Effects of 8-Gy radiation on the microcirculation of muscle flaps in the rat

Combination of radical excision and radiation has been used as a treatment modality for cancer patients. As a result, in reconstructive surgery there is often a need to harvest flaps in the vicinity of previously irradiated t issues. Radiation has been shown to cause progressive injury to the macroci rculation and microcirculation, often jeopardizing flap survival. The purpo se of this study was to examine whether radiation significantly affects the sequence of leukocyte-endothelial interactions or the hemodynamics of the muscle flap in both acute and chronic situations. Male Sprague-Dawley rats (n = 42) were divided into seven groups of six rats each. Rats in group I w ere not irradiated. Groups II through VII received 8-Gy radiation to the ri ght groin and scrotum. Groups II, III, and TV were examined at 4, 24 and 72 hours, respectively, and groups V, VI, and VII were examined at 1, 2 and 1 2 weeks. For intravital microscopy, the cremaster muscle was dissected on i ts neurovascular pedicle. Vessel diameters and red blood cell velocities we re measured in the central cremasteric branches and branch arterioles. Capi llary perfusion was evaluated in 27 visual fields of each flap. Leukocyte-e ndothelial interactions were evaluated by numbers of rolling, adhering, and transmigrating leukocytes in postcapillary venules. In the same postcapill ary venule, we measured the endothelial edema index (constriction index). T he hemodynamics of irradiated flaps did not differ significantly from those of controls. Diameter and red blood cell velocity were increased in the fi rst- and second-order arterioles and were highest at 72 hours and 1 week. A fter irradiation, third-order arterioles were constricted. Radiation reduce d capillary perfusion by 4.3 percent. None of the differences were statisti cally significant. Neither leukocyte behavior nor the constriction indices differed among the groups. In conclusion, low-dose radiation of 8 Gy does n ot affect hemodynamics or leukocyte-endothelial interactions of muscle flap s in the rat. Muscle tissue with intact microvasculature call be harvested for reconstructive procedures after low-dose radiation.