Prediction of flap necrosis with laser induced indocyanine green fluorescence in a rat model

Prediction of necrosis has a clinical relevance in all fields of plastic surgery. The new application of indocyanine green (ICG) fluoroscopy in plastic surgery attows an objective quantification of skin perfusion and a high topographical resolution. The aim of the present study is to determine threshold values for flap perfusion under well-defined experiment at conditions. Twenty random pattern flaps with a length to width ratio of 4:1 (8 X 2 cm(2)) were dissected on the anterior abdominal watt of 20 mate Sprague-Dawley rats. ICG fluoroscopy was performed at the end of the operation. The animals were sacrificed at the seventh postoperative day with a reliable necrosis of the distat part of the flaps. Postoperative ICG fluoroscopy then was analysed both in regions that will survive and undergo necrosis. At day 7 a mean area of 5.5 cm(2) (57% of the total Rap area) survived and a mean of 3.8 cm(2) (43%) became necrotic. The surviving part, of the flap had a mean perfusion index of 62% compared to reference skin. The distal parts of the flap that necrotised showed an average perfusion index of only 19% postoperatively. Differences were statistically highly significant (p < 0.001). Indocyanine green fluoroscopy is a useful toot to evaluate perfusion topographically and predict necrosis. From a statistical point of view a perfusion index of less than 25% of the reference skin can be considered as a sign of developing flap necrosis. (c) 2005 The British Association of Plastic Surgeons. Published by Elsevier Ltd. All rights reserved.