Safety of labetalol-induced controlled hypotension during middle ear microsurgery

In order to study the influence of labetalol on the peroperative oxygenation during deliberate hypotension, 50 patients undergoing middle ear microsurgery were randomly divided in two groups of 25 patients; one group receiving labetalol to induce hypotension, the other group receiving placebo in a double blind manner. In the group receiving labetalol the arterial oxygen tension (PaO2) decreased significantly 5 minutes after the intravenous bolus injection. Within 30 minutes the PaO2 returned to the starting level. The arterial carbon dioxide tension (PaCO2) increased within 5 minutes and also returned to the initial level after 30 minutes. These changes were absent in the control group. It is concluded that, although labetalol produces a statistically significant change in PaO2 and PaCO2, this finding has only minor clinical implications and so labetalol remains a safe drug to be used for the induction of deliberate hypotension during middle ear microsurgery.