EFFECT OF HYPERTONIC SALINE ON LEUKOCYTE ACTIVITY AFTER SPINAL-CORD INJURY

Study Design. The effect of intravenous administration of hypertonic s aline on leukocyte adhesion after compression injury of the spinal cor d was evaluated.Objectives. To investigate changes in leukocyte adhesi on after spinal cord injury and to evaluate the effect of hypertonic s aline on this process. Summary of Background Data. Leukocytes have bee n thought to exacerbate tissue injury after ischemia-reperfusion. Down regulating and reducing the number of circulating leukocytes has atten uated tissue damage in various models of cerebral ischemia. Recently, investigators have reported that leukocytes exacerbate injury in the s pinal cord after trauma. Other recent findings have indicated that hyp ertonic saline may play a role in decreasing leukocyte adhesion and ac tivation. Methods. Sprague-Dawley rats were anesthetized, and a C3-C5 laminectomy was performed. Injury was caused by 35 g of compression ap plied for the cord for 10 minutes. Animals were divided into three gro ups: sham treated, untreated, and treated. The treated animals receive d 7.5% hypertonic saline (5 mL/kg, intravenously) 5 minutes after the injury. Sticking leukocytes and shear rate were measured using fluores cence microscopy. Results. Administration of 7.5% hypertonic saline af ter injury significantly decreased the number of sticking leukocytes i n the venules and arterioles. Shear rate was unchanged between the gro ups. Conclusion. The results show that an increase in leukocyte adhesi on after a compressive injury is attenuated by the administration of 7 .5% hypertonic saline. The decrease in adhesion cannot be attributed t o changes in the shearing forces, because no significant change was ob served in the shear rate. Hypertonic saline may interfere with their a bility to swell and thus may prevent activation.