Intraoperative Oxygen Delivery and Acute Kidney Injury after Liver Transplantation

Although intraoperative hemodynamic variables were reported to be associated with acute kidney injury (AKI) after liver transplantation, the time-dependent association between intraoperative oxygen delivery and AKI has not yet been evaluated. We reviewed 676 cases of liver transplantation. Oxygen delivery index (DO2I) was calculated at least ten times during surgery. AKI was defined according to the Kidney Disease Improving Global Outcomes criteria. The area under the curve (AUC) was calculated as below a DO2I of 300 (AUC < 300), 400 and 500 mL/min/m2 threshold. Also, the cumulative time below a DO2I of 300 (Time < 300), 400, and 500 mL/min/m2 were calculated. Multivariable logistic regression analysis was performed to evaluate whether AUC < 300 or time < 300 was independently associated with the risk of AKI. As a sensitivity analysis, propensity score matching analysis was performed between the two intraoperative mean DO2I groups using a cutoff of 500 mL/min/m2, and the incidence of AKI was compared between the groups. Multivariable analysis showed that AUC < 300 or time < 300 was an independent predictor of AKI (AUC < 300: odds ratio [OR] = 1.10, 95% confidence interval [CI] 1.06–1.13, time < 300: OR = 1.10, 95% CI 1.08–1.14). Propensity score matching yielded 192 pairs of low and high mean DO2I groups. The incidence of overall and stage 2 or 3 AKI was significantly higher in the lower DO2I group compared to the higher group (overall AKI: lower group, n = 64 (33.3%) vs. higher group, n = 106 (55.2%), p < 0.001). In conclusion, there was a significant time-dependent association between the intraoperative poor oxygen delivery < 300 mL/min/m2 and the risk of AKI after liver transplantation. The intraoperative optimization of oxygen delivery may mitigate the risk of AKI.


Supplemental Table S2
The incidence of acute kidney injury (AKI) according to the groups of high and low model for end-stage liver disease (MELD) score or Child class and cumulative time below intraoperative oxygen delivery index < 300 ml/min/m 2 (time <300). 3

Supplemental Figure S1
Comparison of serum hemoglobin concentration (upper), arterial oxygen partial pressure (middle) and arterial oxygen saturation (lower) during liver transplantation between the patients with and without acute kidney injury. 4

Figure S3
The receiver operating characteristic curves to predict posttransplant acute kidney injury of the area under the threshold of oxygen delivery index (DO 2 I) of 300 ml/min/m 2 (AUC<300), cumulative time below the threshold of DO 2 I of 300 ml/min/m 2 (time<300 minutes), mean, nadir, and standard deviation (SD) of intraoperative DO 2 I. 7

Figure S4
Histograms of the distribution of standardized differences and covariate balance plot before and after matching. 8 Supplemental Table S1. Patient characteristics and perioperative parameters of the patients with high and low mean oxygen delivery index (mean DO2I) after propensity score matching. The values are expressed as the median [interquartile range] or number (%). GRWR = graft recipient body-weight ratio, pRBC = packed red blood cells.
Supplemental Table S2. The incidence of acute kidney injury (AKI) according to the groups of high and low model for end-stage liver disease (MELD) score or Child class and cumulative time below intraoperative oxygen delivery index < 300 ml/min/m 2 (time <300).
The incidence of AKI with high time <300 and high MELD score or Child class C was significantly higher than that of AKI with high time <300 and low MELD score or Child class A or B (P <0.001 after Bonferroni correction for multiple testing. The values are expressed as or number (%).
Supplemental Figure S1. Comparison of serum hemoglobin concentration (upper), arterial oxygen partial pressure (middle) and arterial oxygen saturation (lower) during liver transplantation between the patients with and without acute kidney injury.
The areas under the receiver operating characteristic curves (AUROC) were 0.72 (95% AUROC of AUC <300 was significantly larger than that of AUC <400 or AUC <500. AUROC of time <300 was significantly larger than that of time <400 or AUC <500. Supplemental Figure S3. The receiver operating characteristic curves to predict posttransplant acute kidney injury of the area under the threshold of oxygen delivery index (DO2I) of 300 ml/min/m 2 (AUC<300), cumulative time below the threshold of DO2I of 300 ml/min/m 2 (time<300 minutes), mean, nadir, and standard deviation (SD) of intraoperative DO2I.