The combination of propranolol and magnesium does not prevent postoperative atrial fibrillation

Background. Atrial fibrillation is a common complication of cardiovascular surgery. P-Blockers have been shown to decrease the incidence of postoperat ive atrial fibrillation. However, the use of magnesium is more controversia l. It was our hypothesis that adjunctive magnesium sulfate would improve th e efficacy of P-blockers alone in the prevention of postoperative atrial fi brillation. Methods. We prospectively randomized 167 coronary artery bypass patients (m ean age 61 10 years, 115 men) to receive propranolol alone (20 mg four time s daily) or propranolol and magnesium (18 g over 24 hours). Magnesium was b egun intraoperatively, and propranolol was started on admission to the inte nsive care unit. Results. Using an intention-to-treat analysis, the incidence of postoperati ve atrial fibrillation was 19.5% in the propranolol-treated patients and 22 .4% in propranolol + magnesium-treated patients (p = 0.65). Because combina tion therapy resulted in an excess of postoperative hypotension, which requ ired withholding doses of propranolol, an on-treatment analysis was also pe rformed. In this analysis, the incidence of atrial fibrillation was still n ot significantly different (18.5% in propranolol-treated patients and 10.0% in propranolol + magnesium-treated patients, p = 0.20). Conclusions. Adjunctive magnesium sulfate, in combination with propranolol, does not decrease the incidence of postoperative atrial fibrillation. (C) 2000 by The Society of Thoracic Surgeons.