Ischemic tolerance of canine jejunal flaps.

Reconstruction of the upper aerodigestive tract with free jejunal flaps is now an accepted alternative to more conventional techniques. Success rates for microsurgical transfer approach 100 percent; however, complications following this technique are reported despite technical success, ischemia being implicated as an important etiologic factor. A histologic analysis of canine jejunum subjected to progressively increasing normothermic ischemic periods was undertaken. One hundred canine jejunal flaps were randomly assigned ischemia times between 0 and 12 hours and evaluated 48 hours after reperfusion. Results indicate that (1) isolation of a segment of jejunum on a single pedicle results in no light microscopic changes, (2) histologic changes are evident after 30 minutes of warm ischemia, but gross changes are not evident until greater than 2 hours of ischemia, (3) histologic changes that occur with ischemic insults are progressive and cumulative, (4) mucosal ulcerations are evident at 3 hours, (5) partial-thickness muscle necrosis occurs in all segments at 4 hours, (6) 5 hours of ischemia results in spotty full-thickness necrosis of the bowel wall in 80 percent of the flaps, and (7) by 6 hours, full-thickness myonecrosis is present in all segments. Ischemic periods greater than 6 hours result in increasing histologic disarray.