Local vascular effects of isoflurane during regional intestinal hypothermia in cats

The influence of isoflurane on intestinal blood flow (IBF) during regional intestinal hypothermia (28 degrees C intraluminal temperature) was investigated in cats (n = 12) during basal chloralose-nitrous oxide anesthesia. A jejunal segment, which was dissected free in situ and intermittently cooled in a saline bath, was perfused via an extracorporeal arterial circuit which included a roller pump and a variable arterio-venous shunt. Intestinal perfusion pressures were controlled by adjusting the shunt flow. IBF was measured (optical drop-recording) during regional normothermia and hypothermia. The protocol included steady-state recordings at defined perfusion pressures (50, 75, 100, 125 and 150 mmHg in a randomized order; 6.7, 10.0, 13.3, 16.7 and 20.0 kPa, respectively) with and without the addition of 0.7% isoflurane. During normothermia, IBF levels were higher during isoflurane anesthesia than during basal chloralose anesthesia. Regional intestinal hypothermia induced no significant changes in IBF during basal chloralose anesthesia. However, the intestinal vasodilator effects of isoflurane, as shown during normothermia, were efficiently countered by regional cooling of the intestinal segment to 28 degrees C. Accordingly, hypothermia IBF levels were similar, regardless of whether isoflurane was administered or not. This could have an impact on the choice of anesthetic techniques.