Electrolyte and acid-base disturbances caused by blood transfusions

The effect of blood transfusions on the electrolyte, metabolic and hemodynamic status of 31 patients undergoing major laparotomies was studied. Two groups were compared: Group I, 11 patients receiving continuous intraoperative blood transfusions exceeding 5 units at a rate over 0.3 ml/kg/min, and Group II, 20 patients receiving transfusions of 1-5 units at a rate below the limit. Transiently increased potassium values (5.2 +/- 0.3 mmol/l) were found in Group I during the rapid transfusion phase. The difference was statistically significant (P less than 0.05) when compared to Group II (4.3 +/- 0.2 mmol/l). There was also a significant correlation (r = 0.64; P less than 0.05) between the increase in serum potassium concentrations and the respective potassium load caused by the blood transfused. Most of the hyperpotassemic patients had surgery of the abdominal aorta. During the rapid transfusion, the patients in Group I had significantly lower concentrations of serum ionized calcium (P less than 0.05) and higher central venous pressures (P less than 0.05), but more periods of hypotension when compared to Group II. After the transfusion the massively transfused patients had slight metabolic alcalosis, the BE and pH differing significantly (P less than 0.05) from the values of Group II. It is concluded that hyperpotassemia may occur during rapid transfusions (over 0.4 ml/kg/min) of stored blood, especially in patients undergoing surgery of the abdominal aorta, even without simultaneous shock, acidosis or hypothermia. Calcium administration may be of benefit especially in situations where combined hyperpotassemia and hypocalcemia reduce the myocardial performance.