Cardiothoracics Flashcards
Types of cardiomyopathy and how it affects CO, SV, contractility
- Dilated
- low CO, SV and contractility - Hypertrophic
- low CO + SV, high contractility - Restricted
- normal/low CO, low SV, normal contractility
Causes of dilated cardiomyopathy
- Idiopathic
- Ischaemic
- Valvular
- Post-viral
- Peri/post-partum
- Post-chemotherapy
- Sickle cell disease
- Alcohol
- Hypothyroid
- Muscular dystrophy
Pre-assessment DCM
- Baseline ECG
- U&Es if on ACEI
- FBC
- ECHO if not up to date
- Consider CXR
- Sometimes dobutamine stress test
Indications for pre-assessment ECHO
- High risk surgery e.g. open AAA, peripheral vascular surgery
- Ventricular function concerns
- dyspnoea suspected cardiac
- IHD with poor functional capacity
- Known cardiac failure, no ECHO in last 2 years
- Known cardiac failure, worsening symptoms - Valvular concerns
- Undiagnosed systolic murmur
- Significant valvular disease, no ECHO in last 2 years
- Moderate/severe AS, no ECHO in last 1 year
- Valve disease or replacement with worsening symptoms
- Bioprosthetic valve replacement, no ECHO in 5 years
30 day cardiac event rates for non-cardiac surgery
Minor <1%
- breast, dental, endocrine, eye, minor gynae, reconstructive, minor ortho e.g. knee, minor urology
Intermediate 1-5%
- abdominal incl. major gynae, carotid, peripheral arterial angioplasty, endovascular AAA, head and neck, major ortho e.g. hip/spine, major urology
High >5%
- open AAA, peripheral vascular surgery
Medical management of DCM
RAAS inibition (ACEI or ARB if not tolerated)
- Reduced dyspnoea, improved ET
- Reduced hospital stay
- Slow disease progression
- Reduced mortality
** Beta blockers**
- Reduced mortality
Aldosterone inhibitors (spironolactone, eplenerone)
- Reduced mortality
Atrial naturetic peptides
- IV administration only
- Diuresis, naturesis, vasodilation
Anticoagulants if EF< 30%
SGLT-2 inhibitors
- Reduced mortality
Angiotensin nepriolysin inhibitors e.g. sacubitril-valsartan
- Inhibits breakdown of ANP, ACEI prevents side effect of vasoconstriction
Risks of DCM perioperatively
- Arrythmia
- Embolic events
- Congestive heart failure
- Death
Monitoring used intraoperatively for patient with DCM
AAGBI:
- NIBP, temp, SpO2, iCO2, etCO2, expired volatiles, 3-lead ECG, PNS
In addition:
- 5 lead ECG, IABP, CO monitoring
- BIS to titrate anaesthetic agents
- Consider TOE/oesophageal doppler
- Central venous pressures (preload)
How to manage cardiovascular physiology in DCM
- Avoid tachycardia (LV coronary arteries perfused during diastole)
- Maintain sinus rhythm and treat arrhythmias (reliance of atrial contraction for filling)
- Maintain blood pressure (diastolic pressure perfuses LV coronary arteries)
- Avoid rise in SVR e.g. with ketamine (afterload=LV chamber pressure + SVR, already higher in DCM), but also avoid precipitous drop (diastolic pressures perfuse LV coronary arteries)
- Maintain normovolaemia/preload
- Correct electrolytes
- Avoid negative inotropy (provide ionotropic support if required -> PDEI, levosimendan, dobutamine N.B propofol and volatiles cause myocardial suppression)
Post operative management of surgery in pt with DCM
HDU/ITU setting for haemodynamic monitoring and management
Adequate analgesia to avoid increased SVR
Predictors of poor outcome in DCM
- LVEF <20%
- Elevated LVEDP
- Left ventricle hypokinesia
- Non-sustained VT
Pros and Cons of neuraxial block for DCM physiology
Pros:
- reduces SVR
- effective pain control avoids tachycardia
Cons:
- can cause drop in BP so reduced coronary artery perfusion
- treatment of hypotension with fluids risks pulmonary oedema
Non pharmacological treatment of DCM
- Partial left ventriculectomy
- Cardiac resynchronization pacing therapy
- Implantable cardiac defibrillator
- Left ventricular assist device (bridging to transplant)
- Heart transplant
Anaesthetic options in DCM
And haemodynamic goals
- Local - minimal haemodynamic changes, but stress can cause tachycardia and increased SVR
- Neuraxial - reduces afterload so improves cardiac output but risks hypotension and poor LV coronary artery perfusion
- GA - least stress response, asleep patient so easier to provide more invasive monitoring, airway control in event of critical incident but many agents cause negative inotropy. Give slow IV induction with increased opioid component and balanced maintenance (pEEG) if GA.
Aims:
Avoid tachycardia/rise in SVR + afterload
Avoid myocardial depression/negative inotropy
Maintain adequate preload
Prevent increases in afterload
Maintain sinus rhythm
Pathophysiology of HCM
Extracellular fibrosis-> hypertrophy, ventricular stiffness, shape distortion and diastolic impairment with preserved systolic function.
End stage: biventricular systolic dysfunction
Presentation of HCM
- Autosomal dominant so through genetic testing
- Angina
- Heart failure (dyspnoea, syncope, arrhythmia commonly AF)
- CVA
- Sudden death
Risk factors for sudden cardiac death in HCM
- Previous cardiac arrest
- FH sudden cardiac death
- previous VT
- Syncope
- Abnormal blood pressure response to exercise
- LV wall thickness >30mm
Medical management HCM
- Beta blockade (reduces heart rate, prolongs diastole, improves ventriclar filling) - > disopyramide as alternative
- Amiodarone to treat SVT/VT
Non-medical management HCM
- ICD
- Alcohol septal ablation
- Surgical myomectomy
Perioperative aims in HCM
- Adequate preload + afterload
- Maintain SVR
- Avoid sympathetic activation and tachycardia
- Reduce contractility
- Maintain sinus rhythm
- If hypotension with LVOTO, give fluid bolus and alpha-adrenergic agonist e.g. phenylephrine
Spinal causes decreased preload and afterload which can be dangerous - GA is preferred
Indications for endoscopic thoracic sympathectomy
Hyperhydrosis - palms, axilla, head and face
Chronic pain/upper limb regional pain syndrome
Facial blushing
Describe the sympathetic nerve supply to the upper limb
Preganglionic fibres from T1-T5 synapse in the superior, middle and inferior cervical ganglia
- post ganglionic fibres travel to effector cells
Implications of managing a patient for endoscopic thoracic sympathectomy under general anaesthesia
- Rare conversion to open thoracotomy (prep as if thoracotomy)
- Risk of major haemorrhage (ensure large bore IV access and G+S)
- Periods of hypoxia are common due to shunt, atelectasis and fairlure to fully inflate first lung before proceeding with surgery on second side (preoperative assessment of ability to tolerate this e.g. cardiovascular health)
- Hypotension due to capnothorax can happen (consider invasive blood pressure monitoring)
Complications due to patient positioning for endoscopic thoracic sympathectomy
Supine, reverse trendelenburg, arms abducted: brachial plexus injury
Prone: eye damage, dislodged airway, facial damage
Lateral: damage to pressure points e.g. peroneal nerve
Causes of restrictive cardiomyopathy
- Idiopathic
- Amyloidosis
- Sarcoidosis
- Haemochromatosis
- IHD
- HTN
- Valve disease
Pathophysiology restrictive cardiomyopathy
Impaired ventricular diastolic function due to fibrotic/infiltrative changes to myocardium and subendocardium
Symptoms restrictive cardiomyopathy
- Dyspnoea
- Fatigue
- Orthopnoea
- Palpitations
- Chest pain
Signs restrictive cardiomyopathy
- 3rd heart sound
- Raised JVP
- Ascites
- Oedema
- Systolic murmur
Medical treatment restrictive cardiomyopathy
- Beta blockers, CCBs
- Diuretics
- Maintain sinus rhythm (amiodarone, digoxin, beta blockers)
PPM/ICD in advanced conducting system dysfunction
Perioperative aims with restrictive cardiomyopathy
- Maintain adequate preload
- Maintain SVR
- Maintain sinus rhythm
- Minimise myocardial suppression (Can use ketamine)
Arrhythmogenic right ventricle cardiomyopathy pathogenesis, presentation, management
Pathogenesis: adipose and fibrous tissue replaces myocradial cells, re-entry circuits can form, RV becomes thin and dilated
Presentation: arrythmia, syncope, cardiac arrest, sudden death
Management: sotalol/verapamil/amiodarone for arrhthmia, Holter monitoring, catheter ablation as palliative, early ICD can be life saving
Options for airway management for endoscopic thoracic sympathectomy
- One lung ventilation via double lumen tube
- One lung ventilation via endotracheal tube with bronchial blocker
- Endotracheal tube with intrathoracic CO2 insufflation
- LMA with intrathoracic CO2 insufflation
Intraoperative complications during endoscopic thoracic sympathectomy
- Malposition of DLT or bronchial blocker = hypoxia
- One lung ventilation shunt = hypoxia (can be worsened by CPAP or oxygen insufflation to deflated lung reduces hypoxic pulmonary vasoconstriction, PEEP to inflated lung increases resistance to blood flow)
- Atelectasis of re-inflated lung may cause hypoxia in bilateral surgery
- Hypotension due to capnothorax
- Cardiac arrythmia due to intrathoracic diathermy
- Severe sleeding due to blood vessel damage during port insertion
Post-operative complications following endoscopic thoracic sympathectomy
- Ongoing hypoxia due to atelectasis and residual pneumothorax
- Risk of ALI if protective one-lung ventilation not used
- Chest pain
- Compensatory hyperhidrosis
Which vessels are commonly harvested for CABG
Saphenous vein
Internal mammary artery
Radial artery
List advantages of “off-pump” CABG vs “on bypass” CABG
- Reduced platelet dysfunction
- Reduced consumption of clotting factors
- Reduced inappropriate fibrinolysis
- Reduced risk of blood transfusion (because reduction in above coagulation defects)
- Reduced renal dysfunction
- Reduced risk fluid overload/depletion
- Reduced risk electrolyte distrubance
- Reduced risk SIRS
- Reduced risk air emboli
- Reduced risk direct aorta damage
- Reduced risk neurological dysfunction
- Reduced hypothermia
- Earlier extubation
- No ICU stay
- Reduced morbidity/mortality
Causes of haemodynamic instability in “off-pump” CABG
- Ischaemia due to vessel anastomosis
- Mechanical displacement of heart
- Impaired cardiac filling due to immobilisation device
- Arrythmias
- Bleeding
List strategies which can help to minimise haemodynamic instability during “off-pump” CABG
- Minimise heart manipulation
- MInimise periods of ischaemia
- Keep heart rate normal-low
- Monitor and treat electrolyte disturbances
- Ensure patient is adequately filled
- Good communication between anaesthetist and surgeon
Methods to minimise hypothermia during “off-pump” CABG
- Ensure patient temperature is normal before starting
- Minimise periods of leaving patient unconvered
- Warmed intravenous fluids
- Forced air warming blanket
- Under body resistive heating mat
- Raise ambient theatre temperature to a minimum of 21 degrees celcius
- Foil hat
List indications for one lung ventilation
Absolute:
* Isolation of diseased lung to prevent contamination of healthy lung e.g. haemorrhage, empyema
* Control distrubution of ventilation e.g. bronchopleural fistula, major bulla
* VATS
Relative:
* Thoracic surgery
* Thoracic aortic aneurysm
* Oesophagectomy
* Mediastinal mass surgery
* Minimally invasive cardiac surgery
Give specific indications for placement of a right sided double lumen tube
- Surgery that involves the left main bronchus e.g. left pneumonectomy
- Distortion of the left main bronchus anatomy e.g. tumour compressing left main bronchus
List disadvantages of using a double lumen tube for one lung ventilation
- Larger and more rigid tube so increased risk of airway and oral trauma
- More difficult to insert in patients with difficult airway
- May need to exchange for single lumen at end of case if post-operative ventilation required
- Tube can become dislodged and so fail to isolate one lung
How can the risks associated with lung resection be quantified preoperatively?
- Lung function tests e.g. predicted post-operative FEV1 and DLCO based on anatomic calculation, V/Q scans or CT evaluation - (FEV>1.5 or post-op FEV1 and DLCO >40%)
- Higher risk patients may warrant functional assessment e.g. CPET (peak VO2 most useful)
- Mortality risk prediction scores e.g. RESECT-90, thoracoscore
- Cardiac risk prediction e.g. Thoracic Revised Cardiac Risk Index
- Assessment of pre-existing pulmonary hypertension with ECHO
List the steps that may improve hypoxaemia resulting from one lung ventilation
General:
* Call for help
* Increase FiO2
* Alert theatre team
* A-E assessment
Specific:
Quick checks
* Reconfirm position of DLT using fibroptic scope, assess for obstruction in tube e.g. mucus plug
* Ensure haemodynamics and cardiac output optimised, ensure no major haemorrhage, correct Hb
Optimise ventilated lung:
* Recruitment manouevre to ventilated lung
* Increase PEEP to ventilated lung (recuit alveoli, but may impair blood flow causing shunt)
* If pneumonectomy, clamp pulmonary artery to non-ventilated lung
* Consider TIVA (volatiles impair hypoxic vasoconstriction to non-ventilated lung)
Optimise non ventilated lung
* Apply CPAP 1-5cmH2O to non ventilated lung
* Intermittent reinflation of non-ventilated lung
* Severe desaturation: resume bilateral ventilation
Options to maintain anaesthesia for rigid bronchoscopy
Volatile: connect anaesthetic circuit to side port of bronchoscope (intermittent delivery, unreliable but bronchodilation and familiarity)
TIVA: more reliable, more familar now, requires pEEG and is more expensive
Options to manage gas exchange during rigid bronchoscopy
High-flow apnoeic oxygen with leak to avoid baro/volutrauma
High-frequency automated jet ventilation e.g. Monsoon
Manual low-frequency jet ventilation e.g. Sander’s
Controlled ventilation via anaesthetic circuit attached to 22mm side port
Pros and cons of HFJV
Pros:
* Less haemodynamic compromise than conventional PEEP
* Minimal movement of vocal cords/surgical field
* Improved surgical access
* Versatile
* Less ADH production and fluid retention than PPV
Cons:
* Risk of barotrauma
* Air is cool and dry
* etCO2 monitoring is unreliable
* Increased dead-space
* Volatiles are impractical (and contaminate theatre environment)
List laser specific patient safety considerations
- Maintain FiO2 <40%
- Do not use nitrous oxide
- Saline-soaked gauze over mouth, teeth and in airway
- Ensure goggles for patient (and theatre staff)
- Is tube, use laser tube
- Equipment used should be laser compatible
List laser specific safety considerations for theatre (not patient)
- Goggles for staff
- Signs on doors
- Theatre doors locked
- Blinds down
- Laser trained staff members to operate laser
- Equipment maintenance
List anaesthetic complications of rigid bronchoscopy
- Barotrauma
- Awareness
- Inadequate gas exchange
- Laryngospasm, bronchospasm
- Impaired venous retrun (from high intrathoracic pressures)
- Dysrhthmia from jet ventilation
- Airway contamination
Aside from ACT, list laboratory/POC tests that may be used to determine the effectiveness of heparin anticoagulation in CPB patients, with pros and cons for each
Haemodynamic goals for valve lesions
Explain the diagram
- Unassisted aortic end diastolic pressure
- Systolic pressure, unaugmented
- Diastolic pressure augmented by balloon pump
- Reduced aortic end diastolic pressure
Give the haemodynamic goals for the cardiomyopathies, AS and MR
DCM - avoid TACHYCARDIA not bradycardia (coronary perfusion during diastole)
