Effects of phenylephrine and prostaglandin E1 on ventriculo-arterial matching during halothane anaesthesia

We have investigated the effects of phenylephrine alone and combined with prostaglandin E1 (PGE1) on ventriculo-arterial matching during halothane anaesthesia in dogs. The ratio of left ventricular end-systolic elastance (Ees) to effective arterial elastance (Ea) was used as an index of ventriculo-arterial matching. In group 1 (n = 7), measurements were performed at control, 1.5% halothane, halothane+phenylephrine 1-10 micrograms kg-1 min-1, and halothane+phenylephrine+PGE1 0.2-1.0 or 1.0-2.0 micrograms kg-1 min-1. In group 2 (n = 5), dobutamine 2 and 5 micrograms kg-1 min-1 was infused during halothane anaesthesia. Halothane 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 phenylephrine. PGE1 increased cardiac output and reversed the increases in Ea and Ea/Ees during phenylephrine infusion. Dobutamine also reversed halothane-induced decreases in MAP, cardiac output and Ees, and improved Ea/Ees. Our results indicate that combined use of PGE1 with phenylephrine can eliminate the vasoconstrictive property of phenylephrine, resulting in an improvement in ventriculo-arterial matching.