Timing Relationships for Secondary Ischemia in Rodents: The Effect of Venous Obstruction

Abstract

In a previous study, timing relationships were studied for flaps subjected to secondary ischemia by total pedicle interruption. In the current paper, using a rodent epigastric flap, a similar study for flaps subjected to secondary ischemia by venous obstruction was performed. These conditions were designed to mimic a venous thrombosis following flap transfer, as would be performed clinically. In Experiment 1, the time interval between primary and secondary ischemia was varied. When the interval was 72 hr, flaps with secondary ischemia had similar survival to those with primary ischemia. However, when the time interval was 24 hr, flap survival after secondary ischemia was significantly worse than after primary ischemia (p less than 0.01). In Experiment 2, the duration of primary ischemia was varied (15 min, 30 min or 1.5 hr), prior to a fixed interval between primary and secondary ischemia and 5 hr of secondary ischemia. These conditions produced significantly more necrosis than 5 hr of primary ischemia. Thus, even short periods of primary ischemia may have detrimental effects on flap survival after a subsequent period of secondary ischemia. This may have important clinical ramifications.

Effect of the Delay Phenomenon on Survival of Rat Island Skin Flaps with Total Venous Occlusion

“…The onset of venous occlusion is directly proportional to flap survival. This time of onset has been reported at 72 hr in one study 14 . In the same study, the rate of necrosis was higher in flaps in which venous occlusion has lasted for 24 hr.…”

Ischemia/reperfusion injury in microvascular surgery

“…Surgeons and researchers have noted that this second period of ischemia is much more damaging to the flap than the initial ischemic episode. 28 The biochemical changes during secondary ischemia have been analyzed. There was massive intravascular thrombosis in the flaps undergoing secondary ischemia.…”

Evaluation of clinically applicable exsanguination treatments to alleviate venous congestion in an animal skin flap model

“…The control for this experiment has been established in the literature as a positive control for flap failure with timetables developed for primary and secondary ischemia 10,11,24‐26 . Therefore, it was hypothesized that any survival of a skin flap that underwent the primary and secondary ischemic events would be clinically relevant.…”

“…The simple vascular anatomy of the epigastric skin flap facilitates the reproducibility of the model 9 . Studies using this model have determined a timetable of tolerable ischemic events, in order to develop a treatment schedule that is clinically relevant 10,11 . For this model, 2 hours of primary ischemia were followed 24 hours later by 5 hours of secondary ischemia.…”