Hypotensive anaesthesia for microsurgery of the middle ear. A comparison between isoflurane and halothane.

Fifty patients undergoing microsurgery of the ear were anaesthetised using thiopentone, nitrous oxide, oxygen and either halothane or isoflurane, via a low flow circle system with carbon dioxide absorption. Systolic blood pressure was reduced to approximately 70 mmHg by the additional use of increments of labetalol; the patients breathed spontaneously. The degree of haemostasis was assessed by the surgeon who was unaware which volatile agent was being used to supplement anaesthesia. Isoflurane, although it is a potent vasodilator produced operating conditions which were indistinguishable from halothane. Isoflurane is thus a safe and reliable alternative to halothane as a volatile agent used to supplement anaesthesia when using induced hypotension for middle ear surgery.