Shock and Critical Care
Recognition
Shock is inadequate tissue perfusion, not a blood pressure. Use three windows - skin (capillary refill, mottling, temperature), brain (mentation, agitation) and kidney (urine output below 0.5 mL/kg/h) - supported by lactate and base deficit. Classify into hypovolaemic, distributive (septic, anaphylactic, neurogenic), cardiogenic and obstructive, because treatment diverges sharply.
Septic shock: take cultures before antibiotics if this causes no delay, give broad-spectrum antibiotics within one hour, 30 mL/kg crystalloid for hypotension or lactate 4 mmol/L or more, then noradrenaline as first-line vasopressor targeting MAP 65 mmHg. Add vasopressin when noradrenaline requirements rise above 0.25–0.5 µg/kg/min.
Anaphylaxis: intramuscular adrenaline 0.5 mg (1:1000) into the anterolateral thigh, repeated every 5 minutes. Antihistamines and steroids are adjuncts, never first-line. Refractory cases need a titrated adrenaline infusion and generous fluid.
Cardiogenic shock: small fluid challenges only, early noradrenaline, inotropes, and urgent revascularisation in infarction. Obstructive shock is a mechanical problem: needle decompression, pericardiocentesis, thrombolysis.
Traps: relying on systolic pressure - young patients compensate until they collapse, and a chronically hypertensive patient can be shocked at a normal reading; giving repeated 500 mL boluses to a failing heart; using central venous pressure to guide fluid; failing to reassess after each bolus with dynamic measures such as passive leg raise, stroke volume variation or focused ultrasound.
Rule of thumb: warm peripheries with a narrow pulse pressure and a raised lactate is early distributive shock, not a reassuring finding.