Biochemical changes associated with thermal biofeedback treatment of hypertension.

Fifty-two hypertensive patients whose blood pressure (BP) was controlled on two medications received either 16 sessions of thermal biofeedback (n = 30) for hand warming or 8 sessions of progressive muscle relaxation (n = 22) prior to medication withdrawal. A number of biochemical measures, including plasma norepinephrine (NEPI) (supine and standing), plasma renin activity, plasma aldosterone, and urinary sodium and potassium, were taken before treatment and after treatment while medication remained constant. Results for the biofeedback-treated patients showed significant reductions in mean arterial pressure as well as in both supine and standing NEPI, while the other biochemical measures were unchanged. There were no significant changes on any variable for the relaxation-treated patients. Although the group data support a reduction in peripheral sympathetic tone as associated with the decrease in BP for the thermal biofeedback condition, dose-response relations were not significant.