Interactive cardiovascular effects between isoflurane and peroperative events

Abstract. The objective of this five–part (IV) study was to evaluate cardiovascular interactions between isoflurane and some pathophysiological and pharmacological interventions, likely to occur peroperatively. Specific aims were to investigate: Interactive responses between hemorrhage–induced hypovolemia and isoflurane in the intestinal circulations. Interactive response between regional hypothermia (28°C) and isoflurane in the intestinal circulation. Interactive responses between amrinone and isoflurane in the intestinal and renal circulations. Modulation by dopamine of the cardiovascular responses to isoflurane. Modulation by dopamine of the cardiovascular responses to thoracic epidural blockade concurrent with isoflurane administration Intestinal (I–III) and renal (III) blood circulations were studied by optic flowmetry in cat models, with regional perfusion pressures controlled either by an extracorporeal pumpassisted circuit (I, II) or by adjustable abdominal aortic occlusion (III). Central hemodynamics were assessed in cat and dog models (III–V).Isoflurane was found to depress cardiac function in a doserelated fashion. In the regional circulation, isoflurane dose dependently produced vasodilation in the small intestine and in the kidney. The net response from these cardiac and vascular effects of isoflurane was a decrease in arterial pressure. In the small intestine, reflex vasoconstriction, induced by hemorrhage, was overruled by the vasodilator effects of isoflurane. Regional hypothermia in the small intestine attenuated the local vasodilator effects of isoflurane. The phosphor diesterase III inhibitor amrinone induced intestinal and renal responses, which added to the vasodilations induced by a moderate dose of isoflurane. The depressor effect of isoflurane could effectively be controlled by exogenous dopamine through counter–directed actions on cardiac function and through increased systemic vascular tone. The combination of isoflurane and thoracic epidural blockade was associated with depressed cardiac function. Exogenous dopamine effectively countered such actions and, in this situation, increased vascular tone to a greater extent than in control situations.