Role of pre-operative serum magnesium (Mg) concentration on post-operative pain intensity and opioid usage in gynecologic surgery.

Abstract

e20673 Background: Hypomagnesemia is a common problem, occurring in nearly 12% of hospitalized patients. Due to the link of hypomagnesemia with surgery and the potential antinociceptive effects of Mg multiple trials have been conducted. Unfortunately, the role of IV and epidural Mg supplementation in pain management perioperatively remains controversial. An unanswered question from the literature to date is whether low serum Mg concentrations correlate with pain intensity. This review of patients undergoing gynecological surgeries examines whether pre-operative serum Mg level can affect pain scores and opioid use postoperatively. Methods: This was a retrospective study of the electronic medical record at Methodist University Hospital from October 1st, 2011 to July 31st, 2012. Included for analysis are all cases that underwent a gynecologic surgery and were performed under one attending surgeon. Each patient included in the study had perioperative serum Mg levels, resting and moving pain intensity scores, and amount of opioids used. Patients were excluded for any of the following criteria: missing data, discharge in less than 24 hours, robotic surgery, and use of ketamine in anesthesia. Statistical analysis included descriptive statistics, Spearman’s rank correlation coefficient, and logistic regression. Results: The analysis included 121 patients; 54% were Caucasian, the mean age was 51.7 years and 89% of surgeries were for oncologic indications. Pre-operative serum Mg level was not significantly associated with resting or moving pain intensity scores on post operative day (POD) 1 (p=0.66; p=0.68) or POD 2 (p=0.58, p=0.83). Pre-operative Mg level was not significantly associated with opioid use on POD 1 or 2. Two variables had a possible correlation with opioid usage, on average older patients used a lower level of opioid on average and patients with higher BMI used a higher level of opioids. Conclusions: Preoperative magnesium level has no correlation with pain scores or opioid use. While repletion maybe warranted and magnesium supplementation has minimal toxicity and cost, effect on post-operative pain is uncertain. Larger randomized trials may be warranted.