Ionized Hypomagnesemia Is Associated With Increased Incidence of Postoperative Atrial Fibrillation After Esophageal Resection: A Retrospective Study

Introduction: Postoperative atrial fibrillation (POAF) is common after surgery for esophageal cancer and may prolong hospitalization and elevate mortality. POAF and hypomagnesemia are linked, but this is based on studies showing an association of POAF with serum total magnesium (tMg). In contrast, the relationship of POAF with ionized magnesium (iMg), which has physiological activity, has not been examined. In this study, the association between hypomagnesemia and POAF was investigated retrospectively to examine iMg as a possible predictive factor for POAF. Methods: The subjects were 151 patients who underwent right transthoracoabdominal subtotal esophagectomy at Saitama Medical Center between January 2011 and December 2020. The incidence of POAF and predictive factors were examined retrospectively. Perioperative predictive factors were subjected to univariate analysis, and items with P<0.1 were then included in multivariate analysis, along with five potential POAF predictors reported in the literature (age, gender, body mass index, hypertension, and diabetes mellitus). P<0.05 was regarded as significant in the multivariate analysis. Results: Of the 151 patients, 34 (23%) developed POAF. In univariate analysis, six factors with P<0.1 (oral statin, dyslipidemia, iMg level after anesthesia induction, maximum and minimum iMg during surgery, and iMg level immediately before admission to ICU) were identified. In multivariate analysis including these and the five literature factors as explanatory variables, iMg immediately before admission to ICU emerged as a predictive factor for POAF (iMg≥0.46 mmol/L, OR 0.32, 95%CI 0.14-0.74, p=0.01) (standard iMg range: 0.48-0.60 mmol/L). Conclusion: The iMg level immediately before admission to ICU may be associated with the development of POAF. A further study is needed to evaluate changes in iMg in the ICU and iMg at the time of onset of POAF.