To assess the acute effects of alcohol on baroreceptor reflex in moderate and heavy drinkers with essential hypertension and in healthy subjects who drank moderately, four groups of age and sex matched subjects were studied. Group 1 consisted of 10 healthy subjects (age range 21–50 (mean 37.4(10.5) years), who usually drank <200 g of alcohol per week; group 2 patients (age range 21–50 (mean 37.4(10.3) years) with mild or moderate essential hypertension and whose weekly alcohol consumption was <200 g; and groups 3 and 4 patients with mild or moderate hypertension (age range 21-50 (mean 37.2(10.2) years and 21-52 (mean 38.1(10.4) years respectively), who usually drank >700 g of alcohol per week. In groups 1-3 an infusion of alcohol (7 mg·kg−1·min−1) in 500 ml of 5% glucose was administered for 1 h to keep blood concentrations constant (6–7 g·litre−1), whereas in group 4 the dose was doubled (blood concentration 10–11 g·litre−1). Baroreceptor sensitivity was measured by the phenylephrine method before and after alcohol infusion and one or two days later before and after infusion of 500 ml of 5% glucose. In healthy subjects and in moderate drinkers with hypertension the alcohol reduced baroreflex sensitivity significantly (from 17.5(9.5) to 13.8(8.4); p <0.01 and from 15(10) to 10.5(6.7) ms·mmHg−1, p <0.01 respectively), whereas in the heavy drinkers with hypertension it was significantly reduced only at the highest dose of alcohol (from 12.5(6) to 7.9(3.5) ms·mmHg−1; p <0.02). Blood pressure and heart rate were unchanged in all groups during alcohol infusion.
These data show that alcohol, administered acutely, reduces baroreflex sensitivity before any change of blood pressure and heart rate occurs.