A 42-year-old man sustains a gunshot wound to the abdomen and is in shock. Multiple units of packed red blood cells are transfused in an effo to resuscitate him. He complains of numbness around his mouth and displays carpopedal spasm. An electrocardiogram demonstrates a prolonged QT interval. Which of the following is the most appropriate treatment?

Hypocalcemia is associated with physical findings including spasm of the muscles of the forearm and hand when a blood pressure cuff is inflated (Trousseau sign) and spasm of the facial muscles when the facial nerve is stimulated (Chvostek sign). Hypocalcemia is also associated with a prolonged QT interval and may be aggravated by both hypomagnesemia and alkalosis. Additionally, massive transfusion is associated with hypocalcemia secondary to chelation with citrate in banked blood. Severe, symptomatic hypocalcemia, encountered most frequently following parathyroid or thyroid surgery or in patients with acute pancreatitis, should be treated with intravenous calcium gluconate. The myocardium is very sensitive to calcium levels; therefore, calcium is considered a positive inotropic agent. Calcium increases the contractile strength of cardiac muscle as well as the velocity of shoening. In its absence, the efficiency of the myocardium decreases. Hypocalcemia often occurs with hypoproteinemia, even though the ionized serum calcium fraction remains normal.