Remote ischaemic preconditioning reduces myocardial injury in patients undergoing cardiac surgery with cold-blood cardioplegia: a randomised controlled trial

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).

Is There a Mitochondrial Protection via Remote Ischemic Conditioning in Settings of Anticancer Therapy Cardiotoxicity?

PURPOSE OF REVIEW

To provide an overview of (a) protective effects on mitochondria induced by remote ischemic conditioning (RIC) and (b) mitochondrial damage caused by anticancer therapy. We then discuss the available results of studies on mitochondrial protection via RIC in anticancer therapy-induced cardiotoxicity.

RECENT FINDINGS

In three experimental studies in healthy mice and pigs, there was a RIC-mediated protection against anthracycline-induced cardiotoxicity and there was some evidence of improved mitochondrial function with RIC. The RIC-mediated protection was not confirmed in the two available studies in cancer patients. In adult cancer patients, RIC was associated with an adverse outcome. There are no data on mitochondrial function in cancer patients. Studies in tumor-bearing animals are needed to determine whether RIC does not interfere with the anticancer properties of the drugs and whether RIC actually improves mitochondrial function, ultimately resulting in improved cardiac function.

Perspective: mitochondrial STAT3 in cardioprotection

Activation of signal transducer and activator of transcription 3 (STAT3) has been identified as a key cardioprotective signal not only in animal studies but also in humans-in animals, STAT3 is causally involved in cardioprotection. In response to late ischemic conditioning, canonical function of STAT3 activation upregulates the expression of cardioprotective and anti-apoptotic proteins. In its non-canonical function, STAT3 is activated during ischemic conditioning and is part of the cardioprotective cytosolic survival activating factor enhancement pathway. Activated STAT3 is imported and localized to the mitochondria. Mitochondrial STAT3 stimulates the activity of mitochondrial electron transport chain complex I, reduces mitochondrial reactive oxygen species production and mitochondrial permeability transition pore opening. Finally, two novel aspects of STAT activation in cardioprotection are discussed: a genetic variance of the STAT encoding region as a potential primordial confounding variable for cardioprotection, and the cardioprotective potential of sodium-glucose cotransporter 2 inhibitors through STAT3 activation.

Remote ischemic conditioning in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal inflammatory disorder, most prevalent in premature infants, and associated with a high mortality rate that has remained unchanged in the past two decades. NEC is characterized by inflammation, ischemia, and impaired microcirculation in the intestine. Preclinical studies by our group have led to the discovery of remote ischemic conditioning (RIC) as a promising non-invasive intervention in protecting the intestine against ischemia-induced damage during early-stage NEC. RIC involves the administration of brief reversible cycles of ischemia and reperfusion in a limb (similar to taking standard blood pressure measurement) which activate endogenous protective signaling pathways that are conveyed to distant organs such as the intestine. RIC targets the intestinal microcirculation and by improving blood flow to the intestine, reduces the intestinal damage of experimental NEC and prolongs survival. A recent Phase I safety study by our group demonstrated that RIC was safe in preterm infants with NEC. A phase II feasibility randomized controlled trial involving 12 centers in 6 countries is currently underway, to investigate the feasibility of RIC as a treatment for early-stage NEC in preterm neonates. This review provides a brief background on RIC as a therapeutic strategy and summarizes the progression of RIC as a treatment for NEC from preclinical investigation to clinical evaluation.

A Single Bout of Remote Ischemic Preconditioning Suppresses Ischemia-Reperfusion Injury in Asian Obese Young Men

Remote ischemic preconditioning (RIPC) has been shown to minimize subsequent ischemia-reperfusion injury (IRI), whereas obesity has been suggested to attenuate the efficacy of RIPC in animal models. The primary objective of this study was to investigate the effect of a single bout of RIPC on the vascular and autonomic response after IRI in young obese men. A total of 16 healthy young men (8 obese and 8 normal weight) underwent two experimental trials: RIPC (three cycles of 5 min ischemia at 180 mmHg + 5 min reperfusion on the left thigh) and SHAM (the same RIPC cycles at resting diastolic pressure) following IRI (20 min ischemia at 180 mmHg + 20 min reperfusion on the right thigh). Heart rate variability (HRV), blood pressure (SBP/DBP), and cutaneous blood flow (CBF) were measured between baseline, post-RIPC/SHAM, and post-IRI. The results showed that RIPC significantly improved the LF/HF ratio (p = 0.027), SBP (p = 0.047), MAP (p = 0.049), CBF (p = 0.001), cutaneous vascular conductance (p = 0.003), vascular resistance (p = 0.001), and sympathetic reactivity (SBP: p = 0.039; MAP: p = 0.084) after IRI. However, obesity neither exaggerated the degree of IRI nor attenuated the conditioning effects on the measured outcomes. In conclusion, a single bout of RIPC is an effective means of suppressing subsequent IRI and obesity, at least in Asian young adult men, does not significantly attenuate the efficacy of RIPC.

Remote Ischemic Preconditioning Reduces Acute Kidney Injury After Cardiac Surgery: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Results from previous studies evaluating the effects of remote ischemic preconditioning (RIPC) on morbidity and mortality after cardiac surgery are inconsistent. This meta-analysis of randomized controlled trials (RCTs) aims to determine whether RIPC improves cardiac and renal outcomes in adults undergoing cardiac surgery.

METHODS

PubMed, EMBASE, and Cochrane Library were comprehensively searched to identify RCTs comparing RIPC with control in cardiac surgery. The coprimary outcomes were the incidence of postoperative myocardial infarction (MI) and the incidence of postoperative acute kidney injury (AKI). Meta-analyses were performed using a random-effect model. Subgroup analyses were conducted according to volatile only anesthesia versus propofol anesthesia with or without volatiles, high-risk patients versus non-high-risk patients, and Acute Kidney Injury Network (AKIN) or Kidney Disease Improving Global Outcomes (KDIGO) criteria versus other criteria for AKI diagnosis.

RESULTS

A total of 79 RCTs with 10,814 patients were included. While the incidence of postoperative MI did not differ between the RIPC and control groups (8.2% vs 9.7%; risk ratio [RR] = 0.87, 95% confidence interval [CI], 0.76-1.01, P = .07, I2 = 0%), RIPC significantly reduced the incidence of postoperative AKI (22% vs 24.4%; RR = 0.86, 95% CI, 0.77-0.97, P = .01, I2 = 34%). The subgroup analyses showed that RIPC was associated with a reduced incidence of MI in non-high-risk patients, and that RIPC was associated with a reduced incidence of AKI in volatile only anesthesia, in non-high-risk patients, and in the studies using AKIN or KDIGO criteria for AKI diagnosis.

CONCLUSIONS

This meta-analysis demonstrates that RIPC reduces the incidence of AKI after cardiac surgery. This renoprotective effect of RIPC is mainly evident during volatile only anesthesia, in non-high-risk patients, and when AKIN or KDIGO criteria used for AKI diagnosis.

Impact of Maturation on Myocardial Response to Ischemia and the Effectiveness of Remote Preconditioning in Male Rats

Aging attenuates cardiac tolerance to ischemia/reperfusion (I/R) associated with defects in protective cell signaling, however, the onset of this phenotype has not been completely investigated. This study aimed to compare changes in response to I/R and the effects of remote ischemic preconditioning (RIPC) in the hearts of younger adult (3 months) and mature adult (6 months) male Wistar rats, with changes in selected proteins of protective signaling. Langendorff-perfused hearts were exposed to 30 min I/120 min R without or with prior three cycles of RIPC (pressure cuff inflation/deflation on the hind limb). Infarct size (IS), incidence of ventricular arrhythmias and recovery of contractile function (LVDP) served as the end points. In both age groups, left ventricular tissue samples were collected prior to ischemia (baseline) and after I/R, in non-RIPC controls and in RIPC groups to detect selected pro-survival proteins (Western blot). Maturation did not affect post-ischemic recovery of heart function (Left Ventricular Developed Pressure, LVDP), however, it increased IS and arrhythmogenesis accompanied by decreased levels and activity of several pro-survival proteins and by higher levels of pro-apoptotic proteins in the hearts of elder animals. RIPC reduced the occurrence of reperfusion-induced ventricular arrhythmias, IS and contractile dysfunction in younger animals, and this was preserved in the mature adults. RIPC did not increase phosphorylated protein kinase B (p-Akt)/total Akt ratio, endothelial nitric oxide synthase (eNOS) and protein kinase Cε (PKCε) prior to ischemia but only after I/R, while phosphorylated glycogen synthase kinase-3β (GSK3β) was increased (inactivated) before and after ischemia in both age groups coupled with decreased levels of pro-apoptotic markers. We assume that resistance of rat heart to I/R injury starts to already decline during maturation, and that RIPC may represent a clinically relevant cardioprotective intervention in the elder population.

Remote Ischemic Preconditioning Reduces Marathon-Induced Oxidative Stress and Decreases Liver and Heart Injury Markers in the Serum

Clinical studies continue to provide evidence of organ protection by remote ischemic preconditioning (RIPC). However, there is lack of insight into impact of RIPC on exercise-induce changes in human organs' function. We here aimed to elucidate the effects of 10-day RIPC training on marathon-induced changes in the levels of serum markers of oxidative stress, and liver and heart damage. The study involved 18 male amateur runners taking part in a marathon. RIPC training was performed in the course of four cycles, by inflating and deflating a blood pressure cuff at 5-min intervals (RIPC group, n=10); the control group underwent sham training (n=8). The effects of RIPC on levels of oxidative stress, and liver and heart damage markers were investigated at rest after 10 consecutive days of training and after the marathon run. The 10-day RIPC training decreased the serum resting levels of C-reactive protein (CRP), alanine transaminase (ALT), γ-glutamyl transpeptidase (GGT), and malondialdehyde (MDA). After the marathon run, creatinine kinase MB (CK-MB), lactate dehydrogenase (LDH), cardiac troponin level (cTn), aspartate aminotransferase (AST), alkaline phosphatase (ALP), ALT, total bilirubin (BIL-T), and MDA levels were increased and arterial ketone body ratio (AKBR) levels were decreased in all participants. The changes were significantly diminished in the RIPC group compared with the control group. The GGT activity remained constant in the RIPC group but significantly increased in the control group after the marathon run. In conclusion, the study provides evidence for a protective effect of RIPC against liver and heart damage induced by strenuous exercise, such as the marathon.

Remote Ischemic Preconditioning for Prevention of Contrast-Induced Acute Kidney Injury in Patients of CKD Stage III and IV Undergoing Elective Coronary Angiography: A Randomized Controlled Trial

Introduction:

Contrast-induced acute kidney injury (CI-AKI) is a serious complication of coronary angiography (CA). The aim of this randomized, parallel group, single blind, sham-controlled trial was to assess the safety and efficacy of the remote ischemic preconditioning on the prevention of CI-AKI.

Methods:

Patients of 18–80 years of age with CKD 3 and 4, who were admitted for elective coronary angiography in a tertiary care hospital in eastern India were randomized in a 1:1 ratio to standard care with ischemic preconditioning (n = 45; intermittent arm ischemia through 4 cycles of 5-min inflation and 5-min deflation of a blood pressure cuff) or with standard care and sham ischemic preconditioning (n = 42). Overall, both study groups were at moderate risk of developing CI-AKI according to the Mehran risk score. The primary endpoint was the incidence of CI-AKI, defined as an increase in serum creatinine ≥25% or ≥0.5 mg/dL above baseline at 48 h after contrast medium exposure.

Results:

CI-AKI occurred in 8 patients (19.04%) in the control group and 2 (4.4%) in the remote ischemic preconditioning group (odds ratio, 0.198, 95% confidence interval, 0.087 to 0.452; P = 0.04). No major adverse events were related to remote ischemic preconditioning.

Conclusions:

This study indicates that remote ischemic preconditioning is a simple and well-tolerated procedure, which reduces the incidence of CI-AKI in CKD 3 and 4 patients undergoing coronary angiography.

Nitrite and myocardial ischaemia reperfusion injury. Where are we now?

Cardiovascular disease remains the leading cause of death worldwide despite major advances in technology and treatment, with coronary heart disease (CHD) being a key contributor. Following an acute myocardial infarction (AMI), it is imperative that blood flow is rapidly restored to the ischaemic myocardium. However, this restoration is associated with an increased risk of additional complications and further cardiomyocyte death, termed myocardial ischaemia reperfusion injury (IRI). Endogenously produced nitric oxide (NO) plays an important role in protecting the myocardium from IRI. It is well established that NO mediates many of its downstream functions through the 'canonical' NO-sGC-cGMP pathway, which is vital for cardiovascular homeostasis; however, this pathway can become impaired in the face of inadequate delivery of necessary substrates, in particular L-arginine, oxygen and reducing equivalents. Recently, it has been shown that during conditions of ischaemia an alternative pathway for NO generation exists, which has become known as the 'nitrate-nitrite-NO pathway'. This pathway has been reported to improve endothelial dysfunction, protect against myocardial IRI and attenuate infarct size in various experimental models. Furthermore, emerging evidence suggests that nitrite itself provides multi-faceted protection, in an NO-independent fashion, against a myriad of pathophysiologies attributed to IRI. In this review, we explore the existing pre-clinical and clinical evidence for the role of nitrate and nitrite in cardioprotection and discuss the lessons learnt from the clinical trials for nitrite as a perconditioning agent. We also discuss the potential future for nitrite as a pre-conditioning intervention in man.

Remote ischemic preconditioning effects on inflammatory markers and myocardial protection in coronary artery bypass graft surgery

BACKGROUND

Induction of short episodes of ischemia to remote organs, namely upper or lower limbs, literally known as remote ischemic preconditioning (RIPC) has been suggested as a preconditioning approach to ameliorate ischemia/reperfusion injury (IRI). RIPC has been demonstrated to effectively protect various vital organs, including heart, against the next ischemic events in preclinical studies. However, human studies are required to approve its clinical applicability. Present study was performed to evaluate the effect of RIPC on the myocardial protection and inflammatory response markers in patients undergoing coronary artery bypass graft surgery.

METHODS

In this randomized clinical trial, 43 coronary artery bypass graft (CABG) patients from Imam Hossein educational hospital were allocated in two groups, RIPC (21 patients) and control (22 patients). Serum level of interleukin (IL)-4, IL-8, and IL-10, interferon (IFN)-γ and Cardiac Troponin-I (cTnI) were measured in (1) after induction of anesthesia (before incision of skin), (2) after separation from CPB and (3) 24 hours after ICU arrival.Results:increase pack cell transfusions were observed in control group in ICU. Serum level of IL-10 at 24 hours after ICU admission was significantly higher in the RIPC group. Significantly lower amounts of IL-8 at post-CPB time were observed in the RIPC group in comparison with control.Conclusion:RIPC regulates the circulatory inflammatory cytokines, IL-8 decrement and IL-10 elevation, which could be translated into protection against IRI. However, further studies with larger sample sizes with careful consideration of parameters such as use of propofol as an anesthetic in the patients should be conducted to consolidate the findings from the current study.

Remote ischaemic preconditioning in isolated aortic valve and coronary artery bypass surgery: a randomized trial†

OBJECTIVES

This trial was designed and patients were recruited at a time when the benefits of remote ischaemic preconditioning during open-heart surgery were still controversial. We focused on a homogeneous patient population undergoing either isolated aortic valve replacement or coronary artery bypass grafting (CABG) surgery by investigating cardiac injury, metabolic stress and inflammatory response.

METHODS

A 2-centre randomized controlled trial recruited a total of 124 patients between February 2013 and April 2015. Of them, 64 patients underwent CABG and 60 patients underwent aortic valve replacement. Patients were randomized to either sham or preconditioning. Remote ischaemic preconditioning was applied following anaesthesia and before sternotomy. Myocardial injury and inflammatory response were assessed by serially measuring cardiac troponin I, and interleukin-6, 8, 10 and the tumour necrosis factor (TNF-α). Biopsies from the left and the right ventricles were harvested after ischaemic reperfusion injury for nucleotides analysis.

RESULTS

Application of remote ischaemic preconditioning did not alter the degree of troponin I release, levels of inflammatory markers and cardiac energetics in both the CABG and the aortic valve replacement groups.

CONCLUSIONS

Preconditioning did not confer any additional cardioprotection in terms of reducing the levels of troponin I and inflammatory markers and preserving left and right ventricle energy metabolites in patients undergoing isolated CABG or aortic valve surgery.

CLINICAL TRIAL REGISTRATION NUMBER

International Standard Randomized Controlled Trial Number (ISRCTN) registry ID 33084113 (doi: 10.1186/ISRCTN33084113) and UK controlled randomized trial number (UKCRN) registry ID 13672.

Effect of remote ischemic preConditioning on liver injury in patients undergoing liver resection: the ERIC-LIVER trial

OBJECTIVE

Novel hepatoprotective strategies are needed to improve clinical outcomes during liver surgery. There is mixed data on the role of remote ischemic preconditioning (RIPC). We investigated RIPC in partial hepatectomy for primary hepatocellular carcinoma (HCC).

METHODS

This was a Phase II, single-center, sham-controlled, randomized controlled trial (RCT). The primary hypothesis was that RIPC would reduce acute liver injury following surgery indicated by serum alanine transferase (ALT) 24 h following hepatectomy in patients with primary HCC, compared to sham. Patients were randomized to receive either four cycles of 5 min/5 min arm cuff inflation/deflation immediately prior to surgery, or sham. Secondary endpoints included clinical, biochemical and pathological outcomes. Liver function measured by Indocyanine Green pulse densitometry was performed in a subset of patients.

RESULTS

24 and 26 patients were randomized to RIPC and control groups respectively. The groups were balanced for baseline characteristics, except the duration of operation was longer in the RIPC group. Median ALT at 24 h was similar between groups (196 IU/L IQR 113.5-419.5 versus 172.5 IU/L IQR 115-298 respectively, p = 0.61). Groups were similar in secondary endpoints.

CONCLUSION

This RCT did not demonstrate beneficial effects with RIPC on serum ALT levels 24 h after partial hepatectomy.

Effect of Repeated Remote Ischemic Preconditioning on Peripheral Arterial Disease in Patients Suffering from Intermittent Claudication

Background/Objective

Intermittent claudication (IC) is the symptom of peripheral artery disease (PAD) and causes functional disability. Remote ischemic preconditioning (RIPC), is a phenomenon in which a short period of sub-critical ischemia, protects tissues against ischemia/reperfusion/injury. We considered to test the hypothesis that RIPC in PAD patients suffering from IC would increase muscle resistance to ischemia and thus improve walking-capacity.

Materials/Methods

A total of 63 patients with proven-IC underwent two treadmill tests (graded treadmill protocol) with a 28-day interval in between. Patients were consecutively assigned for the non/RIPC-group and RIPC-group procedure one by one. Patients received 5-cycles of alternating 5-minute inflation and 5-minute deflation of blood-pressure cuffs on nondominant upper-limb every day for four weeks. Initial claudication distance (ICD), total walking distance (TWD) and time to relief of claudication (TRC) were recorded during procedure.

Results

Patients receiving-RIPC exhibited a marked increase in ICD and TWD between basal and last tests: 209.1 ± 15.4 m vs. 226 ± 15.0 m and 368.8 ± 21.0 m vs. 394 ± 19.9 m, respectively (p < 0.001). In addition, patients receiving-RIPC represented a significant decrease in TRC between basal and last tests: 7.8 ± 1.3 min vs. 6.4 ± 1.1 min, respectively (p < 0.001). Patients not receiving-RIPC did not exhibit improvement in ICD, TWD, and TRC between basal and last tests: 205.2 ± 12.1 min vs. 207.4 ± 9.9 min, 366.5 ± 24.2 min vs. 369.4 ± 23.2 min and 7.9 ± 1.4 min vs. 7.7 ± 1.3 min, respectively (p > 0.05).

Conclusion

A significant increase in ICD and TWD were observed in last/treadmill test in RIPC-group. In addition, a significant decrease in TRC was observed in last/treadmill test in RIPC-group. In non/RIPC-group, no improvement was observed in ICD, TWD and TRC.

Egr-1 functions as a master switch regulator of remote ischemic preconditioning-induced cardioprotection

Despite improved treatment options myocardial infarction (MI) is still a leading cause of mortality and morbidity worldwide. Remote ischemic preconditioning (RIPC) is a mechanistic process that reduces myocardial infarction size and protects against ischemia reperfusion (I/R) injury. The zinc finger transcription factor early growth response-1 (Egr-1) is integral to the biological response to I/R, as its upregulation mediates the increased expression of inflammatory and prothrombotic processes. We aimed to determine the association and/or role of Egr-1 expression with the molecular mechanisms controlling the cardioprotective effects of RIPC. This study used H9C2 cells in vitro and a rat model of cardiac ischemia reperfusion (I/R) injury. We silenced Egr-1 with DNAzyme (ED5) in vitro and in vivo, before three cycles of RIPC consisting of alternating 5 min hypoxia and normoxia in cells or hind-limb ligation and release in the rat, followed by hypoxic challenge in vitro and I/R injury in vivo. Post-procedure, ED5 administration led to a significant increase in infarct size compared to controls (65.90 ± 2.38% vs. 41.00 ± 2.83%, p < 0.0001) following administration prior to RIPC in vivo, concurrent with decreased plasma IL-6 levels (118.30 ± 4.30 pg/ml vs. 130.50 ± 1.29 pg/ml, p < 0.05), downregulation of the cardioprotective JAK-STAT pathway, and elevated myocardial endothelial dysfunction. In vitro, ED5 administration abrogated IL-6 mRNA expression in H9C2 cells subjected to RIPC (0.95 ± 0.20 vs. 6.08 ± 1.40-fold relative to the control group, p < 0.05), resulting in increase in apoptosis (4.76 ± 0.70% vs. 2.23 ± 0.34%, p < 0.05) and loss of mitochondrial membrane potential (0.57 ± 0.11% vs. 1.0 ± 0.14%-fold relative to control, p < 0.05) in recipient cells receiving preconditioned media from the DNAzyme treated donor cells. This study suggests that Egr-1 functions as a master regulator of remote preconditioning inducing a protective effect against myocardial I/R injury through IL-6-dependent JAK-STAT signaling.

Remote ischemic conditioning: a promising therapeutic intervention for multi-organ protection

Despite decades of formidable exploration, multi-organ ischemia-reperfusion injury (IRI) encountered, particularly amongst elderly patients with clinical scenarios, such as age-related arteriosclerotic vascular disease, heart surgery and organ transplantation, is still an unsettled conundrum that besets clinicians. Remote ischemic conditioning (RIC), delivered via transient, repetitive noninvasive IR interventions to distant organs or tissues, is regarded as an innovative approach against IRI. Based on the available evidence, RIC holds the potential of affording protection to multiple organs or tissues, which include not only the heart and brain, but also others that are likely susceptible to IRI, such as the kidney, lung, liver and skin. Neuronal and humoral signaling pathways appear to play requisite roles in the mechanisms of RIC-related beneficial effects, and these pathways also display inseparable interactions with each other. So far, several hurdles lying ahead of clinical translation that remain to be settled, such as establishment of biomarkers, modification of RIC regimen, and deep understanding of underlying minutiae through which RIC exerts its powerful function. As this approach has garnered an increasing interest, herein, we aim to encapsulate an overview of the basic concept and postulated protective mechanisms of RIC, highlight the main findings from proof-of-concept clinical studies in various clinical scenarios, and also to discuss potential obstacles that remain to be conquered. More well designed and comprehensive experimental work or clinical trials are warranted in future research to confirm whether RIC could be utilized as a non-invasive, inexpensive and efficient adjunct therapeutic intervention method for multi-organ protection.

Perioperative Cardioprotection by Remote Ischemic Conditioning

Remote ischemic conditioning has been investigated for cardioprotection to attenuate myocardial ischemia/reperfusion injury. In this review, we provide a comprehensive overview of the current knowledge of the signal transduction pathways of remote ischemic conditioning according to three stages: Remote stimulus from source organ; protective signal transfer through neuronal and humoral factors; and target organ response, including myocardial response and coronary vascular response. The neuronal and humoral factors interact on three levels, including stimulus, systemic, and target levels. Subsequently, we reviewed the clinical studies evaluating the cardioprotective effect of remote ischemic conditioning. While clinical studies of percutaneous coronary intervention showed relatively consistent protective effects, the majority of multicenter studies of cardiac surgery reported neutral results although there have been several promising initial trials. Failure to translate the protective effects of remote ischemic conditioning into cardiac surgery may be due to the multifactorial etiology of myocardial injury, potential confounding factors of patient age, comorbidities including diabetes, concomitant medications, and the coadministered cardioprotective general anesthetic agents. Given the complexity of signal transfer pathways and confounding factors, further studies should evaluate the multitarget strategies with optimal measures of composite outcomes.

Remote ischaemic preconditioning for renal and cardiac protection in adult patients undergoing cardiac surgery with cardiopulmonary bypass: systematic review and meta-analysis of randomized controlled trials

Background

The main aim of this systematic review was to assess whether remote ischaemic preconditioning (RIPC) protects kidneys and the heart in cardiac surgery with cardiopulmonary bypass (CPB) and to investigate a possible role of anaesthetic agents.

Methods

Randomized clinical trials (RCTs) on the effects of RIPC through limb ischaemia in adult patients undergoing cardiac surgery with CPB were searched (1965-October 2016) in PubMed, Cochrane Library and article reference lists. A random effects model on standardized mean difference (SMD) for continuous outcomes and the Peto odds ratio (OR) for dichotomous outcomes were used to meta-analyse data. Subgroup analyses to evaluate the effects of different anaesthetic regimens were pre-planned.

Results

Thirty-three RCTs (5999 participants) were included. In the whole group, RIPC did not significantly reduce the incidence of acute kidney injury (AKI), acute myocardial infarction, atrial fibrillation, mortality or length of intensive care unit (ICU) and hospital stays. On the contrary, RIPC significantly reduced the area under the curve for myocardial injury biomarkers (MIBs) {SMD -0.37 [95% confidence interval (CI) -0.53 to - 0.21]} and the composite endpoint incidence [OR 0.85 (95% CI 0.74-0.97)]. In the volatile anaesthetic group, RIPC significantly reduced AKI incidence [OR 0.57 (95% CI 0.41-0.79)] and marginally reduced ICU stay. Conversely, except for MIBs, RIPC had fewer non-significant effects under propofol with or without volatile anaesthetics.

Conclusions

RIPC did not consistently reduce morbidity and mortality in adults undergoing cardiac surgery with CPB. In the subgroup on volatile anaesthetics only, RIPC markedly and significantly reduced the incidence of AKI and composite endpoint as well as myocardial injury.

Neuro-autonomic changes induced by remote ischemic preconditioning (RIPC) in healthy young adults: Implications for stress

The mechanisms underlying the protective effects of remote ischemic preconditioning (RIPC) are not presently clear. Recent studies in experimental models suggest the involvement of the autonomic nervous system (ANS) in cardioprotection. The aim of this study was to investigate the changes in ANS in healthy young volunteers divided into RIPC (n = 22) or SHAM (n = 18) groups. RIPC was induced by 1 cycle of 4 min inflation/5 min deflation followed by 2 cycles of 5 min inflation/5 min deflation of a cuff placed on the upper left limb. The study included analysis of heart rate (HR), blood pressure (BP), heart rate variability (HRV), measurements of microcirculation and porphyrin fluorescence in the limb before and after the RIPC. RIPC caused reactive hyperemia in the limb and reduced blood porphyrin level. A mental load (serial sevens test) and mild motor stress (hyperventilation) were performed on all subjects before and after RIPC or corresponding rest in the SHAM group. Reduction of HR occurred during the experiments in both RIPC and SHAM groups reflecting RIPC-independent adaptation of the subjects to the experimental procedure. However, in contrast to the SHAM group, RIPC altered several of the spectral indices of HRV during the serial sevens test and hyperventilation. This was expressed predominantly as an increase in power of the very low-frequency band of the spectrum, increased values of detrended fluctuation analysis and weakening of correlation between the HRV parameters and HR. In conclusion, RIPC induces changes in the activity of ANS that are linked to stress resistance.

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Brief ischemia/reperfusion episodes of distant organs (RIPC) protect other organs.

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Mechanism of RIPC is not known but it involves neuronal activity.

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RIPC applied to volunteers was interspersed with mild mental and physical stress.

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RIPC was confirmed by hyperemia in the limb and metabolic response to hypoxia.

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Heart rate variability shows that RIPC modulates ANS to increase stress resistance.

Differential modulatory effects of Propofol and Sevoflurane anesthesia on blood monocyte HLA-DR and CD163 expression during and after cardiac surgery with cardiopulmonary bypass: a preliminary randomized flow cytometry study

INTRODUCTION

The increase of the anti-inflammatory CD163^highHLA-DR^low blood monocyte subset is one of the mechanisms dampening inflammation during cardiac surgery with cardiopulmonary bypass. We evaluated the effect of two different anesthetic protocols, intravenous Propofol infusion or Sevoflurane-gas administration, on the perioperative frequency of this subset.

METHODS

Blood from patients (Propofol = 11, Sevoflurane = 13) undergoing minimally invasive mitral valve surgery was drawn preoperatively (T1), before declamping (T2), at 6 (T3), 24 (T4), 48 (T5), and 72 hours (T6) after declamping. C-reactive protein, haptoglobin, and lactate dehydrogenase were measured. A hemolytic index, as C-reactive protein/haptoglobin ratio, was introduced. Monocyte expression of HLA-DR, CD163, and the CD163^highHLA-DR^low subset fraction was quantified by flow cytometry. Baseline-referred variations of plasmatic and cellular data at T2 were normalized for clamping times. Subsequent time-point variations were normalized for the final cardiopulmonary bypass times.

RESULTS

Variations of hemolytic index and lactate dehydrogenase were higher with Propofol at T3 (p = 0.004 and p = 0.02, respectively) when compared with Sevoflurane. At T2, the down-modulation of CD163 was higher with Propofol (p = 0.005). Starting from T3, the up-regulatory trend of CD163 was basically higher with Propofol, although not significantly. Propofol induced higher increments of HLA-DR low fractions, at T2 (p = 0.04) and, to a lesser extent, at T4 (p = 0.06). Starting from T3, the CD163^highHLA-DR^low subset variations were higher with Propofol, especially at T4 and T6.

CONCLUSION

Propofol seems to induce a higher postoperative fraction of the CD163^highHLA-DR^low monocyte subset. This could represent either a compensatory mechanism dampening the higher inflammatory condition observed with Propofol at T2 or a consequence of a higher postoperative Propofol-induced hemolysis.

Can human myocardium be remotely preconditioned? The results of a randomized controlled trial

OBJECTIVES

No experimental study has shown that the myocardium of a remotely preconditioned patient is more resistant to a standardized ischaemic/hypoxic insult.

METHODS

This was a single-centre randomized (1:1), double-blinded, sham-controlled, parallel-group study. Patients referred for elective coronary bypass surgery were allocated to either remote ischaemic preconditioning (3 cycles of 5-min ischaemia/5-min reperfusion of the right arm using a blood pressure cuff inflated to 200 mmHg) or sham intervention. One hundred and thirty-four patients were recruited, of whom 10 dropped out, and 4 were excluded from the per-protocol analysis. The right atrial trabecula harvested on cannulation for cardiopulmonary bypass was subjected to 60 min of simulated ischaemia and 120 min of reoxygenation in an isolated organ experiment. Postoperative troponin T release and haemodynamics were assessed in an in vivo study.

RESULTS

The atrial trabeculae obtained from remotely preconditioned patients recovered 41.9% (36.3-48.3) of the initial contraction force, whereas those from non-preconditioned patients recovered 45.9% (39.1-53.7) (P = 0.399). Overall, the content of cleaved poly (ADP ribose) polymerase in the right atrial muscle increased from 9.4% (6.0-13.5) to 19.1% (13.2-23.8) (P < 0.001) after 1 h of ischaemia and 2 h of reperfusion in vitro. The amount of activated Caspase 3 and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells also significantly increased. No difference was observed between the remotely preconditioned and sham-treated myocardium. In the in vivo trial, the area under the curve for postoperative concentration of troponin T over 72 h was 16.4 ng⋅h/ml (95% confidence interval 14.2-18.9) for the remote ischaemic preconditioning and 15.5 ng⋅h/ml (13.4-17.9) for the control group in the intention-to-treat analysis. This translated into an area under the curve ratio of 1.06 (0.86-1.30; P = 0.586).

CONCLUSIONS

Remote ischaemic preconditioning with 3 cycles of 5-min ischaemia/reperfusion of the upper limb before cardiac surgery does not make human myocardium more resistant to ischaemia/reperfusion injury.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01994707.

Protective effect of remote ischemic pre-conditioning on patients undergoing cardiac bypass valve replacement surgery: A randomized controlled trial

Remote ischemic pre-conditioning (RIPC) may have a protective effect on myocardial injury associated with cardiac bypass surgery (CPB). The objective of the present study was to investigate the effect of RIPC on ischemia/reperfusion (I/R) injury and to assess the underlying mechanisms. A total of 241 patients who underwent valve replacement were randomly assigned to receive either RIPC (n=121) or control group (n=120). The primary endpoint was peri-operative myocardial injury (PMI), which was determined by serum Highly sensitive cardiac troponin T (hsTnT). The secondary endpoint was the blood gas indexes, acute lung injury and length of intensive care unit stay, length of hospital stay and major adverse cardiovascular events. The results indicated that in comparison with control group, RIPC treatment reduced the levels of hsTnT at 6 and 24 h post-CPB (P<0.001), as well as the alveolar-arterial oxygen pressure difference and respiratory index after CPB. Furthermore, RIPC reduced the incidence of acute lung injury by 15.3% (54.1% in the control group vs. 41.3% in the RIPC group, P=0.053). It was indicated that RIPC provided myocardial and pulmonary protection during CPB. In addition, the length of the intensive care unit and hospital stay was reduced by RIPC. Mechanistic investigation revealed a reduced content of soluble intercellular adhesion molecule-1, endothelin-1 and malondialdehyde, as well as elevated levels of nitric oxide in the RIPC group compared with those in the control group. This indicated that RIPC protected against I/R injury associated with CPB through reducing the inflammatory response and oxidative damage, as well as improving pulmonary vascular tension. In conclusion, RIPC reduced myocardial and pulmonary injury associated with CPB. This protective effect may be associated with the inhibition of the inflammatory response and oxidative injury. The present study proved the efficiency of this approach in reducing ischemia/reperfusion injury associated with cardiac surgery. Clinical trial registry no. ChiCTR1800015393.

Circulating mediators of remote ischemic preconditioning: search for the missing link between non-lethal ischemia and cardioprotection

Acute myocardial infarction (AMI) is one of the leading causes of mortality and morbidity worldwide. There has been an extensive search for cardioprotective therapies to reduce myocardial ischemia-reperfusion (I/R) injury. Remote ischemic preconditioning (RIPC) is a phenomenon that relies on the body's endogenous protective modalities against I/R injury. In RIPC, non-lethal brief I/R of one organ or tissue confers protection against subsequent lethal I/R injury in an organ remote to the briefly ischemic organ or tissue. Initially it was believed to be limited to direct myocardial protection, however it soon became apparent that RIPC applied to other organs such as kidney, liver, intestine, skeletal muscle can reduce myocardial infarct size. Intriguing discoveries have been made in extending the concept of RIPC to other organs than the heart. Over the years, the underlying mechanisms of RIPC have been widely sought and discussed. The involvement of blood-borne factors as mediators of RIPC has been suggested by a number of research groups. The main purpose of this review article is to summarize the possible circulating mediators of RIPC, and recent studies to establish the clinical efficacy of these mediators in cardioprotection from lethal I/R injury.

The Effect of Remote Ischemic Preconditioning on the Incidence of Acute Kidney Injury in Patients Undergoing Coronary Artery Bypass Graft Surgery: A Randomized Controlled Trial

BACKGROUND

Remote ischemic preconditioning (RIPC) protects other organs from subsequent lethal ischemic injury, but uncertainty remains. We investigated if RIPC could prevent acute kidney injury (AKI) in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

This parallel-group, double-blind, randomized, controlled trial was done on adults undergoing elective or urgent on-pump CABG surgery from 2013 to 2017 in Shiraz, Iran. Patients were allocated to RIPC or control groups through permuted blocking. The patients in the RIPC group received three cycles of 5 min ischemia and 5 min reperfusion in the upper arm after induction of anesthesia. We placed an uninflated cuff on the arm for 30 min in the control group. The study primary endpoint was an incidence of AKI. Secondary endpoints included short-term clinical outcomes. We compared categorical and continuous variables using Pearson χ2 and unpaired t tests, respectively. P<0.05 was considered significant.

RESULTS

of the 180 patients randomized to RIPC (n=90) and control (n=90) groups, 87 patients in the RIPC and 90 patients in the control group were included in the analysis. There was no significant difference in the incidence of AKI between the groups (38 patients [43.7%] in the RIPC group and 41 patients [45.6%] in the control group; relative risk, 0.96; 95% confidence interval, 0.69 to 1.33; P=0.80). No significant differences were seen regarding secondary endpoints such as postoperative liver function, atrial fibrillation, and inpatient mortality.

CONCLUSION

RIPC did not reduce the incidence of AKI, neither did it improve short-term clinical outcomes in patients undergoing on-pump CABG surgery. Trial Registration Number: IRCT2017110537254N1.

Remote ischemic conditioning as a cytoprotective strategy in vasculopathies during hyperhomocysteinemia: An emerging research perspective

Higher levels of nonprotein amino acid homocysteine (Hcy), that is, hyperhomocysteinemia (HHcy) (~5% of general population) has been associated with severe vasculopathies in different organs; however, precise molecular mechanism(s) as to how HHcy plays havoc with body's vascular networks are largely unknown. Interventional modalities have not proven beneficial to counter multifactorial HHcy's effects on the vascular system. An ancient Indian form of exercise called 'yoga' causes transient ischemia as a result of various body postures however the cellular mechanisms are not clear. We discuss a novel perspective wherein we argue that application of remote ischemic conditioning (RIC) could, in fact, deliver anticipated results to patients who are suffering from chronic vascular dysfunction due to HHcy. RIC is the mechanistic phenomenon whereby brief episodes of ischemia-reperfusion events are applied to distant tissues/organs; that could potentially offer a powerful tool in mitigating chronic lethal ischemia in target organs during HHcy condition via simultaneous reduction of inflammation, oxidative and endoplasmic reticulum stress, extracellular matrix remodeling, fibrosis, and angiogenesis. We opine that during ischemic conditioning our organs cross talk by releasing cellular messengers in the form of exosomes containing messenger RNAs, circular RNAs, anti-pyroptotic factors, protective cytokines like musclin, transcription factors, small molecules, anti-inflammatory, antiapoptotic factors, antioxidants, and vasoactive gases. All these could help mobilize the bone marrow-derived stem cells (having tissue healing properties) to target organs. In that context, we argue that RIC could certainly play a savior's role in an unfortunate ischemic or adverse event in people who have higher levels of the circulating Hcy in their systems.

Effect of Remote Ischemic Preconditioning on Outcomes in Adult Cardiac Surgery: A Systematic Review and Meta-analysis of Randomized Controlled Studies

BACKGROUND

Remote ischemic preconditioning (RIPC) has been demonstrated to prevent organ dysfunction in cardiac surgery patients. However, recent large, prospective, multicenter, randomized controlled trials (RCTs) had controversial results. Thus, a meta-analysis of RCTs was performed to investigate whether RIPC can reduce the incidence of acute myocardial infarction (AMI), acute kidney injury (AKI), and mortality in adult cardiac surgery patients.

METHODS

Study data were collected from Medline, Elsevier, Cochrane Central Register of Controlled Trials and Web of Science databases. RCTs involving the effect of RIPC on organ protection in cardiac surgery patients, which reported the concentration or total release of creatine kinase-myocardial band, troponin I/troponin T (TNI/TNT) after operation, or the incidence of AMI, AKI, or mortality, were selected. Two reviewers independently extracted data using a standardized data extraction protocol where TNI or TNT concentrations; total TNI released after cardiac surgery; and the incidence of AKI, AMI, and mortality were recorded. Review Manager 5.3 software was used to analyze the data.

RESULTS

Thirty trials, including 7036 patients were included in the analyses. RIPC significantly decreased the concentration of TNI/TNT (standard mean difference [SMD], -0.25 ng/mL; 95% confidence interval [CI], -0.41 to -0.048 ng/mL; P = .004), creatine kinase-myocardial band (SMD, -0.22; 95% CI, -0.07-0.35 ng/mL; P = .46), and the total TNI/TNT release (SMD, -0.49 ng/mL; 95% CI, -0.93 to -0.55 ng/mL; P = .03) in cardiac surgery patients after a procedure. However, RIPC could not reduce the incidence of AMI (relative risk, 0.89; 95% CI, 0.70-1.13; P = .34) and AKI (relative risk, 0.88; 95% CI, 0.72-1.06; P = .18), and there was also no effect of RIPC on mortality in adult cardiac surgery patients. Interestingly, subgroup analysis showed that RIPC reduced incidence of AKI and mortality of cardiac surgery patients who received volatile agent anesthesia.

CONCLUSIONS

Our meta-analysis demonstrated that RIPC reduced TNI/TNT release after cardiac surgery. RIPC did not significantly reduce the incidence of AKI, AMI, and mortality. However, RIPC could reduce mortality in patients receiving volatile inhalational agent anesthesia.

Acute Hemodynamic Effects of Remote Ischemic Preconditioning on Coronary Perfusion Pressure and Coronary Collateral Blood Flow in Coronary Heart Disease

BACKGROUND

The aim of this study was to assess the acute hemodynamic effects of remote ischemic preconditioning (RIPC) on coronary perfusion pressure and coronary collateral blood flow.

METHODS

A total of 17 patients with coronary heart disease with severe (70%-85%) stenosis in one or two vessels confirmed by angiography were enrolled into this study. They were randomly divided into the RIPC group (9 patients) and the control group (8 patients). Distal pressure of coronary artery stenosis before balloon dilation (non-occlusive pressure, Pn-occl) and distal coronary artery occlusive pressure (Poccl) during balloon dilation occlusion were measured in all patients. The patients in the RIPC group received three cycles of lower limb ischemia-reperfusion preconditioning (5 minutes inflation of a blood pressure cuff, followed by 5 minutes reperfusion). For controls, the cuff was not inflated. After this process, Pn-occl and Poccl were measured again in each patient.

RESULTS

There were no significant differences in angiographic characteristics between the two groups (all p > 0.05). Troponin I (TNI) levels after percutaneous coronary intervention (PCI) were lower in the RIPC group than in the control group (p = 0.004). In the RIPC group, mean Pn-occl and Poccl were significantly increased after RIPC compared to before RIPC [(72.78 ± 10.10) mmHg vs. (79.67 ± 9.79) mmHg, p = 0.002, (20.89 ± 8.61) mmHg vs. (26.78 ± 10.73) mmHg, p = 0.001, respectively].

CONCLUSIONS

RIPC can improve distal coronary perfusion pressure and rapidly increase distal coronary occlusive pressure thereby improving coronary collateral blood flow.

DJ1 and microRNA-214 act synergistically to rescue myoblast cells after ischemia/reperfusion injury

Ischemia/reperfusion injury is a tissue injury occurring post-reperfusion of tissues with pre-existing ischemia. A good blood supply to tissues aids in the survival of ischemic tissue, however, due to prolonged ischemia the levels of ATP decrease and pH declines leading to acidosis. Reduced ATP leads to an increase in the AMP/ATP ratio, causing cessation of intracellular calcium transport, hence calcium overload and cell death. In this study, we demonstrate the synergistic and antagonistic effect of DJ1 and microR-214 (miR-214) in rescuing myoblast C2C12 cells after ischemia/reperfusion in an in vitro model. Both DJ1 and miR-214 were cloned into a hypoxic inducible expression cassette and transfected into the C2C12 cells. We showed that DJ1 and miR-214 have synergistic effects in reducing intracellular lactate dehydrogenase and intracellular transient calcium levels after reoxygenation compared to control cells, in addition to reducing cell death via necrosis. Western blotting revealed a decrease in autophagosome formation in LC3II/I ratio and an increase in AKT expression in cells transfected with DJ1 and miR-214. Using quantitative real-time PCR, we demonstrated that DJ1 and miR-214 significantly reduced the expression of pro-apoptotic factors and autophagy compared to control. The results indicated DJ1 is an endogenous oxidative stress molecule and miR-214 is a potent inhibitor of the sodium calcium exchanger channel. DJ1 had the greatest effect to inhibiting mitochondrial cell death pathways by possibly acting as a modulator of autophagy. Additionally, we have concluded that miR-214 has an inhibitory effect on extrinsic cell death pathways such as necrosis and autophagy.

Effect of Hexadecyl Azelaoyl Phosphatidylcholine on Cardiomyocyte Apoptosis in Myocardial Ischemia-Reperfusion Injury: A Hypothesis

Reperfusion after myocardial ischemia can induce cardiomyocyte death, known as myocardial reperfusion injury. The pathophysiology of the process of reperfusion suggests the confluence multiple pathways. Recent studies have focused on the inflammatory response, which is considered to be the main mechanism during the process of myocardial ischemia-reperfusion injury and can cause cardiomyocyte apoptosis. Peroxisome proliferator-activated receptors gamma activated by endogenous ligands and exogenous ligand can decrease the inflammatory response in cardiomyocytes. Thiazolidinediones are synthetic, high-affinity, selective ligands for peroxisome proliferator-activated receptors gamma, and can inhibit the inflammatory response, decrease myocardial infarct size, and protect cardiac function. However, thiazolidinediones, including rosiglitazone and pioglitazone, can also contribute to adverse cardiovascular events such as congestive heart failure. Therefore, there are some limitations to the use of thiazolidinediones. Most endogenous ligands were of low affinity until hexadecyl azelaoyl phosphatidylcholine was identified as a high-affinity ligand and agonist for peroxisome proliferator-activated receptors gamma. Hexadecyl azelaoyl phosphatidylcholine binds recombinant peroxisome proliferator-activated receptors with an affinity (Kd(app) ≈40 nM) which is equivalent to rosiglitazone. Therefore, hexadecyl azelaoyl phosphatidylcholine is a specific peroxisome proliferator-activated receptors gamma agonist. Given these findings, we hypothesized that the use of hexadecyl azelaoyl phosphatidylcholine can activate the peroxisome proliferator-activated receptors gamma signal pathways and prevent the inflammatory response process of myocardial ischemia-reperfusion injury, with reduced cardiomyocyte apoptosis and death.

RIPHeart (Remote Ischemic Preconditioning for Heart Surgery) Study: Myocardial Dysfunction, Postoperative Neurocognitive Dysfunction, and 1 Year Follow-Up

BACKGROUND

Remote ischemic preconditioning (RIPC) has been suggested to protect against certain forms of organ injury after cardiac surgery. Previously, we reported the main results of RIPHeart (Remote Ischemic Preconditioning for Heart Surgery) Study, a multicenter trial randomizing 1403 cardiac surgery patients receiving either RIPC or sham-RIPC.

METHODS AND RESULTS

In this follow-up paper, we present 1-year follow-up of the composite primary end point and its individual components (all-cause mortality, myocardial infarction, stroke and acute renal failure), in a sub-group of patients, intraoperative myocardial dysfunction assessed by transesophageal echocardiography and the incidence of postoperative neurocognitive dysfunction 5 to 7 days and 3 months after surgery. RIPC neither showed any beneficial effect on the 1-year composite primary end point (RIPC versus sham-RIPC 16.4% versus 16.9%) and its individual components (all-cause mortality [3.4% versus 2.5%], myocardial infarction [7.0% versus 9.4%], stroke [2.2% versus 3.1%], acute renal failure [7.0% versus 5.7%]) nor improved intraoperative myocardial dysfunction or incidence of postoperative neurocognitive dysfunction 5 to 7 days (67 [47.5%] versus 71 [53.8%] patients) and 3 months after surgery (17 [27.9%] versus 18 [27.7%] patients), respectively.

CONCLUSIONS

Similar to our main study, RIPC had no effect on intraoperative myocardial dysfunction, neurocognitive function and long-term outcome in cardiac surgery patients undergoing propofol anesthesia.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01067703.

Clinical translation of myocardial conditioning

Rapid admission and acute interventional treatment combined with modern antithrombotic pharmacologic therapy have improved outcomes in patients with ST elevation myocardial infarction. The next major target to further advance outcomes needs to address ischemia-reperfusion injury, which may contribute significantly to the final infarct size and hence mortality and postinfarction heart failure. Mechanical conditioning strategies including local and remote ischemic pre-, per-, and postconditioning have demonstrated consistent cardioprotective capacities in experimental models of acute ischemia-reperfusion injury. Their translation to the clinical scenario has been challenging. At present, the most promising mechanical protection strategy of the heart seems to be remote ischemic conditioning, which increases myocardial salvage beyond acute reperfusion therapy. An additional aspect that has gained recent focus is the potential of extended conditioning strategies to improve physical rehabilitation not only after an acute ischemia-reperfusion event such as acute myocardial infarction and cardiac surgery but also in patients with heart failure. Experimental and preliminary clinical evidence suggests that remote ischemic conditioning may modify cardiac remodeling and additionally enhance skeletal muscle strength therapy to prevent muscle waste, known as an inherent component of a postoperative period and in heart failure. Blood flow restriction exercise and enhanced external counterpulsation may represent cardioprotective corollaries. Combined with exercise, remote ischemic conditioning or, alternatively, blood flow restriction exercise may be of aid in optimizing physical rehabilitation in populations that are not able to perform exercise practice at intensity levels required to promote optimal outcomes.

Rationale and Study Design for a Single-Arm Phase IIa Study Investigating Feasibility of Preventing Ischemic Cerebrovascular Events in High-Risk Patients with Acute Non-disabling Ischemic Cerebrovascular Events Using Remote Ischemic Conditioning

Background:

Acute minor ischemic stroke (AMIS) or transient ischemic attack (TIA) is a common cerebrovascular event with a considerable high recurrence. Prior research demonstrated the effectiveness of regular long-term remote ischemic conditioning (RIC) in secondary stroke prevention in patients with intracranial stenosis. We hypothesized that RIC can serve as an effective adjunctive therapy to pharmacotherapy in preventing ischemic events in patients with AMIS/TIA. This study aimed to investigate the feasibility, safety, and preliminary efficacy of daily RIC in inhibiting cerebrovascular/cardiovascular events after AMIS/TIA.

Methods:

This is a single-arm, open-label, multicenter Phase IIa futility study with a sample size of 165. Patients with AMIS/TIA receive RIC as an additional therapy to secondary stroke prevention regimen. RIC consists of five cycles of 5-min inflation (200 mmHg) and 5-min deflation of cuffs on bilateral upper limbs twice a day for 90 days. The antiplatelet strategy is based on individual physician's best practice: aspirin alone, clopidogrel alone, or combination of aspirin and clopidogrel. We will assess the recurrence rate of ischemic stroke/TIA within 3 months as the primary outcomes.

Conclusions:

The data gathered from the study will be used to determine whether a further large-scale, multicenter randomized controlled Phase II trial is warranted in patients with AMIS/TIA.

Trial Registration:

ClinicalTrials.gov, NCT03004820; https://www.clinicaltrials.gov/ct2/show/NCT03004820.

Time Window Is Important for Adenosine Preventing Cold-induced Injury to the Endothelium

Cold cardioplegia is used to induce heart arrest during cardiac surgery. However, endothelial function may be compromised after this procedure. Accordingly, interventions such as adenosine, that mimic the effects of preconditioning, may minimize endothelial injury. Herein, we investigated whether adenosine prevents cold-induced injury to the endothelium. Cultured human cardiac microvascular endothelial cells were treated with adenosine for different durations. Phosphorylation and expression of endothelial nitric oxide synthase (eNOS), p38MAPK, ERK1/2, and p70S6K6 were measured along with nitric oxide (NO) production using diaminofluorescein-2 diacetate (DAF-2DA) probe. Cold-induced injury by hypothermia to 4°C for 45 minutes to mimic conditions of cold cardioplegia during open heart surgery was induced in human cardiac microvascular endothelial cells. Under basal conditions, adenosine stimulated NO production, eNOS phosphorylation at serine 1177 from 5 minutes to 4 hours and inhibited eNOS phosphorylation at threonine 495 from 5 minutes to 6 hours, but increased phosphorylation of ERK1/2, p38MAPK, and p70S6K only after exposure for 5 minutes. Cold-induced injury inhibited NO production and the phosphorylation of the different enzymes. Importantly, adenosine prevented these effects of hypothermic injury. Our data demonstrated that adenosine prevents hypothermic injury to the endothelium by activating ERK1/2, eNOS, p70S6K, and p38MAPK signaling pathways at early time points. These findings also indicated that 5 minutes after administration of adenosine or release of adenosine is an important time window for cardioprotection during cardiac surgery.

Remote ischaemic conditioning reduces infarct size in animal in vivo models of ischaemia-reperfusion injury: a systematic review and meta-analysis

Aims

The potential of remote ischaemic conditioning (RIC) to ameliorate myocardial ischaemia-reperfusion injury (IRI) remains controversial. We aimed to analyse the pre-clinical evidence base to ascertain the overall effect and variability of RIC in animal in vivo models of myocardial IRI. Furthermore, we aimed to investigate the impact of different study protocols on the protective utility of RIC in animal models and identify gaps in our understanding of this promising therapeutic strategy.

Methods and results

Our primary outcome measure was the difference in mean infarct size between RIC and control groups in in vivo models of myocardial IRI. A systematic review returned 31 reports, from which we made 22 controlled comparisons of remote ischaemic preconditioning (RIPreC) and 21 of remote ischaemic perconditioning and postconditioning (RIPerC/RIPostC) in a pooled random-effects meta-analysis. In total, our analysis includes data from 280 control animals and 373 animals subject to RIC. Overall, RIPreC reduced infarct size as a percentage of area at risk by 22.8% (95% CI 18.8–26.9%), when compared with untreated controls (P < 0.001). Similarly, RIPerC/RIPostC reduced infarct size by 22.2% (95% CI 17.1–25.3%; P < 0.001). Interestingly, we observed significant heterogeneity in effect size (T2 = 92.9% and I2 = 99.4%; P < 0.001) that could not be explained by any of the experimental variables analysed by meta-regression. However, few reports have systematically characterized RIC protocols, and few of the included in vivo studies satisfactorily met study quality requirements, particularly with respect to blinding and randomization.

Conclusions

RIC significantly reduces infarct size in in vivo models of myocardial IRI. Heterogeneity between studies could not be explained by the experimental variables tested, but studies are limited in number and lack consistency in quality and study design. There is therefore a clear need for more well-performed in vivo studies with particular emphasis on detailed characterization of RIC protocols and investigating the potential impact of gender. Finally, more studies investigating the potential benefit of RIC in larger species are required before translation to humans.

Remote ischaemic preconditioning for coronary artery bypass grafting (with or without valve surgery)

BACKGROUND

Despite substantial improvements in myocardial preservation strategies, coronary artery bypass grafting (CABG) is still associated with severe complications. It has been reported that remote ischaemic preconditioning (RIPC) reduces reperfusion injury in people undergoing cardiac surgery and improves clinical outcome. However, there is a lack of synthesised information and a need to review the current evidence from randomised controlled trials (RCTs).

OBJECTIVES

To assess the benefits and harms of remote ischaemic preconditioning in people undergoing coronary artery bypass grafting, with or without valve surgery.

SEARCH METHODS

In May 2016 we searched CENTRAL, MEDLINE, Embase and Web of Science. We also conducted a search of ClinicalTrials.gov and the International Clinical Trials Registry Platform (ICTRP). We also checked reference lists of included studies. We did not apply any language restrictions.

SELECTION CRITERIA

We included RCTs in which people scheduled for CABG (with or without valve surgery) were randomly assigned to receive RIPC or sham intervention before surgery.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, extracted data and checked them for accuracy. We calculated mean differences (MDs), standardised mean differences (SMDs) and risk ratios (RR) using a random-effects model. We assessed quality of the trial evidence for all primary outcomes using the GRADE methodology. We completed a 'Risk of bias' assessment for all studies and performed sensitivity analysis by excluding studies judged at high or unclear risk of bias for sequence generation, allocation concealment and incomplete outcome data. We contacted authors for missing data. Our primary endpoints were 1) composite endpoint (including all-cause mortality, non-fatal myocardial infarction or any new stroke, or both) assessed at 30 days after surgery, 2) cardiac troponin T (cTnT, ng/L) at 48 hours and 72 hours, and as area under the curve (AUC) 72 hours (µg/L) after surgery, and 3) cardiac troponin I (cTnI, ng/L) at 48 hours, 72 hours, and as area under the curve (AUC) 72 hours (µg/L) after surgery.

MAIN RESULTS

We included 29 studies involving 5392 participants (mean age = 64 years, age range 23 to 86 years, 82% male). However, few studies contributed data to meta-analyses due to inconsistency in outcome definition and reporting. In general, risk of bias varied from low to high risk of bias across included studies, and insufficient detail was provided to inform judgement in several cases. The quality of the evidence of key outcomes ranged from moderate to low quality due to the presence of moderate or high statistical heterogeneity, imprecision of results or due to limitations in the design of individual studies.Compared with no RIPC, we found that RIPC has no treatment effect on the rate of the composite endpoint with RR 0.99 (95% confidence interval (CI) 0.78 to 1.25); 2 studies; 2463 participants; moderate-quality evidence. Participants randomised to RIPC showed an equivalent or better effect regarding the amount of cTnT release measured at 72 hours after surgery with SMD -0.32 (95% CI -0.65 to 0.00); 3 studies; 1120 participants; moderate-quality evidence; and expressed as AUC 72 hours with SMD -0.49 (95% CI -0.96 to -0.02); 3 studies; 830 participants; moderate-quality evidence. We found the same result in favour of RIPC for the cTnI release measured at 48 hours with SMD -0.21 (95% CI -0.40 to -0.02); 5 studies; 745 participants; moderate-quality evidence; and measured at 72 hours after surgery with SMD -0.37 (95% CI -0.59 to -0.15); 2 studies; 459 participants; moderate-quality evidence. All other primary outcomes showed no differences between groups (cTnT release measured at 48 hours with SMD -0.14, 95% CI -0.33 to 0.06; 4 studies; 1792 participants; low-quality evidence and cTnI release measured as AUC 72 hours with SMD -0.17, 95% CI -0.48 to 0.14; 2 studies; 159 participants; moderate-quality evidence).We also found no differences between groups for all-cause mortality after 30 days, non-fatal myocardial infarction after 30 days, any new stroke after 30 days, acute renal failure after 30 days, length of stay on the intensive care unit (days), any complications and adverse effects related to ischaemic preconditioning. We did not assess many patient-centred/salutogenic-focused outcomes.

AUTHORS' CONCLUSIONS

We found no evidence that RIPC has a treatment effect on clinical outcomes (measured as a composite endpoint including all-cause mortality, non-fatal myocardial infarction or any new stroke, or both, assessed at 30 days after surgery). There is moderate-quality evidence that RIPC has no treatment effect on the rate of the composite endpoint including all-cause mortality, non-fatal myocardial infarction or any new stroke assessed at 30 days after surgery, or both. We found moderate-quality evidence that RIPC reduces the cTnT release measured at 72 hours after surgery and expressed as AUC (72 hours). There is moderate-quality evidence that RIPC reduces the amount of cTnI release measured at 48 hours, and measured 72 hours after surgery. Adequately-designed studies, especially focusing on influencing factors, e.g. with regard to anaesthetic management, are encouraged and should systematically analyse the commonly used medications of people with cardiovascular diseases.

Is there a role for ischaemic conditioning in cardiac surgery?

Coronary artery disease (CAD) is a major cause of morbidity and mortality worldwide. Coronary artery bypass graft (CABG) surgery is the revascularisation strategy of choice in patients with diabetes mellitus and complex CAD. Owing to a number of factors, including the ageing population, the increased complexity of CAD being treated, concomitant valve and aortic surgery, and multiple comorbidities, higher-risk patients are being operated on, the result of which is an increased risk of sustaining perioperative myocardial injury (PMI) and poorer clinical outcomes. As such, new treatment strategies are required to protect the heart against PMI and improve clinical outcomes following cardiac surgery. In this regard, the heart can be endogenously protected from PMI by subjecting the myocardium to one or more brief cycles of ischaemia and reperfusion, a strategy called "ischaemic conditioning". However, this requires an intervention applied directly to the heart, which may be challenging to apply in the clinical setting. In this regard, the strategy of remote ischaemic conditioning (RIC) may be more attractive, as it allows the endogenous cardioprotective strategy to be applied away from the heart to the arm or leg by simply inflating and deflating a cuff on the upper arm or thigh to induce one or more brief cycles of ischaemia and reperfusion (termed "limb RIC"). Although a number of small clinical studies have demonstrated less PMI with limb RIC following cardiac surgery, three recently published large multicentre randomised clinical trials found no beneficial effects on short-term or long-term clinical outcomes, questioning the role of limb RIC in the setting of cardiac surgery. In this article, we review ischaemic conditioning as a therapeutic strategy for endogenous cardioprotection in patients undergoing cardiac surgery and discuss the potential reasons for the failure of limb RIC to improve clinical outcomes in this setting. Crucially, limb RIC still has the therapeutic potential to protect the heart in other clinical settings, such as acute myocardial infarction, and it may also protect other organs against acute ischaemia/reperfusion injury (such as the brain, kidney, and liver).

Ischaemic preconditioning for the reduction of renal ischaemia reperfusion injury

BACKGROUND

Ischaemia reperfusion injury can lead to kidney dysfunction or failure. Ischaemic preconditioning is a short period of deprivation of blood supply to particular organs or tissue, followed by a period of reperfusion. It has the potential to protect kidneys from ischaemia reperfusion injury.

OBJECTIVES

This review aimed to look at the benefits and harms of local and remote ischaemic preconditioning to reduce ischaemia and reperfusion injury among people with renal ischaemia reperfusion injury.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register to 5 August 2016 through contact with the Information Specialist using search terms relevant to this review.

SELECTION CRITERIA

We included all randomised controlled trials measuring kidney function and the role of ischaemic preconditioning in patients undergoing a surgical intervention that induces kidney injury. Kidney transplantation studies were excluded.

DATA COLLECTION AND ANALYSIS

Studies were assessed for eligibility and quality; data were extracted by two independent authors. We collected basic study characteristics: type of surgery, remote ischaemic preconditioning protocol, type of anaesthesia. We collected primary outcome measurements: serum creatinine and adverse effects to remote ischaemic preconditioning and secondary outcome measurements: acute kidney injury, need for dialysis, neutrophil gelatinase-associated lipocalin, hospital stay and mortality. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes.

MAIN RESULTS

We included 28 studies which randomised a total of 6851 patients. Risk of bias assessment indicated unclear to low risk of bias for most studies. For consistency regarding the direction of effects, continuous outcomes with negative values, and dichotomous outcomes with values less than one favour remote ischaemic preconditioning. Based on high quality evidence, remote ischaemic preconditioning made little or no difference to the reduction of serum creatinine levels at postoperative days one (14 studies, 1022 participants: MD -0.02 mg/dL, 95% CI -0.05 to 0.02; I2 = 21%), two (9 studies, 770 participants: MD -0.04 mg/dL, 95% CI -0.09 to 0.02; I2 = 31%), and three (6 studies, 417 participants: MD -0.05 mg/dL, 95% CI -0.19 to 0.10; I2 = 68%) compared to control.Serious adverse events occurred in four patients receiving remote ischaemic preconditioning by iliac clamping. It is uncertain whether remote ischaemic preconditioning by cuff inflation leads to increased adverse effects compared to control because the certainty of the evidence is low (15 studies, 3993 participants: RR 3.47, 95% CI 0.55 to 21.76; I2 = 0%); only two of 15 studies reported any adverse effects (6/1999 in the remote ischaemic preconditioning group and 1/1994 in the control group), the remaining 13 studies stated no adverse effects were observed in either group.Compared to control, remote ischaemic preconditioning made little or no difference to the need for dialysis (13 studies, 2417 participants: RR 0.85, 95% CI 0.37 to 1.94; I2 = 60%; moderate quality evidence), length of hospital stay (8 studies, 920 participants: MD 0.17 days, 95% CI -0.46 to 0.80; I2 = 49%, high quality evidence), or all-cause mortality (24 studies, 4931 participants: RR 0.86, 95% CI 0.54 to 1.37; I2 = 0%, high quality evidence).Remote ischaemic preconditioning may have slightly improved the incidence of acute kidney injury using either the AKIN (8 studies, 2364 participants: RR 0.76, 95% CI 0.57 to 1.00; I2 = 61%, high quality evidence) or RIFLE criteria (3 studies, 1586 participants: RR 0.91, 95% CI 0.75 to 1.12; I2 = 0%, moderate quality evidence).

AUTHORS' CONCLUSIONS

Remote ischaemic preconditioning by cuff inflation appears to be a safe method, and probably leads to little or no difference in serum creatinine, adverse effects, need for dialysis, length of hospital stay, death and in the incidence of acute kidney injury. Overall we had moderate-high certainty evidence however the available data does not confirm the efficacy of remote ischaemic preconditioning in reducing renal ischaemia reperfusion injury in patients undergoing major cardiac and vascular surgery in which renal ischaemia reperfusion injury may occur.

Remote ischaemic preconditioning suppresses endogenous plasma nitrite during ischaemia-reperfusion: a randomized controlled crossover pilot study

AIM

The aim of this article is to test the hypothesis that remote ischaemic preconditioning (RIPC) increases circulating endogenous local and systemic plasma (nitrite) during RIPC and ischaemia-reperfusion (IR) as a potential protective mechanism against ischaemia-reperfusion injury (IRI).

METHODS

Six healthy male volunteers (mean age 29.5 ± 7.6 years) were randomized in a crossover study to initially receive either RIPC (4 × 5 min cycles) to the left arm, or no RIPC (control), both followed by an ischaemia-reperfusion (IR) sequence (20 min cuff inflation to 200 mmHg, 20 min reperfusion) to the right arm. The volunteers returned at least 7 days later for the alternate intervention. The primary outcome was the effect of RIPC vs. control on local and systemic plasma (nitrite).

RESULTS

RIPC did not significantly change plasma (nitrite) in either the left or the right arm during the RIPC sequence. However, compared to control, RIPC decreased plasma (nitrite) during the subsequent IR sequence by ~26% (from 118 ± 9 to 87 ± 5 nmol l^-1 ) locally in the left arm (P = 0.008) overall, with an independent effect of -58.70 nmol l^-1 (95% confidence intervals -116.1 to -1.33) at 15 min reperfusion, and by ~24% (from 109 ± 9 to 83 ± 7 nmol l^-1 ) systemically in the right arm (P = 0.03).

CONCLUSIONS

RIPC had no effect on plasma (nitrite) during the RIPC sequence, but instead decreased plasma (nitrite) by ~25% during IR. This would likely counteract the protective mechanisms of RIPC, and contribute to RIPC's lack of efficacy, as observed in recent clinical trials. A combined approach of RIPC with nitrite administration may be required.

Remote Ischemic Conditioning: A Clinical Trial’s Update

Coronary artery disease (CAD) is the leading cause of death and disability worldwide, and early and successful restoration of myocardial reperfusion following an ischemic event is the most effective strategy to reduce final infarct size and improve clinical outcome. This process can, however, induce further myocardial damage, namely acute myocardial ischemia-reperfusion injury (IRI) and worsen clinical outcome. Therefore, novel therapeutic strategies are required to protect the myocardium against IRI in patients with CAD. In this regard, the endogenous cardioprotective phenomenon of “ischemic conditioning,” in which the heart is put into a protected state by subjecting it to one or more brief nonlethal episodes of ischemia and reperfusion, has the potential to attenuate myocardial injury during acute IRI. Intriguingly, the heart can be protected in this manner by applying the “ischemic conditioning” stimulus to an organ or tissue remote from the heart (termed remote ischemic conditioning or RIC). Furthermore, the discovery that RIC can be noninvasively applied using a blood pressure cuff on the upper arm to induce brief episodes of nonlethal ischemia and reperfusion in the forearm has greatly facilitated the translation of RIC into the clinical arena. Several recently published proof-of-concept clinical studies have reported encouraging results with RIC, and large multicenter randomized clinical trials are now underway to investigate whether this simple noninvasive and virtually cost-free intervention has the potential to improve clinical outcomes in patients with CAD. In this review article, we provide an update of recently published and ongoing clinical trials in the field of RIC.

Does Remote Ischaemic Preconditioning Protect Kidney and Cardiomyocytes After Coronary Revascularization? A Double Blind Controlled Clinical Trial

OBJECTIVE

To investigate efficacy of remote ischaemic preconditioning on reducing kidney injury and myocardial damage after coronary artery bypass grafting surgery (CABG).

BACKGROUND

Ischaemic preconditioning of a remote organ reduces ischaemia-reperfusion injury of kidney and myocardium after CABG.

METHOD

To reduce myocardial damage and kidney injury by applying Remote Ischaemic Preconditioning we recruited 100 consecutive patients undergoing elective coronary artery bypass grafting surgery. We applied three cycles of lower limb tourniquet, inflated its cuff for 5 minutes in study group or left un-inflated (sham or control group) before the procedure. The primary outcome was serum creatinine, creatinine clearance and troponin-I Levels at time 0, 6, 12, 24 and 48 h. Secondary outcomes were serum C-reactive protein, inotrope score, ventilation time and ICU stay. Data's were analyzed by MedCalc (MedCalc Software bvba, Acacialaan, Belgium). We compared the two group by student t test, chi-square and Mann-Whitney tests.

RESULTS

The two groups were not statistically different in terms of age, gender, smoking habits, drug use, hypertension, hyperlipidemia and diabetes mellitus. This study showed a higher CRP level in study group comparing with control group (P=0.003), creatinine clearance was slightly higher in study group specially 24 h after procedure but was not statistically significant (p=0.11). Troponin-I level was significantly lower in study group (p=0.001).

CONCLUSION

This study showed a lower Troponin-I level in study group which suggest a cardio-myocyte protective function of RIPC. It also showed slightly lower Creatinine clearance in control group, gap between two group increases significantly 24 hours after procedure which may suggest a potential kidney protection by RIPC. Serum CRP level was higher in study group. A multi-center randomized controlled trial with a longer time for creatinine clearance measurement may show the potential effectiveness of this non-invasive inexpensive intervention on reducing kidney injury after CABG.

Ischaemic conditioning and targeting reperfusion injury: a 30 year voyage of discovery

To commemorate the auspicious occasion of the 30th anniversary of IPC, leading pioneers in the field of cardioprotection gathered in Barcelona in May 2016 to review and discuss the history of IPC, its evolution to IPost and RIC, myocardial reperfusion injury as a therapeutic target, and future targets and strategies for cardioprotection. This article provides an overview of the major topics discussed at this special meeting and underscores the huge importance and impact, the discovery of IPC has made in the field of cardiovascular research.

Time to Give Up on Cardioprotection?

The mortality from acute myocardial infarction (AMI) remains significant, and the prevalence of post-myocardial infarction heart failure is increasing. Therefore, cardioprotection beyond timely reperfusion is needed. Conditioning procedures are the most powerful cardioprotective interventions in animal experiments. However, ischemic preconditioning cannot be used to reduce infarct size in patients with AMI because its occurrence is not predictable; several studies in patients undergoing surgical coronary revascularization report reduced release of creatine kinase and troponin. Ischemic postconditioning reduces infarct size in most, but not all, studies in patients undergoing interventional reperfusion of AMI, but may require direct stenting and exclusion of patients with >6 hours of symptom onset to protect. Remote ischemic conditioning reduces infarct size in patients undergoing interventional reperfusion of AMI, elective percutaneous or surgical coronary revascularization, and other cardiovascular surgery in many, but not in all, studies. Adequate dose-finding phase II studies do not exist. There are only 2 phase III trials, both on remote ischemic conditioning in patients undergoing cardiovascular surgery, both with neutral results in terms of infarct size and clinical outcome, but also both with major problems in trial design. We discuss the difficulties in translation of cardioprotection from animal experiments and proof-of-concept trials to clinical practice. Given that most studies on ischemic postconditioning and all studies on remote ischemic preconditioning in patients with AMI reported reduced infarct size, it would be premature to give up on cardioprotection.

Remote Ischemic Preconditioning in the PICU: A Simple Concept With a Complex Past

OBJECTIVE

In this study, we will review the most recently proposed mechanisms for remote ischemic preconditioning and summarize the past 10 years of clinical studies, as well as potential reasons for why, despite over 20 years of research on remote ischemic preconditioning, it is not routinely used in the pediatric critical care patient. In addition, future directions for remote ischemic preconditioning research will be discussed.

DATA SOURCES

We searched the PubMed database for relevant literature.

STUDY SELECTION AND DATA EXTRACTION

In PubMed, the search terms "ischemic preconditioning" and "remote preconditioning" were used. Randomized controlled trials published from 2006 until the present time that used a blood pressure cuff to induce remote ischemic preconditioning were included. We also reviewed the reference lists of the articles found in the PubMed search and included those thought to contribute to the objectives. All studies pertaining to remote ischemic preconditioning that included pediatric patients were reviewed.

DATA SYNTHESIS AND CONCLUSIONS

Differences in study outcomes in the effect of remote ischemic preconditioning on organ protection have been reported and may have played a large role in limiting the translation of findings into routine clinical practice. Ongoing efforts to protocolize the remote ischemic preconditioning technique in large multicenter trials with clearly delineated patient risk groups, including the use of biomarkers for enrichment, may help to ultimately determine if this procedure can be safely and effectively used for critically ill children.