Do Prolonged Donor Warm Ischemic Times Correlate with Kidney Transplant Outcomes? The Largest Study of Donation After Circulatory Death Donors in the United States

BACKGROUND: Donation after circulatory death (DCD) kidneys are discarded because of long donor warm ischemic times (WIT), despite an unclear association between WIT and outcomes. METHODS: Using Organ Procurement and Transplantation Network data of adult DCD kidney recipients from 2015 to 2022, we examined donor WIT, using total WIT and 6 definitions of functional WIT (agonal, asystolic, and time beyond derangements in blood pressure or oxygen saturation). We fit logistic and Cox regression models for primary nonfunction (PNF) and 1-y death-censored graft failure (DCGF), respectively, treating WIT linearly and with a spline at the 87.5th percentile. RESULTS: Among 13 673 donors and 24 271 recipients, the median total WIT was 26 min and 1474 transplants were performed from donors with >60 min of total WIT. PNF incidence was 2.6%; 1-y DCGF was 3.8 events per 100 patient-years. In both models, asystolic time was associated with increased hazard of 1-y DCGF (adjusted hazard ratio per 5 min with time linear, 1.12; 95% confidence interval [CI], 1.03-1.22; adjusted hazard ratio per 1 min beyond 12 min, 1.07; 95% CI, 1.02-1.13) and increased odds of PNF (adjusted odds ratio per 5 min with time linear, 1.18; 95% CI, 1.07-1.30; adjusted odds ratio per 1 min beyond 12 min, 1.08; 95% CI, 1.02-1.13). Other measures of donor WIT were not associated with DCGF or PNF. Holding other covariates constant, the absolute risk of 1-y DCGF increased by 0.9% when asystolic time increased from 5 to 25 min in the linear model. CONCLUSIONS: Donors with prolonged total and functional WITs, apart from asystolic time, show no association with 1-y DCGF and PNF. We advocate using these kidneys to expand the donor pool.