Enterohepatic haemodynamics in calves during acute systemic anaphylaxis

This study was designed to investigate the splanchnic congestion and gastrointestinal lesions frequently found in calves during anaphylaxis. Calves were sensitised to horse serum and the following cardiovascular parameters monitored; carotid arterial pressure, mesenteric arterial pressure, mesenteric venous pressure, mesenteric arterial flow, and abdominal venous pressure. Responses to histamine, 5-hydroxytryptamine (5HT), bradykinin, dopamine, noradrenaline and horse serum were recorded. Anaphylaxis was characterised by a diphasic arterial hypotension, a parallel rise in mesenteric venous pressure, a fall in mesenteric arterial flow and a threefold rise in mesenteric vascular resistance. It is suggested that during anaphylaxis a rise in hepatic vascular resistance occurs, resulting in pooling of blood in the venous side of the mesenteric vasculature and possibly in the liver itself. This increase in hepatic resistance may be caused by circulating vasoactive agents released by the anaphylactic process, a local Schultz-Dale type reaction, or a reflex triggered by systemic baroreceptors.