Identifying risk factors in renal allografts before transplant: machine-measured renal resistance and posttransplant allograft survival

Knowing When to Ignore the Numbers: Single-Center Experience Transplanting Deceased Donor Kidneys with Poor Perfusion Parameters

BACKGROUND

Hypothermic machine perfusion is frequently used in evaluating marginal kidneys with poor perfusion parameters (PPP) contributing to delays in kidney placement or discard. We examined outcomes in deceased donor kidney transplants with PPP compared with those with optimal perfusion parameters (OPP).

STUDY DESIGN

We conducted a retrospective single-center cohort study from 2001 to 2021 comparing PPP (n = 91) with OPP (n = 598) deceased donor kidney transplants. PPP was defined as terminal flow ≤80 mL/min and terminal resistance ≥0.40 mmHg/mL/min. OPP was defined as terminal flow ≥120 mL/min and terminal resistance ≤0.20 mmHg/mL/min.

RESULTS

Mean terminal flow was PPP 66 ± 16 vs OPP 149 ± 21 mL/min and resistance was PPP 0.47 ± 0.10 vs OPP 0.15 ± 0.04 mmHg/mL/min (both p < 0.001). Donor age, donation after cardiac death, and terminal serum creatinine levels were similar between groups. Mean Kidney Donor Profile Index was higher among PPP donors (PPP 65 ± 23% vs OPP 52 ± 27%, p < 0.001). The PPP transplant group had more females and lower weight and BMI. Delayed graft function was comparable (PPP 32% vs OPP 27%, p = 0.33) even though cold ischemia times trended toward longer in PPP kidneys (PPP 28 ± 10 vs OPP 26 ± 9 hours, p = 0.09). One-year patient survival (PPP 98% vs OPP 97%, p = 0.84) and graft survival (PPP 91% vs OPP 92%, p = 0.23) were equivalent. PPP did predict inferior overall and death-censored graft survival long-term (overall hazard ratio 1.63, 95% CI 1.19 to 2.23 and death-censored hazard ratio 1.77, 95% CI 1.15 to 2.74). At 1 year, the estimated glomerular filtration rate was higher with OPP kidneys (PPP 40 ± 17 vs OPP 52 ± 19 mL/min/1.73 m 2 , p < 0.001).

CONCLUSIONS

Short-term outcomes in PPP kidneys were comparable to OPP kidneys despite higher Kidney Donor Profile Index and longer cold ischemia times, suggesting a role for increased utilization of these organs with careful recipient selection.

Efficacy and Safety of Machine Perfusion for Brain Death Marginal Donor Kidney Transplantation: A Report of 2 Cases

BACKGROUND

After the revised organ transplant law came into effect in Japan, donations of organs under brain death have been increasing; however, because of the expansion of donor indications, donations from expanded criteria donors and cardiac arrest donors (donation after cardiac death) have also increased. In kidney transplantation, ischemia-reperfusion injury results in a high rate of delayed graft function, which adversely affects patients' long-term prognoses. Hypothermic machine perfusion preservation results in superior postoperative function and survival rates compared with cold storage preservation. We used an organ preservation device for kidneys and performed a graft viability evaluation before to kidney transplantation.

METHODS

We used the CMP-X08 perfusion device (Chuo-Seiko Co, Ltd, Asahikawa, Hokkaido, Japan) and Belzer MPS solution to preserve the donated organ. The perfusion pressure and temperature were monitored during cold storage with continuous perfusion. Standard renal transplantation protocols were followed. A renal biopsy was performed 1 hour after transplantation and the renal function was evaluated. This study followed the principles of the Declaration of Helsinki.

RESULTS

The first presented case is of a 63-year-old woman who received a kidney from a middle-aged man with brain death due to hypoxic encephalopathy. The creatinine at the time of admission was 0.9 mg/dL and at the time of excision was 2.86 mg/dL. The total perfusion time was 120 minutes. The total ischemia time was 7 hours and 15 minutes. The recipient urinated 115 minutes postoperatively, and no dialysis was required. The second presented case is of a 47-year-old man with a 15-year history of dialysis who received a kidney from a middle-aged woman with brain death due to subarachnoid hemorrhage. The creatinine at the time of admission was 0.8 mg/dL and at the time of excision was 0.77 mg/dL. The total perfusion time was 240 minutes. The total ischemia time was 13 hours and 14 minutes. The recipient urinated 38 minutes postoperatively, and no dialysis was required.

CONCLUSIONS

Mechanical perfusion storage performed for 2 to 4 hours resulted in a viable organ that was successfully transplanted in both cases.

A Novel Preservation Solution Containing Quercetin and Sucrose for Porcine Kidney Transplantation

In organ transplantation, the University of Wisconsin (UW) solution has been the gold standard for organ preservation. Quercetin (Que) has numerous antioxidant and anti-inflammatory activities, and sucrose (Suc) may be effective for cold storage (CS). This study aimed to investigate the in vitro protective effect of Que and Suc on cold injury to the kidney and to determine whether Que + Suc could improve ischemia-reperfusion injury during CS and hypothermic oxygenated perfusion (HOPE) in autologous transplantation models.

METHODS

BHK-21 cells were stored at 4°C for 3 days in UW solution for CS/machine perfusion (CS/MP-UW) with Que (33.1 μM, 3.3 μM, 0.33 μM) and Suc (0.1 M). In a porcine model of renal autologous transplantation, left kidney grafts were preserved under 3 conditions: group 1, CS preservation for 24 hours; group 2, CS preservation for 22 hours and HOPE with CS/MP-UW solution for 2 hours; and group 3, identical preservation as group 2, with Que and Suc added to the solution. Animals were euthanized on day 7 after autologous transplantation.

RESULTS

After 3 days of CS preservation, the CS/MP-UW solution with Que (33.1 μM, 3.3 μM) and Suc showed significant cell protection against cold injury. In the porcine model of renal autologous transplantation, the last blood Cre level and the blood lipid hydroperoxide on posttransplantation day 2 were significantly different between group 1 and group 3. Moreover, the total endothelial, glomerular, tubular, interstitial (EGTI) histology score in the kidney tissue was also significantly different. Regarding the change in renal resistance in HOPE, the decrease observed in group 3 was significantly larger than that in group 2.

CONCLUSIONS

Our results suggest that the addition of Que and Suc to a UW solution can improve kidney preservation and could potentially enhance the outcome of kidney transplantation.

Delayed graft function and perfusion parameters of kidneys from uncontrolled donors after circulatory death

Better preservation and evaluation of kidneys from donors after circulatory death serve to increase the number of kidneys available for transplantation and hypothermic machine perfusion has been shown to decrease ischemia reperfusion injury and delayed graft function. Data on relation between hemodynamic parameters during hypothermic machine perfusion and delayed graft function in kidneys from donors after circulatory death are so far scarce and not univocal. We aimed at assessing whether hemodynamic parameters measured during hypothermic machine perfusion (flow, mean perfusion pressure, and renal resistance) are associated with delayed graft function in 26 kidneys retrieved from uncontrolled donors after circulatory death. In our series, the incidence of delayed graft function was 57.7% (15/26). Recipients who developed delayed graft function had a longer warm ischemic time (p = 0.04). All hemodynamic parameters measured during hypothermic machine perfusion were comparable between recipients with delayed graft function and those without. According to our data, in kidneys from uncontrolled donors after circulatory death, a longer warm ischemic time (that is the overall time of no flow, as the sum of the no-flow and the no-touch period) is associated with delayed graft function. This finding underscores the pivotal role of ischemic injury in terms of absence of flow in affecting graft function. No association was detectable between hemodynamic parameters during hypothermic machine perfusion and the development of delayed graft function in our series.

Should Immunosuppression After Kidney Transplant Be Adjusted Based on Renal Resistance During Pretransplant Hypothermic Machine Perfusion?

BACKGROUND

The hypothermic machine perfusion reduces delayed graft function after kidney transplant and allows, to some extent, predicting early graft function. However, it is difficult to identify exact perfusion criteria with which to exclude kidneys from transplant or modify post-transplant care. The aim of this study was to analyze whether renal resistance during the fourth hour of hypothermic machine perfusion is useful in the prediction of graft survival and acute rejection.

PATIENTS AND METHODS

Data on pretransplant hypothermic machine perfusion parameters of 407 transplanted kidneys were available. Receiver operating characteristic curve analysis was performed to find an optimal cutoff value of ratio for predicting a higher risk class of considered group of patients. According to this, patients were divided into 2 groups: those who received kidneys with renal resistance lower than 0.19 mm Hg/mL/min (R1; n = 187) and those who received kidneys with renal resistance equal to or higher than 0.19 mm Hg/mL/min (R2; n = 220). Within R2, we additionally analyzed 2 subgroups: patients who received induction therapy (R2-Ind+; n = 124) and those who did not received induction therapy (R2-Ind-; n = 96).

RESULTS

Acute rejection in R1 within 1 month post transplant was 2-fold lower compared with R2 and was 6.4% vs 13.1% (P = .03), respectively. One-year graft survival was higher in R1 compared with R2 and was 94.6% vs 88.5% (P = .03), respectively. Acute rejection in the R2-Ind+ subgroup within 1 month post transplant was 2.46-fold lower compared with the R2-Ind- subgroup and was 8% vs 19.7% (P = .01), respectively.

CONCLUSION

Immunosuppression treatment after transplant should be adjusted to perfusion parameters.

Cold Pulsatile Machine Perfusion versus Static Cold Storage in Kidney Transplantation: A Single Centre Experience

Introduction

We present our experience with hypothermic machine perfusion (HMP) versus cold storage (CS) in relation to kidney transplant outcomes.

Methods

Retrospective analysis of 33 consecutive HMP kidney transplant outcomes matched with those of 33 cold stored: delayed graft function (DGF), length of hospital stay (LOS), estimated glomerular filtration rate (eGFR), and patient and graft survival were compared. Renal Resistive Indexes (RIs) during HMP in relation to DGF were also analysed.

Results

In the HMP group, mean HMP time was 5.7 ± 3.9 hours with a mean cold ischaemic time (CIT) of 15 ± 5.6 versus 15.1 ± 5.3 hours in the CS group. DGF was lower in the HMP group (p=0.041), and donation after Circulatory Death (DCD) was a predictor for DGF (p<0.01). HMP decreased DGF in DCD grafts (p=0.036). Patient and graft survival were similar, but eGFR at 365 days was higher in the HMP cohort (p<0.001). RIs decreased during HMP (p<0.01); 2-hours RI ≥ 0.45 mmHg/mL/min predicted DGF in DCD kidneys (75% sensitivity, 80% specificity; area under the curve 0.78); 2-hours RI ≥ 0.2 mmHg/ml/min predicted DGF in DBD grafts (sensitivity 100%, specificity 91%; area under the curve 0.87).

Conclusion

HMP decreased DGF compared to CS, offering viability assessment pretransplant and improving one-year renal function of the grafts.

The (R)-enantiomer of the 6-chromanol derivate SUL-121 improves renal graft perfusion via antagonism of the α1-adrenoceptor

SUL-compounds are protectants from cold-induced ischemia and mitochondrial dysfunction. We discovered that adding SUL-121 to renal grafts during warm machine reperfusion elicits a rapid improvement in perfusion parameters. Therefore, we investigate the molecular mechanisms of action in porcine intrarenal arteries (PIRA). Porcine kidneys were stored on ice overnight and perfusion parameters were recorded during treatment with SUL-compounds. Agonist-induced vasoconstriction was measured in isolated PIRA after pre-incubation with SUL-compounds. Receptor binding and calcium transients were assessed in α₁-adrenoceptor (α₁-AR) transgenic CHO cells. Molecular docking simulation was performed using Schrödinger software. Renal pressure during warm reperfusion was reduced by SUL-121 (−11.9 ± 2.50 mmHg) and its (R)-enantiomer SUL-150 (−13.2 ± 2.77 mmHg), but not by the (S)-enantiomer SUL-151 (−1.33 ± 1.26 mmHg). Additionally, SUL-150 improved renal flow (16.21 ± 1.71 mL/min to 21.94 ± 1.38 mL/min). SUL-121 and SUL-150 competitively inhibited PIRA contraction responses to phenylephrine, while other 6-chromanols were without effect. SUL-150 similarly inhibited phenylephrine-induced calcium influx and effectively displaced [7-Methoxy-³H]-prazosin in CHO cells. Docking simulation to the α₁-AR revealed shared binding characteristics between prazosin and SUL-150. SUL-150 is a novel α₁-AR antagonist with the potential to improve renal graft perfusion after hypothermic storage. In combination with previously reported protective effects, SUL-150 emerges as a novel protectant in organ transplantation.

Renal resistance thresholds during hypothermic machine perfusion and transplantation outcomes - a retrospective cohort study

Renal resistance (RR), of allografts undergoing hypothermic machine perfusion (HMP), is considered a measure of organ quality. We conducted a retrospective cohort study of adult deceased donor kidney transplant (KT) recipients whose grafts underwent HMP. Our aim was to evaluate whether RR is predictive of death-censored graft failure (DCGF). Of 274 KT eligible for analysis, 59% were from expanded criteria donor. RR was modeled as a categorical variable, using a previously identified terminal threshold of 0.4, and 0.2 mmHg/ml/min (median in our cohort). Hazard ratios (HR) of DCGF were 3.23 [95% confidence interval (CI): 1.12-9.34, P = 0.03] and 2.67 [95% CI: 1.14-6.31, P = 0.02] in univariable models, and 2.67 [95% CI: 0.91-7.86, P = 0.07] and 2.42 [95% CI: 1.02-5.72, P = 0.04] in multivariable models, when RR threshold was 0.4 and 0.2, respectively. Increasing risk of DCGF was observed when RR over the course of HMP was modeled using mixed linear regression models: HR of 1.31 [95% CI: 1.07-1.59, P < 0.01] and 1.25 [95% CI: 1.00-1.55, P = 0.05], in univariable and multivariable models, respectively. This suggests that RR during HMP is a predictor of long-term KT outcomes. Prospective studies are needed to assess the survival benefit of patients receiving KT with higher RR in comparison with staying wait-listed.

Impact of machine perfusion after long static cold storage on delayed graft function incidence and duration and time to hospital discharge

Delayed graft function (DGF) is very high in our center (70%-80%), and we usually receive a kidney for transplant after more than 22 hours of static cold ischemia time (CIT). Also, there is an inadequate care of the donors, contributing to a high rate of DGF. We decided to test whether machine perfusion (MP) after a CIT improved the outcome of our transplant patients. We analyzed the incidence of DGF, its duration, and the length of hospital stay (LOS) in patients who received a kidney preserved with MP after a CIT (hybrid perfusion-HP). We included 54 deceased donors kidneys preserved with HP transplanted from Feb/13 to Jul/14, and compared them to 101 kidney transplants preserved by static cold storage (CS) from Nov/08 to May/12. The median pumping time was 11 hours. DGF incidence was 61.1% vs 79.2% (P = .02), median DGF duration was 5 vs 11 days (P < .001), and median LOS was 13 vs 18 days (P < .011), for the HP compared to CS group. The observed reduction of DGF with machine perfusion did not occur in donors over 50 years old. In the multivariate analysis, risk factors for DGF, adjusted for CIT, were donor age (OR, 1.04; P = .005) and the absence of use of MP (OR, 1.54; P = .051). In conclusion, the use of HP contributed to faster recovery of renal function and to a shorter length of hospital stay.

Randomized Trial of Machine Perfusion Versus Cold Storage in Recipients of Deceased Donor Kidney Transplants With High Incidence of Delayed Graft Function

BACKGROUND

This study compared the use of static cold storage versus continuous hypothermic machine perfusion in a cohort of kidney transplant recipients at high risk for delayed graft function (DGF).

METHODS

In this national, multicenter, and controlled trial, 80 pairs of kidneys recovered from brain-dead deceased donors were randomized to cold storage or machine perfusion, transplanted, and followed up for 12 months. The primary endpoint was the incidence of DGF. Secondary endpoints included the duration of DGF, hospital stay, primary nonfunction, estimated glomerular filtration rate, acute rejection, and allograft and patient survivals.

RESULTS

Mean cold ischemia time was high but not different between the 2 groups (25.6 ± 6.6 hours vs 25.05 ± 6.3 hours, 0.937). The incidence of DGF was lower in the machine perfusion compared with cold storage group (61% vs. 45%, P = 0.031). Machine perfusion was independently associated with a reduced risk of DGF (odds ratio, 0.49; 95% confidence interval, 0.26-0.95). Mean estimated glomerular filtration rate tended to be higher at day 28 (40.6 ± 19.9 mL/min per 1.73 m² vs 49.0 ± 26.9 mL/min per 1.73 m²; P = 0.262) and 1 year (48.3 ± 19.8 mL/min per 1.73 m² vs 54.4 ± 28.6 mL/min per 1.73 m²; P = 0.201) in the machine perfusion group. No differences in the incidence of acute rejection, primary nonfunction (0% vs 2.5%), graft loss (7.5% vs 10%), or death (8.8% vs 6.3%) were observed.

CONCLUSIONS

In this cohort of recipients of deceased donor kidneys with high mean cold ischemia time and high incidence of DGF, the use of continuous machine perfusion was associated with a reduced risk of DGF compared with the traditional cold storage preservation method.

Associations of Perfusate Biomarkers and Pump Parameters With Delayed Graft Function and Deceased Donor Kidney Allograft Function

Hypothermic machine perfusion (HMP) is increasingly used in deceased donor kidney transplantation, but controversy exists regarding the value of perfusion biomarkers and pump parameters for assessing organ quality. We prospectively determined associations between perfusate biomarkers (neutrophil gelatinase-associated lipocalin [NGAL], kidney injury molecule 1, IL-18 and liver-type fatty acid-binding protein [L-FABP]) and pump parameters (resistance and flow) with outcomes of delayed graft function (DGF) and 6-mo estimated GFR (eGFR). DGF occurred in 230 of 671 (34%) recipients. Only 1-h flow was inversely associated with DGF. Higher NGAL or L-FABP concentrations and increased resistance were inversely associated with 6-mo eGFR, whereas higher flow was associated with higher adjusted 6-mo eGFR. Discarded kidneys had consistently higher median resistance and lower median flow than transplanted kidneys, but median perfusate biomarker concentrations were either lower or not significantly different in discarded compared with transplanted kidneys. Notably, most recipients of transplanted kidneys with isolated "undesirable" biomarker levels or HMP parameters experienced acceptable 6-mo allograft function, suggesting these characteristics should not be used in isolation for discard decisions. Additional studies must confirm the utility of combining HMP measurements with other characteristics to assess kidney quality.

Resistance index determination in the pre and post kidney transplantation time points in graft dysfunction diagnosis

BACKGROUND

Donor shortage necessitates the development of tools capable of objectively assessing kidney graft quality from expanded criteria donors and kidneys donated after cardiac death. The deteriorating donor profile is leading to a shift from cold storage toward machine perfusion preservation. Several authors found that renal resistance (RR) at the end of machine perfusion was an independent risk factor for the development of delayed graft function (DGF). In contrast, Doppler ultrasonography in the posttransplant period reveals renal hemodynamics and is useful in diagnosing renal allograft dysfunction. We sought to determine concordance between RR and the resistance index (RI) and their diagnostic value in the assessment of graft viability.

METHODS

RR was determined at the end of perfusion during hypothermic machine preservation and RI was measured by Doppler ultrasonography in the early posttransplant period. Agreement between these 2 measures was established by means of the intraclass correlation coefficient (ICC). Diagnostic validity for RR and RI was determined by sensitivity, specificity and positive and negative predictive values.

RESULTS

The ICC was 0.135, which indicates a slight agreement. RR and RI had limited value in the prediction of DGF for a specific kidney as reflected by a c-statistic of 0.58 and 0.66, respectively.

CONCLUSIONS

There is no agreement between the RR and RI, which may be owing to the different conditions under which measurements are made. The poor predictive power of RR for DGF indicates that kidneys should not be discarded based on RR criteria alone.

Machine perfusion: initial results in an expanded criteria donor kidney transplant program

BACKGROUND

Delayed graft function (DGF) negatively impacts graft survival. Expanded criteria donors (ECD) show a higher rate of DGF. Hypothermic machine perfusion (HMP) has shown a DGF decrease and an increase of survival at 1 year. Several authors found that renal resistance (RR) at the end of machine perfusion was an independent risk factor for the development of DGF and poorer graft survival. The objective of this study was to analyze HMP results in the context of an ECD program and assess the impact of donor parameters and resistance index (RI) during perfusion in graft survival after kidney transplantation.

METHODS

Donor age, terminal creatinine, machine perfusion time, percentage of glomerulosclerosis, and RI at the end of the perfusion were considered as risk predictors. Univariate and multivariate Cox regression analysis was constructed to find independent risk factors of DGF. Finally, diagnostic validity for RR was determined by sensitivity, specificity, and positive and negative predictive values.

RESULTS

Twenty-three percent of patients developed DGF. We found no difference in the ability of flow or RI to predict the development of DGF. The predictive accuracy of RI for DGF by receiver operator characteristic curve was poor, with a c-statistic of 0.66 (95% CI, 0.50-0.81; P = .046). Our analysis did not identify risk factors that predicted graft survival at 1 year. Patient and graft survival were 98.8% and 89.7%, respectively.

CONCLUSIONS

HMP has reduced the rate of DGF in our cohort of recipients of ECD grafts compared with historical data (23.3% vs 38.0%). Analysis did not identify risk pretransplant factors for graft survival at 1 year.