Does metformin improve surgical outcomes for patients with diabetes?

  • Reitz KM & al.
  • JAMA Surg
  • 8 Apr 2020

  • curated by Miriam Tucker
  • Clinical Essentials
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Takeaway

  • Preoperative (≤180 days) metformin prescriptions (PMPs) are associated with reduced postoperative mortality and readmission following major surgery in patients with diabetes.

Why this matters

  • Almost 50% of people with type 2 diabetes require surgery during their lifetime.

Study design

  • Health system electronic health record data for 10,088 adults with diabetes who underwent a major operation during 2010-2016. 
  • 59% had PMPs, and 54% were propensity score matched (2730 each with and without PMPs), followed until December 18, 2018.
  • Funding: UPMC; NIH.

Key results

  • PMPs were associated with significant absolute risk reduction (ARR) for mortality by day 90: 1.28% (0.26%-2.31%).
  • No reduction seen at day 30, however.
  • Patients with PMPs had lower HR for mortality by:
    • Day 90: 0.72 (P=.02); and
    • Year 5: 0.74 (P=.001).
  • With PMP, significant ARRs (95% CIs) were observed for readmission by:
    • Day 30: 2.09% (0.35%-3.82%); and 
    • Day 90: 2.78% (0.62%-4.95%).
  • Association also seen with death as a competing risk at:
    • Day 30: sub-HR, 0.84 (0.72-0.98); 
    • Day 90: 0.86 (0.77-0.97).
  • Patients with PMPs had significantly lower mean preoperative neutrophil-to-leukocyte ratio vs no metformin (4.5 vs 5.0; P<.001>

Limitations

  • Potential residual confounding.
  • Single health care system database.
  • Death, readmission likely underrepresented.
  • Operative duration, metformin dose unknown.
  • Multiple surgery types.