Vasodilators in the canine mesenteric circulation: Evaluation of a potential aid in the diagnosis of gastrointestinal bleeding

Radiodiagnostic potential of intra-arterially injected vasodilating agents was investigated by their effects on total and segmenal resistances (VR) of mesenteric vasculature, blood flow in superior mesenteric artery and its bleeding branch; heart rate and ventricular and systemic blood pressure. Dipyridamole, isox-suprine, prochlorperazine, lidocaine, meglumine diatrizoate and carbon dioxide were poor dilators. Phentolamine produced hypotension; glucagon and serpasil an extremely long dilation. A large and short vasodilation was produced with tolazoline and nylidrin, but both agents increased VR of the postcapillary segment and caused transient hypotension and arrhythmias, nylidrin’s side effects were smaller. Oxygen produced large and long vasodilation and minimal systemic effects. It is concluded that oxygen or possibly nylidrin are suitable agents should an intermittently bleeding mesenteric artery be dilated for diagnostic purposes prior to angiography.