ACC: Anaesthetics

Question 1

What are the key functions of general anaesthetic

Answer 1

1. Amnesia - loss of response and memory to noxious stimuli (i.e. unconscious)
2. Akinesia - loss of muscle contraction (i.e immobilisation)
3. Analgesia

Question 2

Name the two forms of amnesia?

Answer 2

1. Induction agents - induce loss of consciousness by one-arm brain circulation time (IV) effective from 10-20 seconds, lasts 4-10 mins
2. Inhalation/vapours - maintenance of amnesia

Question 3

Name the 4 key induction agents, which is most commonly used?

Answer 3

1. Profolol (95%)
2. Thiopentone
3. Etomidate
4. Ketamine

Question 4

Tell me the type of drug, appearance, dose, beneficial effects, unwanted effects and cautions of propofol?

Answer 4

1. White emulsion (milk like) - lipid based
2. 1-5-2.5mg/kg - must inject at 2-4mg/sec (rapid injection causes CV suppression)
3. lowest incidence of PONV; excellent for airway reflex suppression
4. Increases HR + BP; unwanted movements; pain on injection; resp suppression when combined with narcotics
5. Must not use with extremes of age or egg/soy allergy

Question 5

Tell me the type of drug, dose, beneficial effects and unwanted effects of Thiopentone?

Answer 5

1. Barbiturate
2. 4 - 5mg/kg
3. Rapid sequence induction (quick onset/offest) for full stomachs and high risk vomiting e.g. emergency procedures; Antiepileptic properties which also protect brain
4. decreased BP but increased HR; CI for acute porphyria; thrombosis and gangrene (due to intra-arterial injection) ; bronchoconstriction and rash (due to histamine release); Extravasation (treat with hyaluronidase)

Question 6

Tell me the type of drug, dose, beneficial effects and unwanted effects of Etopomide?

Answer 6

1. Steroid based
2. 0.3mg/kg
3. Used for patients with significant cardiovascular co-morbidities; lowest incidence of hypersensitivity reactions; complete haemodynamic stability
4. Adrenal suppression - inability to maintain BP; pain on injection; highest incidence of PONV; thrombophlebitis at local injection site

Question 7

Tell me the dose, beneficial effects, unwanted effects and CI of Ketamine?

Answer 7

1. 1-1.5mg/kg
2. Slow onset
3. Useful for Burns dressing changes due to dissociative amnesia causing anterograde amnesia and profound analgesia; Increases HR + BP, bronchodilataion (due to sympathetic stem)
4. Emergence phenomenon (vivid dreams, hallucinations, crying), N+V
5. CI: HTN, Stroke, raised ICP, psychiatric patients

Question 8

Which induction agent would you use for burns? And how long does it take to work?

Answer 8

Ketamine - slow acting 90 seconds

Question 9

Which induction agents can you use for a patient with acute porphyria

Answer 9

Propofol
Etopomide
Ketamine

Question 10

Which induction agent is best used for a patient with significant coronary artery disease and IHD?

Answer 10

Etopomide

Question 11

Which induction agent has side effects of bronchospasm, rash, thrombi and gangrene? How does this drug affect BP and HR?

Answer 11

Thiopentone

• releases histamines to cause bronchospasm and rash
• intra-arterial injection causes thrombi and gangrene
• increases HR, decreases BP

Question 12

Which induction agent increase HR and BP?

Answer 12

Ketamine

Question 13

Which drug causes dissociative amnesia and emergence phenomenon?

Answer 13

Ketamine

Question 14

What is the dose of all 4 induction agents?

Answer 14

Profolol (lipid) 1.5-2.5mg
Thiopentone (barbiturate) 4-5mg (fast acting RSI)
Etopomide (steroid) 0.3mg/kg
Ketamine 1-1.5mg/kg

Question 15

What are the uses, CV effects, unwanted effects and MAC concentrations of the inhaled/vapourised agents?

Answer 15

1. Sevflurane (2% MAC) - sweet smelling, good for difficult cannulation, decreases BP (vasodilatation)
2. Isoflurane (1.15%) - least organ effect on organ blood flow. irritant - causes cough i.e. good for organ transplant. Decreases BP but increases HR
3. Desflurane (6%) - lipid based rapid onset/offset (i.e. rapid abrosption to brain, excretion of body). Decreases BP but increases HR
4. Enflurane (1.6%)

Question 16

What are the most commonly used short acting analgesia and when are they used?

Answer 16

High potency, fast acting opioids - Fentanyl (1st line) –> Remifentanil (rapid onset/offset good for long ops) –> alfentanil
intra operative analgesia, laryngoscopy, surgical pain

Question 17

What are the most commonly used long acting analgesia and when are they useD?

Answer 17

Intra and post-operative

1. Morphine (1st line), Oxycodone

Question 18

What are the three common forms of long term analgesia other than strong opioids?

Answer 18

1. Paracetamol 1g QDS
2. NSAIDS: Diclofenac 50mg TDS, Ibuprofen 400mg TDS
3. Weak opioids: Tramadol 50-100mg QDS and dihydrocodeine 30mg QDS

Question 19

What are the two types of muscle relaxants? and how do they work?

Answer 19

1. Depolarising - Nicotinic receptor agonist that works similarly to Ach but broken down slower with Ach-e –> full muscular contraction –> once Ca2+ depletes causes muscle relaxation
2. N-depolarising - blocks nicotinic receptors –> Ach cannot bind –> muscle relaxation

Question 20

Give an example of the depolarising muscle relaxant? explain the dose, effect and side effects.

Answer 20

Suxamethonium - 1-1.5mg/kg; RSI (rapid onset (30-60s) offset (3-5mins)

• Muscle pain (breakdown)
• Fasiculations (muscle fibres contracting)
• Hyperkalaemia
• Malignant hyperthermia
• Rise in ICP, IOP and gastric pressure
• Bradycardia - prevent using atropine

Question 21

Provide examples of non-depolarising muscle relaxants? What are these used for? How can you reverse their effects?

Answer 21

Short acting - atracurium, mivacurium
Intm. acting - vecuronium, racuronium
long acting - pancuronium

Used for (a) following suxamehtonium for long term muscle relaxation (b) non-urgent endotracheal intubation

Reverse using glycopyrrlate or neostigmine

Question 22

How can you reverse the effects of muscle relaxants? what is the mechanism? is there any additional drugs to give with this?

Answer 22

Neostigmine (anti-cholinesterase agent) - increases Ach binding to nicotinic receptors causing increase muscle contraction.
Also causes bradycardia so give glycopyrralate to prevent this (protect heart)

Question 23

What can you do to maintain BP during surgery?

Answer 23

1. Ephedrine - stimulates a+b receptors = increase HR/BP
2. Metraminol + phenylphrine - stimulates a receptors = increase BP, but decrease HR
3. Inotropic agents = dubutamine, adrenaline

Question 24

What are the main anti-emetics and classes?

Answer 24

1st line - Ondansetron (5HT3 receptor) 
2nd line - Dexamethasone (steroid) 
3rd line - Cyclizine (DA antagonist) 
4. Prochloperazine (phenothiazine) 
5. Metoclopramide (DA antagonist)

Question 25

What is the process of reversal of analgesia.

Answer 25

1. Turn off all vapours 2. Oxygenation 100% 3. Reverse muscle relaxant using neostigmine ± glycopyrralate 4. Handover - agents used, any problems etc 5. Prescribe - rescue analgesia (pump usually with morphine), anti-emetic (Ondansetron), fluids (Saline)

Question 26

Explain the overall process of LMA?

Answer 26

1. Oxygenation 2. Opioid 3. Induction agent (profolol) 4. Volatile agent (sevo/iso/des/enflurane) 5. Bag valve mask ventilation 6. LMA

Question 27

Explain the overall process of Intubation?

Answer 27

1. Oxygenation 100% 2. Opioid 3. Induction agent (profolol) 4. Volatile agent (sevo/iso/des/enflurane) 5. Bag valve mask ventilation 6. muscle relaxant (suxamethonium [dep]; atra/mivcurium [n-dep short], vic/racuronium [n-dep intm], pancuronium [n-dep long] 7. Intubation

Question 28

What monitoring would you provide for a patient with hypotension or sepsis?

Answer 28

1. ECG - monitor rate, rhythm and any arrhythmias 2. CVP - use if high risk of fluid shift or loss or where a large change in fluid volume would be detrimental e.g. HF 3. Capnogrpahy - measures partial pressure of CO2 (indicator of ventilation adequacy also if endotracheal tube is in correct position), ETCO2 - maximal amount of CO2 within the lungs at the end of expiration

Question 29

``` State the following features for spinal block: Target area Where along spine Procedure Onset Predictability Density of block Duration of block ```

Answer 29

1. Subarachnoid space (between arachnoid and pia matter) 2. L1 --> S2. Sacrum is fused so locations are L2/3 L3/4 L5/6 3. Two pops - one through ligament flavour into epidural, and one through dura/arachnoid matter into subarachnoid space. Inject single shot (2-3mls) of anaesthesia 4. rapid 5-10 mins 5. Very predictable 6. Dense - esp. motor 7. 2-3 hrs

Question 30

``` State the following features for Epidural block: Target area Where along spine Procedure Onset Predictability Density of block Duration of block ```

Answer 30

1. Epidural space located between ligament flavum/vertebra and dura matter 2. Anywhere along spinal cord. Epidural space ends at sacrocoggygeal hiatus. Danger of spinal damage increases above L1 3. One pop through ligament flavour into epidural space, insert epidural catheter and infuse local anaesthetic ± opioid 4. 15-30 mins 5. not predictable - reliant on catheter position 6. not dense 7. 72hr

Question 31

What are the drugs for RSI?

Answer 31

Thiopentone induction agent (barbiturate 4-5mg/kg) | Suxamethonium (depolarising 1-1.5mg/kg)

Question 32

How does local anaesthetic work?

Answer 32

Blocks NA+ channels in nerves thus preventing action potential from generating

Question 33

How can you spot LA toxicity and what can be done to reverse it?

Answer 33

LA toxicity affects Na+ channels in brain and heart also Mild - Tinnitus, tingling periorbital area and mouth, anxiety, restless, nausea, tremor Severe - Decreases LoC, agitation, tonic-clonic seizures and CV collapse (bradycardia, conduction blocks, arrhythmia, asystole) 1. Stop LA drugs 2. A = secure airway (LMA or intubate if neccessary) 3. B = Ventilate approiately and provide 100% oxygen non-rebreathe 4. C = IV access with 14 gauge cannula, ECG. Provide 1L of fluids 5. D = tx seizures and administer amnesia if required i.e. profolol 6. Intralipid is last choice.

Question 34

Describe the use of lipid emulsion to treat LA toxicity.

Answer 34

(a) Profolol 1.5mg/kg bolus 20% over 1 min AND (b) Profolol 15mg/kg IV infusion over 1 hr 2. Repeat step (a) for a maximum of two more times (at least 5 mins apart) and repeat step (b) but with double rate i.e. 30mg/kg over 1 hr if CV stability not restored or circulating volume has deteriorated

Question 35

State the 6 ASA grades

Answer 35

grade 1 - healthy patient, no significant co-morbidities grade 2- mild-moderate co-morbiditites, no functional limitation grade 3 - severe co-morbidity, functional limitation grade 4 - severe co-morbidity, with constant threat to life grade 5 - moribund morbidity, not expected to survive or benefit from surgery grade 6 - brainstem dead patient, surgery to extract organs for donation

Question 36

State the 4 surgical grades

Answer 36

``` Grade 1 (minor) - skin tag removal, tooth extraction, drainage of middle ear Grade 2 (moderate) - Tonsilectomy, inguinal hernia, haemorrhoid Grade 3 (major) - mastectomy, hysterectomy, fasciectomy Grade 4 (major +) - any CV or resp surgery, colon or gastric incisions, transplant ```

Question 37

State the CEPOD classifications of surgery

Answer 37

1. emergency/immediate - immediate threat to limb or life, organise within minutes 2. urgent - acute onset or deterioration of disease causing potential threat to limb or life, organise within hours 3. expedited - patient requiring early treatment for condition which is not immediate threat to limb or life 4. Elective - no threat to limb or life, planned surgery booked in advance, organise within 18 weeks

Question 38

Explain fasting process (including medications)?

Answer 38

Food > 6hrs Clear liquids > 2hrs (any taken within this period must be <30ml) Breast fed infants > 4hrs Alcohol > 24 hrs Medication - Omit all hypoglycaemic medications and digoxin - Continue regular mediations esp. hypertensive meds

Question 39

Talk through the pre-operative assessment.

Answer 39

1. History a. CV: Hx of chest pain, palpitations, arrhythmias, ACS, HTN, FHx b. Resp: Hx of asthma or COPD (or any obstructive illness), sleep apnoea or ventilation difficulties, Epworth scale (assessment of sleepiness) c. GI: Hx of N+V, bowel abnormalities (pyloric stenosis, hiatus hernia etc), assess risk of aspiration d. Fasting time c. Exercise tolerance - subjective and objective (specific activity scale) d. PMH: DM, epilepsy, ACS, e. Past anaesthetic Hx: allergies, adverse effects, PONV, malignant hyperthermia f. Medications: prescribed and OTC, OCP/HRT (think VTE risk --> compression stockings and fondaparinoux), allergies 2. Examination: CV: Heart sounds, arrhythmias, pulse rate rhythm and character Resp: chest signs of infection, RR, adequacy of ventilation, any sign of obstruction (snoring, gurgling etc) MSK: any reduced RoM or stiffness that may affect positioning Neruo: C-spine and TMJ movements Airway: observe anterior neck swelling, size of mandible, limited neck movements, extent of mouth opening, dental hygiene and bucked, tongue, larynx or tracea deviation, conduct mallam-patti (1-4) 3. Investigations: U+E, FBC, ECG (See notes for details) - Preg test if woman of appropriate age - APTT + INR if on warfarin, anticoagulation or any blood disorders - HbA1c, BMI, BP, Chol if diabetic - Sickle screen (blood film) if A-C - CXR if resp signs

Question 40

How would you assess an obese patient pre-op?

Answer 40

1. Measure height, weight and calculated BMI 2. BMI > 30 = obese 3. CV: Lower threshold for ECG and stress echo 4. Resp: assess ventilation and risk of apnoea (use Epworth scale) if > 10 consider additional Ix

Question 41

How would you assess a diabetic patient pre-op? What are the complications? what interventions would you put in place?

Answer 41

1. Determine type (T1 more problematic), level of control and previous history and risk of complications 2. Ix: HbA1x (if >8, may be unsuitable) Chol, BP 3. Assess macro and microvascular complications 4. Acute: Dehydration, Hypokalaemia, hyper/hypoglycaemia, DKA, Chronic: thrombosis and gangrene (due to diabetic nephropathy) 5. omit all hypoglycaemic drugs, aim to put patient on 1st slot, give glucose and insulin infusion if HbA1c > 10, resume normal diet and meds

Question 42

Which patients are at risk of VTE? What are the interventions?

Answer 42

1. surgical factors: duration > 90min, duration of pelvic or abdominal surgery > 60 mins, inflammatory bowel or gastric surgery 2. patient factors: age >60, obese BMI > 30, OCP/HRT, varicose veins 3. Compression stockings and LWMH (fondaparinoux) or rivaroxiban

Question 43

Name the pain pathway from external stimuli.

Answer 43

Effector of pain --> dorsal root ganglion (cell body of first neutron) --> spinal cord --> thlamus (spinothalamanic tract) --> somatosensory area in post-central gyrus of parietal cortex

Question 44

Name three pain receptors and their triggers

Answer 44

1. Mechanoreceptors - respond to pin prick and pinch 2. Silent Nociceptors - responds to inflammation 3. Polymodal mechanoheat R - responds to excessive pressure, extreme temps (>48 or <18 celsius), allogens

Question 45

Explain the pain management ladder.

Answer 45

Pain = 0 - PRN Paracetamol (1g QDS) Pain = 1 - Reg Paracetamol + PRN NSAIDs (diclofenac 50mg TDS or Iburprofen 400mg QDS) and weak opioid (tramadol 50-100mg QDS, dihydrocodeine 30mg TDS, codeine phosphate 30-60mg QDS) Pain = 2 - same as above but also strong opioid (morphine 5-10mg 4hrly) Pain 3 = Reg Paracetamol + NSAIDs and Reg Strong opioid or PCA or spinal or epidural block

Question 46

Explain the benefits and concept of PCA?

Answer 46

1. Patient controlled analgesia of opioids usually morphine 2. 1g of morphine, possible every 5 mins with lock out period 3. Frequent small boluses prevents spikes of pain

Question 47

Explain the symptoms/signs and management of malignant hyperthermia.

Answer 47

Signs and Symptoms: 1. Unexplained tachycardia and 2. Unexplained rise in ETCO2 and 3. Consumption of oxygen (also muscle ache, cyanosis, arrhythmias, increased body temp > 2 celsius in 1 hr, muscle contraction/rigidity following suxamethonium admin) Treatment: - Stop all trigger agents - Call for help - A = Hyperventilate with 100% O2 - Maintain anaesthesia if required - Abandon/finish surgery asap 1. Dantrolene 2.5mg/kg (repeat 1mg/kg until stabilised, max 10mg/kg) 2. Treat hyperkalaemia - Calcium gluconate, dextrose/insulin (10 IU act rapid, 50ml 50% glucose over 20 mins), salbutamol 3. Treat acidosis - IV bicarbonate, ventilate 4. Treat arrhythmia - Magnesium

Question 48

Explain the signs and symptoms of anaphylaxis and the management of treatment and investigations?

Answer 48

Signs/Symptoms: Pruritis, angiooedema, laryngeal oedema, bronchospasm, wheeze, stridor, raised HR, low BP, Erythema, Coughing on admin of induction agent Management: 1. ABCDE approach 2. remove all causative agents 3. keep patient anaesthetised if already 4. call for help A = maintain patency, intubate if neccessary B = 100% O2 and ventilate with bag valve mask if required C = Gain IV access and give Saline or Hartmans (500ml), IV adrenaline 0.5-1ml (if multiple repeat bolus, consider IV infusion) Secondary management 1. chlophenamine IV 20mg or hydrocortisone 200mg 2. Treat hypotension with vasopressor e.g. metraminol 3. Treat acidosis with IV Bicarb 4. Treat bronchospasm with salt neb Investigation: 1. Mast cell cast tryptase at time of reaction --> 2-4hr --> 24hrs post

Question 49

What is suxamethonium apnoea, how does it present and what is the management?

Answer 49

Rare disorder impairing ability to metabolise suxamethonium. Inherited: Asian and Middle eastern Aquired: Pregnancy, hypothyroid, anti cholinesterase (neostigmine), MAOi, cancer, methotrexate ``` Presentation: Only notice at end of operation Patient has poor effort to cough or breathe Increase in HR/BP Sweats Pupils dilated ``` Management: 1. Identify with muscle nerve stimulation --> if still paralysed keep patient anaesthetised and ventilated 2. ABCDE 3. Monitor with nerve stimulation 4. if train of four muscle contraction then Sux has worn off 5. Keep anaesthetised until confident patient is breathing for themselves 6. Extubate once fully conscious and able to follow commands 7. Use N-depolarising agents in future