Critical Care and Emergency Internal Medicine
The critical care block asks for rapid haemodynamic classification, lung-protective ventilation, and antidote-level knowledge of toxidromes.
Shock
Classify haemodynamics: hypovolaemic (low filling pressures, low cardiac output), cardiogenic (high filling pressures, low output), distributive (low systemic vascular resistance), obstructive (high filling pressures with low output). Norepinephrine is first line for vasodilatory shock; add vasopressin and consider hydrocortisone in refractory septic shock.
ARDS
Berlin definition: onset within 1 week, bilateral opacities, not explained by cardiac failure, and PaO2/FiO2 <300 on PEEP ≥5 cmH2O. Ventilate at 6 mL/kg predicted body weight, keep plateau pressure <30 cmH2O, accept permissive hypercapnia, and prone the patient when PaO2/FiO2 <150.
Toxidromes
- Opioid: pinpoint pupils, respiratory depression - naloxone.
- Anticholinergic: hot, dry, flushed, mydriatic, delirious - supportive care, physostigmine in selected cases.
- Cholinergic: salivation, lacrimation, urination, diarrhoea, bronchospasm - atropine plus pralidoxime.
- Tricyclic overdose: wide QRS and hypotension - sodium bicarbonate.
Post-arrest care
Targeted temperature management at 32-36°C for at least 24 h in comatose survivors, avoid fever, maintain MAP ≥65 mmHg, and treat seizures.
Worked example
A 24-year-old after a tricyclic overdose has QRS 130 ms and BP 80/50. Give IV sodium bicarbonate boluses of 1-2 mEq/kg, titrated to QRS narrowing and pH 7.45-7.55, and avoid class IA and IC antiarrhythmics. Reasoning: the wide QRS reflects sodium-channel blockade, so sodium loading and alkalinisation are the specific therapy rather than vasopressors alone.
Traps that cost marks
- Using 10-12 mL/kg tidal volumes in ARDS.
- Choosing fluid boluses as first-line therapy in cardiogenic shock.
- Giving flumazenil in a mixed overdose, which can precipitate seizures.