Objective: To evaluate the effect of selective intramesenteric artery vasodilator infusion on intestinal viability in a rat model of acute segmental mesenteric vascular occlusion.
Summary background data: Although intramesenteric arterial vasodilator infusion may be an effective treatment for nonocclusive mesenteric ischemia, it has also been advocated to increase collateral blood flow after mesenteric vascular occlusion. However, the authors have previously found that intraarterial vasodilators actually reduce collateral blood flow acutely, by preferentially dilating the vasculature of adjacent, nonischemic mesenteric vascular beds, a phenomenon well established in other organs.
Methods: A segment of rat ileum was acutely devascularized, with blood flow provided only by collateral arterial vessels from adjacent, nonischemic bowel. Papaverine (30 or 40 microg/kg/min), isoproterenol (0.06 microg/kg/min), norepinephrine (0.1 or 0.2 microg/kg/min), or vehicle saline was continuously infused into the cranial (superior) mesenteric artery for 48 hours. Viability was then assessed using previously established, objective gross and microscopic criteria.
Results: Although papaverine increased total mesenteric blood flow in normally vascularized rats, it not only failed to improve but actually significantly reduced the length of the devascularized segment maintained viable by collateral blood flow after 48 hours. Isoproterenol had a similar effect. Norepinephrine infusion decreased both normal mesenteric blood flow and viable segment length.
Conclusions: These findings suggest that intraarterial vasodilator therapy fails to improve intestinal viability after segmental mesenteric vascular occlusion.