Factors Associated With Prolonged Warm Ischemia Time Among Deceased Donor Kidney Transplant Recipients

A Novel Cooling Device for Kidney Transplant Surgery

Background: Prolonged warm ischemia time (WIT) in kidney transplantation is associated with numerous adverse outcomes including delayed graft function and decreased patient and graft survival. Circumventing WIT lies in maintaining renal hypothermia and efficiently performing the vascular anastomosis during this portion of the procedure. Although numerous methods of intra-operative renal cooling have been proposed, most suffer from practical limitations, and none have been widely adopted. Herein we describe a novel device specifically designed to maintain renal hypothermia during kidney transplant surgery.Methods: Aluminum tubing was organized in a serpentine pattern to create a malleable, form-fitting cooling jacket to manipulate renal allografts during transplant surgery. Adult porcine kidneys were used to test the device with 4°C saline as coolant. Kidneys were placed at 24°C; surface and core temperatures were monitored using implanted thermocouples. Anastomosis of porcine kidney vessels to GORE-TEX® vascular grafts in an ex-vivo operative field was performed to assess the functionality of the device.Results: The device maintained surface and core graft temperatures of ≤5°C after 60 minutes of WIT. Furthermore, the device provided hands-free retraction and support for the allograft. We found that ex-vivo anastomosis testing was enhanced by the presence of the cooling jacket.Conclusions: This proof-of-concept study demonstrated that our novel device is a practical tool for renal transplantation and can maintain sufficiently cool graft temperatures to mitigate WIT in an ex-vivo setting. This device is the first of its kind and has the potential to improve kidney transplant outcomes by eliminating WIT during graft implantation.

Bright, photostable and long-circulating NIR-II nanoparticles for whole-process monitoring and evaluation of renal transplantation

Kidney transplantation is the gold standard for the treatment of end-stage renal diseases (ESRDs). However, the scarcity of donor kidneys has caused more and more ESRD patients to be stuck on the waiting list for transplant surgery. Improving the survival rate for renal grafts is an alternative solution to the shortage of donor kidneys. Therefore, real-time monitoring of the surgical process is crucial to the success of kidney transplantation, but efficient methods and techniques are lacking. Herein, a fluorescence technology based on bright, photostable and long-circulating aggregation-induced emission (AIE) active NIR-II nano-contrast agent DIPT-ICF nanoparticles for the whole-process monitoring and evaluation of renal transplantation has been reported. In the aggregated state, DIPT-ICF exhibits superior photophysical properties compared with the commercial dyes IR-26 and IR-1061. Besides, the long-circulating characteristic of the AIE nano-contrast agent helps to achieve renal angiography in kidney retrieval surgery, donor kidney quality evaluation, diagnosing vascular and ureteral complications, and assessment of renal graft reperfusion beyond renovascular reconstruction, which considerably outperforms the clinically approved indocyanine green (ICG).

Multiview Clustering to Identify Novel Kidney Donor Phenotypes for Assessing Graft Survival in Older Transplant Recipients

Key Points

An unsupervised machine learning clustering algorithm identified distinct deceased kidney donor phenotypes among older recipients. Recipients of certain donor phenotypes were at a relatively higher risk of all-cause graft loss even after accounting for recipient factors. The use of unsupervised clustering to support kidney allocation systems may be an important area for future study.

Background

Older transplant recipients are at a relatively increased risk of graft failure after transplantation, and some of this risk may relate to donor characteristics. Unsupervised clustering using machine learning may be a novel approach to identify donor phenotypes that may then be used to evaluate outcomes for older recipients. Using a cohort of older recipients, the purpose of this study was to (1 ) use unsupervised clustering to identify donor phenotypes and (2 ) determine the risk of death/graft failure for recipients of each donor phenotype.

Methods

We analyzed a nationally representative cohort of kidney transplant recipients aged 65 years or older captured using the Scientific Registry of Transplant Recipients between 2000 and 2017. Unsupervised clustering was used to generate phenotypes using donor characteristics inclusive of variables in the kidney donor risk index (KDRI). Cluster assignment was internally validated. Outcomes included all-cause graft failure (including mortality) and delayed graft function. Differences in the distribution of KDRI scores were also compared across the clusters. All-cause graft failure was compared for recipients of donor kidneys from each cluster using a multivariable Cox survival analysis.

Results

Overall, 23,558 donors were separated into five clusters. The area under the curve for internal validation of cluster assignment was 0.89. Recipients of donor kidneys from two clusters were found to be at high risk of all-cause graft failure relative to the lowest risk cluster (adjusted hazards ratio, 1.86; 95% confidence interval, 1.69 to 2.05 and 1.73; 95% confidence interval, 1.61 to 1.87). Only one of these high-risk clusters had high proportions of donors with established risk factors (i.e. , hypertension, diabetes). KDRI scores were similar for the highest and lowest risk clusters (1.40 [1.18–1.67] and 1.37 [1.15–1.65], respectively).

Conclusions

Unsupervised clustering can identify novel donor phenotypes comprising established donor characteristics that, in turn, may be associated with different risks of graft loss for older transplant recipients.

The Impact of Combined Warm and Cold Ischemia Time on Post-transplant Outcomes

Background

Prolonged warm ischemia time (WIT) and cold ischemia time (CIT) are independently associated with post-transplant graft failure; their combined impact has not been previously studied. We explored the effect of combined WIT/CIT on all-cause graft failure following kidney transplantation.

Methods

The Scientific Registry of Transplant Recipients was used to identify kidney transplant recipients from January 2000 to March 2015 (after which WIT was no longer separately reported), and patients were followed until September 2017. A combined WIT/CIT variable (excluding extreme values) was separately derived for live and deceased donor recipients using cubic splines; for live donor recipients, the reference group was WIT 10 to <23 minutes and CIT >0 to <0.42 hours, and for deceased donor recipients the WIT was 10 to <25 minutes and CIT 1 to <7.75 hours. The adjusted association between combined WIT/CIT and all-cause graft failure (including death) was analyzed using Cox regression. Secondary outcomes included delayed graft function (DGF).

Results

A total of 137 125 recipients were included. For live donor recipients, patients with prolonged WIT/CIT (60 to ≤120 minutes/3.04 to ≤24 hours) had the highest adjusted hazard ratio (HR) for graft failure (HR = 1.61, 95% confidence interval [CI] = 1.14-2.29 relative to the reference group). For deceased donor recipients, a WIT/CIT of 63 to ≤120 minutes/28 to ≤48 hours was associated with an adjusted HR of 1.35 (95% CI = 1.16-1.58). Prolonged WIT/CIT was also associated with DGF for both groups although the impact was more driven by CIT.

Conclusions

Combined WIT/CIT is associated with graft loss following transplantation. Acknowledging that these are separate variables with different determinants, we emphasize the importance of capturing WIT and CIT independently. Furthermore, efforts to reduce WIT and CIT should be prioritized.

Insulating jackets thermally protect kidneys in an ex vivo model of second warm ischemia

BACKGROUND

Kidney transplantation is the current optimal treatment for suitable patients with end-stage renal disease. The second warm ischemic time (SWIT) is known to negatively impact delayed graft function, and long-term graft survival, and methods are required to ameliorate the impacts of SWIT on transplantation outcomes.

MATERIALS AND METHODS

This study primarily focused on determining the effect of a novel thermally insulating jacket on the thermal profile of the human kidney and quantifying the reduction in thermal energy experienced using this device (KPJ™). An ex vivo simulated transplantation model was developed to determine the thermal profiles of non-utilized human kidneys with and without KPJ™ (n = 5). Control kidney temperature profiles were validated against the temperature profiles of n = 10 kidneys during clinical kidney transplantation.

RESULTS

Using the ex-vivo water bath model, the thermally insulated human kidney reached the 15°C metabolic threshold temperature at 44.5 ± 1.9 min (vs control: 17.3 ± 1.8 min (p = 0.00172)) and remained within the 18°C threshold until 53.3 ± 1.3 min (vs control: 20.9 ± 2.0 min (p = 0.002)). The specific heat capacity of KPJ™ protected kidney was four-fold compared to the control kidney. The clinical temperature audit, closely correlated with the water bath model, hence validating this ex-vivo human kidney transplant model.

CONCLUSION

Intraoperative thermal protection is a simple and viable method of reducing the thermal injury that occurs during the SWIT and increasing the specific heat capacity of the system. Such technology could easily be translated into clinical kidney transplant practice.

Combined Donor-Recipient Obesity and the Risk of Graft Loss After Kidney Transplantation

Background: As the prevalence of obesity increases globally, appreciating the effect of donor and recipient (DR) obesity on graft outcomes is of increasing importance. Methods: In a cohort of adult, kidney transplant recipients (2000-2017) identified using the SRTR, we used Cox proportional hazards models to examine the association between DR obesity pairing (body mass index (BMI) >30 kg/m2), and death-censored graft loss (DCGL) or all-cause graft loss, and logistic regression to examine risk of delayed graft function (DGF) and ≤30 days graft loss. We also explored the association of DR weight mismatch (>30 kg, 10-30 kg (D>R; D Collapse

Key Words

• body mass index
• graft loss
• kidney transplant outcomes
• obesity
• obesity pairing
• weight mismatch

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MESH Headings

• Adult
• Cohort Studies
• Graft Rejection/epidemiology
• Humans
• Kidney Transplantation/adverse effects
• Obesity/epidemiology
• Risk Factors
• Tissue Donors/statistics & numerical data
• Transplant Recipients/statistics & numerical data
• Treatment Outcome

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Affiliation(s)

Faisal Jarrar Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
Karthik K. Tennankore Faculty of Medicine, Dalhousie University, Halifax, NS, Canada Division of Nephrology, Department of Medicine, Nova Scotia Health Authority, Halifax, NS, Canada
Amanda J. Vinson Faculty of Medicine, Dalhousie University, Halifax, NS, Canada Division of Nephrology, Department of Medicine, Nova Scotia Health Authority, Halifax, NS, Canada

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Interleukin-27 in liver xenotransplantation: A rational target to mitigate ischemia reperfusion injury and increase xenograft survival

Transplantation of xenogeneic organs is an attractive solution to the existing organ shortage dilemma, thus, securing a clinically acceptable prolongation of xenograft survival is an important goal. In preclinical transplantation models, recipients of liver, kidney, heart, or lung xenotransplants demonstrate significant graft damages through the release of pro-inflammatory molecules, including the C-reactive protein, cytokines, and histone-DNA complexes that all foster graft rejection. Recent studies have demonstrated that mitigation of ischemia reperfusion injury (IRI) greatly improves xenograft survival. Organ IRI develops primarily on a complex network of cytokines and chemokines responding to molecular cues from the graft milieu. Among these, interleukin 27 (IL-27) plays an immunomodulatory role in IRI onset due to graft environment-dependent pro- and anti- inflammatory activities. This review focuses on the impact of IL-27 on IRI of liver xenotransplants and provides insights on the function of IL-27 that could potentially guide genetic engineering strategies of donor pigs and/or conditioning of organs prior to transplantation.

But Why Weight: Understanding the Implications of Obesity in Kidney Transplant

Obesity is increasing in prevalence among candidates for kidney transplant. Understanding the influence of obesity on candidate evaluation, surgical risk, peritransplant management, and post-transplant outcomes is critical to ensuring equitable access to transplant for this growing population.

Protection From the Second Warm Ischemic Injury in Kidney Transplantation Using an Ex Vivo Porcine Model and Thermally Insulating Jackets

BACKGROUND

Kidney transplantation is the optimum treatment for kidney failure in carefully selected patients. Technical surgical complications and second warm ischemic time (SWIT) increase the risk of delayed graft function (DGF) and subsequent short- and long-term graft outcomes including the need for post-transplant dialysis and graft failure. Intraoperative organ thermal regulation could reduce SWIT, minimizing surgical complications due to time pressure, and limiting graft ischemia-reperfusion injury.

METHODS

A novel ischemic-injury thermal protection jacket (iiPJ) was designed and fabricated in silicone composite and polyurethane (PU) elastomer prototypes. Both were compared with no thermal insulation as controls. Time to reach ischemic threshold (15°C) and thermal energy transfer were compared. A water bath model was used to examine the thermal protective properties of porcine kidneys, as a feasibility study prior to in vivo translation.

RESULTS

In both iterations of the iiPJ, the time taken to reach the warm ischemia threshold was 35.2 ± 1.4 minutes (silicone) and 38.4 ± 3.1 minutes (PU), compared with 17.2 ± 1.5 minutes for controls (n = 5, P < .001 for both comparisons). Thermal energy transfer was also found to be significantly less for both iiPJ variants compared with controls. There was no significant difference between the thermal performance of the 2 iiPJ variants.

CONCLUSION

Protection from SWIT by using a protective insulation jacket is feasible. With clinical translation, this novel strategy could facilitate more optimal surgical performance and reduce transplanted organ ischemia-reperfusion injury, in particular the SWIT, potentially affecting delayed graft function and long-term outcomes.

Monitoring of the influence of long-term oxidative stress and ischemia on the condition of kidneys using solid-phase microextraction chemical biopsy coupled with liquid chromatography-high-resolution mass spectrometry

The limiting factor in conventional quality assessments of transplanted organs, namely the invasiveness of tissue sample collection, has prompted much research on the field of transplantology to focus on the development of alternative evaluation methods of organ quality. In the present project, we undertake the challenge to address the need for a new analytical solution for graft quality assessments by using a novel metabolomic diagnostic protocol based on low-invasive solid-phase microextraction. Solid-phase microextraction probes of ca. 0.2 mm coated with 4 mm long mixed-mode extraction phase were inserted into rabbit kidneys immediately following euthanasia and after 2, 4, 6, and 21 h of preservation. Liquid chromatography-mass spectrometry analysis of the extracts was performed with the use of a reversed phase column and a Q-Exactive Focus mass spectrometer operated in positive ionization mode. Statistical analysis of significantly changing compounds revealed metabolic profile changes in kidneys induced by ischemia and oxidative stress as a function of the duration of cold storage. The most pronounced alterations were reflected in levels of essential amino acids and purine nucleosides. Our findings demonstrate that the proposed approach may be successfully used to monitor changes in the metabolic profile of organs over time of preservation.

Outcomes From Right Versus Left Deceased-Donor Kidney Transplants: A US National Cohort Study

RATIONALE & OBJECTIVE

There may be important transplant-related differences between right and left kidneys, including logistical/surgical considerations about vessel length for the right compared to the left kidney from the same donor. Because US centers choose between the right and left kidney when their recipient is ranked higher on a "match-run," we sought to determine whether deceased-donor right kidneys have had worse posttransplantation outcomes than left kidneys.

STUDY DESIGN

Paired Organ Procurement and Transplantation Network analysis.

SETTING & PARTICIPANTS

Deceased-donor kidney pairs transplanted during 1990 to 2016.

EXPOSURE

Right versus left kidney controlling for other significant factors.

OUTCOMES

Delayed graft function (DGF), all-cause and death-censored graft failure, and mortality.

ANALYTICAL APPROACH

Multivariable conditional logistic regression for DGF; proportional hazards models (conditional on same donor) for failure/mortality with right kidneys (operationalized as 6-month time-varying coefficients) adjusting for DGF and other confounders.

RESULTS

87,112 recipient pairs shared the following donor characteristics: mean age of 41 ± 14 years, 60% males, and 11% with cardiac death. Recipient characteristics were numerically similar by donor kidney side but with some statistical differences given the sample size. Right kidneys had slightly longer cold ischemia time. DGF occurred more often for right kidneys (28% vs 25.8%; P < 0.001; adjusted OR, 1.15 [95% CI, 1.12-1.17]). The adjusted hazard ratio (aHR) for all-cause graft failure with right kidneys within 6 months was 1.07 (95% CI, 1.03-1.11), and was 0.99 (95% CI, 0.97-1.01) thereafter. The aHRs for death-censored graft failure with right kidneys before and after 6 months were 1.11 (95% CI, 1.06-1.16) and 0.96 (95% CI, 0.93-0.99), respectively; the corresonding aHRs for mortality were 0.99 (95% CI, 0.93-1.04) and 1.00 (95% CI, 0.98-1.03), respectively.

LIMITATIONS

Registry data, different transplant eras, reasons for kidney side unavailable.

CONCLUSIONS

There is modest association for transplantation of right kidneys with DGF and graft loss within the first 6 months, which is lost beyond this time point. These findings do not support the use of laterality of deceased-donor kidneys as an important factor in organ acceptance decisions.

Hydrogen sulphide-induced hypometabolism in human-sized porcine kidneys

Background

Since the start of organ transplantation, hypothermia-forced hypometabolism has been the cornerstone in organ preservation. Cold preservation showed to protect against ischemia, although post-transplant injury still occurs and further improvement in preservation techniques is needed. We hypothesize that hydrogen sulphide can be used as such a new preservation method, by inducing a reversible hypometabolic state in human sized kidneys during normothermic machine perfusion.

Methods

Porcine kidneys were connected to an ex-vivo isolated, oxygen supplemented, normothermic blood perfusion set-up. Experimental kidneys (n = 5) received a 85mg NaHS infusion of 100 ppm and were compared to controls (n = 5). As a reflection of the cellular metabolism, oxygen consumption, mitochondrial activity and tissue ATP levels were measured. Kidney function was assessed by creatinine clearance and fractional excretion of sodium. To rule out potential structural and functional deterioration, kidneys were studied for biochemical markers and histology.

Results

Hydrogen sulphide strongly decreased oxygen consumption by 61%, which was associated with a marked decrease in mitochondrial activity/function, without directly affecting ATP levels. Renal biological markers, renal function and histology did not change after hydrogen sulphide treatment.

Conclusion

In conclusion, we showed that hydrogen sulphide can induce a controllable hypometabolic state in a human sized organ, without damaging the organ itself and could thereby be a promising therapeutic alternative for cold preservation under normothermic conditions in renal transplantation.