Airway

The ability to speak or cry without stridor indicates a patent airway. The presence of adequate breathing as assessed by looking at chest wall movement, listening and feeling for exhaled air also indicates an adequate airway.

Generally, shock affects the airway by reducing conscious level. In acute allergic reaction, airway obstruction (by swelling in the upper airway) and shock due to changes in vascular tone, can both arise as part of the same process.

Breathing

The effort of breathing, efficacy of breathing and effects of inadequate respiration should be examined. Oxygen saturation and respiratory rate should be monitored.

Circulation

This is the crux of shock assessment since homeostatic mechanisms function particularly well in children and compensation for inadequate circulatory function is good. Consequently, in a child it can be difficult to detect circulatory failure until a late stage, hence one needs to be vigilant in detecting the earlier features of compensating shock.

Circulatory assessment should look at both circulatory status and also at the effects of inadequate circulation on other organ systems.

Heart rate and blood pressure are the classical measures of circulatory status but changes in skin perfusion (as shown by capillary refill and by skin pallor or temperature) can be more useful in detecting the early signs of compensated shock.

Heart rate

Tachycardia (relative to age norm) is a key sign of shock (see Chapter 1.1). This tachycardia is a homeostatic response to maintaining cardiac output. Bradycardia may occur pre-terminally in the child with overwhelming shock, and untreated will progress to asystole. The peripheral pulses may be weak, thready or absent.

Blood pressure

While it is true that a child with hypotension is shocked it is not true to say that a child that is normotensive is not shocked. This is because maintenance of blood pressure is the key end point of the homeostatic response, and decompensation (and thereby hypotension) occurs late and may be precipitous. The accurate measurement of blood pressure in a distressed child can be a challenge in itself and a judgement as to whether a particular blood pressure is normal or abnormal in a particular age group in any particular circumstances is also challenging. Many widely quoted normal ranges by age are broad – furthermore many of these were derived in the resting outpatient child rather than in the seriously ill or injured child.

Capillary refill

The capillary refill time is measured by applying pressure to the nail bed or other area with visible circulation for some five seconds and then measuring the length of time it takes for the blanching to disappear. Central capillary refill such as over the sternum is more reliable than the peripheries which can be influenced by vasoconstriction due to the ambient temperature effects. A capillary refill time of less than two seconds is normal. A capillary refill time of greater than four seconds is definitely abnormal. Capillary refill between two and four seconds should prompt further consideration of the presence of shock.

Changes in peripheral circulation (which are brought about by an increase in catecholamines) may also show as an increased core to periphery temperature difference (more than 2°C is a sign of poor perfusion) or as a noticeable centripetal temperature gradient. Reduced skin perfusion may result in a mottled, cyanosed, pale appearance and coolness on palpation. Some infants have physiological mottling (cutis marmoratum) in the first months of life due to ‘immaturity’ of the autonomic control of skin vessels, which commonly occurs with exposure. One must clarify with parents whether this mottled appearance is ‘more than usual’ in their child, as infants with cutis marmoratum will become more mottled if they have an accompanying illness causing shock.