Critical Care
Critical care questions test ventilator strategy, sedation targets, shock management and the definitions that drive ICU management.
ARDS
The Berlin definition requires onset within one week, bilateral opacities not fully explained by effusion, collapse or nodules, respiratory failure not primarily cardiogenic, and a PaO2/FiO2 ratio of 300 or less on PEEP of at least 5 cmH2O. Use lung-protective ventilation with tidal volumes of 6 mL/kg predicted body weight and plateau pressure below 30 cmH2O. Prone positioning for at least 16 hours per day improves survival when PaO2/FiO2 is below 150.
Sedation and delirium
Target a light level of sedation (RASS −2 to 0), use daily interruption, and prefer analgesia-first strategies. Delirium is associated with worse outcomes; non-pharmacological bundles are first line.
Shock and vasopressors
Norepinephrine is first-line; add vasopressin to reduce noradrenaline dose, and consider hydrocortisone for refractory septic shock.
Glycaemic control
Target 140–180 mg/dL; tight control increases hypoglycaemia without benefit.
Worked example
A patient with pneumonia has PaO2/FiO2 of 120 on PEEP 10 with bilateral infiltrates and no heart failure. This is moderate-to-severe ARDS: set tidal volume 6 mL/kg predicted body weight, keep plateau below 30, and prone for 16 hours.
Traps that cost marks
- Using actual rather than predicted body weight for tidal volume.
- Deep sedation as a default.
- Chasing normoglycaemia at the cost of hypoglycaemia.