The effect of remote ischemic postconditioning on graft function in patients undergoing living donor kidney transplantation

Effectiveness of remote ischemic preconditioning in patients undergoing transplant surgery: meta-analysis of randomized control studies

Introduction

Remote ischemic preconditioning (RIPC) is a phenomenon in which the induction of shortened periods of ischemia prior to surgical procedures within a distant tissue preserves other tissues or organs of concern, such as the liver or kidney in transplant surgery, in the event of prolonged ischemic insults. The authors aim to evaluate the effectiveness of RIPC in patients undergoing transplant surgery, specifically kidney and liver transplants.

Materials and methods

PubMed, Embase, and Scopus were searched until 19 December 2023 for trials evaluating RIPC in patients undergoing transplant surgery. A total of 9364 search articles were obtained, which yielded 10 eligible studies. Data analysis was done using RevMan 5.4 software. The risk of bias was done using Cochrane risk of bias tool.

Results and discussion

For graft rejection, the study observed a relative risk of 0.99 (95% CI, 0.49-1.98, P=0.97) from 5 trials, indicating no significant effect of RIPC on graft survival in both kidney and liver transplants. The length of hospital stay also showed no significant decrease for those undergoing RIPC, with mean difference (MD) of -0.58 (95% CI, -1.38 to 0.23, P=0.16). GFR at 1-year post-kidney transplant did not significantly change in the RIPC group compared to controls, as evidenced by an MD of -0.13 (95% CI, -3.79 to 3.54, P=0.95). These results collectively suggest that RIPC may not be effective in reducing patient, or graft, outcomes.

Effect of Remote Ischemic Conditioning on Organ Transplantation: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Remote ischemic conditioning (RIC) has shown great advantages in protecting organs from ischemia-reperfusion loss and applied research on RIC continues to increase. We performed a systematic review and meta-analysis to comprehensively investigate the value of RIC for different organ transplantation.

METHODS

We searched PubMed, EMBASE, and the Cochrane Library from inception to November 1, 2023, for randomized controlled trials investigating whether RIC has an advantage in organ transplantation (including heart, lung, liver, and kidney) compared with controls. The primary outcomes varied according to the transplanted organ, including liver transplantation (graft loss, early allograft dysfunction, acute kidney injury, days in hospital, and mortality); kidney transplantation (delayed graft function, acute rejection (AR), graft loss, 50% decrease in serum creatinine, glomerular filtration rate, days in hospital, and mortality); heart and lung transplantation (AR, mortality). Two investigators independently selected suitable trials, assessed trial quality, and extracted the data.

RESULTS

A total of 11 randomized controlled trials were included in this study, including six kidney transplants, three liver transplants, and one heart and lung transplant each, with 561 RIC cases and 564 controls, and a total of 1125 patients. The results showed that RIC did not reduce mortality in transplant patients compared with controls (liver transplant: RR0.9, 95% confidence interval [0.31-2.66]; kidney transplant: RR 0.76, 95% confidence interval [0.17-3.33]), graft failure rate (liver transplantation: RR 0.3, 95% confidence interval [0.07, 1.19]; kidney transplantation: RR 0.89, 95% confidence interval [0.35, 2.27]), length of hospital stay (liver transplantation: standard mean difference [SMD] 0.14, 95% confidence interval [-0.15, 0.42]; kidney transplantation: SMD -0.1, 95% confidence interval [-0.3, 0.11]). In addition, RIC did not improve early liver function after liver transplantation (RR 0.97, 95% confidence interval [0.55,1.7]), acute kidney injury after liver transplantation (RR 1.17 95% confidence interval [0.9, 1.54]), delayed functional recovery after renal transplantation (RR 0.84, 95% confidence interval [0.62, 1.15]), AR rate (RR 1.04, 95% confidence interval [0.72, 1.49]), 50% serum creatinine decline rate (RR 1.1, 95% confidence interval [0.88, 1.37]), glomerular filtration rate 3 months after surgery (SMD 0.13, 95% confidence interval [-0.05, 0.31]) and postoperative 12 months glomerular filtration rate (SMD 0.13, 95% confidence interval [-0.06, 0.31]).

CONCLUSION

Remote ischemic modulation does not improve clinical outcomes in patients undergoing organ transplantation (heart, lung, liver, and kidney).

Remote ischemic conditioning may improve graft function following kidney transplantation: a systematic review and meta-analysis with trial sequential analysis

BACKGROUND

Remote ischemic conditioning (RIC) has the potential to benefit graft function following kidney transplantation by reducing ischemia-reperfusion injury; however, the current clinical evidence is inconclusive. This meta-analysis with trial sequential analysis (TSA) aimed to determine whether RIC improves graft function after kidney transplantation.

METHODS

A comprehensive search was conducted on PubMed, Cochrane Library, and EMBASE databases until June 20, 2023, to identify all randomized controlled trials that examined the impact of RIC on graft function after kidney transplantation. The primary outcome was the incidence of delayed graft function (DGF) post-kidney transplantation. The secondary outcomes included the incidence of acute rejection, graft loss, 3- and 12-month estimated glomerular filtration rates (eGFR), and the length of hospital stay. Subgroup analyses were conducted based on RIC procedures (preconditioning, perconditioning, or postconditioning), implementation sites (upper or lower extremity), and graft source (living or deceased donor).

RESULTS

Our meta-analysis included eight trials involving 1038 patients. Compared with the control, RIC did not significantly reduce the incidence of DGF (8.8% vs. 15.3%; risk ratio = 0.76, 95% confidence interval [CI], 0.48-1.21, P = 0.25, I2 = 16%), and TSA results showed that the required information size was not reached. However, the RIC group had a significantly increased eGFR at 3 months after transplantation (mean difference = 2.74 ml/min/1.73 m2, 95% CI: 1.44-4.05 ml/min/1.73 m2, P < 0.0001, I2 = 0%), with a sufficient evidence suggested by TSA. The secondary outcomes were comparable between the other secondary outcomes. The treatment effect of RIC did not differ between the subgroup analyses.

CONCLUSION

In this meta-analysis with trial sequential analysis, RIC did not lead to a significant reduction in the incidence of DGF after kidney transplantation. Nonetheless, RIC demonstrated a positive correlation with 3-month eGFR. Given the limited number of patients included in this study, well-designed clinical trials with large sample sizes are required to validate the renoprotective benefits of RIC.

TRIAL REGISTRATION

This systematic review and meta-analysis was registered at the International Prospective Register of Systematic Reviews (Number CRD42023464447).

Effect of Remote Ischemic Conditioning on Bleeding Complications in Surgery: A Systematic Review and Meta-Analysis

Remote ischemic conditioning (RIC) is administered with an inflatable tourniquet by inducing brief, alternating cycles of limb ischemia and reperfusion. RIC possibly impacts the hemostatic system, and the intervention has been tested as protective therapy against ischemia-reperfusion injury and thrombotic complications in cardiac surgery and other surgical procedures. In the present systematic review, we aimed to investigate the effect of RIC on intraoperative and postoperative bleeding complications in meta-analyses of randomized controlled trials including adult patients undergoing surgery. A systematic search was performed on November 7, 2020 in PubMed, Embase, and the Cochrane Central Register of Controlled Trials. Randomized controlled trials comparing RIC versus no RIC in adult patients undergoing surgery that reported bleeding outcomes in English publications were included. Effect estimates with 95% confidence intervals were calculated using the random-effects model for intraoperative and postoperative bleeding outcomes. Thirty-two randomized controlled trials with 3,804 patients were eligible for inclusion. RIC did not affect intraoperative bleeding volume (nine trials; 392 RIC patients, 399 controls) with the effect estimate -0.95 [-9.90; 7.99] mL (p = 0.83). RIC significantly reduced postoperative drainage volume (seven trials; 367 RIC patients, 365 controls) with mean difference -83.6 [-134.9; -32.4] mL (p = 0.001). The risk of re-operation for bleeding was reduced in the RIC group (16 trials; 838 RIC patients, 839 controls), albeit not significantly, with the relative risk 0.65 [0.39; 1.09] (p = 0.10). In conclusion, RIC reduced postoperative bleeding measured by postoperative drainage volume in this meta-analysis of adult patients undergoing surgery.

Remote Ischemic Preconditioning in Microsurgical Head and Neck Reconstruction: A Randomized Controlled Trial

Background:

The free flap failure rate is 5% in head and neck microsurgical reconstruction, and ischemia–reperfusion injury is an important mechanism behind this failure rate. Remote ischemic preconditioning (RIPC) is a recent intervention targeting ischemia–reperfusion injury. The aim of the present study was to investigate if RIPC improved clinical outcomes in microsurgical reconstruction.

Methods:

Head and neck cancer patients undergoing tumor resection and microsurgical reconstruction were included in a randomized controlled trial. Patients were randomized (1:1) to RIPC or sham intervention administered intraoperatively just before transfer of the free flap. RIPC was administered by four 5-minute periods of upper extremity occlusion and reperfusion. Clinical data were prospectively collected in the perioperative period and at follow-up on postoperative days 30 and 90. Intention-to-treat analysis was performed.

Results:

Sixty patients were randomized to RIPC (n = 30) or sham intervention (n = 30). All patients received allocated intervention. No patients were lost to follow up. At 30-day follow-up, flap failure occurred in 7% of RIPC patients (n = 2) and 3% of sham patients (n = 1) with the relative risk and 95% confidence interval 2.0 [0.2;20.9], P = 1.0. The rate of pedicle thrombosis was 10% (n = 3) in both groups with relative risk 1.0 [0.2;4.6], P = 1.0. The flap failure rate did not change at 90-day follow-up.

Conclusions:

RIPC is safe and feasible but does not affect clinical outcomes in head and neck cancer patients undergoing microsurgical reconstruction.

Modulation of Remote Ischemic Preconditioning by Proinflammatory Cytokines in Renal Transplant Recipients

AIM

Remote ischemic preconditioning (RIPC) has been used as a strategy to reduce acute renal injury and ischemia-reperfusion injury (IRI) in renal transplantation (RT) with controversial results.

OBJECTIVE

To determine if RIPC modifies IRI in cadaveric RT recipients through inflammatory mediators and graft function.

METHODS

Twenty-nine RT recipients were studied, 12 in the control group (CG) and 17 in the RIPC group. RIPC which was performed on donors using a pneumatic tourniquet placed on both thighs for 10 min followed by the determination of IL-1, IL-6, TNF-α, VEGF, and ICAM-1, and hematological and biochemical parameters in different phases of RT.

RESULTS

Serum creatinine levels were significantly lower in the RIPC group versus the CG at 15 and 30 days; however, the estimated glomerular filtration rate (eGFR) showed no significant difference in any phase between either group, only TNF-α showed significantly higher values in the RIPC group versus the CG in almost all phases of the study, meanwhile IL6 was increased at 72 hours (hr) and 30 days, IL1 at 72 hr and 15 days and ICAM-1 post reperfusion, contrary to this VEGF showed a decrease at 7 and 15 days.

CONCLUSION

RIPC did not improve eGFR or serum creatinine; however, it modifies the inflammatory response in RT recipients.

Remote Ischemic Conditioning and Renal Protection

Over the course of the last 2 decades, the concept of remote ischemic conditioning (RIC) has attracted considerable research interest, because RIC, in most of its embodiments offers an inexpensive way of protecting tissues against ischemic damage inflicted by a number of medical conditions or procedures. Acute kidney injury (AKI) is a common side effect in the context of various medical procedures, and RIC has been suggested as a means of reducing its incidence. Outcomes regarding kidney function have been reported in numerous studies that evaluated the effects of RIC in a variety of settings (eg, cardiac surgery, interventions requiring intravenous administration of contrast media). Although several individual studies have implied a beneficial effect of RIC in preserving kidney function, 3 recently published randomized controlled trials evaluating more than 1000 patients each (Effect of Remote Ischemic Preconditioning in the Cardiac Surgery, Remote Ischaemic Preconditioning for Heart Surgery, and ERICCA) were negative. However, AKI or any other index of renal function was not a stand-alone primary end point in any of these trials. On the other hand, a range of meta-analyses (each including thousands of participants) have reported mixed results, with the most recent among them showing benefit from RIC, pinpointing at the same time a number of shortcomings in published studies, adversely affecting the quality of available data. The present review provides a critical appraisal of the current state of this field of research. It is the opinion of the authors of this review that there is a clear need for a common clinical trial framework for ischemic conditioning studies. If the current babel of definitions, procedures, outcomes, and goals persists, it is most likely that soon ischemic conditioning will be "yesterday's news" with no definitive conclusions having been reached in terms of its real clinical utility.

Ischemic Conditioning in Kidney Transplantation

Ischemia–reperfusion injury is a composite of the injury sustained during a period of reduced or absent blood flow to a tissue or organ and the additional insult sustained on reperfusion, which limits the amount of tissue that can be salvaged. Ischemia–reperfusion injury is the predominant insult during kidney transplantation, contributing to graft dysfunction, increased rates of acute rejection, and reduced rejection-free graft survival. In this review, we discuss the potential therapeutic benefits of a cost-effective and low-risk intervention, ischemic preconditioning, and its potential for improving kidney function following transplantation.

Limited Clinical Utility of Remote Ischemic Conditioning in Renal Transplantation: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

We conducted this meta-analysis of randomized controlled trials (RCTs) to investigate whether remote ischemic conditioning (RIC) could improve graft functions in kidney transplantation.

METHODS

PubMed, Web of Science, and Cochrane Library were comprehensively searched to identify all eligible studies by October 5, 2016. The treatment effects were examined with risk ratio (RR) and weighted mean difference with the corresponding 95% confidence intervals (CI). The statistical significance and heterogeneity were assessed with both Z-test and Q-test.

RESULTS

A total of six RCTs including 651 recipients, were eventually identified. Compared to the controls, RIC could reduce the incidence of delayed graft function (DGF) after kidney transplantation (random-effects model: RR = 0.89; fixed-effect model: RR = 0.84). However, the decrease did not reveal statistical significance. The subgroup analysis by RIC type demonstrated no significant difference among the three interventions in protecting renal allografts against DGF. Furthermore, no significant difference could be observed in the incidence of acute rejection, graft loss, 50% fall in serum creatinine, as well as the estimated glomerular filtration rate and hospital stay between the RIC and Control groups.

CONCLUSIONS

This meta-analysis suggested that RIC might exert renoprotective functions in human kidney transplantation, and further well-designed RCTs with large sample size are warranted to assess its clinical efficacy.

Current Antioxidant Treatments in Organ Transplantation

Oxidative stress is one of the key mechanisms affecting the outcome throughout the course of organ transplantation. It is widely believed that the redox balance is dysregulated during ischemia and reperfusion (I/R) and causes subsequent oxidative injury, resulting from the formation of reactive oxygen species (ROS). Moreover, in order to alleviate organ shortage, increasing number of grafts is retrieved from fatty, older, and even non-heart-beating donors that are particularly vulnerable to the accumulation of ROS. To improve the viability of grafts and reduce the risk of posttransplant dysfunction, a large number of studies have been done focusing on the antioxidant treatments for the purpose of maintaining the redox balance and thereby protecting the grafts. This review provides an overview of these emerging antioxidant treatments, targeting donor, graft preservation, and recipient as well.

Preclinical Evidence for the Efficacy of Ischemic Postconditioning against Renal Ischemia-Reperfusion Injury, a Systematic Review and Meta-Analysis

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a major cause of kidney damage after e.g. renal surgery and transplantation. Ischemic postconditioning (IPoC) is a promising treatment strategy for renal IRI, but early clinical trials have not yet replicated the promising results found in animal studies.

METHOD

We present a systematic review, quality assessment and meta-analysis of the preclinical evidence for renal IPoC, and identify factors which modify its efficacy.

RESULTS

We identified 39 publications studying >250 control animals undergoing renal IRI only and >290 animals undergoing renal IRI and IPoC. Healthy, male rats undergoing warm ischemia were used in the vast majority of studies. Four studies applied remote IPoC, all others used local IPoC. Meta-analysis showed that both local and remote IPoC ameliorated renal damage after IRI for the outcome measures serum creatinine, blood urea nitrogen and renal histology. Subgroup analysis indicated that IPoC efficacy increased with the duration of index ischemia. Measures to reduce bias were insufficiently reported.

CONCLUSION

High efficacy of IPoC is observed in animal models, but factors pertaining to the internal and external validity of these studies may hamper the translation of IPoC to the clinical setting. The external validity of future animal studies should be increased by including females, comorbid animals, and transplantation models, in order to better inform clinical trial design. The severity of renal damage should be taken into account in the design and analysis of future clinical trials.

Remote ischemic conditioning for kidney protection: A meta-analysis

BACKGROUND

Results from randomized controlled trials (RCTs) concerning kidney effect of remote ischemic conditioning (RIC) are inconsistent.

METHODS

We searched for relevant studies in Medline, Embase, the Cochrane Library, Google Scholar and Chinese database (SinoMed), as well as relevant references from their inception to November 2015. We performed a systematic review and meta-analysis of all eligible RCTs of RIC with kidney events.

RESULTS

We included 37 RCTs from 2007 to 2015 involving 8168 patients. Pooled analyses of all RCTs showed RIC significantly reduced the incidence of investigator-defined acute kidney injury (AKI) compared with control groups (RR 0.84, 95% CI 0.73-0.96, P = .009) (I(2) = 25%). However, the difference was not significant when only RIFLE (Risk, Injury, Failure, Loss, End Stage), AKIN (Acute Kidney Injury Network), or KDIGO (Kidney Disease Improving Global Outcomes) criteria were applied to the definition of AKI (RR 0.87, 95% CI 0.74-1.02, P = .08) (I(2) = 22%). In subgroup analysis, RIC showed a significant benefit on reducing investigator-defined AKI in patients following percutaneous coronary intervention (RR 0.64, 95% CI 0.46-0.87), but not after cardiac surgery (RR 0.93, 95% CI 0.82-1.06). There was no difference for changes in the incidence of renal replacement therapy, estimated glomerular filtration rate or serum creatinine.

CONCLUSIONS

RIC might be beneficial for the prevention of investigator-defined AKI; however, the effect is likely small. Moreover, due to lack of an effect on use of renal replacement therapy, estimated glomerular filtration rate, RIFLE, AKIN, or KDIGO-defined AKI, and serum creatinine, the evidence for RIC is not robust. Finally, recent large-scale RCTs of RIC focusing on patient-centered outcomes do not support the wider application of RIC.

Short-and long-term effects of ischemic postconditioning in STEMI patients: a meta-analysis

Background

Compelling evidence from large randomized trials demonstrates the salutary effects of ischemic postconditioning on cardioprotection against ischemic/reperfusion injury. However, some studies appear negative findings.

This study was designed to assess the short-and long-term effects of postconditioning (Poc) in studies including evolving ST-elevation myocardial infarction (STEMI).

Methods

Relevant studies were identified through an electronic literature search from the PubMed, Library of Congress, Embase, Cochrane Central Register of Controlled Trials, and ISI Web of Science. Studies published up to December 2014 were eligible for inclusion. Patients older than 18 years presenting within 12 h of the first STEMI and eligible for angioplasty were considered for the study.

Results

The 25 trials allocated 1136 patients to perform locational postconditioning cycles at the onset of reperfusion and 1153 patients to usual percutaneous coronary intervention (PCI). Ischemic postconditioning demonstrated a decrease in serum cardiac enzymes creatine kinase (CK) and CK-MB (P < 0.00001 and P =0.25, respectively) in the subgroup analysis based on direct stenting. Reduction in infarct size by imaging was showed during7 days after myocardial infarction (P =0.01), but not in the longterm (P = 0.08). The wall motion score index was improved in both the short term within 7 days (P = 0.009) and the long term over 6 months after receiving Poc (P = 0.02). All included studies were limited by the high risk of performance and publication bias.

Conclusions

Ischemic postconditioning by brief interruptions of coronary blood flow at the onset of reperfusion after PCI appears to be superior to PCI alone in reducing myocardial injury and improving left ventricular function, especially in patients who have received direct stenting in PCI.

Molecular Mechanisms of Renal Ischemic Conditioning Strategies

Ischemia-reperfusion injury is the leading cause of acute kidney injury in a variety of clinical settings such as renal transplantation and hypovolemic and/or septic shock. Strategies to reduce ischemia-reperfusion injury are obviously clinically relevant. Ischemic conditioning is an inherent part of the renal defense mechanism against ischemia and can be triggered by short periods of intermittent ischemia and reperfusion. Understanding the signaling transduction pathways of renal ischemic conditioning can promote further clinical translation and pharmacological advancements in this era. This review summarizes research on the molecular mechanisms underlying both local and remote ischemic pre-, per- and postconditioning of the kidney. The different types of conditioning strategies in the kidney recruit similar powerful pro-survival mechanisms. Likewise, renal ischemic conditioning mobilizes many of the same protective signaling pathways as in other organs, but differences are recognized.

Effect of remote ischemic postconditioning on patients undergoing living donor liver transplantation

The aim of this study was to evaluate the protective effect of remote ischemic postconditioning (RIPostC) on graft function and acute kidney injury (AKI) after living donor liver transplantation (LT). Recipients undergoing elective living donor LT were randomly assigned to either the RIPostC group or the control group. Immediately after reperfusion, 4 cycles of ischemia and reperfusion lasting for 5 minutes each were performed on 1 upper limb in the RIPostC group. Graft function was assessed through evaluations of the serum levels of total bilirubin and liver enzymes and the prothrombin time for 28 days after surgery. The incidence of AKI, as defined by the Risk, Injury, Failure, Loss, and End-Stage Kidney Disease classification, was evaluated within 28 days of the operation. In addition, the incidences of graft dysfunction, acute cellular rejection, and major complications; the 1-, 3-, and 6-month mortality rates; the length of stay in the intensive care unit; and the length of hospital stay were also investigated. In all, 78 patients were enrolled in the analysis (n = 39 in each group). No differences in graft function or clinical outcomes were observed between the groups. The incidences of postoperative AKI were 38% (n = 15) in the RIPostC group and 72% (n = 28) in the control group (P = 0.006). Despite no improvements in postoperative graft function, RIPostC decreased the incidence of postoperative AKI after living donor LT in this study. However, no other clinical benefits with respect to the complication rate, length of hospital stay, or short-term mortality rate were observed. Thus, further studies will be needed to evaluate the clinical efficacy of RIPostC in LT fully.