Shock

Abstract

Shock can be due to a variety of etiologies and is encountered frequently in the Emergency Department, Operating Room, and Pediatric Intensive Care Unit. Parameters of vital signs such as blood pressure, respiratory and heart rates, quality of perfusion, and mental status are frequently incorporated in descriptions of shock. However, the best unifying definition is an acute state of circulatory dysfunction that results in the inability to meet tissue metabolic demands. When dealing with a child in shock, this concept will help guide the evaluation, assessment, and treatment. Of equal importance in treating the patient with shock is time. A rapid evaluation, assessment, and treatment, especially when dealing with hypovolemic or septic shock, are paramount to a favorable outcome.

Appendices

Summary Points

Shock is defined as an acute state of circulatory dysfunction that results in the inability to meet tissue metabolic demands.

Rapid evaluation, assessment and treatment, especially when dealing with hypovolemic or septic shock, are paramount to a favorable outcome.

The initial assessment of a child in shock should include the ABCs.

Unlike adults, children can more easily tolerate circulatory dysfunction, but will decompensate more precipitously once unable to meet their metabolic demands.

In patients with “cold shock,” pulses are diminished, extremities are mottled and cool, and capillary refill is increased to greater than 2 s due to compensatory peripheral vasoconstriction.

Patients with “warm shock” have full and bounding pulses, warm extremities, and brisk capillary refill, due to peripheral vasodilatation from a loss of vasomotor tone.

Management begins with securing an airway, maintaining ventilation, and establishing intravenous access.

Treatment of the child in shock includes rapid fluid resuscitation with crystalloid and, if needed, pressors to support perfusion pressure.

Besides clinical parameters such as heart rate and blood pressure, sensitive measures of tissue perfusion include: capillary refill, urine output, mixed venous oxygen saturation, and lactic acid levels.

Editor’s Comment

A recurring theme in the care of the critically ill child is the need for a calm and systematic approach to the assessment and treatment of the patient in need. All accepted protocols (ACLS, ATLS, PALS) explicitly address the patient in shock. The ABCs should always be assessed first, although, in reality, multiple issues are addressed simultaneously. Most children in shock, unless they respond rapidly to the initial fluid boluses, should be intubated and maintained on mechanical ventilation. After securing the airway and establishing ­adequate ventilation, fluid resuscitation should always be initiated aggressively but judiciously to avoid fluid overload and pulmonary edema. If clinical parameters fail to improve despite seemingly adequate fluid resuscitation, pressors should be considered next; however one must always remember that the goal of therapy is to restore tissue perfusion – any intervention that increases central pressure at the expense of peripheral tissue perfusion will be counter-productive. This is why the use of drugs that induce intense peripheral vasoconstriction (norepinephrine) should be considered only as a last resort, if ever.

Given their characteristic clinical presentations, the common causes of shock (sepsis, hypovolemia, anaphylaxis) and even the less common causes (cardiogenic, neurogenic) are usually fairly easy to spot, especially when the history is known. However, there are rare causes of shock that should be considered when the presentation is not so clear-cut. Spontaneous pneumothorax, typically occurring in tall, lanky teenagers who smoke, can occasionally result in tension pneumothorax and shock. Careful physical examination and immediate thoracostomy can be life-saving (there is no time for a chest X-ray). Pericardial tamponade is also quite rare but should be considered in the child who presents with what otherwise appears to be cardiogenic shock. Physical examination (muffled heart sounds, pulsus paradoxus) and ultrasound (FAST) should be used to confirm the diagnosis. Occult bleeding can cause hypovolemic shock after traumatic injury (scalp laceration, femur fracture, hemothorax), or in association with a GI source (esophageal varices) or massive hemolysis (toxins, rare infections). It is also easy to underestimate the ability of severe dehydration to cause shock in a child. Finally, children with severe respiratory compromise and hypoxia will eventually exhibit signs of cardiovascular collapse if not treated quickly and appropriately: yet another reminder that attention to the ABCs is vitally important in these cases.