Calcium administration for cardiovascular support in critically ill patients: when is it indicated?

Calcium has a fundamental role in the maintenance of myocardial function and vascular tone. The ionized form of calcium is the most important physiologically, and this form needs to be measured to assess physiologically active calcium levels. Ionized hypocalcemia can occur as a result of various pathophysiological disturbances, and it is seen frequently in critically ill patients. Several investigators have observed a poorer prognosis in those patients with ionized hypocalcemia. It is unclear whether calcium supplementation is beneficial in these patients. It may improve cardiovascular performance, but, in contrast, it may contribute to cellular damage (especially during hypoxia following cardiopulmonary resuscitation). In sepsis, there may be an increased cellular influx of calcium, which may be deleterious to cellular function; indeed, calcium entry blockers in this situation may be protective. We review the role of calcium as an inotropic agent, its interaction with other inotropic agents, and its use during blood transfusion and during cardiopulmonary resuscitation.