1. The effect of acute hypercalcaemia on blood pressure, blood volume, haemodynamic indices, plasma catecholamines, renin and aldosterone levels was investigated in 10 patients.

2. Calcium infusion (15 mg/kg over 3 h) increased (P<0.05) plasma calcium and adrenaline levels, blood pressure, total peripheral resistance and packed cell volume. Plasma volume was decreased, and heart rate, cardiac output and plasma renin, aldosterone or dopamine levels were not significantly changed. Plasma noradrenaline was increased only minimally after 3 h of calcium infusion.

3. Mean blood pressure before and during calcium infusion correlated with concomitant serum calcium (r = 0.39; P<0.02) or adrenaline levels (r = 0.57; P<0.01); changes in blood pressure correlated with variations in plasma adrenaline (r = 0.68; P<0.001).

4. Acute hypercalcaemic hypertension is mediated by an increase in peripheral vascular resistance and may be induced by a direct effect of calcium on blood vessels. The calcium-mediated increase in adrenaline release may play a contributory, and plasma volume contraction an inhibitory, role.

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