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Acute beta‐adrenoreceptor blockade and induced hypotension

Thirty patients scheduled for major middle ear surgery and induced hypotension, with a trimetaphan/sodium nitroprusside infusion, were randomly allocated to receive a single oral dose of beta‐adrenoreceptor antagonist 2 hours before surgery. In group 1 ten patients received metoprolol 50 mg, in group 2 ten patients received metoprolol 25 mg and in group 3 ten patients received oxprenolol 20 mg. There were ten controls for each group. The nitroprusside infusion rate was significantly reduced in groups 1 and 3. However, there was an unacceptably high incidence of profound bradycardia after induction of anaesthesia in those patients who had received beta‐adrenoreceptor antagonists pre‐operatively and this technique is not recommended for routine use.