The impact of donor anemia on post-liver transplant outcomes: A stratified analysis by cold ischemia time

Cold ischemia time (CIT) has long been correlated with liver transplant (LT) graft viability. Donor anemia, leading to suboptimal oxygen delivery to the liver, may theoretically worsen the ischemia-reperfusion injury associated with CIT. In this study, we stratify CIT by tertiles and investigate the potential relationship between donor anemia, CIT, and LT-recipient prognosis by varying donor hematocrit (Hct) thresholds. The United Network for Organ Sharing (UNOS) Standard Transplant Analysis and Research (STAR) Database was used to study LT patients between 2005 and 2019. Patients were categorized into tertiles by donor Hct thresholds of < 27.6, 27.6-32.3, and > 32.3, and compared amongst all CIT and set thresholds. Primary outcomes assessed were all-cause mortality and graft failure. All study results are reported in comparison to LT recipients with donor Hct below 27.6. In the composite population encompassing all CIT thresholds, LT recipients experienced higher all-cause mortality (aHR 1.04; 95% CI 1.00-1.08, p=0.05), as well as graft failure (aHR 1.10; 95% CI 1.01-1.20, p=0.02) with donor Hct above 32.3. There were no significant differences in primary outcomes within the first CIT tertile. Recipients within the 2nd CIT tertile experienced higher rates of graft failure with Hct above 32.3 (aHR 1.17; 95% CI 1.01-1.37, p=0.04). Higher all-cause mortality was observed in recipients with donor Hct above 32.3 (aHR 1.07; 95% CI 1.00-1.14, p=0.04) within the 3rd tertile of CIT. Normal donor Hct and mild donor anemia were associated with worse LT-recipient outcomes when compared to moderate-to-severe donor anemia. This may potentially represent a local adaptation in the donor graft from chronic anemia or a multifactorial, organization-based process. These associations warrant further investigation.