Augmentation of blood flow in delayed random skin flaps in the pig: effect of length of delay period and angiogenesis

Skin capillary blood flow and angiogenesis were studied by radioactive microsphere and morphometry technique, respectively, in delayed random skin flaps in the pig. Skin flaps were delayed for 2, 3, 4, 6, or 14 days. Blood flow was measured 6 hours after complete raising of acute and delayed random skin flaps on the opposite flanks of the same pig. It was observed that the capillary blood flow increased significantly (p less than 0.05) within 2 days of delay compared to the acute skin flaps. This capillary blood flow further increased by about 100 percent between days 2 and 3, started to plateau after day 3, and remained unchanged between days 4 and 14 of delay. This increase in capillary blood flow was mainly in the distal portion of the delayed skin flaps. There was no indication of an increase in the density of arteries in all delay periods studied. Our observations did not support the hypotheses that the delay phenomenon involves angiogenesis or long-term adaptation to ischemia, as have been hypothesized previously. The possible mechanism of delay is discussed.