Effect of anemia on the fasciocutaneous flap survival in a rat model

Objective/Hypothesis: Ablative surgery for head and neck cancer that creates large composite defects often results in a significant decrease in the hematocrit level. These defects are best reconstructed with a microvascular free tissue transfer. Effect of the decreased hematocrit on microvascular flap survival is controversial. The purpose of this study was to assess the effect of isovolemic anemia on flap survival in a rat model. Study Design: Prospective analysis. Methods: Ninety rats were used (30 control and 60 experimental animals). Experimental animals were rendered anemic by blood draw and volume resuscitated with either a colloid (30 animals) or crystalloid (30 animals) solution. In all animals a ventral fasciocutaneous flap was raised. A vascular clamp was applied to the arteriovenous pedicle, and different ischemic times were allowed to elapse before clamp removal. Flap survival was assessed at 5 days. Probit analysis was performed for the three animal groups. Results: A significantly increased probability of the flap survival was found in the anemic animals compared with the control group (P ≤.05). No difference was found between the colloid and crystalloid resuscitation groups. Conclusions: A decreased hematocrit level increases fasciocutaneous flap tolerance to ischemia and significantly increases the primary ischemic time in the ventral flap clamp model in rats. Fluid replacement with either crystalloid or colloid produces identical results.