Hypocalcemia: A pervasive metabolic abnormality in the critically ill

Abstract

Hypocalcemia has been reported in critically ill patients, most commonly in association with sepsis syndrome. However, the severity and incidence of hypocalcemia in nonseptic but critically ill patients has not been well defined. Therefore, the goal of this study was to identify and compare the frequency and degree of hypocalcemia in critically ill patients with differing underlying illnesses (those admitted to medical, surgical, trauma, neurosurgical, burn, respiratory, and coronary intensive care units [ICUs]; group A; n = 99). Results were compared with the frequency and degree of hypocalcemia in non-critically ill ICU patients (initially admitted to an ICU but dischargd within 48 hours; group B; n = 50) or hospitalized non-ICU patients (group C; n = 50). Incidences of hypocalcemia (ionized calcium [Ca] < 1.16 mmol/L [less than normal]) were 88%, 66%, and 26% for groups A, B, and C, respectively (P < 0.001). In group A, the frequency of hypocalcemia did not depend on the ICU setting or presence of sepsis. However, the occurrence of hypocalcemia correlated with both Acute Physiology and Chronic Health Evaluation II score (r = −0.39; P < 0.001) and patient mortality (eg, hazard ratio for death, 1.65 for Ca decrements of 0.1 mmol/L; P < 0.002). Hypomagnesemia, number of blood transfusions, and presence of acute renal failure were each associated with depressed Ca levels. A weak association (r = −0.12; P = 0.09) was noted between serum Ca level and QT interval. Clinical concern stemming from hypocalcemia was underscored by the substantial use of intravenous (IV) Ca therapy (∼2 to 3 g IV). We conclude that hypocalcemia is extremely common in hospitalized patients (up to 88%) and correlates with severity of illness, but not with a specific illness per se. Whether it directly impacts patients survival remains unknown. Resolution of this issue appears to be critical because of the frequency with which it leads to high-dose IV Ca therapy.