Haemodynamic effects of loud noise in hypertensive patients treated with combined beta-adrenoceptor blockade and precapillary vasodilatation.

The effects of acute exposure to noise on central and regional (calf and forearm) haemodynamics were studied during placebo therapy and during combined nonselective beta-adrenoceptor blockade and precapillary vasodilatation in 9 patients with essential hypertension. On placebo therapy a loud noise (105 dBA for 10 min) caused a significant increase in diastolic and mean arterial pressure due to vasoconstriction. There was also a significant increase of vascular resistance in the calf. After combined precapillary vasodilatation and non-selective beta-adrenoceptor blockade, the increase in blood pressure during stimulation with noise was not prevented. Thus, systolic as well as diastolic and mean arterial pressures increased significantly. This indicates a temporary resetting of the baroreceptors, allowing a higher level of blood pressure during stimulation with noise. Such a resetting would involve the central nervous system pathways of the baroreflex and this would explain why the peripherally active therapeutic principle--precapillary vasodilatation and beta-adrenoceptor blockade--was unable to inhibit the blood pressure response induced by noise.