Is experimental muscle flap temperature a reliable indicator of its viability?

This study was designed to assess the effects of environmental factors on experimental muscle flap temperature and to critically evaluate temperature as a modality for assessing vascular patency. A brief overview of the physiology of tissue heat transfer is presented. The right vertebral head of the biceps femoris muscle was used in albino New Zealand rabbits for monitoring temperature. Temperature was recorded simultaneously by means of thermocouples placed into the tested muscle, the contralateral control biceps femoris muscle, the ipsilateral control thigh compartment, and rectally (core temperature). The muscle flap temperature was recorded as a function of time during the following flap manipulations: steady state, exposed muscle, muscle elevated and then replaced with pedicles intact, and pedicles ligated. In addition, the effects of environmental manipulations on muscle flap temperature were evaluated. The constant findings demonstrated that the dominant aspects of muscle temperature are the temperature of the surrounding tissue, as well as the prevailing environmental conditions. Vascular occlusion did not alter muscle temperature. In 3 patients who underwent successful free-flap transfer, muscle temperatures were monitored and found to be labile, and altered by environmental manipulations. We concluded that temperature is an unreliable, nonreproducible method of assessing the vascular status of a muscle flap, unless all environmental variables are meticulously monitored and controlled.