Unexpected hypopotassemia after multiple blood transfusions during an operation.

A series of 226 patients undergoing major surgery was studied to asses the influence of the volume of transfused donor blood on the postoperative serum potassium level. Patients with a low serum potassium and with impaired renal function preoperatively and patients receiving medication capable of reducing the total body potassium were excluded from the study. Laboratory studies included complete blood count, electrolyte value measurements, serum creatinine, BUN, glucose, acid-base balance as well as urinalysis. A direct relationship between the volume of transfused blood and a shift of serum potassium was not found. Hyperkalemia did not occur, however, unexpected hypokalemia occurred in 50 patients. Metabolic acidosis and hyperglycemia were found in 57% and 48% respectively and did not seem to have a distinct influence on the potassium balance. As this hypokalemia can cause complications, its presence has to be anticipated and certain drugs like calcium, insulin, bicarbonate and digitalis have to be used with great caution in this situation.