Low serum vitamin D levels are not associated with increased postoperative pain and opioid requirements: a historical cohort study

Abstract

© 2015, Canadian Anesthesiologists' Society. Purpose: Vitamin D deficiency has been associated with chronic non-specific musculoskeletal pain syndromes; however, studies are lacking with respect to its relationship with postoperative pain. We tested the hypothesis that a lower preoperative vitamin D level is associated with increased postoperative pain and/or opioid consumption in morbidly obese patients who had laparoscopic bariatric surgery. Methods: Data from 185 patients who underwent laparoscopic bariatric surgery at the Cleveland Clinic from 2005-2009 and had a vitamin D level checked within three months of their surgery were included in the analysis. We assessed the relationship between vitamin D levels and the time-weighted average (TWA) of pain scores and total opioid consumption using multivariable regression models adjusted for potential confounders. As a secondary analysis, we compared the TWA of pain scores and opioid consumption between patients who were vitamin D deficient (≤ 20 ng·mL−1) and those who were not (vitamin D > 20 ng·mL−1). Results: The mean (SD) TWA pain score was 3.8 (1.5) and the median interquartile range [IQR] total opioid consumption (morphine equivalent) was 15.6 [18.2] mg during the first 72 hr postoperatively. The median [IQR] vitamin D concentration was 21.8 [17.1] ng·mL−1. The vitamin D level was not significantly associated with either the TWA pain score (Pearson correlation: −0.003; 97.5% confidence interval [CI]: −0.17 to 0.16) or opioid consumption (Spearman correlation: −0.13; 97.5% CI: −0.30 to 0.03). After adjusting for confounders, the estimated average change in TWA pain score was 0.01 (97.5% CI: −0.08 to 0.11) for a five-unit increase in vitamin D (P = 0.77). The estimated ratio of geometric means of total opioid consumption was 0.94 (97.5% CI: 0.86 to 1.03) for a five-unit increase in vitamin D concentration (P = 0.12). No difference was found between patients with vitamin D concentrations > 20 ng·mL−1 and ≤ 20 ng·mL−1 in either TWA pain score (P = 0.91) or total opioid consumption (P = 0.18). Conclusion: We did not find any association between preoperative vitamin D levels and postoperative pain scores/opioid consumption in morbidly obese patients undergoing bariatric surgery.