BACKGROUND AND PURPOSE:

• There is insufficient high-quality evidence regarding closed incision negative pressure wound therapy (NPWT) dressings for reducing SSI in women with obesity
  • Many studies are industry-funded
• Gillespie et al. (BMJ, 2021) compared the effectiveness and safety of prophylactic closed incision NPWT vs standard surgical dressings for prevention of SSI in women with obesity undergoing cesarean

METHODS:

• Multicenter, pragmatic, randomized, controlled, parallel group, superiority trial
• Participants
  • Pre-pregnancy BMI ≥30
  • Elective or semi-urgent caesarean (all categories of cesarean except those cases where there is urgent threat to the mother or fetus)
• Intervention
  • Closed incision NPWT
  • Standard dressing
• Study design
  • Randomization prior to cesarean | Emergent cases were not included due to concern regarding obtaining consent
  • Women and clinicians were not masked | Outcome assessors and statistician were blinded to treatment allocation
  • Intention to treat analysis
• Power analysis
  • 5% reduction in SSI considered clinically significant
  • 90% power and 5% significance level
  • 1045 per group required assuming 10% ‘lost to follow up’ rate  
• Primary outcome
  • Cumulative incidence of SSI 30 days after surgery
• Secondary outcomes
  • Depth of SSI: Superficial | Deep | Organ/body space
  • Rates of wound complications
    • Dehiscence | Hematoma | Seroma | Bleeding | Bruising
  • Length of hospital stay
  • Rates of dressing related adverse events

RESULTS:

• Closed incision NPWT: 1017 women | Standard dressing: 1018 women
• There was no significant difference in the incidence of SSI between the intervention groups
  • Closed incision NPWT: 7.4%
  • Standard dressing: 9.7%
  • Risk ratio 0.76 (95% CI, 0.57 to 1.01); P = 0.06
• Post hoc analyses to explore the effect of missing data found the same direction of effect (closed incision NPWT reducing SSI), as well as statistical significance
• Blistering occurred in more women who received closed incision NPWT
  • Closed incision NPWT: 4.0%
  • Standard dressing: 2.3%
  • Risk ratio 1.72 (95% CI, 1.04 to 2.85); P = 0.03

CONCLUSION:

• While there was a 3% absolute risk reduction for SSI using closed incision NPWT, the result was not statistically significant  
• Women who received closed incision NPWT were more likely to experience skin blistering
• Limitations include
  • Exclusion of emergent cesareans which would include women at high risk for SSI
  • Lower than expected cumulative SSI incidence, which could lead to a false negative result (type II error)
• The authors conclude

This difference, although close to statistical significance, possibly underestimates the effectiveness of closed incision NPWT in this population

On balance, the results of the conservative primary, multivariable adjusted model, and post hoc sensitivity analyses should be considered alongside the growing body of evidence of the benefits of closed incision NPWT and given the number of obese women undergoing caesarean section globally

Learn More – Primary Sources:

Closed incision negative pressure wound therapy versus standard dressings in obese women undergoing caesarean section: multicentre parallel group randomised controlled trial

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