Abstract WP214: Comparative Analysis of CSF Drainage from Lumbar and External Ventricular Drains in Aneurysmal Subarachnoid Hemorrhage

Introduction: Delayed cerebral ischemia is the most widely recognized mediator of secondary brain injury in aneurysmal subarachnoid hemorrhage (aSAH), primarily resulting from toxic, blood byproducts in the subarachnoid space. Recent trials have subsequently demonstrated that incorporating lumbar drains (LD) into standard clinical care may improve functional outcomes by accelerating the removal of these blood products from the leptomeningeal space. However, there remains a paucity of data on the differences in measured red blood cell (RBC) concentrations in cerebrospinal fluid (CSF) collected from both LDs and external ventricular drains (EVD) in real-world clinical practice to support this mechanism. Methods: We retrospectively evaluated the first five consecutive patients with aSAH who had both types of drains placed at a single, major academic institution. The CSF cell counts collected from LDs and EVDs at multiple time points were compared, assessing the concentration of RBCs. The time points were grouped by early window (<72 hours) and late window (7-10 days) CSF collection. We used Wilcoxon Signed-Rank tests to evaluate the proportional differences in RBC concentration between the two cohorts, as this approach is robust and well-suited for small sample sizes. To assess SAH resolution qualitatively, computed tomography (CT) imaging studies were additionally reviewed and compared. Results: Five patients with aSAH were included in the study (mean age: 60.6 years, 3 females). All patients had EVDs and LDs placed within 72 hours of index rupture. There were no complications associated with LD placement. RBC concentrations in the collected CSF were dramatically higher in the LD cohort. In the early collection window, the median difference of RBCs collected from LDs compared to EVDs was 569,000[281,000–779,000], reflecting a 9.3-fold higher concentration of RBCs in LD compared to EVD CSF (p=0.031). After 7-10 days of continuous drainage, the LD cohort had higher RBC counts (median difference: 35,400[27,600–398,250]), though this difference did not reach statistical significance (p=0.063). When comparing the volume of SAH on head CT imaging, all patients demonstrated notable reductions after 1 week of continuous drainage. Conclusion: We find that CSF drained from LDs used in the treatment of aSAH exhibited significantly higher concentrations of blood breakdown products, reflected by a 9-fold higher concentration of RBCs compared to ventricular CSF at initial placement.