Anaphylactic shock in rats is characterized by antigen-induced hepatic venoconstriction and the resultant portal hypertension. We determined the role of portal hypertension in anaphylactic hypotension by using the side-to-side portacaval shunt- and sham-operated rats sensitized with ovalbumin (1 mg). We measured the mean arterial blood pressure (MAP), portal venous pressure (PVP), and central venous pressure (CVP) under pentobarbital anesthesia and spontaneous breathing. Anaphylactic hypotension was induced by an intravenous injection of ovalbumin (0.6 mg). In sham rats, the antigen caused not only an increase in PVP from 11.3 cmH(2)O to the peak of 27.9 cmH(2)O but also a decrease in MAP from 103 mmHg to the lowest value of 41 mmHg. CVP also decreased significantly after the antigen. In the portacaval shunt rats, in response to the antigen, PVP increased slightly, but significantly, to the peak of 17.5 cmH(2)O, CVP did not decrease, and MAP decreased to a lesser degree with the lowest value being 60 mmHg. These results suggest that the portacaval shunt attenuated anaphylactic portal hypertension and venous return decrease, partially preventing anaphylactic hypotension. In conclusion, portal hypertension is involved in rat anaphylactic hypotension presumably via splanchnic congestion resulting in decreased venous return and thus systemic arterial hypotension.
Anaphylaxis Anesthesia