Onset of Donor Warm Ischemia Time in Donation After Circulatory Death Liver Transplantation: Hypotension or Hypoxia?

The aim of this study was to investigate the impact of hypoxia and hypotension during the agonal phase of donor warm ischemia time (DWIT) on hepatic ischemia/reperfusion injury (IRI) and complications in donation after circulatory death (DCD) liver transplantation. A retrospective single-center study of 93 DCD liver transplants (Maastricht type III) was performed. DWIT was divided into 2 periods: the agonal phase (from withdrawal of treatment [WoT] until circulatory arrest) and the asystolic phase (circulatory arrest until cold perfusion). A drop to <80% in peripheral oxygenation (SpO(2)) was considered as hypoxia in the agonal phase (SpO(2)-agonal) and a drop to <50 mm Hg as hypotension in the agonal phase (SBP-agonal). Peak postoperative aspartate transaminase level >3000 U/L was considered as severe hepatic IRI. SpO(2) dropped within 2 minutes after WoT <80%, whereas the systolic blood pressure dropped to <50 mm Hg after 9 minutes, resulting in a longer SpO(2)-agonal (13 minutes) than SBP-agonal (6 minutes). In multiple logistic regression analysis, only duration of SpO(2)-agonal was associated with severe hepatic IRI (P = 0.006) and not SBP-agonal (P = 0.32). Also, recipients with long SpO(2)-agonal (>13 minutes) had more complications with a higher Comprehensive Complication Index during hospital admission (43.0 versus 32.0; P = 0.002) and 90-day graft loss (26% versus 6%; P = 0.01), compared with recipients with a short SpO(2)-agonal (13 minutes). Furthermore, Cox proportional hazard modeling identified a long SpO(2)-agonal as a risk factor for longterm graft loss (hazard ratio, 3.30; 95% confidence interval, 1.15-9.48; P = 0.03). In conclusion, the onset of hypoxia during the agonal phase is related to the severity of hepatic IRI and postoperative complications. Therefore, SpO(2) <80% should be considered as the start of functional DWIT in DCD liver transplantation.