Inadequate tissue perfusion, recognised before hypotension appears
Expansion
Early (compensated) signs, before the blood pressure falls
- Tachycardia
- Narrowed pulse pressure
- Cool peripheries, prolonged capillary refill over 2 seconds
- Tachypnoea
- Anxiety, restlessness, then confusion
- Reduced urine output
- Rising lactate
Classifying by the periphery
- Cold and clammy: vasoconstricted, so a low output state. Hypovolaemic, cardiogenic or obstructive
- Warm and flushed with bounding pulses: vasodilated, so distributive. Septic, anaphylactic or neurogenic
Then distinguish within the cold group by filling: a low JVP suggests hypovolaemia; a raised JVP suggests cardiogenic or obstructive, and the latter is suggested by tracheal deviation, absent breath sounds, muffled heart sounds or pulsus paradoxus.
Neurogenic shock is the exception to the tachycardia rule: hypotension with bradycardia and warm peripheries after a high cord injury.
The most important practical point is that young patients compensate extremely well, maintaining a normal blood pressure until they have lost 30 per cent or more of their blood volume, then decompensating abruptly. Trusting the blood pressure in a young trauma patient is a classic and dangerous error.