Calcium does not augment phenylephrine's hypertensive effects.

Ca and phenylephrine, both of which increase mean arterial pressure (MAP), are often administered concurrently during resuscitation of critically ill patients. To determine whether the response to phenylephrine is potentiated by Ca administration, we studied eight adult patients 24 h after aortocoronary bypass surgery. Each patient received three doses of phenylephrine (150, 300, and 450 ng/kg.min), administered both with and without CaCl2 (5 mg/kg bolus followed by a 2-mg/kg.h infusion). Phenylephrine alone at 150, 300, and 450 ng/kg.min increased MAP by 2%, 6%, and 17%, respectively. Ca alone increased serum ionized Ca levels from 1.00 +/- .03 (SEM) to 1.20 +/- .02 mM (p less than .05) and increased MAP from 84 +/- 1 to 90 +/- 2 mm Hg (p less than .05), but had no effect on cardiac index (CI). When administered concurrently with Ca, phenylephrine at 150, 300, and 450 ng/kg.min increased MAP by 6%, 7%, and 13%, respectively. Phenylephrine had no effect on CI, pulmonary capillary wedge pressure, CVP, or heart rate whether or not it was administered with Ca. We conclude that concomitant Ca administration does not augment the hypertensive response to phenylephrine in normotensive patients recovering from open heart surgery.