Magnesium metabolism in open-heart surgery

Area of Science:

• Cardiology
• Biochemistry
• Nephrology

Background:

• Magnesium homeostasis is crucial during cardiac surgery.
• Hypomagnesemia is a known complication of cardiopulmonary bypass.
• Understanding magnesium shifts is vital for patient management.

Purpose of the Study:

• To investigate serum, urine, and erythrocyte magnesium levels in patients undergoing valvular prosthesis surgery.
• To correlate magnesium levels with serum albumin and non-esterified fatty acids (NEFA).
• To evaluate the effect of St. Thomas cardioplegia solution on magnesium balance.

Main Methods:

• Studied 22 patients undergoing cardiac surgery for valvular prosthesis.
• Measured magnesium in serum, urine, and erythrocytes at multiple time points: pre-anesthesia, post-sternotomy, post-heparinization, post-aortic declamping, and 1st postoperative day.
• Correlated magnesium with serum albumin and NEFA.

Main Results:

• A slight decrease in serum magnesium (magnesemia) occurred before extracorporeal circulation (ECC), primarily due to hemodilution.
• Correlation between magnesium and NEFA was significant only after heparinization.
• St. Thomas cardioplegia effectively corrected hypomagnesemia during ECC and postoperatively.
• Moderate hypermagnesemia was observed post-ECC without reaching dangerous levels.
• Increased urinary magnesium losses were noted during and after ECC.
• Erythrocyte magnesium increased pre-ECC but significantly decreased by the end of ECC.

Conclusions:

• St. Thomas cardioplegia solution is effective in preventing and correcting hypomagnesemia during and after cardiac surgery.
• Magnesium levels exhibit dynamic changes in serum, urine, and erythrocytes throughout cardiac surgery.
• Monitoring magnesium is important, especially considering urinary losses and erythrocyte shifts during ECC.