Depressor Effects of Ionized Calcium Infusion in Essential Hypertension

Abstract

The circulatory effects of an acute increase in serum ionized calcium were assessed in 27 patients with mild to moderate hypertension. Following a control period of fifteen minutes with confirmed circulatory variables, 1,375 mg calcium gluconate was infused over three minutes. Systemic mean arterial blood pressure and heart rate were recorded before, at one-minute intervals during, and for five minutes following the infusion. There was a brief increase of serum ionized calcium concentration (from 1.28±0.06 mmol/liter to 1.42±0.07 mmol/liter; p < 0.001) maximum by one minute after infusion with return toward control by a further four minutes. This was accompanied by a significantly decreased mean arterial blood pressure (from 117±8 mmHg to 110±9 mmHg at three minutes; p < 0.05) and heart rate (from 70±11 min-1 to 63±10 min-1 at three minutes; p < 0.01). There was a significant correlation between the change in ionized calcium and that of the systemic arterial blood pressure (r=0.68; p < 0.01). No major side effects were recorded. The blood pressure reduction may theoretically be related to increased membrane stabilization of vascular smooth muscle cells, the acute increase in extracellular ionized calcium impairing calcium ions influx.