What are the specific risks and complications associated with Negative Pressure Wound Therapy (NPWT) on grafts?

NPWT-Specific Risks and Complications on Grafts

While NPWT is generally safe for graft management, clinicians must be vigilant for specific complications including excessive pressure causing tissue damage, bleeding risks, device-related problems, and in orthopedic contexts, a significantly elevated risk of fracture blisters that may contraindicate its use.

Key Complications and Risk Categories

Pressure-Related Tissue Damage

• Excessive negative pressure can cause graft ischemia and tissue injury, particularly when standard pressures (125 mm Hg) are used 1
• Lower pressure settings (75 mm Hg) may mitigate this risk while maintaining therapeutic benefit 1
• In orthopedic patients, NPWT caused fracture blisters in 62.5% of cases compared to only 8.3% with standard dressings (RR 7.50), leading to early trial termination 2

Bleeding and Vascular Complications

• Vessel injury under suction remains a recognized complication, though the incidence is low when NPWT is properly applied 3, 4
• Special precautions are needed near exposed vessels or in highly vascularized wound beds 4
• Hematoma and seroma formation can occur, though rates are not significantly different from standard dressings 2

Dressing-Related Issues

• Maceration at dressing margins occurs when the seal is imperfect or when exudate accumulates at wound edges 3
• Retained foam fragments represent a serious complication requiring meticulous removal technique 4
• Pain during dressing changes is common, with reported scores of 4-5 on visual analog scales, though this tends to decrease over time 1

Device Malfunction and Practical Concerns

• Loss of seal is the most common practical problem, requiring frequent monitoring and reapplication 3
• Device malfunction can compromise therapy effectiveness and requires backup plans 3
• Commercial NPWT systems cost approximately USD 96.51/day versus USD 4.22/day for hospital-made devices, with no difference in clinical outcomes 2

Specific Contraindications and High-Risk Situations

Absolute Caution Scenarios

• Orthopedic surgical wounds: The dramatically elevated blister rate suggests limiting NPWT use until safety is better established in this population 2
• Exposed blood vessels or organs without protective barrier 4
• Untreated osteomyelitis or malignancy in the wound bed 4
• Risk of toxic shock syndrome, particularly with prolonged dressing intervals 4

Relative Contraindications

• Fistula formation risk in certain anatomical locations 4
• Patients unable to tolerate pain associated with therapy 1
• Settings where cost-effectiveness is a primary concern without access to hospital-made alternatives 2

Evidence Quality Considerations

The evidence base shows no significant reduction in surgical site infections, wound dehiscence, or graft failure rates when NPWT is compared to standard dressings in most contexts 2, 5. A 2022 meta-analysis specifically examining radial forearm free flap donor sites concluded that NPWT is not generally recommended due to lack of superiority over conventional dressings 5. The exception is one study showing lower re-operation rates (10.8% vs 25.8%) with hospital-made NPWT devices on skin grafts 2.

Clinical Algorithm for Risk Mitigation

When considering NPWT on grafts:

• Avoid in orthopedic contexts unless benefits clearly outweigh the high blister risk 2
• Use lower pressure settings (75 mm Hg) rather than standard 125 mm Hg to reduce tissue trauma 1
• Ensure meticulous foam removal to prevent retained fragments 4
• Monitor seal integrity every 4-6 hours initially 3
• Protect exposed vessels with non-adherent barriers before foam application 4
• Consider hospital-made devices for equivalent outcomes at substantially lower cost 2