A comparison of the effects of two haemodiluents on monovalent and divalentcations in children undergoing cardiopulmonary bypass and open-heart surgery.

Abstract

The material presented in this paper is part of an ongoing project to study biochemical changes in children undergoing 30 per cent haemodilution during cardiopulmonary bypass for open heart operations. We compared two groups of 5 children undergoing total correction of tetralogy of Fallot and having cardiac bypass times over 50 minutes: the diluent used in Group I was magnesium-containing Plasma-lyte® with dextrose added to make a 1 per cent solution, while that in Group II was 5 per cent dextrose in 0.2 per cent NaCl. The results indicate that the use of magnesium-containing multiple electrolyte solution was of value in maintaining plasma electrolyte values close to normal during the period of cardio-pulmonary bypass, particularly those of magnesium and sodium, but did not appear to have any appreciable effect on the early post-operative hypokalaemia or late post-operative hyponatraemia. The patients of group I were compared with a third group (Group III) of six patients undergoing closure of atrial septal defect with bypass times of less than 30 minutes and using the same multiple electrolyte diluent as in Group I. The short-pump-run cases showed a lower incidence of post-operative hypokalaemia. There were no significant differences in post-operative excretion of sodium or potassium between these two groups (I and III), but there was delayed diuresis until the second post-operative day. For haemodilution we recommend the use of a magnesium-containing multiple electrolyte solution combined with post-operative administration of magnesium supplement in the amount of 1 mEq/kg/day and potassium in the amount of 2 mEq/kg/day for at least 48 hours.