Clinical Trial of a Silver Eluting Dressing System

Rationale:

One of the most common post-operative complications of surgical procedures remains surgical site infection, which causes significant morbidity and healthcare costs (estimated at $1.5 billion per year) among hospitalized patients. Surgical wounds for lower extremity revascularization are particularly prone to infection and dehiscence, with rates in some series as high as 44%(Kent, Bartek et al. 1996). Currently, the Guideline for Prevention of Surgical Site Infection recommends the use of sterile dressing to protect closed incisions for 24 to 48 hour postoperatively. However, no evidence-based recommendations are made with regards to dressing types for use in post-operative incision care.

A plethora of wound dressings are available in the market, with silver-based dressing among these recent innovations. Topical silver treatment is an effective bactericidal agent that does not induce bacterial resistance when used in therapeutic levels. Acticoat Absorbent®(Smith and Nephew, Inc.), an antimicrobial barrier dressing is coated with nanocrystalline silver that delivers a controlled, sustained (up to three days) dose of silver ions. Additionally, this dressing absorbs moisture (minimizing wound maceration), and is safe and effective against a broad range of microorganisms. Acticoat Absorbent® (Acticoat) is indicated for surgical wounds, chronic wounds, and burn wounds; however, data are lacking regarding in its potential role in postoperative surgical incision wound infection prophylaxis.

The Principal Investigator recently completed a non-concurrent, single-institution study of patients who received conventional non-silver containing dressing with Acticoat as post-operative dressing following defined lower extremity revascularizations(Childress, Berceli et al. 2007). The study population comprised 216 patients who underwent 248 cases that met inclusion criteria. Both groups were similar with regards to age at the time of first procedure, gender, race, diabetes, hypertension, current smoking, and renal insufficiency (creatinine >1.5 mg/L). Furthermore, both groups had tissue loss as the most common indication for the lower extremity revascularization procedure, with 47% (55/118) for the control group and 38% (49/130) for the treatment group. Moreover, autogenous vein bypass graft was the most common procedure performed for the control (65/118, 55% of procedures) and treatment (54/130, 42% of procedures) groups.

The surgeons and other providers found the dressing regimen easy to apply and care for post-operatively. Revascularization pulses could be palpated through the dressing, and the low profile permitted identification of post-operative soft tissue changes such as hematomas. Compressive ace bandages could be applied without disturbing the original dressing.

Regarding the primary findings, no substantial dressing material specific complications were noted, including no apparent allergic reactions. The wound complication rate for the control group was 14% (17/118), and for the treatment group was 5% (7/130). Over the intervention phase, the wound overall complication rate fell by 64% (c2 = 5.76, df = 1, p = 0.016).

These findings provide clinical evidence that an Acticoat based dressing system offers a potentially efficacious, cost-effective adjunct to reduce surgical site infections for lower extremity revascularization. Based on this data, we believe that further investigation via multi-center randomized clinical trial is warranted. Thus for the current proposal we hypothesize that immediate application of Acticoat Absorbent® as a post-operative dressing would reduce closed incisional wound complications in patients undergoing lower extremity revascularizations involving infrainguinal skin incisions will result in a clinically significant reduction in wound complication rates compared to standard non-silver eluting dressing material.

Procedure:

• Patient randomized in OR after wound closure completed
• Wound closure technique at the discretion of the surgeon (Dermabond is a dressing and can not be utilized)
• Final OR dressing is test (silver vs standard) dressing, secured per surgeon preference
• Original OR dressing stays in place until gross soiling impairs standard wound hygiene, clinical need to remove, or POD#3, whichever comes first
• Subsequent dressings, wound care at the discretion of providers
• Visual wound checks at least at 2 and 4 weeks (+/- 5 days)

Clinical, economic, patient quality of life, and resource utilization data is then collected at standard clinical encounters

Primary Endpoint: Any wound complication within 30 days

Power and Sample Size Calculations:

• Current endpoint rate at least 25%(Kent, Bartek et al. 1996; Nguyen, Brahmanandam et al. 2007)
• Anticipate 10% absolute (40% relative) wound complication rate reduction(Childress, Berceli et al. 2007)
• Power 0.8
• alpha 0.05
• control event rate of 0.25
• treatment event rate of 0.15
• 1:1 randomization
• -->total study sample size 250 per group (500 total).