Metoprolol decreases the amount of halothane required to induce hypotension during general anaesthesia.

A double-blind, randomized and placebo-controlled study was undertaken to assess the effects of metoprolol on controlled hypotension during halothane anaesthesia. Nineteen patients under-going middle ear or nasal septum surgery were studied. The aim was to achieve a 25% reduction of the mean arterial pressure in both groups. Metoprolol was given by mouth on two occasions in the 10-12 h before operation. In the group pretreated with metoprolol the halothane concentration was reduced by 35.5%. The duration of bleeding and its degree were reduced significantly. The time to awakening was shorter and of better quality after pretreatment with metoprolol. Rate-pressure product was less after pretreatment with metoprolol, and rebound hypertension was well controlled.