There has been a resurgence of interest in peripheral circulation with the introduction of newer vasodilators that are being used and investigated in the management of disease states such as systemic hypertension, angina pectoris, acute and chronic congestive heart failure, valvular heart disease, cardiomyopathies, and limitation of infarct size.
The systemic blood pressure is a product of cardiac output (CO) and systemic vascular resistance (SVR). The principal abnormality in essential and renal vascular hypertension is increased SVR. Elevation in blood pressure initiates a vicious cycle that further increases vascular resistance associated with fibrinoid changes in medium-sized arterioles and impairment of organ function affecting most prominently the kidney, heart, and brain. It is comforting to note that even in hypertensive emergencies the SVR and systemic blood pressure can be reduced by the administration of vasodilators such as sodium nitroprusside and diazoxide. These agents decrease arterial tone by direct action on smooth