Overview
Definition:
Negative pressure wound therapy (NPWT), also known as vacuum-assisted closure (VAC), is a therapeutic technique using a controlled, sub-atmospheric pressure to treat a variety of acute and chronic wounds
It involves applying a foam dressing, an airtight seal, and a vacuum pump to draw wound exudate and infectious material away from the wound bed while promoting granulation tissue formation and wound contraction.
Epidemiology:
NPWT is increasingly used for complex wounds, including surgical dehiscence, diabetic foot ulcers, pressure ulcers, venous leg ulcers, and traumatic wounds
Its application is becoming standard for wounds that fail to heal with conventional treatments, impacting millions of patients annually who suffer from chronic wound complications.
Clinical Significance:
NPWT is crucial for accelerating wound healing, reducing edema, managing exudate, decreasing bacterial burden, and promoting perfusion to the wound bed
For surgical residents and those preparing for DNB and NEET SS exams, understanding its principles, indications, contraindications, and setup is vital for optimal patient outcomes in a variety of surgical and trauma scenarios.
Indications
Wound Types:
Acute and chronic wounds
Surgical incisional wounds that are difficult to close
Dehisced wounds
Flaps and grafts
Partial-thickness burns
Diabetic ulcers
Pressure ulcers
Venous insufficiency ulcers
Traumatic wounds
Fasciotomies.
Wound Characteristics:
Wounds with moderate to heavy exudate
Wounds with significant dead space
Wounds requiring frequent dressing changes
Wounds failing to heal with conventional therapy
Wounds with infectious component.
Goals Of Therapy:
Promote granulation tissue formation
Reduce edema
Remove exudate and infectious material
Enhance wound contraction
Prepare wound bed for closure (secondary intention, flap, or graft)
Reduce bacterial load.
Contraindications
Absolute Contraindications:
Untreated osteomyelitis
Necrotic tissue with eschar present
Malignancy in the wound
Exposed blood vessels, nerves, or organs
Documented allergy to dressing components.
Relative Contraindications:
Anticoagulant therapy
Fragile skin surrounding the wound
Patient tolerance to pain
Active bleeding
Fistulas to organs not surgically managed
Uncontrolled infection not responding to systemic antibiotics.
Preoperative Preparation
Patient Assessment:
Thorough wound assessment including size, depth, exudate amount and type, presence of necrosis, and surrounding skin condition
Assessment of patient's overall health status and comorbidities
Review of current medications, especially anticoagulants.
Wound Bed Preparation:
Debridement of all necrotic tissue and eschar
Thorough irrigation of the wound with saline or antiseptic solution
Control of active bleeding.
Equipment Gathering:
Select appropriate NPWT system (disposable or reusable pump)
Choose correct foam dressing size and type (hydrophobic or hydrophilic)
Obtain transparent drape for sealing
Gather wound prep supplies (gloves, scissors, tape, drain connector, tubing, exudate collection canister).
Procedure Steps
Dressing Application:
Place the foam dressing into the wound cavity, ensuring it fills the entire space without bridging over edges
Trim excess foam if necessary, but maintain contact with the entire wound bed.
Seal Application:
Apply the transparent drape over the foam dressing, extending at least 2-3 cm beyond the wound edges onto intact periwound skin
Smooth out the drape to create an airtight seal, eliminating wrinkles and gaps.
Port Placement And Connection:
Cut a small opening in the drape over the foam dressing, near the edge, but not over the wound
Insert the canister connector (or therapy unit port) through the opening, ensuring it makes good contact with the foam
Secure the connector with adhesive tape to maintain seal integrity.
Pump Connection And Activation:
Connect the therapy unit tubing to the canister connector
Turn on the NPWT pump and set the prescribed pressure (typically -125 mmHg in continuous or intermittent mode)
Verify the seal by observing for leaks and ensuring the pressure holds.
Postoperative Care
Monitoring Frequency:
Monitor the NPWT system daily for the first few days, then as clinically indicated
Check for leaks, canister fill level, and ensure the pump is functioning correctly
Assess wound for drainage volume, color, and odor.
Dressing Changes:
Dressing changes are typically performed every 48-72 hours, or when the canister is full, the seal is compromised, or significant wound debris is present
Re-assess wound bed, perform debridement if necessary, and reapply NPWT dressing
The frequency of changes can be extended based on wound progress and exudate levels.
Exudate Management:
Monitor the volume and characteristics of wound exudate
If excessive, ensure adequate seal and pump function
Consider adjusting therapy mode (continuous vs
intermittent) or dressing type based on exudate load
Regular canister changes are essential.
Patient Education:
Educate the patient and caregivers on the importance of maintaining the seal, recognizing signs of leaks, and reporting any concerns
Advise on mobility and activity restrictions as per surgical plan.
Complications
Early Complications:
Pain at the application site
Skin maceration or irritation from the drape
Leakage of the seal
Ineffective negative pressure
Bleeding from the wound bed.
Late Complications:
Infection of the wound
Delayed healing due to improper use or non-adherence
Granulation tissue overgrowth blocking ports
Allergic reactions to dressing components.
Prevention Strategies:
Proper patient selection and contraindication review
Meticulous wound debridement and preparation
Careful application of dressing and seal to ensure airtightness
Regular monitoring for leaks and pressure integrity
Adequate pain management
Appropriate antibiotic therapy if infection is suspected.
Key Points
Exam Focus:
Understanding indications and contraindications for NPWT is critical for DNB and NEET SS
Know the standard pressure settings (-125 mmHg) and common modes (continuous/intermittent)
Be able to describe the steps of setup and troubleshoot common issues like leaks.
Clinical Pearls:
Ensure complete filling of dead space with foam to prevent undermining
Use the drape to seal the entire wound bed and at least 2-3 cm of surrounding healthy skin
Regular assessment of the wound bed is crucial for progress monitoring and timely intervention.
Common Mistakes:
Applying NPWT over eschar or necrotic tissue
Failing to achieve an airtight seal
Incorrect foam placement leading to bridging or underfilling
Not monitoring the system regularly for leaks or canister fill levels
Inadequate pain management during and after application.