worsening of baseline anaemia, normally triggered by parvovirus B19
* acute chest syndrome (may be precipitated perioperatively) may result in life-threatening hypoxia and respiratory failure
– new lobar infiltration on CXR
– fever >38
– respiratory distress
– chest pain
– good pulmonary toilet, broad spectrum antibiotics, avoidance of hypoxia, normothermia, analgesia, hydration, chest physio, bronchodilators, intermittent incentive spirometry
* multi-system condition
– head/neck/airway - frontal bossing, prominent maxilla, hypertrophy of lymphoid tissue
– respiratory - acute chest syndrome, pulmonary hypertension (recurrent pulmonary infarction), rightward shift of ODC due to increased 2,3-DPG, OSA
– neurological - acute brain syndrome, recurrent infarcts
– cardiovascular - cardiomegaly due to anaemia, CCF
– haematology - anaemia
– musculoskeletal - vaso-occlusive crises to limbs, bone marrow dysplasia
– GI tract - asplenism, gallstones, jaundice
– GU - priapism, renal failure
* diagnosis - sickledex detects levels of HbS >10%, electrophoresis

Anaesthesia for SCD
* aim Hb 100
* avoid hypoxia
* ensure adequate hydration
* maintain normothermia
* optimal analgesia
* consider regional anaesthetic techniques where likely to be effective
* avoid venostasis - caution with tourniquets

Thalassaemia
* reduced or absent production of the alpha or beta-globin chain
* imbalance of globin chain synthesis leads to decreased Hb production and precipitation of excess globin which is toxic
* autosomal recessive
* in major form - severe transfusion dependent anaemia, regular blood transfusions with chelation to remove excess iron
* features - anaemia, extramedullary haematopoiesis, complications of long-term transfusion, increased risk of infections, cholelithiasis
* diagnosis - blood smear (microcytic/hypochromic), Hb electrophoresis, iron stores
* treatment - stem cell transplant, transfusion, iron chelation
* thorough preoperative cardiac evaluation prior to anaesthesia

Hereditary Spherocytosis
* congenital haemolytic anaemia
* autosomal gominant inheritance
* involes genes coding for proteins involved in the attachment of the cytoskeleton to the red cell membrane
* leads to loss of surface area –> spherical, osmotically fragile cells that get trapped in the spleen
* diagnosed by blood film, osmotic fragility test, electrophoresis
* features - haemolytic anaemia, jaundice, splenomegaly, cholelithiasis
* treatment - folate therapy, red cell transfusions, splenectomy

G6PD deficiency
* metabolic disorder of RBCs, provides some protection from malaria
* X-linked disorder, primarily affects men
* predisposes to premature red blood cell breakdown due to defective G6PD enzyme, accumulation of reactive oxygen species that lead to damage
* anaemia may be precipitated by certain drugs or infections
* leads to acute intravascular haemolysis
* triggers - infections, fava beans, surgeru, oxidant drugs e.g. sulfa, dapsone, antimalarial drugs, chloramphenicol
* usually asymptomatic, may have history of neonatal jaundice requiring exchange transfusion, haemolysis, gallstones and splenomegaly
* treatment - avoid triggers, folic acid supplementation, blood transfusion rarely necessary

Question 56

Suxamethonium Apnea

Answer 56

• Autosomal recessive genetic disorder
• Butrylcholinesterase (BChE gene on chromosome 3)
• Reduced or absent abnormal plasma cholinesterase prolongs duration of action of suxamethonium (and mivacurium) for hours to days
• Due to single amino acid substitution
• 1 in 25 have a mildly abnormal enzyme, 1 in 40,000 are homozygous for silent form
• 4 alleles
  — Usual (normal) = full function
  — Silent (absent) = 0.001% of the population are homozygous = absent enzyme function with significantly prolonged action
  — Dibucaine/fluoride resistant (fluoride)
  — Atypical
• Phenotypes
  — Eu - normal (100% activity)
  — Ea - atypical (30% activity)
  — Ef - fluoride resistant (40% activity)
  — Es - silent (0% activity)
  — UA, US, UF - low risk for prolonged paralysis
  — AF, FS - high risk for prolonged paralysis
  — S, AS, A - very high risk for prolonged paralysis

Decreased plasma cholinesterase activity may occur in other conditions:
* pregnancy
* liver disease
* renal disease
* cardiac failure
* thyrotoxicosis
* malnutrition
* cancer
* following plasmapheresis
* certain drugs: neostigmine, organophosphorous compounds, metoclopramide, ketamine, OCP, lithium, lignocaine (and ester LAs)

Management is supportive - continue anaesthesia and ventilatory support until the block wears off (sux has a slow alternative metabolic pathway via non specific plasma esterases), monitor TOF, keep patient warm

Question 57

Tetanus

Answer 57

Potentially lethal condition characterised by muscular rigidity and spasms that may lead to life-threatening respiratory failure and autonomic dysregulation in severe cases.

Types
* cephalic
* local
* generalised
* neonatal

Cause
* toxin released from clostridium tetani (anaerobic spore forming gram positive bacillus)
* tetanolysis and tetanospasmin
* tetanospasmin taken up by motor nerves or haematogensou spread to CNS
* disrupts synaptic transmission by preventing release of neurotransmitters (zinc endopeptidase)
* preferentially prevents discharge from GABA inhibitory interneurons in spinal cord and brainstem –> unrestricted motor nerve activity and autonomic instability

Clinical Features
* triad of rigidity, muscle spasms and autonomic dysfunction
* history of contaminated wound, 3-14 days incubation
* trismus, dysphagia, increased tone in trunk muscles
* spontaneous spasms or provoked by physical or emotional stimuli, laryngospasm
* autonomic disturbance - tachycardia and hypertension may alternate with bradycardia and hypotension, dysrhythmia, cardiac arrest
* salivation, bronchial secretions
* gastric stasis, ileus, diarrhoea
* respiratory compromise - chest wall rigidity, laryngospasm, aspiration, retained secretions

Investigations
* urinary strychnine to exclude this as a cause
* CK, U+Es, Ca for rhabdomyolysis and to rule out low Ca
* ABG

Management
* A - intubate as requires large doses of sedatives to control muscle spasm and to overcome laryngospasm
* B - at risk of aspiration and have copious bronchial secretions requiring frequent suctioning, often ventilated for 2-3 weeks until spasms subside
* C - autonomic dysfunction necessitate monitoring in critical care environment, fluctuant haemodynamics so use short acting agents; fluid loading
* D - benzodiazepines in large doses
* Non depolarising NMBA
* Specific therapy - metronidazole, anti-tetanus immunoglobulin, benzodiazepines, magnesium, consider intrathecal baclofen
* Treat underlying cause and complications - clean and debride wounds
* Immunise 10yrly
* Supportive care and monitoring - calm, nutrition, often require trache, prevention of pressure sores and stress ulcers

Question 58

Thoracic Outlet Syndrome

Answer 58

Group of conditions where there is compression of the nerves, arteries or veins in the superior thoracic aperture. Collection of symptoms in the shoulder and upper extremity area that results in pain, numbness and tingling.

Causes
* congenital abnormalities including cervical rib, prolonged transverse process, muscular abnormalities
* trauma or respetitive strain
* rarer acquired causes - tumours, osteomyelitis

Types
* vascular - arterial and/or venous - swelling of arm, distension or veins, diffuse pain, colour changes, claudication in arm
* neurogenic - true or disputed - cold hands, swelling or blanching with compression of autonomic nerves, painless wasting of hand muscles with weakness, parasthesia of upper limb, painful neck and headache

Diagnosis
* careful neurological and musculokeletal examination
* Adson’s manoeuvres - head extended and bent to one side, deep breath help, followed by rotation to stretch or tether the brachial plexus and/or artery between the muscles
* hyperabduction of arm to stress the outlet
* elevated arm stress test
* CXR, MRI, CT
* Doppler, angiography, venography

Management
* conservative - OT, physio, NSAIDs, injection of trigger points
* surgical intervention may help where there is an obvious physical lesion e.g. microvascular decompression

Question 59

Tuberculosis

Answer 59

• Endemic in most tropical countires
• Mycobacterium tuberculosis usually spread by inhalation of infected droplets, most person to person transmission occurring following prolonged exposure
• Only 5-10% of those who are infected go on to develop active TB, often a period of latency

Features
* cough
* haemoptysis
* constitutional symptoms - fever, weight loss, night sweats, failur to thrive
* extra-pulmonary TB - bones, abdomen, meninges, pericardium, lymph nodes, pleura

Investigations
* CXR - cavitating apical lesion
* Acid fast bacilli on a Ziehl-Neelsen stained sputum smear
* Nucleic acid amplification tests
* Tuberculin skin tests - risk of false positives and negatives

Treatment
* 6 months of combination therapy, ensuring compliance
* Rifampicin, isoniazid, ethambutol and pyrazinamide

Considerations for anaesthesia
* Delay elective surgery until no longer infectious
* Risk of bronchial constriction, pleural infusions, bronchiectasis or fibrosis
* Risk of catastrophic haemoptysis if cavitating lesion erodes into a blood vessel
* PPE! - gloves, eye protection, FFP3 mask
* Change breathing circuits after anaesthetising a patient with active TB
* Sterilize any equipment used
* Consider a tuberculin test +/- chemoprophylaxis if significant exposure
* Rifampicin - inducer of CYP3A4 (metabolises alfentanil, fentanyl, midazolam and lidocaine) - reduces opioid levels in the bloods, affects oral > IV drugs, lowers plasma concentration of diclofenac but not ibuprofen
– thrombocytopenia
* Isoniazid - CYP3A4 inhibitor and CYP2E1 inducer (metabolism of halothane)
– thrombocytopenia
– anaemia or agranulocytosis
– DIC due to hypersensitivity reactions
– peripheral neuropathy
* Risk of drug induced hepatitis with isoniazid, rifampicin or pyrazinamide
* Streptomycin may potentiate effects of non depolarising NMBAs, howere enzyme induction may increase metabolism of aminosteroid NMBAs

Question 60

TURP Syndrome

Also occurs in other procedures requiring large volumes of irrigation

Answer 60

Syndrome causing
* fluid overload
* iso-osmolar hyponatraemia
* CNS inhibitory effects of glycine neurotransmission at GABA receptors
* CNS potentiation of glycine neurotransmission at NMDA receptors
* Cardiodepression from glycine

Risk factors
Absorption of glycine depends on pressure of infusion, venous pressure, exposed vascular bed, duration of irrigation
* surgical time >1hr
* height of bag >70cm
* prostate resected >60g
* large blood loss
* perforation of bladder (rapid absorption from peritoneal cavity)
* large amount of fluid used
* patient factors - poorly controlled CHF, elderly, AKI, coronary disease

Features
* 15 minutes up to 24hrs post-operatively
* Early features - restlessness, headache, tachypnoea, burning sensation in face and hands
* RS - respiratory distress, hypoxia, pulmonary oedema
* GI - N+V
* CNS - confusion, convulsions, coma, visual disturbance
* Renal - AKI
* CVS - reflex bradycardia, dysrhythmias, cardiovascular collapse

Investigations
* hyponatraemia (dilutional)
* hypocalcaemia
* iso-osmolar/mildly hypo-osmolar
* increased osmolar gap
* raised glycine, serine, ammonia
* metabolic acidosis
* haemodilution and haemodialysis

Management
* ABC - address life threats, invasive monitoring
* Fluid overload - frusemide 40mg IV
* Seizures - benzodiazepines, consider magnesium
* Hyponatraemia - hypertonic saline (aim no more than 10-20mmol/24hrs)
* Treat AKI, oedema, dysrhythmias as required
* Treat hypocalcaemia
* Treat underlying cause - stop surgery asap, coagulate bleeding points, stop IV fluid, monitor Hb
* Admit to HDU/ITU

Question 61

VAP

Answer 61

• Most common healthcare-associated infection in adult critical care units
• Combination of clinical, radiological and microbiological criteria
  – radiological evidence of infiltrates on CVR
  – fever
  – leukocytosis
  – purulent secretions
• Wide range of clinical conditions that mimic VAP in ventilated patients
• Clinical Pulmonary Infection Score (CPIS) - prone to considerable inter-observer variability
• Pathogenesis
  – biofilm formation within the tracheal tube and microaspiration of secretions
  – pathogen rich biofilm is pushed into the distal airways by ventilator cycling
  – early onset VAP - strep pneumonia, Hib, MSSA, E-coli, klebsiella, enterobacter, proteus, serratia
  – late onset VAP - MRSA, acinetobacter, pseudomonas, ESBL

Risk Factors
* patient factors
– advanced age
– low serum albumin
– underlying respiratory conditions
– acute respiratory conditions
– trauma and burns
– increased severity of illness
– impaired consciousness/excessive sedation
– large volume gastric aspirates
* interventional factors
– supine body position
– mechanical ventilation for >7 days
– antacids, PPIs and H2 blockers
– frequent circuit changes
– use of NMBAs
– NG tube

Implications
* increased mortality
* increased ICU stay
* increased patient ventilator days

VAP Prevention
* care bundles - group of evidence based interventions which when applied together significantly improve patient outcome
* cuff pressure - 20-30cmH2O - monitor frequently and adjust
* subglottic drainage of secretion
* tapered cuff shape
* ?silver coated TT
* hand hygiene and use of sterile equipment
* minimise ventilator tube changes
* post-pyloric feeding?
* minimise duration of ventilation
* oral decontamination - chlorhexidine mouthwash

Other types of pneumonias - HAP, healthcare associated pneumonia, CAP, atypical pneumonia, aspiration pneumonia, opportunistic pneumonia

Question 62

Ventilator Associated Lung Injury

Answer 62

• Volutrauma
• Barotrauma
• Atelectatrauma
• Biotrauma
  — increased pro inflammatory cytokines and decreased anti inflammatory cytokines
  — pulmonary inflammatory response
  — lots of alveolar compartmentalisation
  — systemic inflammation —> MOF