Infusion-line pressure as a real-time monitor of convection-enhanced delivery in pre-clinical models

Background: Acute convection-enhanced delivery (CED) is a neurosurgical delivery technique that allows for precise and uniform distribution of an infusate to a brain structure. It remains experimental due to difficulties in ensuring successful delivery. Real-time monitoring is able to provide immediate feedback on cannula placement, infusate distribution, and if the infusion is proceeding as planned or is failing due to reflux or catheter obstruction.

New method: Pressure gradient is the driving force behind CED, with the infusion pressure being directly proportional to the flow-rate. The aim of this study was to assess the feasibility of using infusion-line pressure profiling to distinguish in real-time between succeeding and failing CED infusions. To do so we delivered cresyl violet dye at 0.5, 1.0 and 2.0 μl/min via CED in vitro using 0.6% agarose gel and in vivo to the rat striatum.

Results: Infusions that failed in agarose gel models could only be differentiated late during the procedures. In the rat in vivo model, the infusion-line profiles of obstructed infusions were not distinctive from those of successful infusions.

Comparison with existing method: Intraoperative magnetic resonance imaging (MRI) is used for real-time visualisation of cannula placement and infusate distribution. Particularly for animal pre-clinical work, it would be advantageous to supplement MRI with a cheap, accessible technique to monitor infusions and provide a real-time measure of infusion success or failure.

Conclusions: Infusion-line pressure monitoring was of limited value in identifying successful CED with small volume infusions, whilst its utility for large volume infusion remains unknown.