Monitoring of Rat Skin Flap Ischemia by Bioelectrical Impedance Measurements

Abstract

In the current study the authors evaluated McFarlane flap viability by bioelectrical impedance measurements. Opposition to the flow of an alternative electrical current through tissue is called bioelectrical impedance. In 30 rats, a cranially pedicled, 11 x 4-cm McFarlane flap was designed on the dorsum. The flap was divided into 11 virtual zones. Bioelectrical impedance values of these zones was measured using a hand-made bioelectrical impedance meter. Measurements were acquired before flap elevation (control values) and after flap elevation (experimental values) at hour 0, hour 1, hour 2, hour 3, hour 4, hour 5, hour 6, day 1, day 2, day 3, and day 7. Bioelectrical impedance decreased first at 11 cm, which was the most distal part of the flap at 1 hour after flap elevation. Three hours after flap elevation and later, the distal half of the flap persistently displayed lower bioelectrical impedance values than the control, and eventually these zones became necrotic. This study showed that the average bioelectrical impedance value of healthy rat skin was 1,773 kOhm. After flap elevation, all zones with bioelectrical impedance values of 1,650 kOhm or less became necrotic absolutely. Bioelectrical impedance measurements are safe, fast, noninvasive, and cheap compared with other techniques used to predict flap necrosis. In the rat McFarlane flap, it is possible to detect the nonsurviving part of the flap 3 hours after flap elevation. This method could be applied to certain clinical conditions to determine the correct level of debridement.