Topic 1: Airway Management

Surgical Anatomy

Thyroid cartilage: anterior midline, V-shaped, C4–C5 level.
Cricoid cartilage: only complete tracheal ring, C6; inferior to thyroid cartilage.
Cricothyroid membrane (CTM): width ~9 mm, height ~22 mm; superior cricothyroid arteries cross the UPPER border — incise in the INFERIOR THIRD.
Right mainstem bronchus: wider, shorter, more vertical (25° from midline) — preferential right-sided endobronchial intubation if tube advanced too far.

Airway Assessment — LEMON Score

Letter	Assessment	Difficulty Indicator
L	Look externally	Short neck, large tongue, retrognathia, obesity
E	3-3-2 rule	<3 fingers mouth opening / <3 hyoid-chin / <2 thyromental distance
M	Mallampati	Class III or IV
O	Obstruction	Mass, haematoma, Ludwig's angina, foreign body
N	Neck mobility	Cervical spine injury, ankylosing spondylitis, post-RT

Mallampati & Cormack-Lehane

Mallampati Class	Visible Structures	CL Grade	View at Laryngoscopy
I	Soft palate, uvula, fauces, pillars	1	Full glottis visible
II	Soft palate, uvula, fauces	2a	Partial glottis visible
III	Soft palate, base of uvula	2b	Arytenoids only
IV	Hard palate only	3/4	Epiglottis only / nothing

RSI Step-by-Step

Preoxygenate: 100% O₂ x 3–5 min; SpO₂ target >95%; nasal cannula 15 L/min apnoeic oxygenation
Position: Sniffing position; ear-to-sternal-notch alignment in obese patients
Induction: Propofol 1.5–2 mg/kg (stable) OR ketamine 1–2 mg/kg (haemodynamic instability)
NMB: Suxamethonium 1.5 mg/kg OR rocuronium 1.2 mg/kg (if suxamethonium CI)
Laryngoscopy: Blade tip in vallecula; lift along handle axis — never lever on teeth
Tube: ETT 7.0–7.5 F / 7.5–8.0 M; cuff 20–25 cmH₂O; depth 21 cm F / 23 cm M
Confirm: EtCO₂ waveform (gold standard) + bilateral auscultation

Board Fact

Safe apnoea time: ~8 min (healthy adult); ~2–3 min (obese/pregnant). EtCO₂ waveform = gold standard for ETT confirmation. No waveform = oesophageal — pull immediately.

CAUTION: CICO (Cannot Intubate Cannot Oxygenate)

Hesitation is the leading cause of hypoxic brain injury. Once SpO₂ is falling and both intubation and SAD have failed — cut immediately without further attempts using the Scalpel-Bougie Technique.

Topic 2: Anesthetic Pharmacology

Induction Agents

Agent	Dose	Mechanism	CVS Effect	Key Feature
Propofol	1.5–2.5 mg/kg	GABA-A potentiation	MAP ↓ 25–40%	Antiemetic; PRIS >4 mg/kg/h >48h; no analgesia
Ketamine	1–2 mg/kg	NMDA antagonism	HR/BP ↑	Preferred in instability; bronchodilator; raises ICP/IOP
Etomidate	0.3 mg/kg	GABA-A potentiation	Minimal	Most CVS stable; adrenocortical suppression 24–48h
Thiopental	3–5 mg/kg	Barbiturate GABA-A	BP ↓	Reduces CMRO₂/ICP; pH 10.8 — necrosis if extravasated

Volatile Agents & MAC

Agent	MAC (%)	Blood:Gas Coeff.	Key Features
Sevoflurane	2.0	0.65	Smooth induction; paediatric first choice; fast offset; MH trigger
Isoflurane	1.15	1.4	Vasodilation; reduces MAP; MH trigger
Desflurane	6.0	0.45	Fastest onset/offset; airway irritant — not for induction; MH trigger
Nitrous oxide	104	0.47	Cannot provide sole anaesthesia; expands gas cavities; NOT an MH trigger

Board Fact

Lower blood:gas partition coefficient = faster onset/offset. Desflurane (0.45) = fastest. MAC is additive: 0.5 MAC volatile + 0.5 MAC N₂O = 1.0 MAC total. All volatile halogenated agents trigger MH; nitrous oxide is safe.

NMBs & Reversal

Agent	Onset	Duration	Reversal	Notes
Suxamethonium	45–60 s	8–12 min	None	Fastest; K⁺ ↑; CI: burns >24h, crush, denervation, MH
Rocuronium	60–90 s	30–60 min	Sugammadex	Only NMB reversible at full block
Atracurium	3–5 min	25–35 min	Neostigmine	Hofmann elimination; histamine release
Cisatracurium	5–7 min	40–60 min	Neostigmine	Hofmann elim; less histamine; ICU preferred

Board Fact

TOF ratio ≥0.9 required before extubation. Sugammadex doses: 2 mg/kg (moderate) / 4 mg/kg (deep) / 16 mg/kg (immediate reversal of RSI dose). Neostigmine cannot reverse deep block — requires TOF ≥0.4.

Local Anesthetics & LAST

Agent	Class	Max Plain	Max + Adrenaline	Key Feature
Lidocaine	Amide	3 mg/kg	7 mg/kg	Fastest onset; topical airway; IV antiarrhythmic
Bupivacaine	Amide	2 mg/kg	2.5 mg/kg	Most cardiotoxic — R-enantiomer blocks cardiac Na⁺/K⁺
Ropivacaine	Amide	3 mg/kg	4 mg/kg	Less cardiotoxic; motor-sparing at low concentrations

CAUTION: LAST Management

LAST (Local Anesthetic Systemic Toxicity): CNS prodrome (tingling, tinnitus) → seizures → VT/VF. Specific Rx: 20% intralipid 1.5 mL/kg IV bolus (lipid sink). Do NOT use propofol as the lipid source — insufficient lipid concentration plus cardiovascular depressant effects compound the toxicity.

Topic 3: Anesthesia Types & Classifications

Neuraxial Anatomy Layers

Needle path from superficial to deep:

Skin
Subcutaneous fat
Supraspinous ligament
Interspinous ligament
Ligamentum flavum (Loss of Resistance point)
Epidural space (Target for epidural)
Dura mater
Subdural space (potential)
Arachnoid mater
Subarachnoid space containing CSF (Target for spinal)
Pia mater

Landmarks: Conus medullaris ends at L1–L2 in adults. Insert at L3–L4 or L4–L5 only. Tuffier's line (intercristal) crosses L4.

Spinal vs Epidural

Feature	Spinal	Epidural
Target space	Subarachnoid (CSF)	Epidural (fat, veins)
Drug volume	2–3 mL	10–20 mL bolus
Onset	3–5 min	15–20 min
Duration	Fixed ~2–3 h	Indefinite (catheter)
PDPH risk	~1–2% (pencil-point)	~0.5% (inadvertent puncture)
Titratability	None after injection	Yes — incremental dosing

CAUTION: Epidural Haematoma

Back pain + progressive lower limb weakness post-neuraxial = surgical emergency. MRI + neurosurgical decompression within 6–8 hours required to prevent permanent paralysis.

Dermatomal Requirements

Dermatome	Landmark	Procedure
T4	Nipple line	Caesarean section (bilateral T4 required)
T6	Xiphisternum	Upper abdominal surgery
T10	Umbilicus	Hip/knee replacement, inguinal herniorrhaphy, TURP
S1–S3	Perineum / saddle	Anorectal / perineal surgery

ASRA Anticoagulation Guidelines

Agent	Wait Before Block	Wait After Catheter Removal
UFH prophylactic	4–6 hours	1 hour
LMWH prophylactic (40 mg OD)	12 hours	12 hours
LMWH therapeutic (1 mg/kg BD)	24 hours	24 hours
Warfarin	INR ≤1.4	After removal
Clopidogrel	7 days	After removal
DOACs (rivaroxaban, apixaban)	72 hours	6 hours after removal

ASA Physical Status

ASA Class	Description	Periop Mortality	Example
I	Normal healthy	<0.1%	Young fit adult
II	Mild systemic disease	0.1–0.2%	Well-controlled HTN/DM, BMI 30–40, smoker
III	Severe systemic disease	1.8–4.3%	Poorly controlled DM, COPD, morbid obesity
IV	Constant threat to life	7.8–23%	Recent MI, decompensated HF, sepsis
V	Moribund	Up to 51%	Ruptured AAA, massive PE
E suffix	Emergency modifier	Adds risk	Applied to any class

Board Fact

Sedation levels can deepen unpredictably. Rescue preparation must always match the intended level PLUS one level deeper. Planning moderate sedation? Prepare for deep sedation and GA rescue.

Topic 4: Anesthetic Complications

Malignant Hyperthermia (MH)

Gene: RYR1 (ryanodine receptor 1) — chromosome 19; autosomal dominant.
Triggers: ALL volatile halogenated agents (sevo, iso, des, halothane) + suxamethonium.
Safe agents: Propofol, ketamine, all non-depolarising NMBs, nitrous oxide, all local anesthetics.
EARLIEST sign: Rising EtCO₂ despite adequate ventilation — NOT temperature (temperature rise is LATE).
Other features: Muscle rigidity (masseter spasm), tachycardia, temperature >1°C/5 min, rhabdomyolysis, DIC.

CAUTION: MH Treatment

Dantrolene 2.5 mg/kg IV is the only specific treatment. NEVER give calcium channel blockers with dantrolene — causes severe hyperkalaemia and cardiovascular collapse. Use amiodarone for MH-associated arrhythmias.

MH vs Serotonin Syndrome vs NMS

Feature	Malignant Hyperthermia	Serotonin Syndrome	NMS
Trigger	Volatiles + suxamethonium	SSRIs, MAOIs, tramadol	Haloperidol, metoclopramide
Onset	Minutes (intraoperative)	Minutes to hours	Hours to days
Rigidity	Generalised, severe	Clonus > rigidity	Lead-pipe rigidity
Specific Rx	Dantrolene	Cyproheptadine; BZDs	Bromocriptine; dantrolene

Anaphylaxis Protocol

Common triggers: NMBs (rocuronium, suxamethonium) > antibiotics > latex > chlorhexidine.
First-line Rx: Adrenaline — IV 50 mcg boluses; IM 0.5 mg (1:1000) if no IV access.
Secondary agents: Chlorphenamine 10 mg IV; hydrocortisone 200 mg IV; crystalloid 500–1000 mL.
Tryptase sampling: 3 samples: 1–2h (peak), 4–6h (declining), 24h (baseline).
Biphasic reaction: Recurrence 4–12h in up to 23% — admit all patients minimum 12–24h.

PONV — Apfel Score

Apfel factors (1 pt each): female sex / non-smoker / history of PONV or motion sickness / postoperative opioid use.

Apfel Score	PONV Risk	Minimum Prophylaxis
0 / 1	~10% / ~20%	None / 1 agent (ondansetron)
2 / 3	~40% / ~60%	2 agents / 3 agents + consider TIVA
4	~80%	3 agents + TIVA + opioid minimisation

Clinical Pearl

Dexamethasone at induction — peak anti-PONV effect aligns with the recovery period when it is needed most. Giving it at the end of surgery is a common exam trap.

Topic 5: ICU Basics for Surgeons

Mechanical Ventilation

Parameter	Target	Rationale
Tidal volume	6 mL/kg IBW	Prevents volutrauma; reduces ARDS mortality
Plateau pressure	≤30 cmH₂O	Prevents barotrauma
Driving pressure	≤15 cmH₂O	Strongest independent ARDS mortality predictor
PEEP / FiO₂	5–15 cmH₂O / Lowest	Recruits alveoli / Prevents oxygen toxicity

Board Fact

Driving pressure = Plateau pressure − PEEP. A patient on TV 560 mL with IBW 70 kg = 8 mL/kg — reduce to 420 mL (6 mL/kg IBW) immediately. This single change reduces ARDS mortality.

Shock Classification

Type	CO	SVR	CVP	First-Line Rx
Hypovolaemic	Low	High	Low	Volume resuscitation; source control
Distributive (septic)	High (early)	Low	Low/normal	Noradrenaline + source control + fluids
Cardiogenic	Low	High	High	Dobutamine; treat cause; restrict fluids
Obstructive	Low	High	High	Relieve obstruction immediately

Sepsis Definitions

Sepsis: Life-threatening organ dysfunction (SOFA ≥2) from dysregulated host response to infection.
Septic shock: Sepsis + vasopressor for MAP ≥65 + lactate >2 mmol/L despite adequate resuscitation.
qSOFA: RR ≥22 / GCS <15 / SBP ≤100. Score ≥2 triggers escalation.

CAUTION: Time to Source Control

Necrotising fasciitis: mortality rises ~9% per hour of delay in surgical debridement. CT confirms but must NEVER delay the knife when clinical suspicion is high.

AKI — KDIGO Staging

Stage	Creatinine Criterion	Urine Output Criterion
1	×1.5–1.9 baseline OR rise ≥26.5 μmol/L in 48h	<0.5 mL/kg/h for 6–12h
2	×2.0–2.9 baseline	<0.5 mL/kg/h for ≥12h
3	×3.0 OR ≥353.6 μmol/L OR RRT initiated	<0.3 mL/kg/h for ≥24h OR anuria ≥12h

Nutrition & Electrolytes

Feature	Enteral (EN)	Parenteral (PN)
Start timing	Within 24–48h of ICU admission	After 3–5 days failed EN
Gut preservation	Yes	No
Infection risk	Low	High (catheter BSI)
Target	25–30 kcal/kg/day; 1.2–2.0 g/kg/day protein	Same targets

Clinical Pearl

Refeeding syndrome: commencing nutrition after prolonged starvation drives phosphate, K⁺, Mg²⁺ intracellularly → profound hypophosphataemia → respiratory muscle failure → failure to wean.

Electrolyte	Abnormality	Key Cause	Treatment
Na⁺	Hyponatraemia <135	SIADH, hypotonic fluids	Fluid restrict; correct ≤10 mEq/L/24h
K⁺	Hyperkalaemia >5.5	AKI, rhabdomyolysis	Ca-gluconate; insulin/dextrose; dialysis
Ca²⁺	Hypocalcaemia	Post-thyroidectomy	IV calcium gluconate 10 mL 10%
Phosphate	Hypophosphataemia	Refeeding, DKA	IV sodium/potassium phosphate

Board Review MCQs

1. Patient with CL grade 3 view on direct laryngoscopy. What is the most appropriate next step?

Bougie or video laryngoscopy.

2. You have had two failed intubation attempts, a failed supraglottic airway device (SAD) insertion, and the patient's SpO₂ is falling to 72%. What is the immediate next step?

Scalpel cricothyrotomy (FONA - Front of Neck Airway). This is a CICO scenario.

3. What is the gold standard method for confirming endotracheal tube placement?

Continuous EtCO₂ waveform capnography.

4. A patient develops a rapidly expanding neck haematoma post-carotid endarterectomy with stridor. Management?

Evacuate haematoma immediately at the bedside by opening the wound; prepare for emergency intubation.

5. What is the safest incision zone for a surgical cricothyrotomy to avoid bleeding?

The inferior third of the cricothyroid membrane — below the superior cricothyroid arteries.

6. Patient with severe aortic stenosis requires induction. Which agent provides the most stable haemodynamic profile?

Etomidate 0.3 mg/kg.

7. 48 hours post-crush injury, the patient requires emergency intubation. Which NMB is strictly contraindicated?

Suxamethonium (fatal hyperkalaemia risk due to upregulation of extrajunctional receptors).

8. Patient develops a seizure immediately following a supraclavicular brachial plexus block. Specific treatment?

20% intralipid 1.5 mL/kg IV bolus (Treatment for Local Anesthetic Systemic Toxicity - LAST).

9. You need immediate reversal of a deep rocuronium block (0 TOF twitches). What is the correct sugammadex dose?

4 mg/kg (deep block reversal).

10. Rising EtCO₂ and masseter muscle rigidity during laparoscopic cholecystectomy. Immediate specific treatment?

Malignant Hyperthermia — Dantrolene 2.5 mg/kg IV; stop all volatile agents immediately.

11. Post-induction, the patient experiences cardiovascular collapse, severe bronchospasm, and an urticarial rash. First-line therapy?

Adrenaline 50 mcg IV boluses (First-line for Anaphylaxis).

12. Patient develops apnoea, profound bradycardia, and severe hypotension minutes after a spinal block. Diagnosis and management?

High (total) spinal block. Manage with RSI, vasopressors, and supportive mechanical ventilation.

13. A patient with ARDS post-oesophagectomy is on a Tidal Volume of 560 mL (Ideal Body Weight 70 kg). What is the most important ventilator change?

Reduce TV to 420 mL (6 mL/kg IBW). The current TV is 8 mL/kg which causes volutrauma.

14. A patient in septic shock has a MAP of 56 mmHg despite 30 mL/kg fluid resuscitation. First-line vasopressor?

Noradrenaline (first-line in distributive shock).

15. Post-total thyroidectomy patient complains of perioral tingling and shows a prolonged QTc on ECG. Treatment?

Hypocalcaemia. Give IV calcium gluconate 10 mL of 10% solution.

16. A severely malnourished patient is started on aggressive enteral feeding. Day 3: phosphate is 0.38 mmol/L and they fail a spontaneous breathing trial. Diagnosis?

Refeeding syndrome — resulting hypophosphataemia causes respiratory muscle weakness.

Rapid Reference: Critical Numbers & Doses

Drug / Parameter	Value	Context
Suxamethonium RSI	1.5 mg/kg IV	Onset 45–60 sec; CI: burns >24h, crush, MH
Rocuronium RSI	1.2 mg/kg IV	Onset 60–90 sec; reversible with sugammadex 16 mg/kg
Sugammadex (moderate)	2 mg/kg	TOF ratio detectable
Sugammadex (deep)	4 mg/kg	1–2 twitches on TOF
Sugammadex (RSI reversal)	16 mg/kg	Immediate reversal of full RSI rocuronium dose
Dantrolene (MH)	2.5 mg/kg IV q5min	Only specific MH treatment; blocks RYR1
Intralipid (LAST)	1.5 mL/kg IV bolus	20% lipid emulsion; lipid sink mechanism; NOT propofol
Adrenaline (anaphylaxis)	50 mcg IV boluses OR IM 0.5 mg	Always first-line; antihistamines/steroids are secondary
Bupivacaine max (plain)	2 mg/kg	Most cardiotoxic LA
Lidocaine max (+adrenaline)	7 mg/kg	Fastest onset LA
TOF ratio for extubation	≥0.9	<0.9 = residual NMB → aspiration/hypoxia risk
ARDSNet TV	6 mL/kg IBW	Reduces ARDS mortality
Driving pressure	≤15 cmH₂O	Strongest independent ARDS mortality predictor
MAP target (septic shock)	≥65 mmHg	Noradrenaline first-line vasopressor
Antibiotic timing (sepsis)	Within 1 hour	Each hour delay = +7–9% mortality
CTM height/width	~22 mm / ~9 mm	Incise inferior third only
ETT depth at teeth	21 cm F / 23 cm M	Verify with CXR
Safe apnoea time	~8 min (healthy)	2–3 min in obese/pregnant
RSBI for extubation	<105 (RR ÷ TV in L)	Predicts SBT success
T4 dermatome	Nipple line	Required block level for Caesarean section
T10 dermatome	Umbilicus	Required for hip/knee replacement, inguinal hernia
RASS target (ICU)	−1 to 0 (light sedation)	Deep sedation increases delirium and mortality
Apfel score ≥3	3-drug PONV prophylaxis	Dexamethasone at INDUCTION; ondansetron at END