Systemic and Regional Haemodynamic Profile of Diuretics and Alpha- and Beta-blockers. A Review Comparing Acute and Chronic Effects

The influence of the acute and chronic administration of antihypertensive agents on blood flow to various organs which are known targets of hypertension is important in the determination of drug therapy for this disorder. In association with the frequently observed fall in cardiac output and increase in total peripheral resistance in response to acute administration, beta-blockers may induce a decrease in blood flow to the brain and kidney. However, during chronic treatment it has been widely shown that total peripheral resistance returns to pretreatment levels (except for labetalol, a beta-blocker with alpha-blocking properties) whilst renal and cerebral blood flows are unaffected. Although alpha-blockers acutely lower blood pressure and induce a baroreflex-mediated increase in heart rate and cardiac output while not affecting cerebral blood flow, during chronic treatment no change in systemic or cerebral or renal blood flow is observed. Diuretics and dietary sodium restriction, which are the most widely used therapeutic interventions, are usually well tolerated; however, in aged patients in whom renal adaptation to sodium depletion is impaired, deterioration of renal function may be observed.