Introduction: Kidneys are particularly susceptible to anoxic damage and ischemia due to their aerobic metabolism. Hypothermia protects against anoxia by reducing the energy dependent metabolic activities and is optimally achieved at 1-2^oC for cold storage and 4-8^oC for machine perfusion during transportation. There are no effective methods to prevent warming during implantation. The warming of a donor kidney during the vascular anastomosis of a transplant i.e., second warm-ischemia time (SWIT), is independently associated with higher rates of delayed graft function, premature graft failure, and the discard of high-risk kidneys. SWIT is protracted in patients with complex anatomy, obesity, and in minimally invasive transplantation. Elimination of SWIT via intra-operative thermal regulation has the potential to increase the donor pool and proffer significant cost-savings.

Method: The objective biodesign process was used to identify this clinical need through observation, develop a needs statement, and filter the need against others. A needs-specification document was developed outlining stakeholder value propositions, health-economic value, and existing intellectual property. ASTS surgeons (n=185) and organ-preservation specialists were surveyed to develop the needs-criteria for a device. The invention step resulted in several embodiments that addressed the clinical need, population, and outcome outlined in our needs statement. Following objective concept selection, a prototype device applied to the kidney immediately prior to anastomosis was built using stretchable hydrogel and phase-change gel. Adult porcine kidneys were used to test the device in a validated retroperitoneal-model placed within a water bath at 37^oC (98.6^oF). Core temperatures were monitored using implanted probes at 30 second intervals. Time to reach the maximum ischemic threshold of necrosis (15^oC, 59^oF) was compared to an ice + gauze control.

Results: A single-use device to facilitate the vascular anastomosis and eliminate SWIT was developed. The needs-criteria were addressed with a retraction handle, no tubing, a low profile, and a flexible material to accommodate variable kidney sizes. The device-covered kidneys (n=3) did not reach the ischemic threshold at the 60-minute cutoff and remained below 6^oC compared with the ice + gauze covered control kidneys (17±1.8 minutes, n=3, p <0.001).

Conclusion: A breakthrough designated medical device to facilitate the vascular anastomosis and effectively eliminate second-warm-ischemia time was successfully developed. Device-covered kidneys remained well below the ischemic threshold of necrosis for a duration exceeding 95% of vascular anastomoses. Use of this device will enhance the surgical workflow and enable minimally-invasive transplantation and has the potential to significantly impact rates of delayed graft function, organ longevity, and organ acceptance practices.