Effect of intra-arterial vasodilators on blood flow in ischemic dog colon

The vasodilators papaverine hydrochloride, tolazoline hydrochloride, and isoproterenol hydrochloride were infused into the superior mesenteric artery (SMA) of dogs in which an ischemic Thiry-Vella colon loop had been formed. The washout of an intra-arterial injection of xenon Xe 133 to the normal and ischemic colon segments was used to measure bowel wall blood flow. Tolazoline and papaverine significantly increased the washout of 133Xe, but isoproterenol did not. Papaverine increased SMA flow. Neither of these two drugs altered the systemic blood pressure or pulse. However, isoproterenol augmented the SMA flow and pulse by factors of 1.8 and 1.5, respectively. These results support the favorable clinical reports that have found papaverine and tolazoline of use in the treatment of nonocclusive bowel ischemia.