The effect of hypothermia and tissue perfusion on extended myocutaneous flap viability.

The salutary effect of hypothermia and tissue perfusion on extending the ischemic tolerance of the canine latissimus dorsi myocutaneous flap was demonstrated in this experimental study. A total of 175 flaps from 89 adult mongrel dogs were elevated with one-half the flaps perfused with iced Collins renal preservation solution. With the exception of control flaps kept at ambient temperature, the remaining flaps were stored at 4 degrees C for periods ranging from 24 to 192 hours followed by transplantation into the groins of recipient dogs, with anastomosis of the thoracodorsal artery and vein in an end-to-side manner to the femoral artery and vein, respectively. The study was divided into two distinct sections. The acute phase involved the transplantation of 77 flaps into random recipient dogs, and following a 3-hour period of systemic perfusion, the flaps were removed, weighed, and sectioned for later histologic study. Progressive increase in flap weight was observed up to 96 hours of hypothermia with a sharp decline in weight at 120 hours of hypothermia. The increase in flap weight in the nonperfused flaps was significantly greater than the previously perfused flaps. Histologically, at 120 hours of hypothermia, loss of vascular integrity was noted, suggestive of a no-reflow phenomenon. In the second, or extended-flap, study, 98 flaps were transplanted into the groins of the original donor animal and allowed to remain in situ for a 2-week period. The flaps were then carefully observed for viability, removed, and sectioned for histologic study. Hypothermic support of up to 96 hours extended viability in both perfused and nonperfused flaps, although beyond this hypothermic period viability was seen only in previously perfused flaps. The clinical implications of this study include hypothermic perfusion of a major-extremity amputation prior to replantation or the temporary storage of a free myocutaneous flap.