# Hypothermic Machine Perfusion Allows Safe Delay in Kidney Transplantation After Cold Storage

## TL;DR

Using hypothermic machine perfusion after cold storage for kidney transplants reduces delayed graft function without harming long-term outcomes.

## Contribution

Demonstrates that sequential hypothermic machine perfusion after cold storage is safe and reduces delayed graft function in kidney transplants.

## Key findings

- Delayed graft function occurred less frequently in the SCS+HMP group (17.6%) compared to the SCS group (39.2%).
- HMP was independently associated with lower odds of delayed graft function (OR 0.34; 95% CI 0.13–0.82).
- Patient and death-censored graft survival and renal function were comparable between the two groups over 24 months.

## Abstract

Background/Objectives: Static cold storage (SCS) remains the standard method of kidney preservation. As a referral transplant center, we frequently receive kidneys initially preserved with SCS and subsequently initiate prolonged hypothermic machine perfusion (HMP) to extend allocation time and optimize recipient matching. The clinical impact of this sequential preservation strategy remains incompletely defined. To compare outcomes between kidneys preserved with SCS followed by prolonged HMP (SCS+HMP) and SCS alone. Methods: This single-center retrospective study included 200 adult recipients of kidney transplants from brain-dead donors (67 SCS+HMP; 133 SCS). Outcomes were primary graft non-function (PNF), delayed graft function (DGF), patient and death-censored graft survival, and renal function over 24 months. Univariable and multivariable analyses identified predictors of DGF. Propensity score matching was performed to adjust for baseline imbalances. Results: In the SCS+HMP group, grafts underwent a median of 244 min of SCS followed by 1300 min of HMP, resulting in longer total cold ischemia time than SCS alone (1545 vs. 1104 min; p < 0.001). After matching, 51 pairs (n = 102) were analyzed. In the matched cohort, PNF occurred in 2 patients (3.9%) in the SCS+HMP group and 3 patients (5.9%) in the SCS group (p = 1.0). DGF occurred less frequently in the SCS+HMP group than in the SCS group (17.6% vs. 39.2%; p = 0.027). In multivariable Firth penalized logistic regression, HMP was independently associated with lower odds of DGF (OR 0.34; 95% CI 0.13–0.82). During the 24-month follow-up, patient survival, death-censored graft survival, and creatinine trajectories were comparable between groups. Conclusions: Sequential HMP after initial SCS enables extended preservation and was associated with a lower incidence of delayed graft function. This strategy does not compromise patient survival, death-censored graft survival, or renal function at 24 months.