Assessment of the fluorescein dye test for prediction of skin flap viability in pigs

Abstract

The visual fluorescein dye test for prediction of actual skin flap viability was evaluated in pigs. Two delayed random (4 × 10 cm) and arterial (4 × 20 cm) skin flaps were constructed on one flank of a pig, and four mirror-image skin flaps were raised acutely on the other flank of the same pig. Sodium fluorescein dye (15 mg/kg) was injected intravenously 1 and 18 hr after raising of flaps. The maximum length and area of dye stain in these flaps ( N = 24) were assessed under Wood's lamp illumination, 15 min after dye injection. The actual maximum lengths and areas of skin survival of these flaps in the same pig were measured 7 days postoperatively. It was observed that visual fluorescein dye test performed 1 hr after surgery significantly ( P < 0.05) underestimated the maximum length and area of actual skin survival. On the other hand, when the fluorescein dye test was performed 18 hr postoperatively, the maximum length of dye stain and the maximum length of actual skin viability were highly correlated ( r = 0.97, N = 24, P < 0.01). Their mean values were similar (10.6 ± 0.8 vs 10.8 ± 0.7 cm, mean ± SEM), and their mean coefficient of variation was 5.6 ± 1.6%. Similarly, there was a high degree of correlation ( r = 0.89, N = 24, P < 0.01) between the maximum area of dye stain and actual skin flap viability. Their mean values were similar (68.3 ± 4.5 vs 71.8 ± 3.9%), and their mean coefficient of variation was 8.7 ± 2.4%. It was concluded that the visual fluorescein dye test performed 18 hr after flap surgery provided an accurate prediction of actual skin viability in flap surgery in pigs. This conclusion was confirmed in multiple acute random skin flaps ( N = 32) constructed on the flanks of eight pigs, and also in arterial buttock flaps ( N = 10) and latissimus dorsi myocutaneous flaps ( N = 10) constructed on both flanks of five pigs.