A comparison of glyceryl trinitrate and labetalol as hypotensive agents in microsurgery of the middle ear

Ninety-five patients undergoing microsurgery of the middle ear were anaesthetised using thiopentone, nitrous oxide, oxygen and halothane via a low flow circle system, with carbon-dioxide absorption. Systolic blood pressure was reduced to approximately 65 mmHg either by the use of increments of labetalol, or by an infusion of glyceryl trinitrate (GTN). The degree of haernostasis achieved was assessed by the surgeon who was unaware which hypotensive agent was being used. Both hypotensive agents produced good conditions in all patients. Thus GTN is a suitable agent to induce hypotension for this type of microsurgery.