Postoperative serum level and urinary excretion of magnesium following heart surgery.

The level of serum magnesium was examined in relation to open-heart surgery. A significant fall below normal values was observed during the first postoperative day, probably caused by haemodilution during bypass. Serum concentrations were normal from the second postoperative day onwards. This result differs from observations at other centres. Two possible causes for this divergency are suggested: (1) a habitiually high dietary intake of magnesium from the drinking water and (2) a postoperative regime emphasizing the maintenance of a positive blood and plasma balance, thus supplying the patients with a considerable amount of magnesium. It is concluded that no indications for pre- , per- or postoperative supplementation of magnesium in association with cardiopulmonary bypass were found.