Anaesthetics

Question 1

Reducing risk of gastric aspiration

Answer 1

1. Reduce gastric residual volume
   Adequate period of fasting, avoid drugs delaying gastric emptying, insertion on NG tube, prominent if drugs (metoclopramide)
2. Increase pH of gastric contents
   NaCitrate, H2 antagonists e.g ranitidine, PPIs e.g omeprazole
3. Cricoid pressure (sellicks manoeuvre)

Question 2

Sellicks manoeuvre

Answer 2

Pressure to anterior aspect of cricoid cartilage forcing whole ring backwards as compressing oesophagus against sixth cervical vertebra
One hand should stabilise from back
Maintain pressure even if vomiting

Question 3

Rapid sequence induction of anaesthesia

Answer 3

Gain IV access
Preoxygenate
Gentle cricoid pressure
Induction agent given as fast running IV infusion
Suxamethonium given
Mask held against face but not ventilated
Once fasciculations end, perform intubation
Confirm position
Release cricoid pressure

Question 4

Obstetric patient prophylaxis against acid aspiration

Answer 4

Elective c sections: a H2 antagonist OR PPI the evening before and morning of surgery
Emergency: a H2 antagonist and 30ml 0.3M sodium citrate immediately before surgery

Question 5

Anaesthesia techniques for c sections

Answer 5

Spinal: provides rapid intense reliable relief. Intrathecal diamorphine should be offered as improves post op pain control and reduces need for additional analgesia
Epidural: can be extended from labour epidural but slow process and risk of inadequacy
General: mainly used for urgent emergency c sections due to immediate threat of maternal or foetal life, refusal of regional or failure/contraindication to regional anaesthesia

Question 6

Specific risks of GA in obstetric patients

Answer 6

Regurgitation and aspiration due to progesterone relaxation of LOS + increased abdominal pressure

Failed intubation 10x more likely (predominant breast tissue, engorged airway mucosa and full set of teeth)

Increase risk of desat and hypoxia ( reduced FRC and increased oxygen consumption)

Maternal awareness (inadequate dosing due to concern of over sedating foetus)

Aortocaval compression (IvC and aorta therefore reduced BP and reduced perfusion to uterus causing foetal hypoxia) reduce with 15deg left lateral tilt

Question 7

Positioning for obstetric woman

Answer 7

15 degree left lateral tilt

Question 8

Signs of gastric aspiration

Answer 8

Coughing at induction or recovery from anaesthesia/ during anaesthesia with supraglottic airway

Gastric contents in pharynx at laryngoscopes or around edge of face mask

Progressive hypoxia, bronchospasm, respiratory obstruction (if severe)

Question 9

Management of aspiration at induction before neuromuscular agents given in non essential surgery

Answer 9

100% O2 by facemask
Allow patient to recover
Treat bronchospasm with salbutamol or ipratropium
Chest X-ray and physio
Consider ICU/HDU depending on degree of aspiration

Question 10

Management of gastric aspiration at induction before NM blockade in essential surgery

Answer 10

Empty stomach with NG tube
30mL sodium citrate via NG
Allow patient to recover
Continue surgery with regional block or RSI with intubation
After intubation, aspirate tracheobronchial tree (consider bronchoscopy)
Treat bronchospasm with salbutamol/ipratropium
Arrange for post op cheat X-ray and physio
Recovery in ICU/HDU with oxygen therapy
+- post op ventilation if required

Question 11

Management of gastric aspiration at induction after deliver of neuromuscular blocking agents

Answer 11

Intimate with cuffed tube
Aspirate tracheobronchial tree before beginning positive pressure ventilation
Consider bronchopulmonary saline lab age
Treat bronchospasm with salbutamol or ipratropium
Pass NG tube and empty stomach
If patient stable, surgery may continue
Post op care in ICU/HDU

Question 12

Management of intraoperative gastric aspiration with a supraglottic airway

Answer 12

Get help
Stop surgery if safe to do so
Turn patient into left lateral position with head down tilt
Remove supraglottic airway
Suction oro pharynx
Maintain ventilation with 100% oxygen ensure ongoing anaesthesia
Cricoid pressure
Give fast acting neuromuscular block and intubation trachea

Question 13

Causes for anaphylaxis in anaesthetics

Answer 13

Anaesthetic drugs:

• muscle relaxants 50% (suxamethonium, rocuronium etc)
• latex 17%
• antibiotics 8% (

Question 14

Clinical features of anaphylaxis

Answer 14

Rapid onset
Severe hypotension
Severe bronchospasm - cough and wheeze
Widespread flushing
Hypoxaemia
Urticaria
Angioedema (May involve airway)
Pruritus, nausea and vomiting

Question 15

Immediate management of anaphylaxis

Answer 15

Discontinue trigger
Call for help
Maintain patent airway
Administer 100% oxygen (high-flow, 10-15L/min)
Elevate legs without compromising ventilation
0.5mg IM adrenaline (or if ECG monitoring available, 50micrograms IV slowly)
Further dose every 2 minutes until responding
Rapid IV fluid infusion
Monitor O2 sats, BP, HR/ECG, end tidal CO2
Transfer to ICU for further treatment and monitoring ASAP

Steroids used once stable to prevent biphasic reaction from occurring 6 hours later

Question 16

Failed intubation protocols

Answer 16

Plan B:
Face mask, oxygenation and ventilation, max head extension and jaw thrust, oral or nasal airway

If failed oxygenation with facemask->
Plan C:
LMA oxygenate and ventilate, awaken patient
Max 2 attempts at insertion

Can't intubate can't ventilate situation with increasing Hypoxaemia
Plan D:
Emergency airway (cannula or surgical cricothyroidotomy)

Question 17

Techniques to help with difficult intubation

Answer 17

BURP procedure
Use of a boogie or stylet
Fibre-optic bronchoscope (usually if identified pre-admission and prepared)
Insert LMA as conduit to pass endotracheal tube
Video laryngoscopes/ other indirect layngoscopy

Question 18

Risk of bleeding

Answer 18

HAS BLED

Hypertension >160 systolic
Abnormal liver or renal function
Stroke
Bleeding
Labile INR
elderly >65
Drugs and alcohol

Question 19

Factors predisposing to aspiration

Answer 19

Full stomach (inadequate time of fasting, increased gastric contents due to outflow obstruction, distension after face mask ventilation)
Delayed gastric emptying (opiates, trauma, peritoneal irritation, blood in stomach, pain and anxiety)
Obstetric patients
Other (GORD, hiatus hernia, obesity, head down position, bulbar palsy, oesophageal pouch or stricture)

Question 20

Pros and Cons of inhalational induction anaesthesia

Answer 20

Pros:
lack of suitable veins
uncooperative patients
patients with airway compromised (IV drugs may cause apnoea and loss of airway patency)
Children
(Sevovlurane is the most pleasant agent to use)

Cons:
Slower onset than IV
Mostly unpleasant to breathe
Hypotension and reduced cardiac output with increasing concentration, difficult to treat without IV access
Causes Vasodilation and hypercapnia (due to respiratory depression) leading to increased cerebral flow - thus unsuitable in patients with raised ICP

Question 21

Transversus abdominis plane (TAP) block

Answer 21

Local anaesthetic in plane between transverse abdominis and internal oblique muscles
Anaethetises skin and muscles of abdo wall + parietal peritoneum
US guidance to locate plane
Midaxillary line, midway between costal margin and iliac crest
bilateral blocks required for midline incisions
most useful in lower abdo surgeries (hernia, appendix, hysterectomy etc.)

Question 22

Brachial Plexus blocks (types)

Answer 22

Supraclavicular/Interscalene:
Above the level of the clavicle
Used for shoulder surgery

Axillary:
used for operations below the elbow

Question 23

Lignocaine Max. doses

Answer 23

Without adrenaline: 3mg/kg up to 200mg
With adrenaline: 6-7mg/kg up to 500mg

Do not use with adrenaline at end arterial sites e.g. fingers, nosetip, ears

Reduce dose in elderly, frail, shocked and liver impaired patients

Question 24

Benefits of regional anaesthesia

Answer 24

Reduced need for systemic drugs
Reduced risk of aspiration
Increased post-op analgesia
Reduced autonomic response for painful procedures
No need for mechanical ventilation (e.g. good in patients with airway disease/difficult airways)
Reduced disturbance of control of systemic diseases e.g. DM
Profound muscle relaxation and contraction o bowel, leads to improved access for laparotomy
Reduced blood loss with controlled hypotension

Question 25

Contraindications to epidural or spinal anaesthesia

Answer 25

``` Hypovolaemia Coagulopathy Low, fixed cardiac output (e.g. Severe AS) Local skin sepsis Raised ICP Known allergy to amide local drugs Totally uncooperative +/- Concurrent CNS disease +/- Hx of spinal surgery/abnormal anatomy of spine ```

Question 26

Signs/Symptoms of local anaesthetic toxicity

Answer 26

Mild/Early: Circumoral paraesthesia, tongue numbness, visual disturbances, light-headedness, slurred speech, twitching, restlessness, mild hypotension and bradycardia Severe/Late: Grand mal convulsions, coma, respiratory depression - apnoea, cardiovascular collapse with profound hypotension and bradycardia - cardiac arrest

Question 27

Management of local anaesthetic toxicity

Answer 27

``` STOP GIVING LOCAL ANAESTHETIC Airways +/- intubation B: 100% O2 C: Colloid/Crystalloid fluid, IV atropine D: diazpam for convulsions ```

Question 28

Confirming position of a tracheal tube

Answer 28

``` Measureing CC2 in expired case (waveform capnometry) Direct visualisation of tube passing between cords Oesophageal detector (no resistance to aspiration of air) Fogging of clear plastic tube connectors during expiration ``` Less reliable signs: breath sounds on auscultation, chest movement on ventilation, "gurgling/burping" sounds over epigastrium, O2 saturation (late sign)

Question 29

Opioid reversal

Answer 29

Naloxone: Pure antagonist 0.1-0.4mg IV initially lasts 30-45 minutes, 60s onset Limited effect against partial or mixed opioids Duration of action shorter than most opioids - infusion required in severe overdoses

Question 30

Common risks associated with anaesthesia (1 in 10-1 in 100)

Answer 30

``` Bruising/soreness from IV access attempts Sore throat Headache Dizziness PONV Itching Retention of urine ```

Question 31

Uncommon risks associated with anaesthesia (less than 1 in 100)

Answer 31

``` Dental damage Chest infection Muscle Pains Worsening of existing condition (e.g. IHD) Awareness ``` ``` VERY RARE: Allergies Eye injury Nerve damage Hypoxic brain injury Death ```

Question 32

Indicators of difficult intubation

Answer 32

``` Mallampati grade III or IV Thyromental distance Receded mandible Loose teeth, caps, crowns, dentures Large tongue Soft tissue swelling at front of neck Deviation of larynx or trachea Limitations in flexion and extension of cervical spine Limitation of mouth opening ```

Question 33

Tracheal intubation complications

Answer 33

Unrecognised oesophageal intubation Failed intubation, inability to ventilate Failed ventilation Aspiration of regurgitated gastric content Direct trauma to all structures lips-lungs Trauma to adjacent structures during the procedure Hypertension and arrhythmias Vomiting

Question 34

Risk Factors for post-operative nausea and vomiting

Answer 34

Female gender non-smoker History of PONV or motion sickness Opioids as part of anaesthetic technique

Question 35

Complications of central neural blockade (spinal or epidural)

Answer 35

``` Hypotension Nausea Bradycardia Vomiting Dysrhythmias Post-dural puncture headache (spinal only) ```

Question 36

Uses of capnometry

Answer 36

Indicator of degree of alveolar ventilation - allows controlled hypocapnia in neurosurgery - avoid hypocapnia in impaired cerebral perfusion Disconnection indicator Confirms ETT in trachea Indicates degree of rebreathing Indicates cardiac output (V/Q mismatch - low CO2) Firs clue of development of malignant hyperpyrexia

Question 37

Limitations of pulse oximetry

Answer 37

Fails to appreciate severity of hypoxia (sats 90% =PaO2 8kPa) Unreliable in severe vasoconstriction Unreliable with carboxyHb (high estimates) and metHB (low estimates >85%) Underreads sats if Hb falls (not affected by polycythaemia) Affected by extraneous light Unreliable with excessive movement of patient Not an indicator of alveolar ventilation

Question 38

Central effects of opioid analgesics

Answer 38

``` Analgesia Sedation Euphoria Nausea and Vomiting Pupillary constriction Depression of ventilation - rate more than depth - reduced response to CO2 Depression of vasomotor centre Addiction ```

Question 39

Reversal of neuromuscular block

Answer 39

Anticholinesterases: neostigmine (2.5mg IV) + atropine 1.2mg Sugammadex: newer drug, reverses aminosteroids (e.g. rocuronium etc.) Used in emergencies (can't intubate can't ventilated) post-rocuronium Not used routinely, due to cost

Question 40

Suxamethonium side effects

Answer 40

Malignant hyperpyrexia Raised intraocular pressure Muscular pain H2 release (usually localised, maybe anaphylactic) Prolonged apnoea (pseudocholinesterase deficiencies) Raised serum K+ - 0.5-0.7 mmol predicted in all patients - significant rise in patients with burns, denervation injury (e.g. post SCI), muscle dystrophies, crush injury

Question 41

Complications of peripheral venous cannulation

Answer 41

``` Failure Haematoma Extravasation of fluid/drugs Damage to local structures Air embolus Shearing of cannula Thrombophlebitis ```

Question 42

Indications for mechanical ventilation

Answer 42

In setting of neuromuscular blocks Thoracotomy (prevent paradoxial movement) Neurosurgery (control CO2 thus cerebral blood flow) Prolonged surgical procedures Where anaesthetic will cause unacceptable respiratory depression Surgery where intubation is required (e.g. prone position, full stomach, shared airway)

Question 43

Opioid Classes

Answer 43

Pure agonists: morphine, fentanyl, pethidine Weak agonists: tramadol Partial agonist: buprenorphine (30x as potent as morphine)

Question 44

Absolute contraindications to NSAID use

Answer 44

``` pre-existing renal dysfunction Hyperkalaemia Cardiac failure Severe hepatic dysfunction History of GI bleeding Hypersensitivity to NSAIDs Aspirin-induced asthma ```

Question 45

Opioid regulation

Answer 45

Schedule 1: hallucinogenic drugs (no recognised therapeutic use) Schedule 2: opioids, major stimulants (amphetamines, cocaine) Schedule 3: drugs less likley to be misused than 2 (barbituates, minor stimulants, buprenorphine, temaze) Schedule 4: benzos (excl temaze), ketamine (potential for abuse) OR androgenic steroids, GH, clenbuterol Schedule 5: preparations with very low concentration of codeine or morphine e.g. cough mixtures

Question 46

Anti-emetics (5 classes)

Answer 46

Dopamine antagonists - metoclopramide - end of surgery 5-HT antagonists - ondansetron - end of surgery (better used to treat established vomiting) Antihistamines - Cyclizine - end of surgery Anticholinergics - hyoscine - >4h before Sx (transdermal patch) Corticosteroids - dexamethasone - at induction (also has anti-inflammatory thus analgesic effects)

Question 47

Contraindications and Precautions for using opioid PCA for post-operative analgesia

Answer 47

- Mental or physical barriers (e.g. SCI, cognitive impairment) - concurrent sedative use - History of opioid use or concurrent opioid use - Airway compromise - Acute alcohol intoxication - OSA, COPD or asthma (may increase risk of respiratory depression) - Morbid obesity - Renal impairment - Hepatic impairment - Previous allergy or sensitivity to a specific opioid

Question 48

Types of opioid receptors

Answer 48

μ, κ, δ

Question 49

Actions of activation of μ receptors

Answer 49

``` Analgesia Nausea/vomiting Bradycardia Respiratory depression Miosis Reduced gut motility Pruritus ```

Question 50

Actions of activation of κ receptors:

Answer 50

Analgesia Sedation Dysphoria Diuresis

Question 51

Actions of activation of δ receptors:

Answer 51

Analgesia only

Question 52

Endogenous agnoists of μ receptors

Answer 52

β-endorphins

Question 53

Endogenous agnoists of κ receptors

Answer 53

dynorphins

Question 54

Endogenous agonists of δ receptors

Answer 54

Enkephalins

Question 55

Paracetamol metabolism

Answer 55

Produces hepatotoxic metabolite that is normally inactivated by hepatic glutathione In paracetamol overdose, this pathway is saturated, leading to accumulation of metabolite and hepatic cell necrosis Renally excreted

Question 56

Opioid sparing effect of NSAIDS (%)

Answer 56

20-40%

Question 57

Complications of severe post-op pain

Answer 57

Myocardial ischaemia (HR, TPR, BP) VTE (mobility, stasis, clotting) Hypoxaemia and pneumonia (sputum retention, reduced lung volume, atelectasis, diaphragmatic splinting and cough suppression) Delayed gastric emptying and reduced gut motility Urinary retention Impaired wound healing/immune function, increased protein breakdown (increased cortisol, catecholamines etc.) Risk of Chronic pain Psych: anxiety, sleeplessness, fatigue, distress

Question 58

Morphine metabolism

Answer 58

Least lipid soluble of commonly used opioids Mostly metabolised in liver (only 10% excreted unchanged) Renal excretion (accumulation in red GFR) 1 major metabolite is more potent than morphine, 1 is inactive

Question 59

Fentanyl metabolism

Answer 59

Highly lipid soluble - suitable for transdermal administration and short duration of action due to rapid tissue uptake Inactive metabolites

Question 60

Codeine metabolism

Answer 60

Prodrug for morphine - approx 10% converted to morphine | Requires CYP2D6 which 10% of caucasions lack (thus no effect)

Question 61

Adrenaline and amiodarone dosing and timing in adult ALS

Answer 61

Shockable: Adrenaline 1mg after 2nd shock Amiodarone 300mg after 3rd shock Non-schockable: Adrenaline 1mg immediately and then after every 2nd cycle

Question 62

Dose of adrenaline and amiodarone in paediatric ALS

Answer 62

0.1mL/kg of 1:1000 (10 mcg/kg) adrenaline | 5mg/kg amiodarone after every 3rd shock in shockable rhythms