Peripheral vascular tone in patients with cirrhosis: role of the renin-angiotensin and sympathetic nervous systems.

Abstract

The aims of the study were to establish the roles of angiotensin II and of the cardiopulmonary baroreceptor reflex in the regulation of peripheral vascular tone in patients with cirrhosis. Forearm blood flow responses to subsystemic, locally active intrabrachial infusions were measured in patients with Child's Grade C cirrhosis and matched controls using bilateral venous occlusion plethysmography. Responses were determined to the angiotensin II type I receptor antagonist, losartan, noradrenaline, angiotensin II and the nitric oxide synthase inhibitor, L-NG-monomethyl arginine. Losartan at 30 and 90 micrograms/min caused no significant change in blood flow in controls, but caused 23 +/- 6% and 27 +/- 5% increases in patients respectively (p < 0.001). Lower body negative pressure caused a mean bilateral reduction in forearm blood flow of 20 +/- 4% in controls (p < 0.001) but only tended to reduce flow (9 +/- 5%; p = 0.06) in patients (p < 0.001; controls vs. patients). Noradrenaline, angiotensin II and L-NG-monomethyl arginine caused significant vasoconstriction (p < 0.001) in both patients and controls although angiotensin II caused significantly less vasoconstriction in patients (p = 0.01). We conclude that angiotensin II makes an important contribution to basal peripheral vascular tone in patients with cirrhosis in the face of reduced vascular responses to its local administration. In addition, the vasoconstrictor response to cardiopulmonary baroreceptor unloading is attenuated despite normal vascular responses to noradrenaline. These responses are consistent with chronic activation of the renin-angiotensin and sympathetic nervous systems in patients with advanced cirrhosis.