Long-Term Metoprolol Therapy and Neuroleptanesthesia in Coronary Artery Surgery

Patients receiving metoprolol before cardiac revascularization surgery were randomly divided into those in whom metoprolol was discontinued before the operation (N = 10) and those in whom metoprolol was continued up to the time of operation (N = 10). Cardiovascular responses to neuroleptanesthesia and sternotomy were studied. Coronary sinus catheterization for blood-flow measurement and sampling was performed in 5 patients in each group. Two of 10 patients had a myocardial infarction after discontinuation of metoprolol and surgery was therefore postponed. Tachycardias were common during intubation after discontinuation of metoprolol, but otherwise hemodynamic responses and myocardial oxygen consumption were similar in both groups. Recurrent ST-T depression occurred in 7 of 8 patients and myocardial lactate release in 2 of 5 patients in whom metoprolol was withdrawn, whereas patients who continued to receive metoprolol showed few episodes of ST-T depression (2 of 10) and no lactate release. The latter had lower plasma norepinephrine (NE) levels, but myocardial release of NE was similar in both groups. Preoperative metoprolol withdrawal seemed to precipitate myocardial ischemia, whereas maintenance of therapy was well tolerated.