How can shock be recognized?
To recognize shock, consider both the consequences of inadequate perfusion and the patient’s compensatory mechanisms. The clinical manifestations of shock are those of inadequate perfusion and compensation . Inadequate perfusion of the brain results in an alteration in the child’s level of consciousness. Inadequate perfusion of the kidneys results in decreased urine output.
As perfusion decreases, compensatory changes occur. These changes improve delivery of oxygen and nutrients and direct blood flow to the vital organs. The first compensatory mechanism is usually an increased heart rate; tachycardia out of proportion to the child’s clinical picture (i.e., fever, distress) should be a red flag . Because cardiac output is equal to the rate multiplied by the stroke volume, an increased heart rate can maintain cardiac output in the face of decreased stroke volume. Additionally, peripheral vasoconstriction helps to maintain blood flow to the central organs and to the brain. The patient therefore has pale, cool extremities and a delayed capillary refilling time. This increased vascular tone also affects the measured blood pressure. The diastolic pressure is slightly elevated, so the difference between the systolic and diastolic pressures—the pulse pressure—is smaller. This is referred to as a “narrowed” pulse pressure.
To compensate for both the decreased oxygen delivery and the acidosis created by underperfusion of peripheral tissues, the respiratory rate increases. The blood pressure eventually falls, but this is a late, ominous finding and may signal that the shock state is irreversible.