Effects of anaesthesia induction drugs on circulation in denervated intestinal loop preparation

The effect of anaesthesia induction drugs on the intestinal circulation was evaluated in an isolated loop preparation in 28 dogs. Selected intestinal loops were perfused with aortic blood by a pump at a constant pressure of 100 mmHg. A mixture of 86Rb and 9 microns spheres labeled with 141Ce was injected into the arterial cannula supplying the intestinal segment while mesenteric venous blood was collected for activity counting. Diazepam in a dose of 3 mg X kg-1 was accompanied by a significantly lower clearance (Cl-Rb), and permeability-surface area product (PS) than pentobarbitone; there were no differences between diazepam and pentobarbitone in total blood flow (BF), vascular resistance (VR) and oxygen consumption in the intestinal segments. Circulatory variable observed after midazolam, 8 mg X kg-1 and an additional 16 mg X kg-1, did not significantly differ from those seen during pentobarbitone. Ketamine in a dose of 8 mg X kg-1 was accompanied by a significantly lower BF, Cl-Rb, microsphere entrapment (Cl-Sph), PS, and higher VR and arterio-venous oxygen content difference. Sixteen mg X kg-1 of ketamine did not lead to any additional changes in determined variables of the intestinal circulation. Alpha-adrenoceptor blockade completely abolished vasoconstriction caused by ketamine, suggesting that the long-lasting vasoconstricting effect of ketamine on the intestinal circulation is mediated through catecholamines.