Ischaemic preconditioning during cardiac surgery: systematic review and meta-analysis of perioperative outcomes in randomised clinical trials

DJ-1: Potential target for treatment of myocardial ischemia-reperfusion injury

Ischemic heart disease (IHD) is a significant global health concern, resulting in high rates of mortality and disability among patients. Although coronary blood flow reperfusion is a key treatment for IHD, it often leads to acute myocardial ischemia-reperfusion injury (IRI). Current intervention strategies have limitations in providing adequate protection for the ischemic myocardium. DJ-1, originally known as a Parkinson's disease related protein, is a highly conserved cytoprotective protein. It is involved in enhancing mitochondrial function, scavenging reactive oxygen species (ROS), regulating autophagy, inhibiting apoptosis, modulating anaerobic metabolism, and exerting anti-inflammatory effects. DJ-1 is also required for protective strategies, such as ischemic preconditioning, ischemic postconditioning, remote ischemic preconditioning and pharmacological conditioning. Therefore, DJ-1 emerges as a potential target for the treatment of myocardial IRI. Our comprehensive review delves into its protective mechanisms in myocardial IRI and the structural foundations underlying its functions.

Remote Ischemic Conditioning Improves Cardiovascular Function in Heart Failure Patients

Background

Recently, it has been shown that remote ischemic conditioning (RIC) can be used as a healthy regimen to reverse disease and aging. With this in mind, we are studying the consequences of RIC on cardiovascular function in heart failure patients.

Methods

Forty patients with stable heart failure were prospectively enlisted and randomly divided into RIC (n = 20) and control (n = 20) groups. The RIC protocol consists of a 3-min inflation and then deflation of the blood pressure cuff attached to the upper arm to produce transient ischemia of the arm. RIC treatment was performed once daily for 1 year. NYHA class, left ventricular ejection fraction (LVEF), left atrial and ventricular dimensions were all assessed in two groups.

Results

RIC was well tolerated. After 1 year of treatment, New York Heart Association (NYHA) class improved and LVEF showed a significant increase from 37.11% to 52.44% (P < 0.0001). Additionally, the dimensions of the left atrium (from 50.55 to 43.25 mm) and ventricle (from 53.04 to 50.15 mm) were significantly reduced in the RIC group.

Conclusion

This study suggests that 1 year of RIC treatment as a health strategy could improve cardiovascular function in heart failure patients, leading to its widespread use in these patients.

Novel Strategies to Improve the Cardioprotective Effects of Cardioplegia

The use of cardioprotective strategies as adjuvants of cardioplegic solutions has become an ideal alternative for the improvement of post-surgery heart recovery. The choice of the optimal cardioplegia, as well as its distribution mechanism, remains controversial in the field of cardiovascular surgery. There is still a need to search for new and better cardioprotective methods during cardioplegic procedures. New techniques for the management of cardiovascular complications during cardioplegia have evolved with new alternatives and additives, and each new strategy provides a tool to neutralize the damage after ischemia/reperfusion events. Researchers and clinicians have committed themselves to studying the effect of new strategies and adjuvant components with the potential to improve the cardioprotective effect of cardioplegic solutions in preventing myocardial ischemia/reperfusion-induced injury during cardiac surgery. The aim of this review is to explore the different types of cardioplegia, their protection mechanisms, and which strategies have been proposed to enhance the function of these solutions in hearts exposed to cardiovascular pathologies that require surgical alternatives for their corrective progression.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Microvascular Leakage as Therapeutic Target for Ischemia and Reperfusion Injury

Reperfusion injury is a very common complication of various indicated therapies such as the re-opening of vessels in the myocardium or brain as well as reflow in hemodynamic shutdown (cardiac arrest, severe trauma, aortic cross-clamping). The treatment and prevention of reperfusion injury has therefore been a topic of immense interest in terms of mechanistic understanding, the exploration of interventions in animal models and in the clinical setting in major prospective studies. While a wealth of encouraging results has been obtained in the lab, the translation into clinical success has met with mixed outcomes at best. Considering the still very high medical need, progress continues to be urgently needed. Multi-target approaches rationally linking interference with pathophysiological pathways as well as a renewed focus on aspects of microvascular dysfunction, especially on the role of microvascular leakage, are likely to provide new insights.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their 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 comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

A review of potential mechanisms and uses of SGLT2 inhibitors in ischemia-reperfusion phenomena

Recently added to the therapeutic arsenal against chronic heart failure as a first intention drug, the antidiabetic drug-class sodium-glucose cotransporter-2 inhibitors (SGLT2i) showed efficacy in decreasing overall mortality, hospitalization, and sudden death in patients of this very population, in whom chronic or acute ischemia count among the first cause. Remarkably, this benefit was observed independently from diabetic status, and benefited both preserved and altered ventricular ejection fraction. This feature, observed in several large randomized controlled trials, suggests additional effects from SGLT2i beyond isolated glycemia control. Indeed, both in-vitro and animal models suggest that inhibiting the Na⁺/H⁺ exchanger (NHE) may be key to preventing ischemia/ reperfusion injuries, and by extension may hold a similar role in ischemic damage control and ischemic preconditioning. Yet, several other mechanisms may be explored which may help better target those who may benefit most from SGLT2i molecules. Because of a large therapeutic margin with few adverse events, ease of prescription and potential pharmacological efficacity, SGLT2i could be candidate for wider indications. In this review, we aim to summarize all evidence which link SGLT2i and ischemia/reperfusion injuries modulation, by first listing known mechanisms, including metabolic switch, prevention of lethal arrythmias and others, which portend the latter, and second, hypothesize how the former may interact with these mechanisms.

Effects of ischaemic postconditioning in aortic valve replacement: a multicenter randomized controlled trial

OBJECTIVES

The effect of ischaemic postconditioning (IPost) on postcardioplegic cardiac function is not known. We hypothesized that IPost was cardioprotective in adult patients undergoing elective aortic valve replacement.

METHODS

In a multicentre, prospective, randomized trial, patients (n = 209) were randomized to either a standard operation (controls) or postconditioning. Immediately before the cross-clamp was released, patients in the postconditioning group underwent 3 cycles of flow/non-flow (2 min each) of normothermic blood via the antegrade cardioplegia line. The primary end point was cardiac index. Secondary end points included additional haemodynamic measurements, biomarkers of cardiomyocyte injury, renal function parameters, intra- and postoperative arrhythmias and use of inotropic agents.

RESULTS

There was no significant difference between the groups regarding cardiac index [mean between-group difference, 95% confidence interval (CI), 0.11 (-0.1 to 0.3), P = 0.27]. Postconditioning had no effect on other haemodynamic parametres. There was no between-group difference regarding troponin T or creatine kinase MB. Postconditioning reduced the relative risk for arrhythmias by 45% (P = 0.03) when postoperative atrial fibrillation and intraoperative ventricular fibrillation were combined. There were no differences in patients with/without diabetes, patients above/below 70 years of age or between the centres. However, after postconditioning, the cardiac index [95% CI, 0.46 (0.2-0.7), P = 0.001], cardiac output (P < 0.001), mean arterial pressure (P < 0.001) and left ventricular stroke work index (P < 0.001) were higher in males compared to females.

CONCLUSIONS

IPost had no overall cardioprotective effects in patients undergoing aortic valve replacement but improved postoperative cardiac performance in men compared to women.

Myocardial protection in cardiac surgery: how limited are the options? A comprehensive literature review

For patients undergoing cardiopulmonary bypass, myocardial protection is a key for successful recovery and improved outcomes following cardiac surgery that requires cardiac arrest. Different solutions, components and modes of delivery have evolved over the last few decades to optimise myocardial protection. These include cold and warm and blood and crystalloid solution through antegrade, retrograde or combined cardioplegia delivery approach. However, each method has its own advantages and disadvantages, posing a challenge to establish a gold-standard cardioplegic solution with an optimised mode of delivery for enhanced myocardial protection during cardiac surgery. The aim of this review is to provide a brief history of the development of cardioplegia, explain the electrophysiological concepts behind myocardial protection in cardioplegia, analyse the current literature and summarise existing evidence that warrants the use of varying cardioplegic techniques. We provide a comprehensive and comparative overview of the effectiveness of each technique in achieving optimal cardioprotection and propose novel techniques for optimising myocardial protection in the future.

From Detecting the Vulnerable Plaque to Managing the Vulnerable Patient: JACC State-of-the-Art Review

The past decades have seen tremendous progress on elucidating mechanisms leading to acute coronary syndrome and sudden cardiac death. Pathology and imaging studies have identified features of coronary atherosclerosis that precede acute coronary events. However, many factors influence the risk of adverse events from coronary atherosclerotic disease and available data support our transition from focusing on individual "vulnerable plaque," coronary arterial stenosis, and inducible myocardial ischemia to understanding coronary heart disease as multifactorial, chronic disease. The concept of the vulnerable patient has evolved, with the atheroma burden, its metabolic activity, and the disposition to vascular thrombosis building a platform for assessing central aspects of coronary heart disease. In turn, this model has directed us to a focus on controlling the activity of atherosclerotic disease and on modifying the susceptibility of vascular thrombosis which has led to reduced morbidity and mortality from coronary heart disease.

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.

Rationale and Design for the Remote Ischemic Preconditioning for Carotid Endarterectomy Trial

BACKGROUND

While the perioperative stroke rate after carotid endarterectomy (CEA) is low, "silent" microinfarctions identified by magnetic resonance imaging (MRI) are common and have been correlated with postoperative neurocognitive decline. Our study will investigate the role of remote ischemic preconditioning (RIPC) as a potential neuroprotective mechanism. RIPC is a well-tolerated stimulus that, through neuronal and humoral pathways, generates a systemic environment of greater resistance to subsequent ischemic insults. We hypothesized that patients undergoing RIPC before CEA will have improved postoperative neurocognitive scores compared with those of patients undergoing standard care.

METHODS

Patients undergoing CEA will be randomized 1:1 to RIPC or standard clinical care. Those randomized to RIPC will undergo a standard protocol of 4 cycles of RIPC. Each RIPC cycle will involve 5 min of forearm ischemia with 5 min of reperfusion. Forearm ischemia will be induced by a blood pressure cuff inflated to 200 mm Hg or at least 15 mm Hg higher than the systolic pressure if it is >185 mm Hg. This will occur after anesthesia induction and during incision/dissection but before manipulation or clamping of the carotid; thus, patients will be blinded to their assignment. Before carotid endarterectomy, all patients will undergo baseline neurocognitive testing in the form of a Montreal Cognitive Assessment (MoCA) and National Institutes of Health (NIH) Toolbox. MoCA testing only will be conducted on postoperative day 1 in the hospital. The full neurocognitive testing battery will again be conducted at 1-month follow-up in the office. Changes from baseline will be compared between arms at the follow-up time points. Assuming no drop-ins or dropouts and a 10% loss to follow-up, we would need a sample size of 43 patients for 80% power per treatment arm. The primary endpoint, change in MoCA scores, will be analyzed using a random effects model, and secondary outcomes will be analyzed using either linear or logistic regression where appropriate.

CONCLUSIONS

RIPC, if shown to be effective in protecting patients from neurocognitive decline after CEA, represents a safe, inexpensive, and easily implementable method of neuroprotection.

Effect of ischemic preconditioning on cardiovascular outcomes in patients with symptomatic coronary artery disease: a cohort study

BACKGROUND

Despite the powerful myocardial protection of ischemic preconditioning (IP) observed in experimental studies, it remains a challenge to observe such protection in humans. Thus, the aim of this study was to evaluate the possible effects of IP on clinical outcomes in patients with coronary artery disease (CAD).

PATIENTS AND METHODS

In this cohort study, patients with multivessel CAD, preserved systolic ventricular function, and stable angina were prospectively selected. They underwent two sequential exercise stress tests (EST) to evaluate IP presence. IP was considered present if patients had an improvement in the time to the onset of 1.0-mm STsegment deviation in the second EST. The primary end point was the composite rate of cardiac death, nonfatal myocardial infarction, or revascularization during 1-year follow-up. Patients with (IP+) and without (IP-) the cardioprotective mechanism were compared regarding clinical end points.

RESULTS

A total of 229 patients completed EST and had IP evaluated: 165 (72%) were IP+ and 64 (28%) were IP - patients. Of these, 218 patients had complete follow-up. At 1-year, event-free survival regarding the primary end point was 95.5 versus 83.6% (P = 0.0024) and event-free survival regarding cardiac death or myocardial infarction was 99.4 versus 91.7% (P=0.0020), respectively, in IP + and IP - groups. The unadjusted hazard ratio (IP + /IP-) for the primary end point was 4.63 (1.52-14.08). After multivariate analysis, IP was still significantly associated with better clinical outcomes (P = 0.0025).

CONCLUSION

This data suggest that IP may contribute to better clinical outcomes in patients with ischemic heart disease.

Glutathione-related substances maintain cardiomyocyte contractile function in hypoxic conditions

Severe hypoxia leads to decline in cardiac contractility and induces arrhythmic events in part due to oxidative damage to cardiomyocyte proteins including ion transporters. This results in compromised handling of Ca2+ ions that trigger heart contractile machinery. Here, we demonstrate that thiol-containing compounds such as N-acetylcysteine (NAC), glutathione ethyl ester (et-GSH), oxidized tetraethylglutathione (tet-GSSG), oxidized glutathione (GSSG) and S-nitrosoglutathione (GSNO) are capable of reducing negative effects of hypoxia on isolated rat cardiomyocytes. Preincubation of cardiomyocytes with 0.1 mM GSNO, 0.5 mM et-GSH, GSSG, tet-GSSG or with 10 mM NAC allows cells 5-times longer tolerate the hypoxic conditions and elicit regular Ca2+ transients in response to electric pacing. The shape of Ca2+ transients generated in the presence of GSNO, et-GSH and NAC was similar to that observed in normoxic control cardiomyocytes. The leader compound, GSNO, accelerated by 34% the recovery of normal contractile function of isolated rat heart subjected to ischemia-reperfusion. GSNO increased glutathionylation of Na,K-ATPase alpha-2 subunit, the principal ion-transporter of cardiac myocyte sarcolemma, which prevents irreversible oxidation of Na,K-ATPase and regulates its function to support normal Ca2+ ion handling in hypoxic cardiomyocytes. Altogether, GSNO appears effective cardioprotector in hypoxic conditions worth further studies toward its cardiovascular application.

Human Tissue-Engineered Model of Myocardial Ischemia-Reperfusion Injury

IMPACT STATEMENT

Reducing ischemia-reperfusion injury would significantly improve patient survival. Current preclinical models are inadequate because they rely on animals, which do not emulate human physiology and the clinical setting. We developed a human tissue platform that allowed us to assess the human cardiac response, and demonstrated the platform's utility by measuring injury during ischemia-reperfusion and the effects of cardioprotective strategies. The model provides a foundation for future studies on how patient-specific backgrounds may affect response to therapeutic strategies. These steps will be necessary to help translate therapies into the clinical setting.

Resistance exercise mediates remote ischemic preconditioning by limiting cardiac eNOS uncoupling

BACKGROUND

Currently viewed as a complementary non-pharmacological intervention for preventing cardiac disorders, long-term aerobic training produces cardioprotection through remote ischemic preconditioning (RIPC) mechanisms. However, RIPC triggered by acute exercise remains poorly understood. Although resistance exercise (RE) has been highly recommended by several public health guidelines, there is no evidence showing that RE mediates RIPC. Hence, we investigated whether RE induces cardiac RIPC through nitric oxide synthase (NOS)-dependent mechanism.

METHODS AND RESULTS

Acute RE at 40% of the maximal load augmented systemic nitrite levels, associated with increased cardiac eNOS phosphorylation, without affecting nNOS activity. Using an experimental model of myocardial infarction (MI) through ischemia-reperfusion (IR), RE fully prevented the loss of cardiac contractility and the extent of MI size compared to non-exercised (NE) rats. Moreover, RE mitigated aberrant ST-segment and reduced life-threatening arrhythmias induced by IR. Importantly, inhibition of NOS abolished the RE-mediated cardioprotection. After IR, NE rats showed increased cardiac eNOS activity, associated with reduced dimer/monomer ratio. Supporting the pivotal role of eNOS coupling during MI, non-exercised rats displayed a marked generation of reactive oxygen species (ROS) and oxidative-induced carbonylation of proteins, whereas RE prevented these responses. We validated our data demonstrating a restoration of physiological ROS levels in NE + IR cardiac sections treated with BH₄, a cofactor oxidatively depleted during eNOS uncoupling, while cardiac ROS generation from exercised rats remained unchanged, suggesting no physiological needs of supplemental eNOS cofactors.

CONCLUSION

Together, our findings strongly indicate that RE mediates RIPC by limiting eNOS uncoupling and mitigates myocardial IR injury.

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).

Pilot randomized controlled trial on early and late remote ischemic preconditioning prior to complex cardiac surgery in young infants

BACKGROUND

Remote ischemic preconditioning involves providing a brief ischemia-reperfusion event to a tissue to create subsequent protection from a more severe ischemia-reperfusion event to a different tissue/organ. The few pediatric remote ischemic preconditioning studies in the literature show conflicting results.

AIM

We conducted a pilot randomized controlled trial to determine the feasibility of conducting a larger trial and to gather provisional data on the effect of early and late remote ischemic preconditioning on outcomes of infants after surgery for congenital heart disease.

METHODS

This single-center, double-blind randomized controlled trial of remote ischemic preconditioning vs control (sham-remote ischemic preconditioning) in young infants going for surgery for congenital heart disease at the Stollery Children's Hospital. Remote ischemic preconditioning was performed at 24-48 h preoperatively and immediately prior to cardiopulmonary bypass. Remote ischemic preconditioning stimulus was performed with blood pressure cuffs around the thighs. Primary outcomes were feasibility and peak blood lactate level on day 1 postoperatively.

RESULTS

Fifty-two patients were randomized but seven patients became ineligible after randomization leaving 45 patients included in the study. In the included patients, 7 (15%) had protocol deviations (five infants did not have the preoperative intervention and two did not receive the intervention in the operating room). From a comfort point of view, only one subject in the control group and two in the Remote ischemic preconditioning group received sedation during the preoperative intervention. There were no study-related adverse events and no complications to the limbs subjected to preconditioning. There were no significant differences between the Remote ischemic preconditioning group and the control group in the highest blood lactate level on day 1 postoperatively (mean difference, 1.28; 95%CI, -0.22, 2.78; P-value = 0.093).

CONCLUSION

In infants who underwent surgery for congenital heart disease, our pilot randomized controlled trial on early and late remote ischemic preconditioning proved to be feasible but did not find any significant difference in acute outcomes. A larger trial may be necessary.

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.

Repeated remote ischemic preconditioning and isoflurane anesthesia in an experimental model of renal ischemia-reperfusion injury

Background

In animal studies, remote ischemic preconditioning (RIPC) and anesthetic preconditioning are successful in reducing renal ischemia reperfusion injury (IRI), however the protective effect of RIPC may be improved by repeating the RIPC stimulus.

Methods

Sprague-Dawley rats underwent unilateral nephrectomy followed by 30 min of renal pedicle clamping. Animals were allocated into six groups: sham, control (IRI), RepISO (daily isoflurane anesthesia), RIPC (single dose isoflurane anesthesia and single dose RIPC), RepISO + RIPC (7-day isoflurane anesthesia and single dose RIPC) and RepISO + RepRIPC (7-day isoflurane anesthesia with 7-day RIPC). RIPC was applied by 3×5 min of cuff inflation on both thighs. Serum creatinine and urea levels were measured and histology was obtained at day two.

Results

RepISO diminished renal IRI, as reflected by a significant reduction in serum creatinine levels as compared to the control group, 170 ± 74 resp. 107 ± 29 μmol/L. The other preconditioning protocols showed similar reduction in serum creatinine levels as compared to the control group. No significant differences were observed between the different preconditioning protocols. For urea levels, only RepISO + RIPC resulted in significantly lower levels as compared to the control group, 14 ± 4 resp. 22 ± 7 mmol/L (p = 0.010). In the preconditioning groups only RepISO showed less histological damage as compared to controls 1.73 ± 1.19 resp. 2.91 ± 1.22 (p = 0.032).

Conclusions

In this study no additional protective effect of repeated ischemic preconditioning was observed as compared to single dose RIPC. Repeated administration of isoflurane provided stronger protection against renal IRI as compared to single dose isoflurane.

Clinical Efforts to Reduce Myocardial Infarct Size—The Next Step

Prompt myocardial reperfusion reduces infarct size in patients experiencing coronary occlusion. However, its clinical value is limited because reperfusion also causes ischemic myocardial reperfusion injury (IMRI). Considerable research to reduce IMRI has been conducted. Three interventions appear to be promising: 1) myocardial conditioning, which consists of repetitive occlusions of coronary or other arteries prior to or at the time of myocardial reperfusion; 2) the administration of cyclosporine A; and 3) the administration of adenosine. A plan for the testing of these interventions in patients with acute myocardial infarction is described.

Novel cardioprotective and regenerative therapies in acute myocardial infarction: a review of recent and ongoing clinical trials

Following the original large-scale randomized trials of aspirin and β-blockade, there have been a number of major advances in pharmacological and mechanical treatments for acute myocardial infarction. Despite this progress, myocardial infarction remains a major global cause of mortality and morbidity, driving a quest for novel treatments in this area. As the understanding of mitochondrial dynamics and the pathophysiology of reperfusion injury has evolved, the last three decades have seen advances in ischemic conditioning, pharmacological and metabolic cardioprotection, as well as biological and stem-cell therapies. The aim of this review is to provide a synopsis of adjunctive cardioprotective and regenerative therapies currently undergoing or entering early clinical trials in the treatment of patients with acute myocardial infarction.

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.

Cardiac troponin T is an important predictor of mortality after cardiac surgery

PURPOSE

Serum troponin (cTnT) levels, a commonly measured biomarker of myocardial injury, has rarely been considered in risk models after cardiac surgery.

MATERIALS AND METHODS

Retrospective study of patients undergoing any cardiac surgery between 2004 and 2012. Patients with a history of recent myocardial injury (<21 days) were excluded. The minimum P value approach was used to determine categories of peak cTnT associated with in-hospital death. A multivariable analysis was performed to identify independent predictors of mortality.

RESULTS

A total of 5318 patients without evidence of preoperative ischemia underwent a number of cardiac surgical interventions ranging from isolated coronary revascularization to combined valve coronary artery bypass grafting. The unadjusted in-hospital mortality rate was 3.3% (n = 175 patients). Four categories of peak cTnT were identified using the minimum P value approach: less than or equal to 0.6 ng/mL, 0.7 to 1.9 ng/mL, 2.0 to 3.1 ng/mL, and greater than 3.1 ng/mL with unadjusted mortality rates of 1.0%, 3.6%, 10.1%, and 33.1%, respectively. Multivariate logistic regression demonstrated that all peak cTnT levels greater than 0.6 ng/mL were independent predictors of in-hospital mortality in a dose-dependent manner.

CONCLUSIONS

We demonstrate that in patients without preoperative myocardial ischemia, the demonstration of myocardial injury (>0.6 ng/mL) in the postoperative period is highly predictive of in-hospital death.

Cardiac Remote Ischemic Preconditioning Prior to Elective Vascular Surgery (CRIPES): A Prospective, Randomized, Sham-Controlled Phase II Clinical Trial

BACKGROUND

Remote ischemic preconditioning (RIPC) has been shown to reduce infarct size in animal models. We hypothesized that RIPC before an elective vascular operation would reduce the incidence and amount of a postoperative rise of the cardiac troponin level.

METHODS AND RESULTS

Cardiac Remote Ischemic Preconditioning Prior to Elective Vascular Surgery (CRIPES) was a prospective, randomized, sham-controlled phase 2 trial using RIPC before elective vascular procedures. The RIPC protocol consisted of 3 cycles of 5-minute forearm ischemia followed by 5 minutes of reperfusion. The primary endpoint was the proportion of subjects with a detectable increase in cardiac troponin I (cTnI) and the distribution of such increases. From June 2011 to September 2015, 201 male patients (69±7, years) were randomized to either RIPC (n=100) or a sham procedure (n=101). Indications for vascular surgery included an expanding abdominal aortic aneurysm (n=115), occlusive peripheral arterial disease of the lower extremities (n=37), or internal carotid artery stenosis (n=49). Of the 201 patients, 47 (23.5%) had an increase in cTnI above the upper reference limit within 72 hours of the vascular operation, with no statistically significant difference between those patients assigned to RIPC (n=22; 22.2%) versus sham procedure (n=25; 24.7%; P=0.67). Among the cohort with increased cTnI, the median peak values (interquartile range) in the RIPC and control group were 0.048 (0.004-0.174) and 0.017 (0.003-0.105), respectively (P=0.54).

CONCLUSIONS

In this randomized, controlled trial of men with increased perioperative cardiac risks, elevation in cardiac troponins was common following vascular surgery, but was not reduced by a strategy of RIPC.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01558596.

Sevoflurane preconditioning in on-pump coronary artery bypass grafting: a meta-analysis of randomized controlled trials

PURPOSE

Sevoflurane preconditioning (SevoPreC) has been proved to prevent organ ischemia/reperfusion (I/R) injury in various animal models and preclinical studies. Clinical trials on cardioprotection by SevoPreC for adult patients undergoing coronary artery bypass graft (CABG) revealed mixed results. The aim of this meta-analysis was to evaluate the cardiac effect of SevoPreC in on-pump CABG.

METHODS

Randomized controlled trials (RCT) comparing the cardiac effect of SevoPreC (compared with control) in adult patients undergoing CABG were searched from PubMed, Embase, and the Cochrane Library (up to November 2015). The primary endpoints were postoperative troponin levels. Additional endpoints were CK-MB levels, mechanic ventilation (MV) duration, intensive care unit (ICU) stay, and hospital length of stay (LOS).

RESULTS

Six trials with eight comparisons enrolling a total of 384 study patients reporting postoperative troponin levels were identified. Compared with controls, SevoPreC decreased postoperative myocardial troponin levels [standardized mean difference (SMD) = -0.38; 95 % CI, -0.74 to -0.03; P = 0.04; I ² = 63.9 %]. However, no significant differences were observed in postoperative CK-MB levels [weighted mean difference (WMD) = -1.71; P = 0.37; I ² = 37.7 %], MV duration (WMD = -0.53; P = 0.47; I ² = 0.0 %), ICU stay (WMD = -0.91; P = 0.39; I ² = 0.9 %), and hospital LOS (WMD = 0.08; P = 0.86; I ² = 8.0 %).

CONCLUSION

Available evidence from the present systematic review and meta-analysis suggests that sevoflurane preconditioning may reduce troponin levels in on-pump CABG. Future high-quality, large-scale clinical trials should focus on the early and long-term clinical effect of SevoPreC in on-pump CABG.

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.

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.

Is "Attenuation of Oxidative Stress" Helpful to Understand the Mechanism of Remote Ischemic Preconditioning in Cardiac Surgery?

OBJECTIVES

The aim of this study was to determine the effect of remote ischemic preconditioning (RIPC) on markers of cardiac ischemia and response to oxidative stress in patients undergoing coronary artery bypass grafting (CABG) surgery.

DESIGN

A prospective, randomized, and blinded study.

SETTING

A single-center university hospital.

PARTICIPANTS

This study included patients who underwent isolated CABG surgery with cardiopulmonary bypass who were selected carefully to prevent confounding with factors known to affect markers of ischemia-reperfusion and response to oxidative stress.

INTERVENTIONS

The authors randomly assigned patients to RIPC to the left lower extremity using a blood pressure cuff (study group) or a cuff that was applied but not inflated or deflated (control group).

MEASUREMENTS AND MAIN RESULTS

At 6 hours after CABG surgery, high-sensitivity cardiac troponin T levels were significantly lower in the study group than in the control group. Levels of superoxide dismutase, an antioxidant enzyme, were significantly greater 15 minutes after release of the cross-clamp in the study group, whereas malondialdehyde levels were lower (not significantly) at 1 and 15 minutes after release of the cross-clamp. Hemodynamic parameters were not significantly different at any time point during the study.

CONCLUSIONS

The authors' method of RIPC before CABG surgery resulted in less myocardial ischemia, as indicated by lower troponin levels. Changes in levels of endogenous antioxidant enzymes supported the hypothesis that this protection from ischemia-reperfusion injury was related to scavenging of free oxygen radicals. Future studies might include a more heterogeneous population and medications that lower the body's response to oxidative stress.

Preconditioning Shields Against Vascular Events in Surgery (SAVES), a multicentre feasibility trial of preconditioning against adverse events in major vascular surgery: study protocol for a randomised control trial

BACKGROUND

Patients undergoing vascular surgery procedures constitute a 'high-risk' group. Fatal and disabling perioperative complications are common. Complications arise via multiple aetiological pathways. This mechanistic redundancy limits techniques to reduce complications that target individual mechanisms, for example, anti-platelet agents. Remote ischaemic preconditioning (RIPC) induces a protective phenotype in at-risk tissue, conferring protection against ischaemia-reperfusion injury regardless of the trigger. RIPC is induced by repeated periods of upper limb ischaemia-reperfusion produced using a blood pressure cuff. RIPC confers some protection against cardiac and renal injury during major vascular surgery in proof-of-concept trials. Similar trials suggest benefit during cardiac surgery. Several uncertainties remain in advance of a full-scale trial to evaluate clinical efficacy. We propose a feasibility trial to fully evaluate arm-induced RIPC's ability to confer protection in major vascular surgery, assess the incidence of a proposed composite primary efficacy endpoint and evaluate the intervention's acceptability to patients and staff.

METHODS/DESIGN

Four hundred major vascular surgery patients in five Irish vascular centres will be randomised (stratified for centre and procedure) to undergo RIPC or not immediately before surgery. RIPC will be induced using a blood pressure cuff with four cycles of 5 minutes of ischaemia followed by 5 minutes of reperfusion immediately before the start of operations. There is no sham intervention. Participants will undergo serum troponin measurements pre-operatively and 1, 2, and 3 days post-operatively. Participants will undergo 12-lead electrocardiograms pre-operatively and on the second post-operative day. Predefined complications within one year of surgery will be recorded. Patient and staff experiences will be explored using qualitative techniques. The primary outcome measure is the proportion of patients who develop elevated serum troponin levels in the first 3 days post-operatively. Secondary outcome measures include length of hospital and critical care stay, unplanned critical care admissions, death, myocardial infarction, stroke, mesenteric ischaemia and need for renal replacement therapy (within 30 days of surgery).

DISCUSSION

RIPC is novel intervention with the potential to significantly improve perioperative outcomes. This trial will provide the first evaluation of RIPC's ability to reduce adverse clinical events following major vascular surgery.

TRIAL REGISTRATION

www.clinicaltrials.gov NCT02097186 Date Registered: 24 March 2014.

New technique of local ischemic preconditioning induction without repetitive aortic cross-clamping in cardiac surgery

Background

Several studies have demonstrated that local ischemic preconditioning can reduce myocardial ischemia–reperfusion injury in cardiac surgery patients; however, preconditioning has not become a standard cardioprotective intervention, primarily because of the increased risk of atheroembolism during repetitive aortic cross-clamping. In the present study, we aimed to describe and validate a novel technique of preconditioning induction.

Methods

Patients undergoing coronary artery bypass grafting (12 women and 78 men; mean age, 56 ± 11 years) were randomized into 3 groups: (1) Controls (n = 30), (2) Perfusion (n = 30), and (3) Preconditioning (n = 30). All patients were operated under cardiopulmonary bypass using normothermic blood cardioplegia. Preconditioning was induced by subjecting the hemodynamically unloaded heart to 2 cycles of 3 min of ischemia and 3 min of reperfusion with normokalemic blood prior to cardioplegia. In the Perfusion group, the heart perfusion remained unaffected for 12 min. Troponin I (TnI) levels were analyzed before surgery, and 12, 24, 48 h, and 7 days after surgery. The secondary endpoints included the cardiac index, plasma natriuretic peptide level, and postoperative use of inotropes.

Results

Preconditioning resulted in a significant reduction in the TnI level on the 7th postoperative day only (0.10 ± 0.05 and 0.33 ± 0.88 ng/ml in Preconditioning and Perfusion groups, respectively, P < 0.05). In addition, cardiac index was significantly higher in the Preconditioning group than in the Control and Perfusion groups just after weaning from cardiopulmonary bypass. The number of patients requiring inotropic support with ≥ 2 agents after surgery was significantly lower in the Preconditioning and Perfusion group than in the Control group (P < 0.05). No complications of the procedure were recorded in the Preconditioning group.

Conclusions

The preconditioning procedure described can be performed safely in cardiac surgery patients. The application of this technique of preconditioning was associated with certain benefits, including improved left ventricular function after weaning from cardiopulmonary bypass and a reduced need for inotropic support. However, the infarct-limiting effect of preconditioning in the early postoperative period was not evident. The procedure does not involve repetitive aortic cross-clamping, thus avoiding possible embolic complications.

Comparison of femoral and aortic remote ischaemia preconditioning for cardioprotection against myocardial ischaemia/reperfusion injury in a rat model

OBJECTIVES

Remote ischaemia preconditioning (RIPC) induces some protection against heart ischaemia/reperfusion (IR) injury. However, many different methods were tried in the past, and no consensus exists. The aim of this study was to compare femoral and aortic ischaemia preconditioning on cardiac markers and on heart injury after IR.

METHODS

Sixty male Sprague-Dawley rats were randomly allocated into four groups: the sham group, control group, femoral group (F, bilateral femoral artery ischaemia) and aorta group (A, abdominal aorta ischaemia). They were submitted to 30 min occlusion of the left coronary artery and to 180 min reperfusion (except the sham group) after different preconditioning protocols (femoral versus aortic). Cardiac markers, infarct area and cardiomyocyte apoptosis index were compared between groups using analysis of variance.

RESULTS

Creatine kinase-MB, lactate dehydrogenase and cardiac troponin I levels were lower in Group F compared with the control group, while there was no difference between Group A and the control group for these three parameters. There were significant differences between the control and experimental groups in myocardial infarct size (control: 48.34 ± 6.79% vs F: 29.64 ± 4.51% and A: 31.81 ± 9.62%, P <0.001). Group F had a lower cardiomyocyte apoptosis index than controls (18.32 ± 9.30 vs 31.75 ± 10.65%, P = 0.016), but there was no difference between Group A and controls (23.25 ± 4.77%, P = 0.107).

CONCLUSIONS

These results confirmed the cardioprotection of RIPC against myocardial IR injury. However, they did not provide sufficient supporting evidence for the enhancement of cardioprotection with an increased area of remote ischaemia preconditioning in rat, or with different ischaemia sites.

Adjuvant cardioprotection in cardiac surgery: update

Cardiac surgery patients are now more risky in terms of age, comorbidities, and the need for complex procedures. It brings about reperfusion injury, which leads to dysfunction and/or loss of part of the myocardium. These groups of patients have a higher incidence of postoperative complications and mortality. One way of augmenting intraoperative myocardial protection is the phenomenon of myocardial conditioning, elicited with brief nonlethal episodes of ischaemia-reperfusion. In addition, drugs are being tested that mimic ischaemic conditioning. Such cardioprotective techniques are mainly focused on reperfusion injury, a complex response of the organism to the restoration of coronary blood flow in ischaemic tissue, which can lead to cell death. Extensive research over the last three decades has revealed the basic mechanisms of reperfusion injury and myocardial conditioning, suggesting its therapeutic potential. But despite the enormous efforts that have been expended in preclinical studies, almost all cardioprotective therapies have failed in the third phase of clinical trials. One reason is that evolutionary young cellular mechanisms of protection against oxygen handling are not very robust. Ischaemic conditioning, which is among these, is also limited by this. At present, the prevailing belief is that such options of treatment exist, but their full employment will not occur until subquestions and methodological issues with the transfer into clinical practice have been resolved.

Preconditioning provides neuroprotection in models of CNS disease: paradigms and clinical significance

Preconditioning is a phenomenon in which brief episodes of a sublethal insult induce robust protection against subsequent lethal injuries. Preconditioning has been observed in multiple organisms and can occur in the brain as well as other tissues. Extensive animal studies suggest that the brain can be preconditioned to resist acute injuries, such as ischemic stroke, neonatal hypoxia/ischemia, surgical brain injury, trauma, and agents that are used in models of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Effective preconditioning stimuli are numerous and diverse, ranging from transient ischemia, hypoxia, hyperbaric oxygen, hypothermia and hyperthermia, to exposure to neurotoxins and pharmacological agents. The phenomenon of "cross-tolerance," in which a sublethal stress protects against a different type of injury, suggests that different preconditioning stimuli may confer protection against a wide range of injuries. Research conducted over the past few decades indicates that brain preconditioning is complex, involving multiple effectors such as metabolic inhibition, activation of extra- and intracellular defense mechanisms, a shift in the neuronal excitatory/inhibitory balance, and reduction in inflammatory sequelae. An improved understanding of brain preconditioning should help us identify innovative therapeutic strategies that prevent or at least reduce neuronal damage in susceptible patients. In this review, we focus on the experimental evidence of preconditioning in the brain and systematically survey the models used to develop paradigms for neuroprotection, and then discuss the clinical potential of brain preconditioning.

Modifications in rat plasma proteome after remote ischemic preconditioning (RIPC) stimulus: identification by a SELDI-TOF-MS approach

Remote ischemic preconditioning’s (RIPC) ability to render the myocardium resistant to subsequent prolonged ischemia is now clearly established in different species, including humans. Strong evidence suggests that circulating humoral mediators play a key role in signal transduction, but their identities still need to be established. Our study sought to identify potential circulating RIPC mediators using a proteomic approach. Rats were exposed to 10-min limb ischemia followed by 5- (RIPC 5′) or 10-min (RIPC 10′) reperfusion prior to blood sampling. The control group only underwent blood sampling. Plasma samples were isolated for proteomic analysis using surface-enhanced laser desorption and ionization - time of flight - mass spectrometry (SELDI-TOF-MS). A total of seven proteins, including haptoglobin and transthyretin, were detected as up- or down-regulated in response to RIPC. These proteins had previously been identified as associated with organ protection, anti-inflammation, and various cellular and molecular responses to ischemia. In conclusion, this study indicates that RIPC results in significant modulations of plasma proteome.