CLINICAL PRESENTATION OF SHOCK

Signs of poor tissue perfusion include:

• Cold peripheries (except in the earlier stages of septic shock)
• Prolonged capillary refill time (>2s)
• Inability to get a pulse oximeter trace
• Tachycardia
• Tachypnoea
• Poor urine output (indicating poor renal perfusion)
• Agitation/Obtundation (indicating poor cerebral perfusion)
• Lactic acidosis
• Hypotension (pre-terminal sign)
• Bradycardia (pre-terminal sign)

Tachycardia and tachypnoea are relatively early signs of shock whereas a lactic acidosis and hypotension are late signs. Two of the earliest organs to suffer the effects of tissue hypo-perfusion are the kidneys and brain. Decreased urine output and decreased conscious level are therefore early indicators of hypo-perfusion and end organ disorder.

Hypotension is a pre-terminal sign.  This doesn't mean that blood pressure is not a useful physiological observation. It should be performed and reviewed regularly. 

Hypovolaemic shock

If there is volume depletion the child may complain of thirst and have cold and clammy peripheries and a decreased capillary refill time. There may be a history of blood loss (e.g. gastrointestinal bleed, recent surgery or trauma) with a resultant drop in haemoglobin levels, or evidence of increased fluid losses (e.g. diarrhoea, vomiting or losses due to small bowel obstruction). Iatrogenic factors may contribute to hypovolaemia due to inadequate fluid prescription or inappropriate use of diuretics.

Septic shock

Septic shock will have many of the features common to other types of shock but with some important differences, which will help to differentiate it from other causes. Children with sepsis often present with a fever, tachycardia but feel warm to touch with a bounding pulse due to the raised cardiac output in the early stages.  In younger children warm shock is relatively uncommon and cold shock is far more commonly seen.

Cardiogenic shock

The clinical features of cardiogenic shock are similar to hypovolaemic shock. There is loss of cardiac output due to reduced contractility (rather then reduced preload seen in hypovolaemic shock) with a resultant increase in SVR due to circulating catecholamines. Therefore features include cold clammy peripheries, reduced capillary refill and other signs of reduced tissue perfusion.  These infants often appear "grey" and their peripheries are very cold, making cannulation difficult to impossible.
A careful history and examination will help to elicit the cause with additional information gained from an ECG or echocardiogram.

Obstructive shock

Tension pneumothorax may well be diagnosed during your assessment of the Breathing part of ABCDE, but often hypotension is a predominant feature. Cardiac tamponade is rare and difficult to diagnose. It occurs when fluid accumulates within the pericardial space faster than the sac can stretch, causing back pressure on the heart.

Table: Physiological changes in shock