Tissue Oxygenation and Wound Healing in Vascular Surgery

Abstract

Are there simple adjuncts that can be applied in patients with peripheral vascular disease that could enhance wound healing and tissue oxygenation? Two large-scale clinical studies were conducted with the aims of targeting two stages of care, namely (i) perioperative treatments to enhance peripheral oxygenation by influencing oxygen delivery via chemical and thermal vasodilation (high-dose oxygen, a prostacyclin analogue, and extended active warming) during bypass surgery to the lower limbs, and (ii) topical negative therapy (TNP) dressings for high-risk foot wounds, such as following debridement or minor amputations in the diabetic foot. These therapies have been shown to be of benefit in other clinical settings, such as abdominal surgery and to treat abdominal wounds. How these adjuncts would help in patients with vascular disease is unknown. Mechanisms underlying the potential effects of these treatments on wound healing were assessed biochemically by quantifying hydroxyproline (a surrogate marker of collagen), growth factors, cytokines, and their respective mRNAs. Healing rates were determined by changes in wound volume over time using an innovative stereophotographic device (FastScan™). Tissue oxygenation was measured using hyperspectral technology (OxyVu™). The reliability and feasibility of using these devices was tested in clinical studies. Measurements obtained using these innovative instruments yielded excellent inter-operator and intra-operator reliability and correlated well with other methods of measurement, thus showing promise for assessment of tissue oxygenation and wound healing in clinical settings. No benefits were demonstrated in 71 patients with regard to surgical wound healing or tissue oxygenation in bypass surgery by perioperative adjunctive treatment. OxyVu identified increased tissue oxygenation in the foot in the acute phase following bypass surgery, validating its clinical use. In acute foot wounds treated with TNP, there was no significant difference in wound volume reduction at 2 weeks when compared with traditional dressings (44.2% for TNP versus 20.9% for the control; p=0.15). However, there was a trend towards an enhanced healing rate, and maximum wound depth was significantly less than that achieved using traditional dressings (36.0% for TNP versus 17.6% for the control; p=0.03). Given that no differences were found in hydroxyproline levels, growth factors, or tissue oxygenation, the benefits of TNP might involve more than merely enhanced production of granulation tissue, possibly involving mechanical (macrostrain) effects.