[Comparison of secondary ischemia tolerance between free skin flap and island skin flap raised on the buttock of the pig].

Objective: This study was to compare skin viability of the free skin flap and the island skin flap in the pig.

Methods: The comparison was made between the 8 cm x 11 cm surgically denervated free skin flap and the pedicle island skin flap raised contralaterally on the buttock of 50 pigs. The free flap and the pedicle flap were subjected to 2 h of primary warm ischemia followed by 12 h of reperfusion and 0, 2, 4, 6, 10 h of secondary warm ischemia (n = 10). Skin viability was assessed 7 days after secondary ischemia.

Results: Pedicle skin flaps tolerated up to 10 h secondary ischemia without skin necrosis. However, incidences of flap failure (partial or total) in free flaps subjected to 0, 2, 4, 6, 10 h of secondary ischemia were 0, 10%, 50%, 80%, 100%, respectively. In a separate experiment, skin blood flow was studied in contralateral free skin flaps and pedicle island flaps (n = 20) subjected to 4 h of secondary ischemia. The skin reperfusion was very slow in 8 out of 20 free skin flaps at 1, 5 h after secondary is chemia, and the mean skin blood flow measured by 15 microns microspheres in these 8 free skin flaps was only 8% of their contralateral pedicle skin flaps. The mean skin blood flow in the remaining 12 free skin flaps was 76% of their contralateral pedicle skin flap.

Conclusion: These observations were interpreted to indicate that buttock free skin flaps in the pig were less tolerant to secondary ischemia compared with their contralateral pedicle skin flaps subjected to the same ischemic protocol, and this reduced ischemic tolerance in free skin flaps was associated with compromised skin blood flow.