Introducing an lsoprenaline Eluting Guidewire: Report on its Design and the Results of the Dose-Determining Pilot Study

Introduction: Retrograde intrarenal surgery is associated with complications, many of which are related to the intrarenal pressure (IRP). We aim to describe the design of a novel isoprenaline-eluting guidewire ("IsoWire") and present the results from the first in vitro release studies and the first animal studies showing its effect on IRP. Materials and Methods: The IsoWire comprises a nitinol core surrounded by a stainless-steel wire wound into a tight coil. The grooves created by this coil created a reservoir for adding a hydrogel coating into which isoprenaline, a beta-agonist, was loaded. Animal studies were performed using a porcine model. For the control, IRP, heart rate (HR), and mean arterial pressure (MAP) were measured continuously for six minutes with a standard guidewire in place. For the experiment, the standard hydrophilic guidewire was removed, the IsoWire was inserted into the renal pelvis, and the same parameters were measured. Results In vitro analysis of the isoprenaline release profile showed that most (63.9 ± 5.9%) of the loaded drug mass was released in the first minute, and almost all of the drug was released in the first 4 minutes exponentially. Porcine studies showed a 25.1% reduction in IRP in the IsoWire that released 10 μg in the first minute; however, there was a marked increase in HR. The average percentage reduction in IRP was 8.95% and 21.3% in the IsoWire that released 5 μg and 7.5 μg of isoprenaline, respectively, with no changes in HR or MAP. Conclusions IsoWire, which releases 5 μg and 7.5 μg of isoprenaline in the first minute, appears to be safe and effective in reducing the IRP. Further studies are needed to establish if the isoprenaline-induced ureteric relaxation will render easier insertion of a UAS, reduce IRP during sheathless RIRS or even promote the practice of sheathless RIRS.