L. A. Graham1,2, S. S. Illarmo1, S. Mudumbai6,7, M. C. Odden3,4, S. M. Wren2,5 1VA Palo Alto Healthcare Systems, Health Economics Resource Center (HERC), Palo Alto, CA, USA 2Stanford University, Surgery, Palo Alto, CA, USA 3Stanford University, Epidemiology And Population Health, Palo Alto, CA, USA 4VA Palo Alto Healthcare Systems, Geriatric Research, Education, And Clinical Center (GRECC), Palo Alto, CA, USA 5VA Palo Alto Healthcare Systems, Surgical Services, Palo Alto, CA, USA 6Stanford University, Anesthesiology, Perioperative, And Pain Medicine, Palo Alto, CA, USA 7VA Palo Alto Healthcare Systems, Anesthesiology And Perioperative Care Service, Palo Alto, CA, USA
Introduction: Magnesium, an essential mineral with a multitude of physiological functions, has garnered increasing attention for its potential role in postoperative pain management, specifically in multimodal analgesia protocols. In animal studies, magnesium has been shown to interact with the NMDA receptor, a key player in pain signaling pathways, thereby exerting a modulatory influence on pain perception. However, the research in human subjects remains mixed and inconclusive due to small sample sizes, heterogeneity across surgical procedures, and older data. In light of the recent focus on multimodal pain management protocols, our goal was to update the current literature on the impact of magnesium on postoperative pain in a larger and more recent population of general surgery inpatients.
Methods: Intraoperative magnesium administrations were obtained for 2,759 general surgery inpatients undergoing surgery within the Veterans Health Administration (VA) between January 1, 2017, and December 31, 2022. Data were obtained from Picis Clinical Solutions Software, a platform used to collect and store perioperative data, and supplemented with VA Corporate Data Warehouse data. Maximum self-reported pain and opioid use (standardized as oral morphine equivalents, OME) in the 24 hours after surgery were compared among patients receiving intraoperative magnesium versus patients not receiving intraoperative magnesium. Bivariate statistics and multivariable generalized negative binomial and linear models included patient demographics, comorbidity burden, surgery characteristics, pain medication use, and prior pain experience.
Results: 15.1% of patients received intraoperative magnesium (Mean dose=1,793mg, standard deviation (1,311mg)). Intraoperative magnesium use increased drastically from 4.2% in 2017 to 19.1% in 2022 (<0.01) and was more common among patients who underwent shorter, less complex operations, had lower self-reported preoperative pain scores (Mean 3.1 vs. 3.6, p=0.01), or who received other forms of nonopioid analgesia. After adjusting for patient and surgery characteristics, intraoperative magnesium use was associated with marginally significant increases in 24-hour postoperative pain (Mean 6.7 vs. 6.4, p=0.06), pre-to-postoperative pain delta (Mean delta=3.3 vs. 3.0, p=0.07), and 24-hour postoperative OMEs (Mean 14.0 vs. 10.1 OME, p=0.05) as compared patients who did not receive intraoperative magnesium.
Conclusion: In 2022, 20% of general surgery patients received intraoperative magnesium despite limited evidence for its efficacy. Additionally, incorporating magnesium as an analgesic adjunct in multimodal pain management for surgery may not effectively reduce pain and opioid consumption.