Hypocalcemia

In the operating room, hypocalcemia is most commonly caused by acute hyperventilation or the infusion of citrated blood in excess of 1.5 mL/kg/min. The most common cause of hypocalcemia (plasma concentration less than 4.5 mEq/L) in hospitalized patients is a low albumin level, such as in critically ill patients with severe sepsis, burns, or acute renal failure and in patients after extensive transfusions. Many critically ill patients have low plasma albumin and low plasma calcium levels with normal ionized calcium levels.^[51] There is no reason to correct the calcium deficiency, but overall nutrition should be improved. The major signs and symptoms of hypocalcemia include mental status changes, tetany, positive Chvostek and Trousseau signs, laryngospasm, hypotension, and dysrhythmias. Electrocardiographic evaluation may show prolongation of the QT interval or even heart block in severe cases. Treatment involves intravenous infusion of 10% calcium chloride (1.36 mEq/mL) or calcium gluconate (0.45 mEq/mL). When equivalent calcium doses are administered, both preparations are equally efficacious in restoring the calcium level to normal ( Table 46-12 ).

When hypocalcemia is caused by large-volume infusion of isotonic saline (as seen during resuscitation in shock), it may be accompanied by hypomagnesemia. Hypomagnesemia may impair the actions of vitamin D

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