Resident physician UW Madison Madison, Wisconsin, United States
Disclosure(s):
Joyce Koueik, MD, MS: No financial relationships to disclose
Introduction: We’ve previously shown that chronic shunt overdrainage is a major cause of proximal shunt obstruction and that anti-siphon devices or second valves added in series with the primary valve decrease proximal shunt obstruction rates. The present study aims to test the effectiveness of valves placed in series in decreasing overdrainage on a benchtop valve testing platform.
Methods: We developed a pseudo-ventricle (PV) benchtop valve testing platform that comprises a rigid pseudo-ventricle, compliance chamber, pulse generator, and pressure sensors. The PV was used to measure flow rates through a differential pressure shunt valve over 15 minutes under the following simulated physiological conditions: orientation (horizontal/vertical), compliance (low/medium/high), and pulsation generator force (none/low/medium/high). Shunt outflow was tested after a Miethke ball-and-cone valve was placed distally at various distances (1, 5, 10 and 20 cm) from a medium pressure differential valve.
Results: We confirmed the existence of two phases of CSF drainage; a transient phase of rapid rise in flow, and a steady state. The presence of 2 valves in series significantly decreased the outflow in the transient state by 39-76% depending on pulsations and compliance (p < 0.0001). The period of time spent in the transient state before a steady state is reached doubled in the presence of the second valve (p < 0.0001).
Conclusion : Shunt overdrainage can be mitigated by using multiple valves in series. These data confirm both prospective and retrospective cohort studies of shunt patients, and may significantly impact the rate of proximal shunt obstructions.
