Correlation of forearm vascular and catecholamine responses of hypertensive patients to baroreceptor stimulation

Abstract

The relationship between changes in forearm vascular hemodynamics and plasma catecholamine levels during the performance of the Valsalva maneuvre by pretrained hypertensive patients was examined. Eleven mild to moderate hypertensives (supine diastolic pressures from 95 to 105 mmHg), experienced in the consistent performance of the Valsalva maneuvre, had their previous medications withdrawn over a period of one week and were then administered placebo twice daily for the next four weeks. At the end of this period, and 3 h after the last dose of placebo, each patient had a retrograde catheter inserted into an antecubital vein followed by a 30 min rest period in the supine position. Blood was sampled for resting catecholamine determination, followed by measurement of resting systolic and diastolic blood pressures together with forearm bloodflow. Each patient then performed the Valsalva maneuvre (40 mmHg, 40 s) with continuous recording of heart rate. Forearm bloodflow was again recorded after 25 s of straining while blood was sampled at the point of bradycardia after straining. During a duplicate Valsalva maneuvre, systolic and diastolic blood pressures were recorded after 30 s of straining. All patients exhibited the appropriate heart rate responses to the Valsalva maneuvre (resting 76 +/- 15 beats/min; tachycardia 101 +/- 13, P less than 0.001; bradycardia 65 +/- 18, P less than 0.01). Forearm bloodflow was reduced (P less than 0.001) during the maneuvre while mean arterial pressure (P less than 0.001), forearm vascular resistance (P less than 0.001), plasma noradrenaline (P less than 0.001) and adrenaline (P less than 0.05) levels were all increased.(ABSTRACT TRUNCATED AT 250 WORDS)