Hemodynamic changes associated with strangulation obstruction in cats

While changes in blood flow associated with simple intestinal obstruction have been studied extensively, little is known about blood flow changes associated with strangulation obstruction. Closed loop strangulation was produced in anesthetized cats by means of a baby pressure gasket. Intestinal blood flow was measured by transit time flowmetry. Blood pressure was measured in a carotid artery and in veins of a closed loop of small intestine. The gasket pressure was increased stepwise in 10 mm Hg increments after which the intestinal venous pressure was kept constant at 50 mm Hg for 5 h. Increasing gasket pressure was followed by a corresponding increase in venous pressure in the closed bowel loop. Blood flow in the closed loop decreased with increasing venous pressure and was closely related to the arteriovenous perfusion pressure under stepwise increase of the gasket pressure and during prolonged periods with increased venous pressure. At constant elevated venous pressure the intestinal blood flow was determined by the arterial pressure. The vascular resistance in the closed loop increased exponentially with increasing venous pressure and especially at very low blood flow. In conclusion, we have found that strangulation obstruction is associated with increased venous pressure in the closed loop which contributes to maintaining intestinal blood flow during the obstruction.