[Potassium metabolism in warm heart surgery].

The dynamic balance of potassium getting in and out the body during and after operation was surveyed in 26 adult patients who underwent cardiac surgery with normothermic cardiopulmonary bypass (CPB). We found that during CPB, because of the continous perfusion of warm oxygenated blood cardioplegia solution, a large volume of potassium entered the body; meanwhile, only a little potassium removed from the body in urine. At the moment of CPB finish, the volume of residual potassium in the body was as large as 74.5mmol (mean), that was 1.2mmol/kg body weight. The mean plasma potassium level at the points of aorta cross clamp release and CPB finish were 6.8mmol/L and 5.5mmol/L respectively, and all in normal range at several times measured from the end of operation (usually 12-2pm) to the second postoperative day 7am. The volume of potassium replenishment according to urine output in this group was much less than those in hypothermic CPB patients from the end of operation to the first postoperative day 7am. During CPB extracellular potassium shifted into intracellular fluid, but the shifting became opposite around the operative day 6pm, and the final equilibrium of potassium metabolism was achieved at the second postoperative day 7am. The remarkable hyperkalemia at the point of aorta cross clamp release may delay the heart rebeating ( > 5min, 35%), but the automatic rebeating rate was still very high (96%). With regard to the prevention of hyperkalemia during CPB, we also give some suggestions in this paper.