E18 - Effect of Indwelling Subarachnoid Catheters on Systemic Inflammatory Markers and CSF in Healthy Adult Horses

Abstract: Background- Long-term subarachnoid catheterization (SAC) in horses has rarely been described in the literature. A better understanding of the local and systemic effects of prolonged catheterization will expand clinical and research applications. Objectives- To describe the effects of indwelling SAC at the lumbosacral (LS) space in healthy adult horses via complete hematology and CSF evaluation. Animals- Two healthy adult horses used in a study evaluating the pharmacokinetics of diclazuril. Methods- Prospective longitudinal pilot study. Subarachnoid catheters were placed at the LS space. CSF was collected at 0 h (placement), 19 h, and every 24 h thereafter until 211 h. Whole blood was collected concurrently into EDTA tubes for same-day CBC and fibrinogen. CSF was stored at 1–6 °C and analyzed within 24 h for total nucleated cell count, RBC count, total protein and cytopathologic evaluation by a clinical pathologist. Results- Horses remained afebrile with normal CBCs and plasma fibrinogen concentrations aside from a mild band neutrophilia at 163 h. One horse developed a mild neutrophilic pleocytosis at 91 h that progressed to a marked neutrophilic pleocytosis with rare intracellular bacteria at 211 h. The second horse developed a moderate neutrophilic pleocytosis at 19h that improved to a mild neutrophilic pleocytosis by 91 h but further CSF collection was inhibited by catheter patency. Conclusions and Clinical Importance- Despite inflammatory changes in CSF, systemic inflammatory markers remained largely unremarkable. These preliminary findings suggest SAC is well tolerated and local inflammation may not result in obvious systemic effects before 211 h.