Myocardial cations and trace metals in cardioplegia: a clinical study

Cations and trace metals play important roles in the pathophysiology of myocardium, and understanding their changes during cardioplegia may be important in further refining the technique of myocardial protection. Serial myocardial, blood and urine samples were taken from 12 patients undergoing cardiac operation under cold cardioplegia. The concentrations of calcium, magnesium, zinc and copper were measured with an atomic absorption spectrometer. Myocardial magnesium levels were found to be significantly (P less than 0.05) depleted when the "cardioplegic" solution contained 0.69 mmol/l of magnesium, but this could be prevented by increasing the magnesium concentration of the infusate to 2.2 mmol/l. With calcium-free infusate, the myocardial calcium concentration decreased, but zinc and copper values did not change significantly. There were decreased serum concentrations of these cations and trace metals during tbe hemodilution cardiopulmonary bypass but their 24-hour excretions in urine were within normal range. Although the clinical importance of such changes remains to be elucidated, the information may be valuable in designing future cardioplegic solutions with optimal compositions.