Rat Hepatic and Splanchnic Vascular Responses to Anaphylactic Shock, Compared with Hemorrhagic or Vasodilator-induced Shock

Background: Hemodynamics during anaphylactic shock remain unclear. We determined hepatic and splanchnic responses to anaphylactic hypotension, compared with hemorrhage or sodium nitroprusside (SNP)-induced hypotension, in anesthetized rats. Materials and Methods: Portal pressure, systemic arterial pressure (SAP), central venous pressure, portal and hepatic arterial blood flow were measured. Splanchnic (Rspl), portal venous (Rpv), and hepatic arterial (Rha) resistances were determined. Results: In rats with anaphylaxis induced by an intravenous injection of the ovalbumin antigen (n=6), hemorrhage (n=6), and SNP (2 mg/kg, n=6), SAP decreased similarly. During anaphylaxis, Rha and Rspl decreased only at 30 s after the antigen injection. Notably, Rpv increased markedly. During hemorrhage, Rspl and Rha increased and decreased, respectively, with Rpv not changing. After SNP, Rha and Rspl decreased with Rpv not changing. Conclusion: Hepatic and splanchnic vascular responses differ according to the type of shock. Anaphylactic hypotension is characterized by markedly increased portal venous resistance. Splanchnic and hepatic artery dilatation occurs only at the beginning of hypotension in anesthetized rats.