THE EFFECT OF NITRIC-OXIDE SYNTHASE INHIBITION ON PORTAL PRESSURE ANDAZYGOS BLOOD-FLOW IN PATIENTS WITH CIRRHOSIS

It has been proposed that the hyperdynamic circulation found in cirrho sis is mediated by nitric oxide released through the induction of nitr ic oxide synthase. To investigate this the effect of the nitric oxide synthase inhibitor, N-G-monomethyl-L-arginine (L-NMMA), was studied up on the portal circulation. After a 30-min infusion of 3 mg/kg of L-NMM A there was a significant fall in heart rate from 83.2+/-4.4 to 74.2+/ -3.9 bpm (p=0.005), and a significant rise in mean arterial pressure f rom 91.6+/-2.2 to 103.7+/-3.2 mmHg, p=0.004). There was, however, no c hange in hepatic venous pressure gradient (16.7+/-1.5 to 16.1+/-1.7 mm Hg, p=0.477) nor in azygos venous blood flow (366+/-26 to 368+/-145 ml /min, p=0.683). On subgroups analysis by Child-Pugh grade, significant changes occurred in heart rate and mean arterial pressure only in gra de A and B patients (p=0.0061 and p=00068, respectively). Regional per ipheral blood how was studied using hand thermography, All patients wh o had anisothermic hands (relatively cold fingers compared to palmar t emperature) at the start of the study developed an isothermic pattern after the L-NMMA infusion. This study demonstrates a significant syste mic effect of nitric oxide synthase inhibition in patients with cirrho sis but no effect upon the portal or portosystemic collateral circulat ions at this dose.