Perfusion, viability, and pedicle dependence in acute and delayed rat island skin flaps.

Purpose: Although surgical delay phenomenon has been widely investigated, its pathophysiology has not been fully elucidated.

Methods: In 25 Spraque-Dawley rats, an 8 x 8 cm2 epigastric skin flap consisting of 4 vertical zones A through D (farthest from vascular pedicle) was outlined. All animals were perfused twice with colored fluorescent microspheres: immediately before and after flap elevation (Acute, n = 10) and before and after pedicle ligation on POD 8 (Delayed, n = 15).

Results: After acute flap elevation, peripheral perfusion dropped significantly in zone C (0.29 +/- 0.01 vs. 0.19 +/- 0.04 ml g(-1) min(-1); P < 0.01) and zone D (0.33 +/- 0.09 vs 0.01 +/- 0.01 ml g(-1) min(-1); P < 0.01), while global flap perfusion remained unchanged. Total and regional blood flow did not change in the Delayed group after pedicle ligation.

Conclusions: Elevation of a pedicled flap caused significant decrease in distal flap perfusion while maintaining proximal and total flap perfusion. Eight-day delay was adequate to establish sufficient flap perfusion independent of the vascular pedicle.