June 25, 2019 – Summer Biomechanics, Bioengineering, and Biotransport Conference, Seven Springs, Pennsylvania – Lucas R. Sass, Mohammadreza Khani, et al
Lucas R. Sass1, Mohammadreza Khani1, Gabryel Conley Natividad1, Elliott Marsden1, Shavaine Byass1, Omolola Bangudu1, Aaron R. McCabe2, Laura M. Zitella Verbick2, Shivanand P. Lad3, Bryn A. Martin1
- Department of Biological Engineering, University of Idaho, Moscow, ID, USA
- Minnetronix Neuro, Inc. St. Paul, MN, USA
- Department of Neurological Surgery, Duke University, Raleigh, NC, USA
Introduction
Complications following subarachnoid hemorrhage (SAH) such as delayed cerebral ischemia, vasospasm and hydrocephalus account for the poor prognosis and death of many patients[1]. SAH releases blood into the cerebrospinal fluid (CSF) exposing the surrounding tissue to inflammatory clotting byproducts[2]. Removal of blood via lumbar drain has been shown to positively impact clinical outcomes and the rapid removal of blood from the CSF is the target of a new device aimed at improving patient outcomes. The presented work outlines the assembly and testing of an in vitro platform (Figure 3) modeling active clearance of SAH using a dual lumen catheter-based CSF filtration device[3][4] (NeurapheresisTM System; Minnetronix Neuro, St. Paul, MN). This device introduces a flow loop aimed at improving particle clearance from the CSF.
Results
CSF Geometry: Final cranial and spinal CSF volumes were 215.0 ml and 97.0 ml respectively with a total CSF system volume of 312.0 ml. The final model included realistic spinal nerve root detail as well as a subject specific ventricular system. Spatial-temporal tracer concentration revealed Neurapheresis therapy to dramatically decreased tracer concentration compared to lumbar drain (Figure 2). The difference in concentration decrease was strongest within the upper thoracic spine. At 24 hours, tracer concentration 20 cm below the foramen magnum (FM) had decreased to 1.5% for Neurapheresis therapy and 8.5% for lumbar drain from the initial uniform distribution of 10%.
Discussion
Findings: The developed anthropomorphic in vitro model allowed parametric evaluation of CSF tracer clearance for a subject specific geometry and physiologic conditions. Neurapheresis therapy increased tracer clearance at all time points after ~10 minutes. These changes were most pronounced within the dual-lumen catheter flow-loop region and also extended to the cortical subarachnoid space. Distribution of tracer concentration was relatively uniform around the spinal cord. CSF production stemming from the 4th ventricle outlets decreased local tracer concentration near that region (ie. cisterna magna).
Limitations: Several anatomic simplifications were necessary in the cranial
model due to limitations in 3D printing capabilities and MR image resolution. The model also assumes a rigid CSF space geometry (non-compliant) that
resulted in a constant CSF flow rate throughout the model.
Future work: Effect of Neurapheresis under various physiologic boundary conditions is ongoing. Additional work on a computational analog is also in progress; See companion abstract #423 (Mohammadreza Khani).
References
1. H. Lantigua, et al., Critical Care, vol. 19, Aug 31 2015.
2. J. Bardutzky, et al., Trials, vol. 12, p. 203, Sep 14 2011.
3. G. J. Smilnak, et al., J Infect Dis, vol. 218, pp. 1147-1154, Aug 24 2018.
4. S. L. Blackburn, et al., Oper Neurosurg (Hagerstown), Jun 5 2018.
5. L. R. Sass, Fluids Barriers CNS, vol. 14, p. 36, Dec 19 2017.
Neurapheresis is a trademark of Minnetronix Neuro, Inc.