Anesthesia and Critical Care: Physiology Under Pressure
This domain tests applied physiology and ventilator management. Understand oxygen delivery, ventilation-perfusion relationships, and the determinants of cardiac output.
Core content
Know the types of shock and their hemodynamic profiles: hypovolemic (low preload), cardiogenic (low output, high filling pressures), distributive (low systemic vascular resistance), and obstructive. Learn mechanical ventilation basics - tidal volume, positive end-expiratory pressure, plateau pressure, and lung-protective strategies. Understand sedation, analgesia, and neuromuscular blockade. Recognize acute respiratory distress syndrome, sepsis, and acute kidney injury in the critically ill. Learn perioperative risk and airway assessment.
Traps
Questions often confuse oxygenation with ventilation: hypoxemia is corrected with oxygen and PEEP, whereas hypercapnia requires increased minute ventilation. Beware of choosing a fluid bolus in cardiogenic shock without addressing the pump. Do not overlook sedation as a cause of hemodynamic instability. Also distinguish permissive hypercapnia from dangerous acidosis.
Rule of thumb
In shock, ask what the preload, contractility, and afterload are doing. In respiratory failure, ask whether the problem is oxygenation or ventilation - the fix differs.
Worked example
A ventilated patient with rising peak pressures, hypotension, and distended neck veins may have tension pneumothorax or auto-PEEP. Immediate decompression or disconnection from the ventilator can be lifesaving before imaging.