[Effect of potassium canrenoate on serum magnesium levels after extracorporeal circulation]

Serum magnesium (Mg) levels were measured before and after operations involving extracorporeal circulation in thirty-five patients. Twenty patients were administered potassium canrenoate 200 mg/day from 2 days before operation to the 3rd postoperative day. Another 15 patients to whom there had been no administration of potassium canrenoate served as controls. We investigated the difference of serum Mg levels between the two groups. The serum Mg levels significantly decreased immediately after operations as compared to the values before surgery as from 1.9 +/- 0.2 to 1.5 +/- 0.2mEq/l (p less than 0.001) and from 1.8 +/- 0.2 to 1.4 +/- 0.2mEq/l (p less than 0.001) in the medicated and control groups, respectively. Serum Mg levels on the 2nd postoperative day recovered to within the normal range and it was significantly higher in the medicated group (1.7 +/- 0.2mEq/l versus 1.5 +/- 0.3mEq/l; p less than 0.05). Hypomagnesemia (Mg less than or equal to 1.2mEq/l) was found in seven patients (46.7%) in the control group and in two patients (10.0%) in the medicated group. Thus, there was a significant difference in the incidence of hypomagnesemia between the two groups (p less than 0.05). These results suggested that administration of potassium canrenoate is useful for keeping and improving serum Mg levels after extracorporeal circulation.