*Purpose: Histidine-tryptophan-ketoglutarate (HTK) and University of Wisconsin (UW) solutions are the two primary solid-organ preservation solutions used in the United States (>95%), but flush volumes vary markedly by region and center. This study analyzes data from a single organ procurement organization (OPO) to determine the actual clinical flush volumes used for HTK and UW for liver and pancreas grafts.

*Methods: All procurements at Indiana Donor Network were analyzed (2016-2020), and data were extracted from the on-site records. Variables included procuring center, solution, volumes, and vessels flushed. Brand and generic versions were considered equivalent. Donation after circulatory death (DCD) procurements were analyzed separately. No clinical transplant outcomes were available.

*Results: Data were analyzed from 1,097 liver and 262 pancreas procurements by over 70 U.S. centers representing 10 of 11 UNOS regions. Of 877 non-DCD adult liver procurements, the large majority of grafts were preserved with HTK (n=792, 90%; UW n=85, 10%). For these liver grafts, more total solution of UW was infused compared to HTK (7L UW vs 4.5L HTK, p=<0.001), with higher volumes of UW used in aortic flush (4L UW vs 3L HTK, p=0.01) and similar volumes in in situ portal flush (2L vs 2L, p=0.02). Of DCD liver procurements, volumes of UW and HTK were similar. Of 206 non-DCD adult pancreas procurements, more total solution of UW was infused (4L UW vs 3L HTK, p=0.04). All DCD pancreas procurements were infused with HTK solution. Solutions were infused at a volume of 61 mL/Kg for non-DCD livers (UW 89mL/kg and HTK 58mL/kg, p<0.001) and for pancreas a volume of 46mL/kg (UW 58mL/kg and HTK 44mL/kg, p=0.03). Flush volumes per kilogram were similar for two solutions in DCD procurements. Of 45 pediatric liver procurements, HTK and UW solutions were infused at similar volumes. Of 17 pancreas, greater UW was infused (2.5L UW vs 2L HTK, p=0.07). For liver procurements, solutions were infused at a volume of 141mL/kg (UW 166mL/kg and HTK 134mL/kg, p=0.3). Of pancreas procurements, overall volume was 86mL/kg (UW 119mL/kg and HTK 79mL/kg, p=0.03).

*Conclusions: Organ flush volume for non-DCD adult liver and pancreas procurements is higher for UW than HTK, while it is similar for DCD procurements. Among pediatrics, the volumes infused of HTK and UW were similar in liver procurements, but higher for UW in pancreas procurements. Overall volumes per kg are much higher for pediatrics than for adults. These data demonstrate that low-volume HTK flush is commonly used, and this practice may be considered as a cost-saving measure for adult and pediatric procurements.

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