POSTOPERATIVE ARRHYTHMIAS AND MYOCARDIAL ELECTROLYTES IN PATIENTS UNDERGOING CORONARY-ARTERY BYPASS-GRAFTING

Electrolyte changes in right atrial and skeletal muscle pre- intra- an d postoperatively, and their relationship to the development of postop erative atrial fibrillation or flutter were evaluated in 31 patients w ith coronary artery bypass grafting (CABG). Such postoperative arrhyth mias occurred in 14 patients (45%). Before CABG the skeletal muscle po tassium concentration was lower in these patients than in the others: median 261.4 (range 148.2-329.5) vs 298.6 (167.1-416.4) mu mol/g dry w eight, p = 0.017. The right atrial potassium concentration was normal, but sodium levels were higher in the patients with, than in those wit hout postoperative arrhythmias: median 340.3 (263.7-454.9) vs 296.3 (2 03.9-355.0) mu mol/g dry weight, p = 0.008, indicating disturbed trans membrane electrolyte transfer. During CABG the potassium levels fell a nd sodium increased in both right atrium and skeletal muscle, and on p ostoperative day 2 the potassium content in skeletal muscle was not ye t restored. Magnesium levels showed no changes in right atrium or skel etal muscle, but serum magnesium declined postoperatively. As the obse rved electrolyte derangements may be important in the development of p ostoperative arrhythmias, concomitant potassium and magnesium suppleme nt postoperatively may be beneficial in restoring cellular potassium c oncentration.