Preoperative metformin use associated with better outcomes after major surgery
medwireNews: People with type 2 diabetes who are treated with metformin prior to undergoing major surgical interventions may have better postoperative outcomes than those without exposure to the drug, researchers report.
These findings are based on a retrospective cohort study of 5460 US adults with type 2 diabetes who underwent major surgery – most commonly general (30%) or orthopedic (29%) – between 2010 and 2016. Patients were aged an average of 67.7 years, had a mean BMI of 33.5 kg/m2, and were followed up for a median of approximately 4.6 years.
As reported in JAMA Surgery, the mortality rate within 90 days of surgery was 3% among the 2730 patients with a metformin prescription in the 180 days prior to surgery or inclusion of metformin on their active medication list prior to surgery, compared with 5% for the 2730 propensity score-matched patients with no prior metformin exposure.
These findings translated into a significant 28% lower mortality risk among metformin-treated patients at 90 days, and the difference remained significant at the 5-year follow-up, with rates of 13% and 17% in the metformin and no metformin groups, respectively. However, the 30-day mortality rate was the same in both groups, at 2%.
Christopher Seymour (Clinical Research, Investigation, and Systems Modeling of Acute Illness Center, Pittsburgh, Pennsylvania, USA) and team also found that hospital readmission rates were significantly lower among metformin- versus non-metformin-treated patients at 30 days (11 vs 13%) and at 90 days (20 vs 23%).
These findings “suggest that preoperative metformin prescriptions may be associated with decreased postoperative mortality and readmission compared with no preoperative exposure to this medication, but further research is needed to ascertain if this relationship is causal,” write the researchers.
They note that their study had a number of limitations, including a lack of information on the preoperative duration and dose of metformin, and limited generalizability given that the study population “consisted of primarily older individuals with diabetes who had substantial preoperative comorbidities.” Approximately three-quarters of the study population had comorbid hypertension, while around a quarter had coronary artery disease.
Writing in an accompanying commentary, Elizabeth George and Sherry Wren, both from Stanford University School of Medicine in California, USA, say that “[t]his study demonstrates how variables besides coexisting medical diseases can affect surgical outcomes,” with metformin joining “β-blockers, statins, and immunonutrition as preoperative agents associated with improved surgical outcomes.”
The commentators caution, however, that statins were not considered as a confounding variable in the study, and recommend that future studies consider statin use given that “both statins and metformin are anti-inflammatory and immunomodulatory agents.”
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