Effect of remote ischemic preconditioning on renal dysfunction after complex valvular heart surgery: a randomized controlled trial

A MultiCenter Pilot Randomized Controlled Trial of Remote Ischemic Preconditioning in Major Vascular Surgery

A pilot randomized controlled trial that evaluated the effect of remote ischemic preconditioning (RIPC) on clinical outcomes following major vascular surgery was performed. Eligible patients were those scheduled to undergo open abdominal aortic aneurysm repair, endovascular aortic aneurysm repair, carotid endarterectomy, and lower limb revascularization procedures. Patients were randomized to RIPC or to control groups. The primary outcome was a composite clinical end point comprising any of cardiovascular death, myocardial infarction, new-onset arrhythmia, cardiac arrest, congestive cardiac failure, cerebrovascular accident, renal failure requiring renal replacement therapy, mesenteric ischemia, and urgent cardiac revascularization. Secondary outcomes were components of the primary outcome and myocardial injury as assessed by serum troponin values. The primary outcome occurred in 19 (19.2%) of 99 controls and 14 (14.1%) of 99 RIPC group patients ( P = .446). There were no significant differences in secondary outcomes. Our trial generated data that will guide future trials. Further trials are urgently needed.

Remote Ischemic Preconditioning May Attenuate Renal Ischemia-Reperfusion Injury in a Porcine Model of Supraceliac Aortic Cross-Clamping

AIM

The effect of remote ischemic preconditioning (RIPC) in decreasing renal ischemia-reperfusion injury (IRI) during a suprarenal aortic cross-clamping was examined in a swine model.

MATERIALS AND METHODS

Four groups of pigs were examined: (a) ischemia-reperfusion (IR) group, renal IRI produced by 30 min of supraceliac aortic cross-clamping; (b) RIPC I group, the same renal IRI following RIPC by brief occlusion of the infrarenal aorta (15 min ischemia and 15 min reperfusion); (c) RIPC II group, the same renal IRI following RIPC by brief occlusion of the infrarenal aorta (3 cycles of 5 min ischemia and 5 min reperfusion); (d) sham group. Renal function was assessed before and after IRI by examining creatinine, neutrophil gelatinase-associated lipocalin (NGAL), TNF-α, malondialdehyde (MDA), cystatin C and C-reactive protein (CRP) from renal vein blood samples at specific time intervals.

RESULTS

Both RIPC groups presented significantly less impaired results compared to the IR group when considering MDA, cystatin C, CRP and creatinine. Between the two RIPC groups, RIPC II presented a better response with regard to CRP, NGAL, TNF-α, MDA and cystatin C.

CONCLUSIONS

Remote IR protocols and mainly repetitive short periods of cycles of IR ameliorate the biochemical kidney effects of IRI in a model of suprarenal aortic aneurysm repair.

Interaction of risk factors, comorbidities, and comedications with ischemia/reperfusion injury and cardioprotection by preconditioning, postconditioning, and remote conditioning

Pre-, post-, and remote conditioning of the myocardium are well described adaptive responses that markedly enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and provide therapeutic paradigms for cardioprotection. Nevertheless, more than 25 years after the discovery of ischemic preconditioning, we still do not have established cardioprotective drugs on the market. Most experimental studies on cardioprotection are still undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of cardiovascular risk factors. However, ischemic heart disease in humans is a complex disorder caused by, or associated with, cardiovascular risk factors and comorbidities, including hypertension, hyperlipidemia, diabetes, insulin resistance, heart failure, altered coronary circulation, and aging. These risk factors induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Moreover, some of the medications used to treat these risk factors, including statins, nitrates, and antidiabetic drugs, may impact cardioprotection by modifying cellular signaling. The aim of this article is to review the recent evidence that cardiovascular risk factors and their medication may modify the response to cardioprotective interventions. We emphasize the critical need to take into account the presence of cardiovascular risk factors and concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple risk factors.

Clinical applications of remote ischaemic preconditioning in native and transplant acute kidney injury

Ischaemia-reperfusion (IR) 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 upon reperfusion that limits the amount of tissue that can be salvaged. IR injury plays a central role in both native and transplant acute kidney injury (AKI). Native AKI is associated with increased morbidity and mortality in hospital inpatients, and transplant AKI contributes to graft dysfunction, ultimately limiting graft longevity. In this review, we discuss the potential therapeutic benefits of a cost-effective and low-risk intervention, remote ischaemic preconditioning (RIPC), and its applicability in the prevention and reduction of AKI.

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.

Remote ischaemic conditioning on recipients of deceased renal transplants, effect on immediate and extended kidney graft function: a multicentre, randomised controlled trial protocol (CONTEXT)

INTRODUCTION

Delayed graft function due to ischaemia-reperfusion injury is a frequent complication in deceased donor renal transplantation. Experimental evidence indicates that remote ischaemic conditioning (RIC) provides systemic protection against ischaemia-reperfusion injury in various tissues.

METHODS AND ANALYSIS

'Remote ischaemic conditioning in renal transplantation--effect on immediate and extended kidney graft function' (the CONTEXT study) is an investigator initiated, multicentre, randomised controlled trial investigating whether RIC of the leg of the recipient improves short and long-term graft function following deceased donor kidney transplantation. The study will include 200 kidney transplant recipients of organ donation after brain death and 20 kidney transplant recipients of organ donation after circulatory death. Participants are randomised in a 1:1 design to RIC or sham-RIC (control). RIC consists of four cycles of 5 min occlusion of the thigh by a tourniquet inflated to 250 mm Hg, separated by 5 min of deflation. Primary end point is the time to a 50% reduction from the baseline plasma creatinine, estimated from the changes of plasma creatinine values 30 days post-transplant or 30 days after the last performed dialysis post-transplant. Secondary end points are: need of dialysis post-transplant, measured and estimated-glomerular filtration rate (GFR) at 3 and 12 months after transplantation, patient and renal graft survival, number of rejection episodes in the first year, and changes in biomarkers of acute kidney injury and inflammation in plasma, urine and graft tissue.

ETHICS AND DISSEMINATION

The study is approved by the local ethical committees and national data security agencies. Results are expected to be published in 2016.

TRIAL REGISTRATION NUMBER

NCT01395719.

Remote ischemic preconditioning for kidney protection: GSK3β-centric insights into the mechanism of action

Preventing acute kidney injury (AKI) in high-risk patients following medical interventions is a paramount challenge for clinical practice. Recent data from animal experiments and clinical trials indicate that remote ischemic preconditioning, represented by limb ischemic preconditioning, confers a protective action on the kidney. Ischemic preconditioning is effective in reducing the risk for AKI following cardiovascular interventions and the use of iodinated radiocontrast media. Nevertheless, the underlying mechanisms for this protective effect are elusive. A protective signal is conveyed from the remote site undergoing ischemic preconditioning, such as the limb, to target organs, such as the kidney, by multiple potential communication pathways, which may involve humoral, neuronal, and systemic mechanisms. Diverse transmitting pathways trigger a variety of signaling cascades, including the reperfusion injury salvage kinase and survivor activating factor enhancement pathways, all of which converge on glycogen synthase kinase 3β (GSK3β). Inhibition of GSK3β subsequent to ischemic preconditioning reinforces the Nrf2-mediated antioxidant defense, diminishes the nuclear factor-κB-dependent proinflammatory response, and exerts prosurvival effects ensuing from the desensitized mitochondria permeability transition. Thus, therapeutic targeting of GSK3β by ischemic preconditioning or by pharmacologic preconditioning with existing US Food and Drug Administration-approved drugs having GSK3β-inhibitory activities might represent a pragmatic and cost-effective adjuvant strategy for kidney protection and prophylaxis against AKI.

Additive Effect on Survival of Anaesthetic Cardiac Protection and Remote Ischemic Preconditioning in Cardiac Surgery: A Bayesian Network Meta-Analysis of Randomized Trials

INTRODUCTION

Cardioprotective properties of volatile agents and of remote ischemic preconditioning have survival effects in patients undergoing cardiac surgery. We performed a Bayesian network meta-analysis to confirm the beneficial effects of these strategies on survival in cardiac surgery, to evaluate which is the best strategy and if these strategies have additive or competitive effects.

METHODS

Pertinent studies were independently searched in BioMedCentral, MEDLINE/PubMed, Embase, and the Cochrane Central Register (updated November 2013). A Bayesian network meta-analysis was performed. Four groups of patients were compared: total intravenous anesthesia (with or without remote ischemic preconditioning) and an anesthesia plan including volatile agents (with or without remote ischemic preconditioning). Mortality was the main investigated outcome.

RESULTS

We identified 55 randomized trials published between 1991 and 2013 and including 6,921 patients undergoing cardiac surgery. The use of volatile agents (posterior mean of odds ratio = 0.50, 95% CrI 0.28-0.91) and the combination of volatile agents with remote preconditioning (posterior mean of odds ratio = 0.15, 95% CrI 0.04-0.55) were associated with a reduction in mortality when compared to total intravenous anesthesia. Posterior distribution of the probability of each treatment to be the best one, showed that the association of volatile anesthetic and remote ischemic preconditioning is the best treatment to improve short- and long-term survival after cardiac surgery, suggesting an additive effect of these two strategies.

CONCLUSIONS

In patients undergoing cardiac surgery, the use of volatile anesthetics and the combination of volatile agents with remote preconditioning reduce mortality when compared to TIVA and have additive effects. It is necessary to confirm these results with large, multicenter, randomized, double-blinded trials comparing these different strategies in cardiac and non-cardiac surgery, to establish which volatile agent is more protective than the others and how to best apply remote ischemic preconditioning.

Investigating the effect of remote ischaemic preconditioning on biomarkers of stress and injury-related signalling in patients having isolated coronary artery bypass grafting or aortic valve replacement using cardiopulmonary bypass: study protocol for a randomized controlled trial

Background

Ischaemia-reperfusion injury occurs during heart surgery that uses cardiopulmonary bypass (CPB) and cardioplegic arrest. It is hypothesised that remote ischaemic preconditioning (RIPC) protects the heart against such injury. Despite the numerous studies investigating the protective effects of RIPC, there is still uncertainty about the interpretation of the findings as well as conflicting results between studies. The objective of this trial is to investigate the cardioprotective effect of RIPC in patients having coronary artery bypass grafting (CABG) or aortic valve replacement surgery. This will be achieved by estimating the effect of the intervention in the two groups of pathologies and by investigating the signalling mechanisms that may underpin the cardioprotective effect.

Methods/Design

A two-centre randomised controlled trial will be used to investigate the effects of RIPC in two pathologies: patients having isolated CABG and those having aortic valve replacement surgery (AVR) with CPB. Participants will be randomised to RIPC or control (sham RIPC), stratified by surgical stratum. The intervention will be delivered by a research nurse. Data will be collected by a research nurse blinded to the intervention. The patient and the theatre staff are also blinded to the allocation. Markers of myocardial injury and inflammation will be measured in myocardial biopsies and in blood samples at different times.

Discussion

This trial is designed to investigate whether RIPC will reduce myocardial injury and inflammation following heart surgery and whether there is a difference in effect between participants having CABG or AVR. This trial is a unique opportunity to study the mechanisms associated with RIPC using human myocardial tissue and blood, and to relate these to the extent of myocardial injury/protection.

Trial registration

Current Controlled Trials ISRCTN33084113 (25 March 2013).

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-015-0696-z) contains supplementary material, which is available to authorized users.

Cystatin C in acute kidney injury diagnosis: early biomarker or alternative to serum creatinine?

BACKGROUND

Early acute kidney injury (AKI) diagnosis is needed to pursue treatment trials. We evaluated cystatin C (CysC) as an early biomarker of serum creatinine (SCr)-AKI and an alternative to define AKI.

METHODS

We studied 160 non-cardiac children in the intensive care unit (ICU). We measured daily CysC and SCr. AKI was staged by KDIGO (Kidney Disease: Improving Global Outcomes) guidelines using SCr and CysC (CysC-AKI). We calculated area under the curve (AUC) for (1) neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1) and urine CysC to diagnose SCr- and CysC-AKI; and (2) for CysC to diagnose SCr-AKI. We evaluated AKI associations with length of stay and ventilation duration.

RESULTS

We found that 44 % of patients developed SCr-AKI; 32 % developed CysC-AKI. Early ICU NGAL was most diagnostic of CysC-AKI (AUC 0.69, 95% CI 0.54-0.84); IL-18 was most diagnostic for SCr-AKI (AUC 0.69 95% CI 0.55-0.82). Combining SCr and CysC-AKI definition led to higher biomarker diagnostic AUC's. CysC-AKI was not more strongly associated with clinical outcomes. Early ICU CysC predicted SCr-AKI development (AUC 0.70, 95 % CI 0.53-0.89).

CONCLUSIONS

Our findings do not support replacing SCr by CysC to define AKI. Early ICU CysC predicts SCr-AKI development and combined SCr-CysC-AKI definition leads to stronger AKI biomarker associations.

Ischemic preconditioning-an unfulfilled promise

Myocardial reperfusion injury has been identified as a key determinant of myocardial infarct size in patients undergoing percutaneous or surgical interventions. Although the molecular mechanisms underpinning reperfusion injury have been elucidated, attempts at translating this understanding into clinical benefit for patients undergoing cardiac interventions have produced mixed results. Ischemic conditioning has been applied before, during, or after an ischemic insult to the myocardium and has taken the form of local induction of ischemia or ischemia of distant tissues. Clinical studies have confirmed the safety of differing conditioning techniques, but the benefit of such techniques in reducing hard clinical event rates has produced mixed results. The aim of this article is to review the role of ischemic conditioning in patients undergoing percutaneous and surgical coronary revascularization.

The deep hypothermic circulatory arrest causes more kidney malfunctions based on a novel rabbit model

BACKGROUND AND OBJECTIVES

High incidences of acute kidney injury after cardiopulmonary bypass (CPB) were observed in previous reports. However, whether deep hypothermic circulatory arrest (DHCA) leads to more severe kidney injury than CPB without DHCA remains controversial. The aim of the study was to investigate the effects of DHCA on renal function in a novel rabbit model of using closed-thoracic DHCA.

DESIGN AND SETTINGS

Experimental study on New Zealand white rabbits performed in the Department of Cardiac Surgery, the First Affiliated Hospital of China Medical University.

METHODS

Thirty rabbits were randomly divided into 3 groups : the sham-operated group (Group A, N=10), the CPB group (Group B, N=10), and the DHCA group (Group C, N=10). Serum creatinine (Scr), blood urea nitrogen (BUN), serum cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), malondialdehyde (MDA) levels, superoxide dismutase (SOD) activities, histopathologic llesions, and apoptosis were assessed.

RESULTS

Each single rabbit in Groups B and C died during surgery. Animals received DHCA exhibited more severe kidney impairments than those received CPB and those that were sham operated. Scr and BUN concentrations at 24 and 48 hours after surgery; cystatin C and NGAL concentrations at 12, 24, and 48 hours after surgery; MDA levels, histopathological lesions, and apoptosis score of the kidneys were the highest in Group C, followed by Group B, and were the lowest in Group A (all P < .05). The activities of SOD were the lowest in Group C, followed by Group B, and were the highest in Group A (P < .05).

CONCLUSION

Our study established a simple, convenient, economical, and long-term surviving rabbit model for the study of DHCA-induced organic injury. Based on more significant kidney injuries, including elevated levels of serum cystatin C and NGAL at an early time, increased lipid peroxidation, decreased renal antioxidative ability, enhanced histological lesions, and increased tubular epithelial apoptosis from DHCA animals, we concluded that DHCA has more kidney dysfunctions than CPB without DHCA.

Effect of remote ischaemic preconditioning on clinical outcomes in patients undergoing cardiac bypass surgery: a randomised controlled clinical trial

OBJECTIVES

Remote ischaemic preconditioning (RIPC), using brief cycles of limb ischaemia/reperfusion, is a non-invasive, low-cost intervention that may reduce perioperative myocardial injury (PMI) in patients undergoing cardiac surgery. We investigated whether RIPC can also improve short-term clinical outcomes.

METHODS

One hundred and eighty patients undergoing elective coronary artery bypass graft (CABG) surgery and/or valve surgery were randomised to receive either RIPC (2-5 min cycles of simultaneous upper arm and thigh cuff inflation/deflation; N=90) or control (uninflated cuffs placed on the upper arm and thigh; N=90). The study primary end point was PMI, measured by 72 h area under the curve (AUC) serum high-sensitive troponin-T (hsTnT); secondary end point included short-term clinical outcomes.

RESULTS

RIPC reduced PMI magnitude by 26% (-9.303 difference (CI -15.618 to -2.987) 72 h hsTnT-AUC; p=0.003) compared with control. There was also evidence that RIPC reduced the incidence of postoperative atrial fibrillation by 54% (11% RIPC vs 24% control; p=0.031) and decreased the incidence of acute kidney injury by 48% (10.0% RIPC vs 21.0% control; p=0.063), and intensive care unit stay by 1 day (2.0 days RIPC (CI 1.0 to 4.0) vs 3.0 days control (CI 2.0 to 4.5); p=0.043). In a post hoc analysis, we found that control patients administered intravenous glyceryl trinitrate (GTN) intraoperatively sustained 39% less PMI compared with those not receiving GTN, and RIPC did not appear to reduce PMI in patients given GTN.

CONCLUSIONS

RIPC reduced the extent of PMI in patients undergoing CABG and/or valve surgery. RIPC may also have beneficial effects on short-term clinical outcomes, although this will need to be confirmed in future studies.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov ID: NCT00397163.

Device-Based Therapy in the Prevention of Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is a common condition that is associated with short- and, likely, long-term adverse outcomes. Although periprocedural intravenous hydration is the simplest and most widely used technique to prevent CIN, the limited ability of this approach to mitigate the CIN risk in high-risk populations has provided an impetus to develop new preventive strategies. A range of potentially useful device-based approaches offers new preventive techniques. Well-designed and adequately powered randomized studies of these device-based therapies are urgently needed to determine the expanding role they will play in future clinical practice.

Remote preconditioning and major clinical complications following adult cardiovascular surgery: systematic review and meta-analysis

BACKGROUND

A number of 'proof-of-concept' trials suggest that remote ischaemic preconditioning (RIPC) reduces surrogate markers of end-organ injury in patients undergoing major cardiovascular surgery. To date, few studies have involved hard clinical outcomes as primary end-points.

METHODS

Randomised clinical trials of RIPC in major adult cardiovascular surgery were identified by a systematic review of electronic abstract databases, conference proceedings and article reference lists. Clinical end-points were extracted from trial reports. In addition, trial principal investigators provided unpublished clinical outcome data.

RESULTS

In total, 23 trials of RIPC in 2200 patients undergoing major adult cardiovascular surgery were identified. RIPC did not have a significant effect on clinical end-points (death, peri-operative myocardial infarction (MI), renal failure, stroke, mesenteric ischaemia, hospital or critical care length of stay).

CONCLUSION

Pooled data from pilot trials cannot confirm that RIPC has any significant effect on clinically relevant end-points. Heterogeneity in study inclusion and exclusion criteria and in the type of preconditioning stimulus limits the potential for extrapolation at present. An effort must be made to clarify the optimal preconditioning stimulus. Following this, large-scale trials in a range of patient populations are required to ascertain the role of this simple, cost-effective intervention in routine practice.

Ischaemic conditioning strategies for the nephrologist: a promise lost in translation?

Over the last quarter of a century, a huge effort has been made to develop interventions that can minimise ischaemia reperfusion injury. The most potent of these are the ischaemic conditioning strategies, which comprise ischaemic preconditioning, remote ischaemic preconditioning and ischaemic postconditioning. While much of the focus for these interventions has been on protecting the myocardium, other organs including the kidney can be similarly protected. However, translation of these beneficial effects from animal models into routine clinical practice has been less straightforward than expected. In this review, we examine the role of ischaemic conditioning strategies in reducing tissue injury from the 'bench to the bedside' and discuss the barriers to their greater translation.

Neutrophil gelatinase associated lipocalin in acute kidney injury

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a member of the lipocalin family of proteins. Usually, NGAL is produced and secreted by kidney tubule cells at low levels, but the amount produced and secreted into the urine and serum increases dramatically after ischemic, septic, or nephrotoxic injury of the kidneys. The purpose of our review article is to summarize the role of NGAL in acute kidney injury (AKI), emergent, and intensive care.

METHODS

A PubMed search was performed (only English-language articles concerning human subjects were considered) using each of the following search term combinations: neutrophil gelatinase-associated lipocalin OR NGAL and acute kidney injury OR AKI; cardiac surgery; heart failure OR cardiology; intensive care; emergency department OR emergency medicine; nephropathy OR nephrotoxicity and transplantation.

RESULTS

The results of our search yielded 339 articles. Of the 339 articles, 160 were eligible for review based on the predefined criteria for inclusion.

CONCLUSION

Based on the evidence reviewed, it is clear that patient NGAL level is an appropriate, sensitive, and specific early biomarker of AKI caused by a variety of different etiologies. It is advised that a multidisciplinary group of experts come together to make recommendations and propose a consensus of clinical procedures to advance the most efficacious NGAL monitoring protocol for early detection and treatment of patients with AKI.

Remote ischemic preconditioning and renoprotection: from myth to a novel therapeutic option?

There is currently no effective prophylactic regimen available to prevent contrast-induced AKI (CI-AKI), a frequent and life-threatening complication after cardiac catheterization. Therefore, novel treatment strategies are required to decrease CI-AKI incidence and to improve clinical outcomes in these patients. Remote ischemic preconditioning (rIPC), defined as transient brief episodes of ischemia at a remote site before a subsequent prolonged ischemia/reperfusion injury of the target organ, is an adaptational response that protects against ischemic and reperfusion insult. Indeed, several studies demonstrated the tissue-protective effects of rIPC in various target organs, including the kidneys. In this regard, rIPC may offer a novel noninvasive and virtually cost-free treatment strategy for decreasing CI-AKI incidence. This review evaluates the current experimental and clinical evidence for rIPC as a potential renoprotective strategy, and discusses the underlying mechanisms and key areas for future research.

The role of remote ischemic preconditioning in the treatment of atherosclerotic diseases

BACKGROUND

Remote ischemic preconditioning (RIPC) is the application of a transient and brief ischemic stimulus to a distant site from the organ or tissue that is afterward exposed to injury ischemia, and has been found to reduce ischemia-reperfusion injury (IRI) in various animal models. RIPC appears to offer two distinct phases of endothelial IRI protection, which are presumably mediated through neuronal and humoral pathways.

METHODS

We conducted a comprehensive literature review on the available published data about the potential effect of RIPC in patients undergoing IRI in one or more vital organs.

RESULTS

Our search highlighted 24 randomized clinical trials about the effect of RIPC on variable clinical settings (abdominal aortic aneurysm repair, open heart surgery, percutaneous coronary intervention, living donor renal transplantation, coronary angiography, elective decompression surgery, carotid endarterectomy, recent stroke, or transient ischemic attack combined with intracranial carotid artery stenosis). Most of the trials focused on postoperative cardiac or renal function after RIPC with conflicting results. Preconditioning protocols, age limits, comorbidities, and concomitant drug use varied significantly across trials, and therefore no firm conclusions can be drawn using the available data. However, no severe local adverse events were observed in any patient undergoing limb or arm preconditioning.

CONCLUSIONS

RIPC is a safe and well-tolerated procedure that may constitute a potentially promising innovative treatment in atherosclerotic diseases. Large, multicenter, randomized clinical trials are required to determine an optimal protocol for the RIPC procedure, and to evaluate further the potential benefits of RIPC in human ischemic injury.

The role of remote ischemic preconditioning in organ protection after cardiac surgery: a meta-analysis

BACKGROUND

Remote ischemic preconditioning (RIPC) appears to protect distant organs from ischemia-reperfusion injury. We undertook meta-analysis of clinical studies to evaluate the effects of RIPC on organ protection and clinical outcomes in patients undergoing cardiac surgery.

METHODS

A review of evidence for cardiac, renal, and pulmonary protection after RIPC was performed. We also did meta-regressions on RIPC variables, such as duration of ischemia, cuff pressure, and timing of application of preconditioning. Secondary outcomes included length of hospital and intensive care unit stay, duration of mechanical ventilation, and mortality at 30 days.

RESULTS

Randomized control trials (n = 25) were included in the study for quantitative analysis of cardiac (n = 16), renal (n = 6), and pulmonary (n = 3) protection. RIPC provided statistically significant cardiac protection (standardized mean difference [SMD], -0.77; 95% confidence interval [CI], -1.15, -0.39; Z = 3.98; P < 0.0001) and on subgroup analysis, the protective effect remained consistent for all types of cardiac surgical procedures. However, there was no evidence of renal protection (SMD, 0.74; 95% CI, 0.53, 1.02; Z = 1.81; P = 0.07) or pulmonary protection (SMD, -0.03; 95% CI, -0.56, 0.50; Z = 0.12; P = 0.91). There was no statistical difference in the short-term clinical outcomes between the RIPC and control groups.

CONCLUSIONS

RIPC provides cardiac protection, but there is no evidence of renal or pulmonary protection in patients undergoing cardiac surgery using cardiopulmonary bypass. Larger multicenter trials are required to define the role of RIPC in surgical practice.

Protection of organs other than the heart by remote ischemic conditioning

Organ or tissue dysfunction due to acute ischemia-reperfusion injury (IRI) is the leading cause of death and disability worldwide. Acute IRI induces cell injury and death in a wide variety of organs and tissues in a large number of different clinical settings. One novel therapeutic noninvasive intervention, capable of conferring multiorgan protection against acute IRI, is 'remote ischemic conditioning' (RIC). This describes an endogenous protective response to acute IRI, which is triggered by the application of one or more brief cycles of nonlethal ischemia and reperfusion to one particular organ or tissue. Originally discovered as a therapeutic strategy for protecting the myocardium against acute IRI, it has been subsequently demonstrated that RIC may confer protection against acute IRI in a number of different noncardiac organs and tissues including the kidneys, lungs, liver, skin flaps, ovaries, intestine, stomach and pancreas. The discovery that RIC can be induced noninvasively by applying the RIC stimulus to the skeletal tissue of the upper or lower limb has facilitated its application to a number of clinical settings in which organs and tissues are at high risk of acute IRI. In this article, we review the experimental studies that have investigated RIC in organs and tissues other than the heart, and we explore the therapeutic potential of RIC in preventing organ and tissue dysfunction induced by acute IRI.

The emerging application of remote ischemic conditioning in the clinical arena

Remote ischemic conditioning (RIC) is an intervention, in which intermittent episodes of ischemia and reperfusion in an organ or tissue distant from the target organ requiring protection, provide armour against lethal ischemia-reperfusion injury. Although the exact mechanisms underlying the protection mediated through RIC have not been clearly established, the release of humoral factors and the activation of neural pathways have been implicated. There is now clinical evidence suggesting that this form of protection can be induced by a simple, noninvasive, and cost-effective procedure such as inflation and deflation of a blood pressure cuff and that this intervention provides increased organ protection in a variety of clinical scenarios, for example, in myocardial infarction. Here we provide an overview of the history and evolution of RIC, the potential mechanisms underlying its protective effects, and published randomized clinical trials in cardiovascular procedures.

The role of remote ischemic preconditioning on postoperative kidney injury in patients undergoing cardiac and vascular interventions: a meta-analysis

The objective of this study was to perform a meta-analysis of randomized controlled trials (RCTs) investigating whether a remote ischemic preconditioning (RIPC) protocol provides renal protection to patients undergoing cardiac and vascular interventions. Searches were conducted in the databases PUBMED, EMBASE and Cochrane Library. RCTs that fulfilled the inclusion criteria and addressed the clinical questions of this analysis were further assessed. We identified ten studies with a total of 924 patients undergoing cardiac and vascular interventions with or without RIPC. There was a significantly lower incidence of acute kidney injury in the RIPC group compared with control group using the fixed effect model (RR 0.69, 95% CI 0.53 to 0.90, P = 0.007), but not with the random effects model (RR 0.73, 95% CI 0.50 to 1.06, P = 0.10). There was no difference in the levels of renal biomarkers, incidence of renal replacement therapy, mortality, hospital stay, and intensive care unit stay between two groups. In conclusion, there is no enough evidence that RIPC provided renal protection in patients undergoing cardiac and vascular interventions. Large-scale RCTs are necessary to confirm the potential role of RIPC on renal impairment.

Effect of remote ischaemic preconditioning on renal protection in patients undergoing laparoscopic partial nephrectomy: a 'blinded' randomised controlled trial

OBJECTIVE

To evaluate whether remote ischaemic preconditioning (RIPC) reduces renal injury in patients undergoing laparoscopic partial nephrectomy (LPN).

PATIENTS AND METHODS

In all, 82 patients undergoing LPN were randomly assigned to either the RIPC or control group, with 40 and 38 patients, respectively completing 6-months follow-up. RIPC was conducted after induction of anaesthesia, which consisted of three 5-min cycles of right lower limb ischaemia and 5 min of reperfusion during each cycle. The primary outcome was the absolute change in glomerular filtration rate (GFR) of the affected kidney by renal scintigraphy from baseline to 6 months. The secondary outcomes included urinary retinol-binding protein (RBP) levels measured at 24 and 48 h, serum creatinine, and estimated GFR (eGFR) at 1 and 6 months, and changes in GFR by renal scintigraphy.

RESULTS

There were no differences in the change of GFR of the affected kidney at 6 months, while it was significantly decreased by 15.0% in the control group vs 8.8% in the RIPC group at 1 month (P = 0.034). The urinary RBP levels increased 8.4-fold at 24 h in the control group compared with a lower increase of 3.9-fold in the RIPC group (P < 0.001). There were no differences in the serum creatinine level or eGFR at 1 and 6 months between the two groups.

CONCLUSIONS

In patients undergoing LPN, RIPC using transient lower limb ischaemia may reduce renal impairment in the short term, but failed in the longer term despite a non-significant trend in favour of RIPC. These novel data support the need for a larger study of RIPC during LPN surgery.

Acute kidney injury clinical trial design: old problems, new strategies

Apart from supportive dialysis there are no universally accepted interventions in acute kidney injury (AKI). We have summarized the outcomes of all published randomized, placebo-controlled studies of non-dialysis treatment of AKI. Forty-nine trials were identified, only one of which was in a paediatric population. Sixteen trials had positive outcomes; these trials are not comparable in terms of methodology used or outcomes assessed, and they share many of the problems of the negative trials. We discuss the flaws in clinical trial design that have contributed to poor or uncertain outcomes and propose minimum requirements for future trials. In particular, future trials should incorporate biomarkers specific to the etiology of the AKI, and treatment should match the phase of injury.

Translating cardioprotection for patient benefit: position paper from the Working Group of Cellular Biology of the Heart of the European Society of Cardiology

Coronary heart disease (CHD) is the leading cause of death and disability worldwide. Despite current therapy, the morbidity and mortality for patients with CHD remains significant. The most important manifestations of CHD arise from acute myocardial ischaemia-reperfusion injury (IRI) in terms of cardiomyocyte death and its long-term consequences. As such, new therapeutic interventions are required to protect the heart against the detrimental effects of acute IRI and improve clinical outcomes. Although a large number of cardioprotective therapies discovered in pre-clinical studies have been investigated in CHD patients, few have been translated into the clinical setting, and a significant number of these have failed to show any benefit in terms of reduced myocardial infarction and improved clinical outcomes. Because of this, there is currently no effective therapy for protecting the heart against the detrimental effects of acute IRI in patients with CHD. One major factor for this lack of success in translating cardioprotective therapies into the clinical setting can be attributed to problems with the clinical study design. Many of these clinical studies have not taken into consideration the important data provided from previously published pre-clinical and clinical studies. The overall aim of this ESC Working Group Cellular Biology of the Heart Position Paper is to provide recommendations for optimizing the design of clinical cardioprotection studies, which should hopefully result in new and effective therapeutic interventions for the future benefit of CHD patients.

β-blockers and volatile anesthetics may attenuate cardioprotection by remote preconditioning in adult cardiac surgery: a meta-analysis of 15 randomized trials

OBJECTIVE

Clinical trials on cardioprotection by remote ischemic preconditioning (RIPC) for adult patients undergoing cardiac surgery revealed mixed results. Previous meta-analyses have been conducted and found marked heterogeneity among studies. The aim of this meta-analysis was to evaluate the factors affecting cardioprotection by remote preconditioning in adult cardiac surgery.

DESIGN

A meta-analysis of randomized controlled trials.

SETTING

University hospitals.

PARTICIPANTS

Adult subjects undergoing cardiac surgery.

INTERVENTIONS

RIPC.

MEASUREMENTS AND MAIN RESULTS

Fifteen trials with a total of 1,155 study patients reporting postoperative myocardial biomarker (CK-MB or troponin) levels were identified from PubMed, Embase, and the Cochrane Library (up to July 2012). Compared with controls, RIPC significantly reduced postoperative biomarkers of myocardial injury (standardized mean difference = -0.31, p = 0.041; heterogeneity test: I(2) = 83.5%). This effect seemed more significant in valve surgery (standardized mean difference = -0.74, p = 0.002) than in coronary artery surgery (standardized mean difference = -0.23; p = 0.17). Univariate meta-regression analyses suggested that the major sources of significant heterogeneity were β-blockers (%) (coefficient = 0.0161, p = 0.022, adjusted R(2) = 0.37) and volatile anesthetics (coefficient = 0.6617, p = 0.065, adjusted R(2) = 0.22). These results were further confirmed in multivariate regression and subgroup analyses.

CONCLUSIONS

Available data from this meta-analysis further confirmed the cardioprotection conferred by RIPC in adult cardiac surgery. Moreover, the cardioprotective effect may be attenuated when combined with β-blockers or volatile anesthetics.

Effect of combined remote ischemic preconditioning and postconditioning on pulmonary function in valvular heart surgery

BACKGROUND

The aim of this study was to evaluate the lung-protective effect of combined remote ischemic preconditioning (RIPCpre) and postconditioning (RIPCpost) in patients undergoing complex valvular heart surgery.

METHODS

In this randomized, placebo-controlled, double-blind trial, 54 patients were assigned to an RIPCpre plus RIPCpost group or a control group (1:1). Patients in the RIPCpre plus RIPCpost group received three 10-min cycles of right-side lower-limb ischemia of 250 mm Hg at both 10 min after anesthetic induction and weaning from cardiopulmonary bypass. The primary end point was to compare postoperative Pao(2)/Fio(2). Secondary end points were to compare pulmonary variables, incidence of acute lung injury, and inflammatory cytokines.

RESULTS

In both groups, Pao(2)/Fio(2) at 24 h postoperation was significantly decreased compared with each corresponding baseline value. However, intergroup comparisons of pulmonary variables, including Pao(2)/Fio(2) and incidence of acute lung injury, revealed no significant differences. Serum levels of IL-6, IL-8, IL-10, and tumor necrosis factor-α were all significantly increased in both groups compared with each corresponding baseline value, without any significant intergroup differences. There were also no significant differences in transpulmonary gradient of IL-6, IL-10, and tumor necrosis factor-α between the groups.

CONCLUSIONS

RIPCpre plus RIPCpost as tested in this randomized controlled trial did not provide significant pulmonary benefit following complex valvular cardiac surgery.

Cardiac surgery-associated acute kidney injury

Cardiac surgery-associated acute kidney injury (AKI) is a major health problem that is extremely common and has a significant effect on cardiac surgical outcomes. AKI occurs in nearly 30 % of patients undergoing cardiac surgery, with about 1-2 % of these ultimately requiring dialysis. The development of AKI predicts a significant increase in morbidity and mortality independent of other risk factors. The pathogenetic mechanisms associated with cardiac surgery-associated AKI include several biochemical pathways, of which the most important are hemodynamic, inflammatory and nephrotoxic factors. Risk factors for AKI have been identified in several models, and these facilitate physicians to prognosticate and develop a strategy for tackling patients predisposed to developing renal dysfunction. Effective therapy of the condition is still suboptimal, and hence the accent has always been on risk factor modification. Thus, strategies for reducing preoperative anemia, perioperative blood transfusions and surgical re-explorations may be effective in attenuating the incidence and severity of this complication.

Remote ischemic conditioning to protect against ischemia-reperfusion injury: a systematic review and meta-analysis

Background

Remote ischemic conditioning is gaining interest as potential method to induce resistance against ischemia reperfusion injury in a variety of clinical settings. We performed a systematic review and meta-analysis to investigate whether remote ischemic conditioning reduces mortality, major adverse cardiovascular events, length of stay in hospital and in the intensive care unit and biomarker release in patients who suffer from or are at risk for ischemia reperfusion injury.

Methods and Results

Medline, EMBASE and Cochrane databases were searched for randomized clinical trials comparing remote ischemic conditioning, regardless of timing, with no conditioning. Two investigators independently selected suitable trials, assessed trial quality and extracted data. 23 studies in patients undergoing cardiac surgery (15 studies), percutaneous coronary intervention (four studies) and vascular surgery (four studies), comprising in total 1878 patients, were included in this review. Compared to no conditioning, remote ischemic conditioning did not reduce mortality (odds ratio 1.22 [95% confidence interval 0.48, 3.07]) or major adverse cardiovascular events (0.65 [0.38, 1.14]). However, the incidence of myocardial infarction was reduced with remote ischemic conditioning (0.50 [0.31, 0.82]), as was peak troponin release (standardized mean difference −0.28 [−0.47, −0.09]).

Conclusion

There is no evidence that remote ischemic conditioning reduces mortality associated with ischemic events; nor does it reduce major adverse cardiovascular events. However, remote ischemic conditioning did reduce the incidence of peri-procedural myocardial infarctions, as well as the release of troponin.

Cardioprotection during cardiac surgery

Coronary heart disease (CHD) is the leading cause of morbidity and mortality worldwide. For a large number of patients with CHD, coronary artery bypass graft (CABG) surgery remains the preferred strategy for coronary revascularization. Over the last 10 years, the number of high-risk patients undergoing CABG surgery has increased significantly, resulting in worse clinical outcomes in this patient group. This appears to be related to the ageing population, increased co-morbidities (such as diabetes, obesity, hypertension, stroke), concomitant valve disease, and advances in percutaneous coronary intervention which have resulted in patients with more complex coronary artery disease undergoing surgery. These high-risk patients are more susceptible to peri-operative myocardial injury and infarction (PMI), a major cause of which is acute global ischaemia/reperfusion injury arising from inadequate myocardial protection during CABG surgery. Therefore, novel therapeutic strategies are required to protect the heart in this high-risk patient group. In this article, we review the aetiology of PMI during CABG surgery, its diagnosis and clinical significance, and the endogenous and pharmacological therapeutic strategies available for preventing it. By improving cardioprotection during CABG surgery, we may be able to reduce PMI, preserve left ventricular systolic function, and reduce morbidity and mortality in these high-risk patients with CHD.