Examining microcirculation improves the angiosome theory in explaining the delay phenomenon in a rabbit model.

Topographic and temporal changes in circulation were studied with laser Doppler flowmetry in rabbit dorsal skin flaps comprised of three vascular territories. The reduced caliber vessels along the dorsal median line, rather than the vessels interconnecting the thoracodorsal and deep circumflex iliac vascular trees, behaved as true choke vessels. The authors found an increased proximal circulation lasting for 48 to 72 hr. This coincided with the reported rapid phase of choke vessel dilatation. The increase in distal circulation began after postoperative day 3, coinciding with the resolution of proximal hyperemia but not with the earlier prominent vasodilatation. Secondary elevation of the flaps at 3 weeks did not disturb the homogeneous distribution of circulation and did not cause a hyperemic response at postoperative 24 hr. Based on these findings, the authors postulate that the same mechanisms may underlie the rapid choke vessel dilatation and microvascular dilatation observed at 48 to 72 hr postoperatively. Surgical delay may work not only by diminishing the resistance to blood flow along the flap, but also by diminishing the steal effect of increased proximal microcirculation, which characterizes this period, over the distal circulation.