1992 Volume 28 Issue 1 Pages 1-9
To investigate the influence of open heart surgery using extracorporeal circulation (ECC), on perioperative hypokalemia and also on neurohumoral factors of potassium metabolism' a prospective balance study was made in 21 patients (mean age 61 ± 43 months) with various congenital heart disease. Population of the patients were : ventricular septal defects 6, atrial septal defects 4, tetralogy of Fallot 2, complete atrioventricular septal defect 2, coarctation complex 2, triatrial heart 2, and so on. Plasma potassium was measured before and during operation, and hourly for 24 hours after closing the chest. Urinary values of potassium, aldosterone and antidiuretic hormone (ADH) were also measured in accumulated urine before and during ECC, and every 6 hours for 24 hours after operation. The following results were obtained ; 1) Plasma potassium was significantly lower during ECC (3.1 ± 0.12 mEq/L) and during the first 6 hours postoperatively (3.2 ± 0.09 mEq/L) than before operation (4.2 ± 0.08 mEq/L). 2) Urinary excretion of potassium increased markedly from the beginning of ECC and continues until closure of the chest, and this increase correlated with the urine volume (r = 0.77, p < 0.01). 3) The balance study of potassium during this period, however, demonstrated that, the amount of replenished potassium was larger than the urinary potassium excretion and the difference correlated inversely with the rectal temperature (r = -0.65, p < 0.0l). 4) Plasma potassium correlated inversely with PH (r= -0.56, p < 0.01) and positively with Pco_2 (r = 0.57, p < 0.01) during the first 6 hours postoperatively. 5) Urinary aldosterone correlated positively with urinary potassium (r = 0.54, p < 0.05) and inversely with plasma potassium (r = -0.49, p < 0.05) during the period from 18 hours until 24 hours postoperatively. 6) The urinary aldosterone and ADH increased markedly after ECC and remained high until 24 hours postoperatively, while the plasma ANP did not change significantly. These results draw us to conclude that both increased urinary excretion of potassium and potassium influx into cells during hypothermic ECC may play important roles as the causes of the hypokalemia seen in the early postoperative periods. Furthermore, respiratory alkalosis and hyperaldosteronism may exaggerate the hypokalemia.
