Deformability and electrolyte changes of erythrocytes in connection with open heart surgery

Red cell damage was studied in 16 patients undergoing open heart surgery. The damage was assessed by red cell deformability measuring red cell filtration rate (RFR) using a microfiltration technique. Simultaneous estimations of red cell sodium, potassium and water content were carried out. During and after cardiopulmonary bypass (CPB) RFR decreased with simultaneous loss of potassium and gain in sodium. These ionic changes are known to induce an increase in cellular calcium content via raised calcium influx. Since elevated intracellular calcium content provokes reduced deformability of the red cells the observed reduction in RFR in connection with CPB might at least partly be secondary to the reduction in the K+-Na+ ratio. A comparison between the regression lines between K+/Na+ and RFR for cold blood not subjected to the trauma caused by the heart-lung machine and for patient blood suggests that approximately 20% of the reduction in RFR observed in connection with CPB is due to the reduction in K+/Na+. The severity of the erythrocyte electrolyte changes was positively correlated to the amount of oxygen used in the heart-lung machine. The results suggest that the flow of oxygen and blood through the heart-lung machine should be kept as low as possible.