Effects of a noncompressive hematoma on free flap viability

Microvascular free tissue transfer has become an integral component of head and neck reconstructive surgery and historically has a greater than 95% success rate. Hematomas have long been known to cause skin flap necrosis by a variety of mechanisms including direct pressure necrosis, cellular damage secondary to the effects of free radicals, and inflammation. Compression from a hematoma is known to cause free flap compromise. To our knowledge, however, there have been no studies documenting the effect of a noncompressive hematoma surrounding the vascular pedicle on free flap viabiliry. This animal study was designed to assess the effects of a noncompressive hematoma on free flap survival. A right groin cutaneous free flap was created in 32 male Spraque Dawley rats. The rats were then divided into three groups: (1) 10 rats had no fluid added to the anastomotic compartment; (2) 11 rats had 0.5 cc of blood, taken from the femoral artery at the time it was cut, instilled in the anastomotic compartment via the 18-gauge angiocath; and (3) 11 rats had 0.5 cc of pentastarch instilled in the anastomotic compartment via the 18-gauge angiocath. There was 100% free flap survival in all three groups. All vessels examined at the time of sacrifice revealed intact anastomoses and no evidence of luminal clots. This study strongly suggests that in the cutaneous groin free flap model, a perianastomotic noncompressive hematoma has no effect on free flap survival.