Portal pressure reduction induced by partial mechanical obstruction of the superior mesenteric artery in the anesthetized dog.

In an effort to avoid the potentially dangerous side effects of vasopressin infusions, we attempted to reproduce mechanically the splanchnic hemodynamic changes induced by vasopressin without its systemic effects. Superior mesenteric arterial pressure was reduced to 50 to 70 mm Hg for 30 to 60 min in 10 normal dogs by partial balloon obstruction of the superior mesenteric artery. Balloon inflation caused a decrease in portal venous pressure (5.6 +/- 0.6 versus 2.8 +/- 0.7 mm Hg), hepatic vein wedge pressure (4.8 +/- 0.4 versus 2.3 +/- 0.5 mm Hg), and portal vein flow 424 +/- 53 versus 275 +/- 52 ml per min), and an increase in hepatic arterial blood flow (172 +/- 19 versus 217 +/- 29 ml per min). Total hepatic blood flow and oxygen delivery to the liver were unchanged. Partial balloon obstruction caused an increase in cardiac output (1950 +/- 203 versus 2317 +/- 376 ml per min) and mean arterial pressure 138 +/- 6 versus 151 +/- 7 mm Hg), whereas heart rate did not change. Partial balloon obstruction of the superior mesenteric artery caused similar changes in splanchnic hemodynamics to those of vasopressin infusions into the superior mesenteric artery, but without the potential deleterious effects of vasopressin on systemic hemodynamics.