Acute effect of plasma exchange on arterial blood pressure and plasma renin activity.

Blood pressure (BP) decreases significantly in patients with immune complex nephritis and hypertension in the course of therapeutic plasma exchange (TPE). To investigate possible underlying mechanisms of this effect, the variations of supine and upright BP and plasma renin activity (PRA) acutely induced by PE (performed by isovolumetric replacement of plasma with 4% albumin in saline solution) were analyzed in six patients. On the average, both supine and upright BP decreased after TPE; however, statistical significance was obtained only for upright systolic BP. Supine and upright PRA did not change significantly, although a clearly blunted response to posture was observed in three patients. The changes of BP induced by TPE were apparently not due to a functional depression of the renin-angiotensin system, since the more marked decrements in BP were observed in the patients with lower basal PRA.