The blood flow and oxygen consumption of the brain in patients with essential hypertension before and after adrenalectomy.

It has been shown that cerebral oxygen consumption and blood flow are normal and cerebral vascular resistance is increased in patients with essential hypertension (1). Clinicians have questioned the advisability of lowering arterial pressures in hypertensive patients because of the possible untoward effects consequent to decreased cerebral blood flow (2, 3). We have studied the effect of hypotension, induced by various means, on the oxygen consumption and blood flow of the brain. During the hypotension obtained one hour after the injection of dihydroergocornine (4), protoveratrine (5), hexamethonium (6), and 1-hydrazinophthalazine (7), cerebral blood flow and oxygen uptake were unchanged. Cerebral oxygen uptake was unchanged and cerebral vascular resistance was decreased during the hypotension induced by differential spinal sympathetic block (8). After thoracolumbar sympathectomy, cerebral blood flow and oxygen uptake remained constant and the cerebral vascular resistance was reduced toward normal values three weeks to six months after operation (9). Thus, in most of these instances, cerebral blood flow was not reduced and cerebral oxygen consumption remained unchanged when the arterial pressure was lowered either by the drugs tested or by surgical sympathectomy. These hemodynamic observations suggested that the cerebral circulation remains adequate when the blood pressure is lowered. The increased cerebral vascular resistance in hypertension apparently can be reduced by certain measures without reducing cerebral oxygen consumption and cerebral blood flow.