The effect of seven vasopressors of halothane MAC in dogs.

We evaluated the effects of ephedrine, mephentermine, metaraminol, phenylephrine, methoxamine, noradrenaline and adrenaline on halothane anaesthetic requirement (MAC) in dogs. MAC increased significantly only during ephedrine infusion (50%) although significance was approached with mephentermine (21%). Phenylephrine, metaraminol, methoxamine, noradrenaline and adrenaline did not change MAC. Arterial pressure was increased 50-100% with all agents. Our results support the hypothesis that anaesthetic requirement may be related, in part, to release of brain noradrenaline.