The effect of distension of the stomach on coronary blood flow in anaesthetized pigs

Abstract

The present study was undertaken in anaesthetized pigs to determine whether distension of the stomach reflexly affects coronary blood flow. Experiments were performed on 17 pigs anaesthetized with ketamine and sodium pentobarbitone and artificially ventilated. Coronary blood flow was measured with an electromagnetic flowmeter positioned around the origin of the left circumflex coronary artery. The stomach was distended by injecting 0.8l warm Ringer solution into a balloon positioned within the stomach (mean gastric transmural pressure of about 13 mm Hg). Changes in aortic blood pressure and heart rate were prevented by a pressurized reservoir connected to the left femoral artery and by atrial pacing respectively. Distension of the stomach always caused a decrease in mean coronary blood flow. In five pigs, the magnitude of the decrease in coronary blood flow was graded by step increments in the gastric distending volume from 0.6l to 1l. The response of coronary blood flow was not affected by the administration of atropine (12 pigs), while it was abolished by the administration of bretylium tosylate (eight pigs) and by bilateral vagotomy (eight pigs; four cervical, four subdiaphragmatic vagotomy). These results show that innocuous distension of the stomach in anaesthetized pigs reflexly decreases coronary blood flow. This reflex response is mediated by sympathetic effects and its afferent limb involves the vagal nerves.