Experimental mesenteric ischaemia in sheep: gut peptide release and haemodynamic changes

Mesenteric ischaemia remains a frequently lethal condition. An improvement in survival is only likely with earlier diagnosis. Even with action upon early diagnosis and re-establishment of circulation, fatal shock often follows. This study was designed to determine the possible role of gastrointestinal regulatory peptides in the haemodynamic pathophysiology of acute mesenteric arterial ischaemia and whether measurement of these peptides would have diagnostic potential. Fourteen anaesthetized sheep were studied, seven with acute superior mesenteric artery (SMA) occlusion and seven with acute superior mesenteric and coeliac artery (SMA + CA) occlusion. Changes in peptide levels and haemodynamic changes were similar in the two experimental groups, but were more pronounced in the more severe ischaemia of SMA + CA occlusion. No major changes in systemic plasma gastrin, pancreatic polypeptide, neurotensin and vasoactive intestinal polypeptide (VIP) occurred during ischaemia. There was, however, a five-fold increase in VIP in portal venous plasma during SMA + CA occlusion. In the reperfusion period there were increases in VIP concentrations in both systemic and portal circulations in both groups. During ischaemia there was a rise in mean arterial pressure and peripheral resistance and a fall in cardiac output. Reperfusion was characterized by systemic and splanchnic vasodilation coincident with the rise in systemic plasma VIP. It is concluded that VIP which is released from the ischaemic intestine is likely to mediate a component of vasodilation seen during reperfusion.