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Temporary Targeted Blood Flow Interruption using a Reverse Thermosensitive Polymer to Facilitate Bloodless Partial Nephrectomy
Niall J. Harty, M.D.1, Jessica M. DeLong, M.D. 1, Spencer I. Kozinn, M.D. 1, Alireza Moinzadeh, M.D. 1, Sebastian Flacke, M.D. 1, Jim Benn, PhD2, John A. Libertino, M.D. 1, Peter N. Madras, M.D. 2
1Lahey Clinic, Burlington, MA, 2Pluromed Inc, Woburn, MA

BACKGROUND: Previous work has demonstrated that Lumagel™ (Pluromed Inc., Woburn, MA), a non-toxic, non-ionic polymer with reverse thermosensitive properties, may be used to obtain a bloodless operative field for robotic partial nephrectomy in a porcine model. We extend this work to laparoscopic and open partial nephrectomy, in which we obtain targeted renal ischemia for resection while allowing normal perfusion to the remaining kidney. There are configurations of renal vasculature which require complete flow interruption for bloodless partial nephrectomy. We adapt our technique to allow main renal artery occlusion and compare polymer occlusion to clamping in this setting.
METHODS: Seven pigs were included in this study. Five pigs underwent a total of 9 angiographic segmental and 3 main renal artery occlusions, while two pigs underwent main renal artery clamping. Four partial nephrectomies were performed in an open fashion to directly assess vascular occlusion, and three were performed laparoscopically. Duration of selective ischemia was recorded and location of vascular occlusion was noted both angiographically and visually. All resection sites were reinforced with a bolster dressing. Degree of venous backbleeding was assessed by making a small incision into the ischemic portion of the kidney prior to resection. Reliability of polymer reversal from a solid back to a liquid state with iced saline allowing reperfusion was evaluated. Following surgery, all pigs were euthanized.
RESULTS: Selective renal ischemia was achieved in all cases using Lumagel™ injected through an automated power injector. Initial injections of 0.4cc for segmental branches and 1.0cc for main renal occlusion were used. Incremental doses of 0.02 to 0.10cc were used as needed to a maximum total dose of 2cc. Perfusion hemostasis was achieved for 30 minutes in all main and segmental renal artery occlusions. Correlation of radiographic, laparoscopic, and visual assessment of vascular occlusion was consistent. Surgical resection time averaged 11.0 minutes (range 10-13) and 23.3 (range 9-40) in the open and laparoscopic groups, respectively. One laparoscopic partial nephrectomy was complicated by significant blood loss secondary to an insufficient dose of Lumagel™ within the segmental artery. This was corrected by injecting more polymer at the occlusion site and subsequent partial nephrectomy was performed in a near bloodless field. Minimal venous backbleeding was noted with isolated main renal artery occlusion. Reversal of the polymer to a liquid state was consistent angiographically and visually in all seven cases. Time to complete flow return averaged 7 and 2.5 minutes for Lumagel™ and arterial clamping, respectively
CONCLUSIONS: We have developed a reliable and reproducible technique for delivery of Lumagel™ for temporary vascular occlusion in both main and segmental renal arteries. Flow return to the kidney is slower with Lumagel™ compared to clamping. Preparations are underway for acute trials in the calf model to assure success with larger vessels and chronic trials for safety studies in the porcine model.


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