Hypocalcemia is common in the
critically ill patient. In this population, however, the diagnosis of
hypocalcemia is complicated by limitations in the interpretation of the total plasma
calcium concentration. These limitations are principally the result of the effects of
hypoalbuminemia and disorders of acid-base balance on the total
calcium concentration. Thus, measurement of ionized
calcium can be critical in determining an individual's true serum
calcium status. In this review, we first describe the regulation of normal
calcium metabolism and then focus on the various etiologies of
hypocalcemia, including congenital and acquired disorders of
parathyroid hormone and
vitamin D, which are encountered in the neonatal, pediatric, and adult
critical care settings. The approach to the treatment of
hypocalcemia and the current consensus on treatment of
hypocalcemia in the
critically ill patient is also presented.