Hepatic microvascular pressure during circulatory shock

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The main purpose of this study is to measure the hepatic microvascular pressure during circulatory shock in anesthetized rats. The transmural pressure (Pμhv) of the hepatic venule (the diameter 30-50μm) at the liver surface was measured, using a servonull micropipette pressure-measuring system. At first, we compared Pphv with the hepatic occlusion pressures determined with the hepatic vascular occlusion methods developed by the authors (Am. J. Physiol. 286:H121-H130, 2004) in isolated perfused rat livers during the basal states and hepatic venoconstriction induced by norepinephrine, increased blood flow and hepatic anaphylaxis. We found that Pphv is close to the double ooclusion pressure rather than the hepatic venous occlusion pressure. The second, we measured Pphv during anaphylactic hypotension in anesthetized rats. Anaphylactic hypotension was induced by an intravenous injection of 0.6 mg ovalbumin. When the antigen was injected, the systemic arterial pressure decreased profoundly … More to approximately 45 mmHg, which was accompanied by an increase in Ppv and Pphv: Pphv only transiently increased by 5.7 cmH_2O at lmin and then rapidly returned to the baseline within 2 min, when Ppv continued to increase and reached the peak of 36 cm H_2O at 3.5 min. This indicated that the constriction of the portal veins and the sinusoids much predominate over that of the hepatic veins. Along with this hepatic pre and sinusoidal constriction, the liver lobe thickness significantly decreased by 4% after antigen. Presinusoidal constriction during anaphylactic shock in anesthetized rats increased the portal venous pressure while the hepatic venular pressure only increased slightly and transiently. This predominant presinusoidal constriction is accompanied by a passive decrease in liver volume. Finally, we measured Pphv during endotoxin shock in anesthetized rats. Similar to anaphylactic hypotension, only transient and small increase in Pμhv was observed in response to an intravenous injection of E. coli endotoxin (10〜30mg/kg), indicating that the presinusoidal constriction was predominant during endotoxin shock in anesthetized rats. Less