Mechanics of the carotid artery wall and baroreflex sensitivity after acute ethanol administration in young healthy volunteers

The effects of ethanol administered orally (300 mg/kg in 250 ml of water) o r intravenously (7.5 mg(.)min(-1.)kg(-1) in 250 ml of saline over 40 min) o n common carotid haemodynamics, wall mechanics and baroreflex sensitivity w ere compared with the effects of the intravenous infusion of 250 ml of sali ne. Ethanol or saline was administered to 10 healthy volunteers after 30 mi n of supine rest, and measurements were obtained 40 min (median; range 34-4 6 min) after administration. After ethanol administration, the plasma alcoh ol level rose from 0 to 0.3 +/- 0.07 g/l. Mean arterial blood pressure had risen slightly at 20 min, but was normalized by 40 min, the time at which t he haemodynamic study was performed. Heart rate decreased after infusion of either saline or alcohol, but was unchanged after oral ethanol administrat ion. Both oral and intravenous ethanol administration were associated with significant decreases in baroreflex sensitivity, carotid shear stress and b lood velocity, compared with resting values, while the mean carotid artery diameter was increased, and blood viscosity and mean blood flow were unchan ged. No changes were observed in these parameters after saline administrati on. Ethanol, administered either intravenously or orally, increased the sti ffness of the carotid artery and decreased the pulsatility (systo-diastolic changes) of its diameter. A direct, statistically significant correlation was found between the decrease in shear stress and the decrease in barorefl ex heart rate control sensitivity after both modes of alcohol administratio n, while no such correlation was found between the increase in the Peterson elastic modulus and the decrease in carotid diameter pulsatility on the on e hand or the decrease in baroreflex sensitivity on the other. In conclusio n, reduced shear stress associated with vasodilatation of the carotid arter y wall may contribute to the decrease in baroreflex sensitivity observed af ter acute ethanol administration.