EFFECTS OF ISOFLURANE ON FELINE INTESTINAL BLOOD FLOW DURING HEMORRHAGE-INDUCED HYPOVOLEMIA

The influence of isoflurane on intestinal reflex vasoconstriction during hemorrhage was investigated in cats (n = 10) during basal chloralose-nitrous oxide anesthesia. Intestinal blood flow (IBF) was studied in a model with controllable intestinal perfusion pressures to exclude local myogenic vascular responses related to changes in intraluminal pressure. A jejunal segment, which was dissected free in situ, was perfused via an extracorporeal arterial circuit which included a roller pump and a variable arterio-venous shunt. Intestinal perfusion pressure was controlled by adjusting the shunt flow. IBF was measured (optical drop-recording) before and after hemorrhage (8% of estimated blood volume). 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% (MAC 1.0) isoflurane. IBF levels were consistently higher during isoflurane anesthesia than during basal chloralose anesthesia in the perfusion pressure range 75-150 mmHg (10.0-20.0 kPa). During basal anesthesia, a hemorrhage-induced decrease in IBF was demonstrated throughout the perfusion pressure range 50 to 150 mmHg (6.7-20.0 kPa). The magnitude of the hemorrhage-induced decrease in IBF was not significantly influenced by the addition of isoflurane. Thus, IBF, following hemorrhage, was significantly higher during isoflurane anesthesia than during basal chloralose anesthesia at perfusion pressures 50, 100, 125 and 150 mmHg (6.7, 13.3, 16.7 and 20.0 kPa).