Interactive effects of isoflurane and amrinone in the feline intestinal and renal circulation

Interactive effects of the phosphodiesterase-III inhibitor amrinone and isoflurane were investigated in cats. Cardiac output (thermodilution method), and intestinal (IBF) and renal (RBF) blood flows (optical flowmetry) were measured. Intestinal (IVR) and renal (RVR) vascular resistances were derived. To discriminate between pressure-related local myogenic vascular responses and primary vascular drug effects, intestinal and renal perfusion pressures (50 mmHg; 6.7 kPa) were controlled. The protocol included steady-state recordings with and without isoflurane in a randomized order, both before and after the administration of amrinone (2 mgkg-1 i.v. + 2 mgkg-1 i.v.). Amrinone induced no significant changes in IVR or RVR during basal chloralose anesthesia. During administration of 0.8% isoflurane, amrinone produced decreases in IVR and RVR, which were more pronounced than the vasodilator responses induced by this dose of isoflurane alone. On the other hand, with 1.6% isoflurane, amrinone did not add to the vasodilation. The cardiac effects of isoflurane and amrinone were small. Our data indicate that the vascular tone before administration of amrinone could be crucial for the vascular response of the drug and that isoflurane can significantly influence the regional circulatory effects of amrinone.