Bipolar Coagulation of Occluding Tissue in VP Shunts

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DESCRIPTION (provided by applicant): Development of a bipolar coagulator is proposed for electrosurgical coagulation or cutting of adherent brain tissue that is occluding the flow of cerebrospinal fluid (CSF) into the intake holes of an implanted ventricular catheter. Currently, during revision surgery for ventriculoperitoneal (VP) shunts, monopolar coagulators are used to clear the occluding tissue, either to reestablish the function of the catheter or to allow it to be safely removed and replaced. For this application, however, bipolar coagulators offer better control of the distribution of the electrical current and may reduce the likelihood of serious complications. In particular, blood vessel damage and severe subarachnoid hemorrhages in some patients have been associated with the use of monopolar coagulation in VP shunt revision surgery. The proposed Phase I project will first establish a User Requirements Specification and then develop a set of prototypes for bipolar coagulators with electrode configurations suitable for operation inside a ventricular catheter. The prototypes will be integrated with available electro-surgical generators and inserted into ventricular catheters which have been immersed in fresh egg white. The testing will compare the bipolar prototypes with currently-used monopolar stylets with regard to the volume of coagulum produced, in order to accomplish a given coagulation task. As a last step, electrocautery will be applied to sheep brain tissue, obtained frozen from a suitable supplier, and analysis of the resulting lesion sizes will allow correction, if necessary, of the results obtained in egg white for brain tissue. Phase II is expected to verify the hypothesized benefits of bipolar coagulation in this application with animal models. Ventriculoperitoneal shunts are a life-saving treatment for hydrocephalus patients, but shunt catheters commonly become blocked over time and must be replaced to resolve this life-threatening situation. Neurosurgeons routinely employ off-label use of monopolar cautery to reduce the known risk of intraventricular hemorrhage (IVH) during the roughly 23,000 ventricular catheter revisions performed each year in the United States. However, IVH remains a risk, and recent case studies suggest an emerging risk of aneurysm formation associated with monopolar cautery in this application. The proposed bipolar coagulator is intended as a safer means for removal of occluded ventricular catheters from hydrocephalus patients undergoing shunt revision surgery.