Atrial fibrillation and changes in serum and urinary electrolyte levels after coronary artery bypass grafting surgery

Objective. Our study was designed to assess the incidence of atrial fibrillation, changes in serum electrolyte concentrations and urinary electrolyte excretion following coronary artery bypass grafting surgery.
Material and methods. A total of 165 patients who underwent elective coronary artery bypass grafting surgery at the Department of Cardiac Surgery (Heart Center) during the period of 2004–2005 were enrolled. Serum K+, Na+, Mg2+, Ca2+, Cl–, and P– concentrations were measured before cardiopulmonary bypass (CPB), on the arrival to an intensive care unit, and 15–18 hours after the surgery. Urinary excretion of K+, Na+, Mg2+, Ca2+, Cl–, and P– was estimated 24 hours before the surgery, during the surgery, and 24 hours after the surgery. Cardiac rhythm was monitored throughout the study. All patients randomly were divided into the group 1 (n=55), which received magnesium sulphate infusion, and group 2 (n=110), which did not receive magnesium sulphate.
Results. The overall incidence of atrial fibrillation was 27.4%. The patients in the group 1 had significantly higher levels of serum magnesium before CPB and serum chloride after the surgery. Urinary magnesium and calcium excretion was significantly higher in the group 1 during and after the surgery. Before the surgery and 24 hours after the surgery, phosphate excretion was significantly higher in the group 1.
Conclusions. The incidence of atrial fibrillation after myocardial revascularization surgery remains high (27.4%). Serum electrolyte concentrations after myocardial revascularization varied within normal ranges. Magnesium sulphate infusion did not decrease the rate of postoperative atrial fibrillation during the early postoperative period in normomagnesemic patients.