Detecting arterial and venous obstruction in flaps.

Island skin flaps based on the latissimus dorsi muscle were raised in domestic pigs. Flap circulation, maintained only by the vascular pedicle, was monitored by laser Doppler flowmetry, laser photometry, and transcutaneously measured carbon dioxide tension. Both arterial and venous occlusion were accompanied by very low laser Doppler flow values. In laser photometry, the backscattered intensity of light remained unchanged or was slightly increased during arterial occlusion. In response to venous occlusion, however, the light intensity decreased markedly. Transcutaneous carbon dioxide tension increased in both venous and arterial occlusion. When venous outflow pressure was raised incrementally, both the laser Doppler flow value and the total backscattered light intensity fell proportionately. Laser Doppler flowmetry might thus be useful clinically to detect decreased blood flow in transferred flaps, and laser photometry may determine if the decreased flow is related to the arterial or venous side.