Magnesium in patients undergoing open-heart surgery.

Measurements of serum and urinary magnesium levels were made together with the other electrolytes, haematocrit, pH, and albumin in patients comprising two groups-one group of 50 patients undergoing heart valve replacement, and the other, 30 patients undergoing non-perfusion thoracic operations. Low serum magnesium levels were found in some patients admitted to hospital who were or had recently been in congestive heart failure. All patients were found to have low serum magnesium levels postoperatively, but to a greater degree and for a longer period following open-heart surgery. The latter group exhibited hypomagnesuria postoperatively. The literature is reviewed in an attempt to explain the reasons for the changes in the magnesium levels. It is concluded that the changes observed in this limited study warrant further detailed investigation including the use of a double blind trial for assessing the therapeutic value of administering magnesium salts to patients undergoing open-heart surgery.