Ultrasonic Debridement for the Treatment of Infected Vascular Graft

Introduction : Vascular surgical site infection (SSI) is a feared complication of major vascular surgery procedures. Depending on the virulence of the infectious pathogen and the site of surgery, its presentation is extremely variable, ranging from severe sepsis to slow-evolving prosthetic colonisation by bacterial biofilm. Usually it is associated with poor patients’ prognosis and low rates of limb salvage. Medical treatment alone is not effective, given the very low penetration of antibiotic into the bacterial biofilm. Radical surgical treatment is the current mainstay, consisting of complete graft removal and reconstruction with autogenous or extra-anatomic conduits. Unfortunately it is burdened by high morbidity and mortality rates, especially in those patients who are unfit for open major vascular procedures, furthermore recurrent SSI is not to be ruled out. Less invasive surgical techniques, allowing partial or no graft excision, have therefore been recently introduced. Aim of our study is to evaluate the results of a novel SSI treatment consisting of associated ultrasonic debridement and antibiotic therapy in a subset of patients considered at extremely high risk for major surgery. We used this technique to achieve the best tissue and or graft debridement while minimising the invasiveness of surgery. Materials/Methods Ultrasound (US) technology and its interaction with living tissues has been already studied: the largest experience comes from dentistry for cleansing purpose and lately ultrasonic debridement has gained a role in the treatment of nonhealing chronic leg ulcers. When applied to infected wounds, US generate mechanical and cavitational energy that preferentially disrupts necrotic tissues, due to their lower tensile strength, and stimulate formation of granulation tissue. Besides, US enhancement of antibiotic action against bacterial biofilms associated with implant infection has been well documented by several in-vivo experimental studies. We used an ultrasonic generator operating through a piezoelectric probe vibrating at 26 KHz with a vibratory amplitude of 15-30 µm and irrigating normal saline. Patients with a prosthetic vascular graft infection and poor medical condition or unavailable autogenous graft underwent an extensive US debridement on the graft and wound tissues to allow a less invasive reconstruction. Non incorporated vascular prostheses and surrounding tissues were treated with this device by moving the probe over their surfaces until all necrotic parts and fibrin were removed and the colour of the graft and tissue returned to appear normal. Ultrasonic debridement was followed by local antibiotic irrigation and was associated to antibiogram-oriented systemic antimicrobial treatment. Graft removal and Sartorius muscle flap to cover the inguinal region were selectively employed Patients’ charts were reviewed to extract their history, lab data, operative details, cultures and follow up. Results Our study involved 12 patients with a mean age of 73 years (range 57-92) composed of 7 males and 5 females. SSI onset was early in 8 cases and late in 4. Possible clinical presentations were draining sinus tract (5 patients), wound dehiscence (5 patients) and acute hemorrhage due to prosthesis’ detachment (2 patients). Prosthetic materials were Dacron (8 patients), PTFE (1 patient), composite Dacron-PTFE (2 patients) and bovine pericardium (1 patient). US debridement was performed after partial graft excision in order to allow an in situ reconstruction with a Silver prosthetic graft in 5 patients, while 7 patients underwent US debridement without graft removal. A Sartorius flap to cover the groin was carried out in 5 cases. Cultures revealed a single infectious pathogen (4 patients) or ≥2 pathogens (6 patients); in the two remaining patients no microorganism was found. We noticed no harm on Dacron grafts even when an intensive and prolonged debridement was done; PTFE grafts needed a special attention, because of a slight loss of impermeability after long ultrasound exposure. However no major damage occurred to any of our grafts. Estimated freedom from recurrent infection was 91.6% at 6 months (1 early recurrence) and 83.3% at 1 and 2 years (1 late recurrence). Limb survival was 81.8% at 6 months, 72.7% at 1 year and 63.6% at 2 years. Early post-operative mortality was 8.3% (1 patient died because of cardiac complications). Conclusions In our experience ultrasonic debridement of infected grafts obtained promising results. We believe that it can be considered as another viable option for the treatment of this dramatic complication. An extensive debridement of the graft and of surrounding tissues allowed us to treat patients more conservatively without compromising the chance of eradication of the infectious pathogen.