Introduction: The outcomes of DCD liver transplantation have been inferior to those of donation after brain death liver transplantation and careful donor and recipient selection are required to optimise the results of DCD liver transplantation. Warm ischaemia time has been identified as an important risk factor for adverse outcome after DCD liver transplantation.  However, current definitions of warm ischaemia involve recording the time between different key time points. They do not account for the total exposure to hypotension, which is a function of both blood pressure and time, during the agonal period after withdrawal of cardiorespiratory support (WCRS). The aim of this study is to identify risk factors for primary non-function (PNF) after DCD liver transplantation, with particular attention to hypotension exposure.
Methods: Cases were identified and data were extracted from the Liver Transplant Unit Victoria’s prospectively maintained database. The study period was a 10-year period from 1 October 2007 to 30 September 2017.
Hypotension exposure was defined as the ideal blood pressure (100 mmHg for systolic, 80 mmHg for mean and 60 mmHg for diastolic) multiplied by the time in minutes between WCRS and perfusion minus the area under curve (AUC) of the blood pressure (for each of systolic, mean and diastolic) versus time that was observed between WCRS and asystole.
PNF was defined as death or retransplantation within 1 week of transplantation in the absence of a definable cause, such as hepatic artery thrombosis.
Categorical variables were analysed using chi square and continuous variables, using Mann-Whitney U test. AUC of the receiver operator characteristic curve was calculated for each of systolic, mean and diastolic hypotension exposure. The Youden’s J statistic was used to calculate the ideal cutoff values and sensitivity and specificity were calculated for these.
Results: Forty DCD liver transplants were performed during the study period. PNF occurred in three of 40 (7.5%) cases. Cases of PNF in comparison to those with no PNF had higher systolic hypotension exposure (4,227+/-1,572 vs 2,807+/-708 mmHg.min, respectively, OR 1.002, 95% CI 1.000-1.0040, P = 0.035), mean hypotension exposure (3,829+/-1,509 vs 2,539+/-600 mmHg.min, respectively, OR 1.003, 95% CI 1.000-1.006, P = 0.032) and diastolic hypotension exposure (3,357+/-1,405 vs 2,166+/-537 mmHg.min, respectively, OR 1.004, 95% CI 1.000-1.008, P = 0.045). The AUC was 0.865 for systolic hypotension exposure (cutoff 1,821 mmHg.min, sensitivity 100%, specificity 73%), 0.873 for mean hypotension exposure (cutoff 1,498 mmHg.min, sensitivity 100%, specificity 73%) and 0.853 for diastolic hypotension exposure (cutoff 1,077 mmHg.min, sensitivity 100%, specificity 78%).
Conclusion: Hypotension exposure is predictive of PNF following DCD liver transplantation and could be used to aid in the decision of whether to transplant DCD livers.