title: Intravenous administration of metoprolol is more effective than oral administration in the prevention of atrial fibrillation after cardiac surgery.
abstract: BACKGROUND
  Atrial fibrillation (AF) is the most common arrhythmia to occur after cardiac surgery, with an incidence of 20% to 40%. AF is associated with postoperative complications, including increased risk of stroke and need of additional treatment, as well as prolonged hospital stay and increased costs. It has been shown that prophylactic oral administration of beta-blocker therapy reduces the incidence of postoperative AF after cardiac surgery. However, it is possible that absorption of drugs is impaired after cardiopulmonary perfusion associated with cardiac surgery. The purpose of this prospective, controlled, randomized trial was to study compare intravenous and per oral metoprolol administration in the prevention of AF after cardiac surgery.
  
  
  RESULTS
  240 consecutive patients who were scheduled to undergo their first on-pump coronary artery bypass graft (CABG), aortic valve replacement, or combined aortic valve replacement and CABG were randomized to receive 48-hour infusion of metoprolol or oral metoprolol starting on the first postoperative morning. Patients were excluded if they had contraindications for beta-blocker or had to stay >1 day in the intensive care unit. Dosage of metoprolol was adjusted according to heart rate. The dosage was 1 to 3 mg/h in the intravenous group and from 25 mg twice per day to 50 mg 3 times per day in the oral group. The incidence of postoperative AF was significantly lower in the intravenous group than in the oral group (16.8% versus 28.1%, P=0.036). No serious adverse effects were associated with intravenous metoprolol therapy.
  
  
  CONCLUSIONS
  Our study suggests that intravenous metoprolol is well-tolerated and more effective than oral metoprolol in the prevention of AF after cardiac surgery.
authors.affiliation: Department of Surgery, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland. jari.halonen@kuh.fi
authors.forename: Jari
authors.initials: J
authors.lastname: Halonen
authors.forename: Tapio
authors.initials: T
authors.lastname: Hakala
authors.forename: Tommi
authors.initials: T
authors.lastname: Auvinen
authors.forename: Jari
authors.initials: J
authors.lastname: Karjalainen
authors.forename: Anu
authors.initials: A
authors.lastname: Turpeinen
authors.forename: Ari
authors.initials: A
authors.lastname: Uusaro
authors.forename: Pirjo
authors.initials: P
authors.lastname: Halonen
authors.forename: Juha
authors.initials: J
authors.lastname: Hartikainen
authors.forename: Mikko
authors.initials: M
authors.lastname: Hippeläinen
mesh_terms: D000284:Administration, Oral; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage* / Q000627:therapeutic use; D000368:Aged; D001021:Aortic Valve / Q000601:surgery*; D001281:Atrial Fibrillation / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D001026:Coronary Artery Bypass; D004562:Electrocardiography; D005260:Female; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008790:Metoprolol / Q000008:administration & dosage* / Q000627:therapeutic use; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011183:Postoperative Complications / Q000517:prevention & control*
chemical_list: D000319:Adrenergic beta-Antagonists; D008790:Metoprolol