A study of serum magnesium levels in postoperative ICU patients undergoing major GI surgeries.

Background: Magnesium (Mg++) deficiency can result in life-threatening complications. The incidence of hypomagnesemia, as well as any coexisting hypokalemia and Electrocardiography (ECG) abnormalities, was studied in patients undergoing major gastrointestinal (GI) surgeries.

Methods: This observational study on 51 consecutive adult Intensive Care Unit (ICU) patients recorded serum Mg++ and serum potassium (K+) levels, and 12 lead ECGs, preoperatively and postoperatively, at 48 h and 72 h. Paired "t" test, Pearson Correlation Coefficient and chi-square test were used to statistically assess the difference, correlation, and association between serum Mg++, serum K+, and abnormal ECGs, respectively.

Results: Mean values for serum Mg++ were 1.72 mg/dl and 1.71 mg/dl on day 2 and 3 postops, respectively, while for serum K+ it was 4.14 meq/l and 4.02 meq/l. The incidence of postop hypomagnesemia was 52.9% with a 95% confidence interval (39.2-66.2) on Day 2 and 47.1%, with a 95% confidence interval (33.7-60.7) on Day 3. The incidence of coexisting hypokalemia was 33.3% on Day 2 and 29.2% on Day 3. There was no significant difference between pre and postop serum Mg++ and serum K+ values. The incidence of abnormal ECG was 33.3% on Day 2 postop and 28.6% on Day 3 and had a significant association with incidence of hypomagnesemia on Day 2 ( = 0.02).

Conclusion: Incidence of hypomagnesemia showed no significant difference pre and postoperatively. A significant association was present between the incidence of hypomagnesemia with abnormal ECG on the second postop day, but this was not found significant when compared with cases of hypomagnesemia with coexisting hypokalemia.