Emergency Medicine

16 Critical Care Emergencies

SHOCKED PATIENT

end in cardiac arrest with pulseless electrical activity. Once shock

deteriorates to this degree, it is difficult or impossible to reverse.

2 Aim to identify abnormal tissue perfusion early, ideally before the systolic

blood pressure (SBP) drops, treat aggressively and avoid the irreversible

phase. Investigation and treatment are concurrent – get senior help early.

(i) A normal blood pressure does not exclude the diagnosis of shock.

(ii) The absolute value of the SBP associated with poor perfusion

varies greatly, but an SBP <90 mmHg is usually insufficient to

maintain adequate vital organ perfusion.

3 Consider causes in four broad categories (see Fig. 1.2). Often more than one

mechanism is present:

Cardiogenic shock

Depressed contractility

Acute coronary syndrome

Myocarditis

Cardiomyopathy

Drug toxicity

Acute valvular dysfunction

Arrhythmia

Bradyarrhythmia

Tachyarrhythmia

Obstructive shock

Pulmonary embolism

Tension pneumothorax

Traumatic

Non-traumatic

Cardiac tamponade

Traumatic

Non-traumatic

Dynamic hyperinflation

Hypovolaemic shock (most common)

Haemorrhage

Traumatic























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Non-traumatic







External (revealed)







Internal (concealed)

Non-haemorrhagic

External fluid loss

Distributive shock

Anaphylaxis

Sepsis

Neurogenic

Drug related

Acute adrenal

insufficiency

Figure 1.2 Different types of shock.