[Vascular hyperreactivity to vasopressin in mild essential arterial hypertension].

The aim of the present study was to evaluate the hemodynamic effects of arginine vasopressin (AVP) infusion in essential hypertension. To this end, 9 hypertensive patients and 10 normotensive controls were evaluated. After one hour rest, AVP was infused at a dosage of 0.5 and 2 ng/(kg/min), in 20 minutes periods. After AVP infusion, mean arterial pressure increased only in hypertensive patients (from 125.8 +/- 7 to 131.8 +/- 7, p less than 0.01 and to 135.6 +/- 6 mmHg, p less than 0.01). Peripheral vascular resistance was significantly increased in both groups during AVP infusion, although the percent increase was higher in hypertensive patients during the last period of infusion (18.3 +/- 10 versus 4.6 +/- 4, p less than 0.05). Cardiac index decreased in both groups during infusion, although this reduction was significantly higher in hypertensive patients than in healthy controls in the last period of infusion (-8.16 +/- 6 versus -1.8 +/- 4%, p less than 0.05). These results confirm that in essential hypertension there is an exaggerated pressor response to AVP infusion, suggesting that it is due to an increased vascular response to this hormone. The compensatory reduction of cardiac output and the inhibition of sympathetic nervous activity mediated through baroreceptor reflexes do not apparently play a role in this pressor response.