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

We have investigated the effects of phenylephrine alone andcombined with prostaglandin E₁ (PGE₁) on ventriculo-arterialmatching during halothane anaesthesia in dogs. The ratio ofleft ventricular end-systolic elastance (Ees) to effective arterialelastance (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 µgkg^–1 min^–1, and halothane + phenylephrine + PGE₁,0.2–1.0 or 1.0–2.0 µg kg^–1 min^–1.In group 2 (n = 5), dobutamine 2 and 5 µg kg^–1 min^–1was infused during halothane anaesthesia. Halothane 1.5% decreasedmean arterial pressure (MAP), cardiac output and Ees. Phenylephrinerestored MAP, but further decreased cardiac output. The decreasein Ees produced by halothane was reversed by phenylephrine.PGE₁ increased cardiac output and reversed the increases inEa and Ea/Ees during phenylephrine infusion. Dobutamine alsoreversed halothane-induced decreases in MAP, cardiac outputand Ees, and improved Ea/Ees. Our results indicate that combineduse of PGE₁ with phenylephrine can eliminate the vasoconstrictiveproperty of phenylephrine, resulting in an improvement in ventriculo-arterialmatching.