Vasodilation due to impaired vascular tone is common in liver failure. Vasoconstrictor drugs are almost always required during the anhepatic phase of a liver transplant to maintain blood pressure unless venovenous bypass is employed. Arginine-vasopressin can be used as a vasoconstrictor instead of or in addition to norepinephrine for this purpose, but the effect of vasopressin on the portal vein pressure and flow in this setting is unknown. Portal vein pressure, portal vein blood flow, hemodynamic variables, and plasma vasopressin levels were measured in 16 patients during liver transplantation after ligation of the hepatic artery before and after a vasopressin infusion of 3.8 ± 1.1 units/hour. Measurements were performed on the native liver prior to caval clamping. After vasopressin infusion, the portal vein pressure decreased significantly from 24.0 ± 6.5 to 21.5 ± 7.4 mm Hg [mean ± standard deviation (SD), P = 0.006]. The portal vein blood flow also decreased (from 1.01 ± 0.53 to 0.76 ± 0.53 L/minute, mean ± SD, P < 0.0001), as did the portal vein blood flow to cardiac output ratio (from 0.14 ± 0.06 to 0.10 ± 0.07, mean ± SD, P < 0.0001). In conclusion, vasopressin significantly decreased portal vein pressure and flow of the native liver without decreasing cardiac output or intestinal perfusion in patients undergoing liver transplantations.
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