EVALUATION OF PEDICLED SKIN FLAP VIABILITY BY PH, TEMPERATURE AND FLUORESCEIN - AN EXPERIMENTAL-STUDY

In order to test methods of predicting skin flap viability, a skin fla p model in Sprague-Dawley rats was established. As criteria for studyi ng skin flap survival, we compared measurement of skin pH, temperature , as well as fluorescence photography and computer aided digital morph ometry (CADM). Ninety male Sprague-Dawley rats were divided into three groups in which pedicles were clamped for 10, 15, or 20 h. A standard ized bipedicled skin flap was prepared, maintained by the epigastric a rtery, vein and nerve. All flaps were sutured back in place immediatel y after clamping. We found that postoperative prediction of flap survi val based solely upon external appearance was impossible until the 2nd postoperative day. Changes in pH were not statistically significant i n the prediction of vital or necrotic flaps. The temperature measureme nts showed, that in the event of viability the decrease in flap temper ature versus the reference temperature (rectal temperature) was signif icant (P < 0.0094 in Group II, 15 h of ischaemia) or at least a tenden cy to significance (P < 0.059 in Group III, 10 h of ischaemia) bigger than in the event of partial or total flap necrosis. The photographic documentation using fluorescein showed that all coloured areas survive d. Group I (20 h) showed predominantly total flap necrosis. Most flaps in Group LII (10 h) exhibited a small necrotic area at the tip. In Gr oup II (15 h) no typical staining pattern could be observed. Furthermo re, computer aided digital morphometry demonstrated a decrease of the necrotic area by 7% between the 2nd and 4th postoperative day in Group s II and III. The method which gave the most exact prediction about vi ability was the fluorescein staining of the flaps via the tail vein.