Oxygenation and microcirculation during skin stretching in undermined and nonundermined skin.

The aim of this experimental study was to assess the skin microcirculation of undermined and nonundermined wound edges closed with a skin-stretching device. In eight piglets, 9 x 9-cm wounds were created on both flanks by excision of the skin and the subcutaneous layer down to the muscular fascia, with general anesthesia. On one flank, the surrounding skin was completely undermined. For a period of 30 minutes, wound closure was performed with a stretching device, using the principle of load cycling. The device stretched the skin and moved the opposing wound edges toward each other. During this period, laser Doppler flowmetry and transcutaneous oximetry were simultaneously used to monitor microcirculation and oxygenation in the stretched skin of both flanks. Undermining of the surrounding skin produced a 12 percent decrease in the laser Doppler flowmetry signal and a 21 percent decrease in the transcutaneous oximetry value. Skin stretching resulted in decreases in the laser Doppler flowmetry signals and the transcutaneous oximetry values, whether or not the skin was undermined. Releasing the stretching device resulted in rapid normalization of the laser Doppler flowmetry values in undermined and nonundermined skin and a slow return of the transcutaneous oximetry values to close to baseline levels in nonundermined skin. The transcutaneous oximetry values in undermined skin did not return to baseline levels; each period of skin stretching resulted in an additional decrease in the transcutaneous oximetry values. Stretching of undermined skin for 30 minutes produced a significant (p < 0.0001) decrease in skin oxygenation. As a result, 50 percent of the undermined stretched skin demonstrated skin necrosis at the wound edges, which was still present after 1 week. Wound healing in the nonundermined stretched skin proceeded without problems. It is concluded from these experiments that the viability of undermined skin becomes compromised as a result of significantly decreased oxygen availability in the skin during and after stretching. Consequently, it is recommended that skin stretching be performed on nonundermined skin, rather than undermined skin. In addition, when skin is stretched to close a large defect, it is logical to use cyclic loading, so that recuperation of the skin circulation can occur. Furthermore, laser Doppler flowmetry seemed to produce atypical signals in monitoring of skin viability of wound edges closed with a skin-stretching device.