EFFECTS OF PHENYLEPHRINE AND PROSTAGLANDIN E(1) ON VENTRICULOARTERIALMATCHING DURING HALOTHANE ANESTHESIA

We have investigated the effects of phenylephrine alone and combined w ith prostaglandin E(1) (PGE(1)) on ventriculo-arterial matching during halothane anaesthesia in dogs. The ratio of left ventricular end-syst olic elastance (Ees) to effective arterial elastance (Ea) was used as an index of ventriculoarterial matching. In group 1 (n = 7), measureme nts were performed at control, 1.5% halothane, halothane + phenylephri ne 1-10 mu g kg-l min(-1), and halothane + phenylephrine + PGE(1) 0.2- 1.0 or 1.0-2.0 mu g kg(-1) min(-1). In group 2 (n = 5), dobutamine 2 a nd 5 mu g kg(-1) min(-1) was infused during halothane anaesthesia. Hal othane 1.5% decreased mean arterial pressure (MAP), cardiac output and Ees. Phenylephrine restored MAP, but further decreased cardiac output . The decrease in Ees produced by halothane was reversed by phenylephr ine. PGE(1) increased cardiac output and reversed the increases in Ea and Ea/Ees during phenylephrine infusion. Dobutamine also reversed hal othane-induced decreases in MAP, cardiac output and Ees, and improved Ea/Ees. Our results indicate that combined use of PGE(1) with phenylep hrine can eliminate the vasoconstrictive property of phenylephrine, re sulting in an improvement in ventriculo-arterial matching.