Urine and serum potassium levels after potassium cardioplegia

Potassium cardioplegia for myocardial preservation is being used extensively in heart operations. This study was designed to determine the effect of potassium cardioplegia on serum and urine potassium levels. A control group of 11 patients was compared to a study group of 24 patients. Myocardial preservation in the control group was achieved by whole body cooling to 20 degrees to 30 degrees C and in the study group, by repeated injections every 30 minutes of 500 to 700 ml of cold pump blood, containing potassium chloride 30 mEq/L, into the aortic root after aortic clamping. Total potassium dose in the study group was 46 +/- 21 mEq (mean +/- SD). Mean serum potassium level was significantly higher during and after bypass in the study group (after bypass: control 3.65 +/- 0.11 mEq/L, study 4.24 +/- 0.10 mEq/L [mean +/- SE], p less than 0.005), but was within normal limits in both groups. Urine potassium levels and excretion rates were significantly higher in the study group (potassium excretion rate after bypass: control 6.1 +/- 0.7 mEq/hr, study 11.3 +/- 0.9 mEq/hr [mean +/- SE], p less than 0.0025). We conclude that no special measures are required to facilitate potassium excretion when total potassium cardioplegia dose is not greater than 50 mEq.