Effect of trauma dose on spinal cord edema.

The spinal cord of anesthetized cats was subjected to impact trauma of different intensities to determine how changes in trauma magnitude affect the formation and distribution of edema. All animals underwent a laminectomy to expose the cord segments corresponding to the T5--7 vertebrae. Fourteen cats were injected with fluorescein-labeled albumin, and then subjected to 260, 360, 500, or 700 gm-cm injury to the spinal cord. They were sacrificed at 8 hours after trauma. Twelve cats were injected with fluorescein-labeled dextrans of 20,000, 40,000, 70,000, or 150,000 molecular weight (MW) prior to 500 gm-cm injury, and sacrificed 8 hours after trauma. Serial cord sections from both groups were studied by fluorescence microscopy. In nine cats, sections of cord were removed 8 hours after trauma of 260, 360, or 500 gm-cm impact, and 1-cm sections were assayed for dry weight. Extravasated tracers were present in areas of hemorrhage at the site of impact in all animals. Extension of tracers and increases in tissue water rostrally and caudally from the site of impact were observed consistently with time only in animals receiving 500 or 700 gm-cm trauma. The distance of migration was similar for all tracers. The longitudinal distribution of increased tissue water was consistent with the distribution of fluorescein markers. The findings indicate that the longitudinal extension of posttraumatic edema is directly related to the amount of initial trauma.