The role of remote ischemic preconditioning in organ protection after cardiac surgery: a meta-analysis. J Surg Res. 2014;186:207-216. [PMID: 24135377 DOI: 10.1016/j.jss.2013.09.006]

Cardiopulmonary bypass associated acute kidney injury: better understanding and better prevention

Cardiopulmonary bypass (CPB) is a common technique in cardiac surgery but is associated with acute kidney injury (AKI), which carries considerable morbidity and mortality. In this review, we explore the range and definition of CPB-associated AKI and discuss the possible impact of different disease recognition methods on research outcomes. Furthermore, we introduce the specialized equipment and procedural intricacies associated with CPB surgeries. Based on recent research, we discuss the potential pathogenesis of AKI that may result from CPB, including compromised perfusion and oxygenation, inflammatory activation, oxidative stress, coagulopathy, hemolysis, and endothelial damage. Finally, we explore current interventions aimed at preventing and attenuating renal impairment related to CPB, and presenting these measures from three perspectives: (1) avoiding CPB to eliminate the fundamental impact on renal function; (2) optimizing CPB by adjusting equipment parameters, optimizing surgical procedures, or using improved materials to mitigate kidney damage; (3) employing pharmacological or interventional measures targeting pathogenic factors.

Effect of Delayed Remote Ischemic Preconditioning on Acute Kidney Injury and Outcomes in Patients Undergoing Cardiac Surgery: A Randomized Clinical Trial

BACKGROUND

Remote ischemic preconditioning (RIPC) has 2 time windows for organ protection: acute and delayed. Previous studies have mainly focused on the organoprotective effects of acute RIPC. We aimed to determine whether delayed RIPC can reduce the occurrence of acute kidney injury (AKI) and postoperative complications in patients undergoing cardiac surgery.

METHODS

This prospective, single-center, double-blind, randomized controlled trial involved 509 patients at high risk for AKI who were scheduled for elective cardiac surgery requiring cardiopulmonary bypass. Patients were randomized to receive RIPC (4 cycles of 5-minute inflation and 5-minute deflation on 1 upper arm with a blood pressure cuff) 24 hours before surgery or a sham condition (control group) that was induced by 4 cycles of 5-minute inflation to a pressure of 20 mm Hg followed by 5-minute cuff deflation. The primary end point was the incidence of AKI within the prior 7 days after cardiac surgery. The secondary end points included renal replacement therapy during hospitalization, change in urinary biomarkers of AKI and markers of myocardial injury, duration of intensive care unit stay and mechanical ventilation, and occurrence of nonfatal myocardial infarction, stroke, and all-cause mortality by day 90.

RESULTS

A total of 509 patients (mean age, 65.2±8.2 years; 348 men [68.4%]) were randomly assigned to the RIPC group (n=254) or control group (n=255). AKI was significantly reduced in the RIPC group compared with the control group (69/254 [27.2%] versus 90/255 [35.3%]; odds ratio, 0.68 [95% CI, 0.47-1.00]; P=0.048). There were no significant between-group differences in the secondary end points of perioperative myocardial injury (assessed by the concentrations of cardiac troponin T, creatine kinase myocardial isoenzyme, and NT-proBNP [N-terminal pro-brain natriuretic peptide]), duration of stay in the intensive care unit and hospital, and occurrence of nonfatal myocardial infarction, stroke, and all-cause mortality by day 90.

CONCLUSIONS

Among high-risk patients undergoing cardiac surgery, delayed RIPC significantly reduced the occurrence of AKI.

REGISTRATION

URL: https://www.chictr.org.cn; Unique identifier: ChiCTR2000035568.

Integrative care: acupuncture based neuromodulation therapy for diabetes and heart failure

The relationship between heart failure and diabetes is intricate and bidirectional. Individuals with diabetes face an elevated risk of developing heart failure due to factors like insulin resistance, chronic inflammation, and metabolic irregularities. Elevated blood sugar levels can harm blood vessels and nerves, culminating in the buildup of fatty deposits in arteries, atherosclerosis, and hypertension, which significantly contribute to heart failure. Furthermore, diabetes can adversely impact the structure and function of the heart muscle, impairing its pumping capacity. Conversely, heart failure can also contribute to the onset of diabetes by disrupting the body's metabolic processes and amplifying insulin resistance. The complex interaction between these conditions mandates a comprehensive approach to managing individuals with both diabetes and heart failure, underscoring the importance of addressing both aspects for enhanced patient outcomes. Although existing pharmacological treatments are limited and frequently associated with undesirable side effects, acupuncture has established itself as a traditional practice with a legacy. It remains a supplementary option for treating cardiovascular diseases. Heart failure and diabetes are both heavily associated with chronic upregulation of the sympathetic nervous system, which has been identified as a pivotal factor in the progression of disease. Mechanistic interplays such as the attenuation of central nitric oxide signaling may interfere with the production or availability of nitric oxide in key areas of the central nervous system, including the brainstem and hypothalamus. This review will delve into the current understanding of acupuncture on the autonomic nervous system and offer insights into its potential role in the future treatment landscape for diabetes and heart failure.

Effect of remote ischemic preconditioning on lung function after surgery under general anesthesia: a systematic review and meta-analysis

Remote ischemic preconditioning (RIPC) protects organs from ischemia-reperfusion injury. Recent trials showed that RIPC improved gas exchange in patients undergoing lung or cardiac surgery. We performed a systematic search to identify randomized controlled trials involving RIPC in surgery under general anesthesia. The primary outcome was the PaO2/FIO2 (P/F) ratio at 24 h after surgery. Secondary outcomes were A-a DO2, the respiratory index, duration of postoperative mechanical ventilation (MV), incidence of acute respiratory distress syndrome (ARDS), and serum cytokine levels. The analyses included 71 trials comprising 7854 patients. Patients with RIPC showed higher P/F ratio than controls (mean difference [MD] 36.6, 95% confidence interval (CI) 12.8 to 60.4, I2 = 69%). The cause of heterogeneity was not identified by the subgroup analysis. Similarly, A-a DO2 (MD 15.2, 95% CI - 29.7 to - 0.6, I2 = 87%) and respiratory index (MD - 0.17, 95% CI - 0.34 to - 0.01, I2 = 94%) were lower in the RIPC group. Additionally, the RIPC group was weaned from MV earlier (MD - 0.9 h, 95% CI - 1.4 to - 0.4, I2 = 78%). Furthermore, the incidence of ARDS was lower in the RIPC group (relative risk 0.73, 95% CI 0.60 to 0.89, I2 = 0%). Serum TNFα was lower in the RIPC group (SMD - 0.6, 95%CI - 1.0 to - 0.3 I2 = 87%). No significant difference was observed in interleukin-6, 8 and 10. Our meta-analysis suggested that RIPC improved oxygenation after surgery under general anesthesia.Clinical trial number: This study protocol was registered in the University Hospital Medical Information Network (registration number: UMIN000030918), https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000035305.

Bilateral Remote Ischaemic Conditioning in Children (BRICC) trial: protocol for a two-centre, double-blind, randomised controlled trial in young children undergoing cardiac surgery

INTRODUCTION

Myocardial protection against ischaemic-reperfusion injury is a key determinant of heart function and outcome following cardiac surgery in children. However, with current strategies, myocardial injury occurs routinely following aortic cross-clamping, as demonstrated by the ubiquitous rise in circulating troponin. Remote ischaemic preconditioning, the application of brief, non-lethal cycles of ischaemia and reperfusion to a distant organ or tissue, is a simple, low-risk and readily available technique which may improve myocardial protection. The Bilateral Remote Ischaemic Conditioning in Children (BRICC) trial will assess whether remote ischaemic preconditioning, applied to both lower limbs immediately prior to surgery, reduces myocardial injury in cyanotic and acyanotic young children.

METHODS AND ANALYSIS

The BRICC trial is a two-centre, double-blind, randomised controlled trial recruiting up to 120 young children (age 3 months to 3 years) undergoing primary repair of tetralogy of Fallot or surgical closure of an isolated ventricular septal defect. Participants will be randomised in a 1:1 ratio to either bilateral remote ischaemic preconditioning (3×5 min cycles) or sham immediately prior to surgery, with follow-up until discharge from hospital or 30 days, whichever is sooner. The primary outcome is reduction in area under the time-concentration curve for high-sensitivity (hs) troponin-T release in the first 24 hours after aortic cross-clamp release. Secondary outcome measures include peak hs-troponin-T, vasoactive inotrope score, arterial lactate and central venous oxygen saturations in the first 12 hours, and lengths of stay in the paediatric intensive care unit and the hospital.

ETHICS AND DISSEMINATION

The trial was approved by the West Midlands-Solihull National Health Service Research Ethics Committee (16/WM/0309) on 5 August 2016. Findings will be disseminated to the academic community through peer-reviewed publications and presentation at national and international meetings. Parents will be informed of the results through a newsletter in conjunction with a local charity.

TRIAL REGISTRATION NUMBER

ISRCTN12923441.

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.

Effects of Combined Remote Ischemic Pre-and Post-Conditioning on Neurologic Complications in Moyamoya Disease Patients Undergoing Superficial Temporal Artery-Middle Cerebral Artery Anastomosis

Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis is the most commonly used treatment for Moyamoya disease. During the perioperative period, however, these patients are vulnerable to ischemic injury or hyperperfusion syndrome. This study investigated the ability of combined remote ischemic pre-conditioning (RIPC) and remote ischemic post-conditioning (RIPostC) to reduce the occurrence of major neurologic complications in Moyamoya patients undergoing STA-MCA anastomosis. The 108 patients were randomly assigned to a RIPC with RIPostC group (n = 54) or a control group (n = 54). Patients in the RIPC with RIPostC group were treated with four cycles of 5-min ischemia and 5-min reperfusion before craniotomy and after STA-MCA anastomosis (RIPostC). The incidence of postoperative neurologic complications and the duration of hospital stay were determined. The overall incidence of neurologic complication was significantly higher in the control group than in the RIPC with RIPostC group (13 vs. 3, p = 0.013). The duration of hospital stay was significantly longer in the control group than in the RIPC with RIPostC group (17.8 (11.3) vs. 13.8 (5.9) days, p = 0.023). Combined remote ischemic pre- and post-conditioning can be effective in reducing neurologic complications and the duration of hospitalization in Moyamoya patients undergoing STA-MCA anastomosis.

Intermittent systemic hypoxic-hyperoxic training for myocardial protection in patients undergoing coronary artery bypass surgery: first results from a single-centre, randomised controlled trial

Background

Although remote ischaemic preconditioning (RIP) provides protection against myocardial ischaemia and reperfusion injury during cardiac surgery, it is not widely used. Systemic intermittent hypoxic–hyperoxic training (IHHT) may be a suitable alternative.

Methods

This is a prospective, single-centre, randomised controlled trial. 127 patients with ischaemic heart disease and indication for coronary artery bypass graft (CABG) surgery from the Cardiology Clinic IM Sechenov First Moscow State Medical University were randomly assigned to IHHT, IHHT-control or RIP. Primary endpoint was serum concentration of troponin I and lactate 2 and 24 hours after surgery.

Results

Median value for troponin I 24 hours after surgery was 1.068 (0.388–1.397) ng/mL in the IHHT group and was significantly lower compared with IHHT-controls with 1.980 (1.068–3.239) ng/mL (p=0.012) and to the RIP group with 1.762 (1.288–2.186) ng/mL (p=0.029), while there was no significant difference between RIP and the IHHT-control. Serum lactate after surgery was 1.74 (1.23–2.04) mmol/L in the IHHT group and was also significantly lower compared with IHHT-controls with 2.10 (1.80–2.29) mmol/L (p=0.045) and RIP with 2.12 (1.91–2.33) mmol/L (p=0.032). No significant complications or serious adverse events were observed during IHHT. Intraoperative and early postoperative complications did not differ significantly between groups.

Conclusions

The results of this first trial using IHHT for myocardial protection against perioperative ischaemic myocardial injury in patients undergoing CABG surgery are promising and further larger trials should be done with adequate power to detect clinical rather than surrogate marker benefits.

Remote ischaemic preconditioning reduces acute kidney injury in adult patients undergoing cardiac surgery with cardiopulmonary bypass: a meta-analysis

This article represents the first attempt to perform a pooled analysis about remote ischaemic preconditioning (RIPC) in reduction of acute kidney injury (AKI) of adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). A systematic search was performed using PubMed (1966-5 January 2016), the Cochrane Library (1996-5 January 2016), the Web of Science (1986-5 January 2016) and Chinese database (SinoMed) (1978-5 January 2016) to identify studies that have described the effect of RIPC on AKI in adult patients undergoing cardiac surgery with CPB. The outcomes used for this analysis included the incidence of AKI and the need for renal replacement therapy (RRT). Thirteen randomized controlled trials (4370 participants) were included in this analysis. RIPC significantly reduced the risk of AKI (risk ratio, 0.81; 95% confidence interval, [0.66, 0.99]; P = 0.04; I2 = 46%) for adult patients compared with control group. However, there was no significant difference with respect to the incidence of RRT between the two groups. The present meta-analysis found that RIPC may reduce the incidence of AKI among adult patients following cardiac surgery with CPB. Adequately powered trials are warranted to provide further corroboration of our findings in the future.

Ischaemic preconditioning - Current knowledge and potential future applications after 30 years of experience

Ischaemic preconditioning (IPC) phenomenon has been known for thirty years. During that time several studies showed that IPC provided by brief ischaemic and reperfusion episodes prior to longer ischaemia can bestow a protective effect to both preconditioned and also remote organs. IPC affecting remote organs is called remote ischaemic preconditioning. Initially, most IPC studies were focused on enhancing myocardial resistance to subsequent ischaemia and reperfusion injury. However, preconditioning was found to be a universal phenomenon and was observed in various organs and tissues including the heart, liver, brain, retina, kidney, skeletal muscles and intestine. Currently, there are a lot of simultaneous studies are underway aiming at finding out whether IPC can be helpful in protecting these organs. The mechanism of local and remote IPC is complex and not well known. Several triggers, intracellular pathways and effectors, humoral, neural and induced by genetic changes may be considered potential pathways in the protective activity of local and remote IPC. Local and remote IPC mechanism may potentially serve as heart protection during cardiac surgery and may limit the infarct size of the myocardium, can be a strategy for preventing the development of acute kidney injury development and liver damage during transplantation, may protect the brain against ischaemic injury. In addition, the method is safe, non-invasive, cheap and easily applicable. The main purpose of this review article is to present new advances which would help to understand the potential mechanism of IPC. It also discusses both its potential applications and utility in clinical settings.

Clinical Outcomes of Remote Ischemic Preconditioning Prior to Cardiac Surgery: A Meta-Analysis of Randomized Controlled Trials

Background

Multiple randomized controlled trials of remote ischemic preconditioning (RIPC) prior to cardiac surgery have failed to demonstrate clinical benefit. The aim of this updated meta‐analysis was to evaluate the effect of RIPC on outcomes following cardiac surgery.

Methods and Results

Searches of PubMed, Cochrane, EMBASE, and Web of Science databases were performed for 1970 to December 13, 2015. Randomized controlled trials comparing RIPC with a sham procedure prior to cardiac surgery performed with cardiopulmonary bypass were assessed. All‐cause mortality, acute kidney injury (AKI), and myocardial infarction were the primary outcomes of interest. We identified 21 trials that randomized 5262 patients to RIPC or a sham procedure prior to undergoing cardiac surgery. The majority of patients were men (72.6%) and the mean or median age ranged from 42.3 to 76.3 years. Of the 9 trials that evaluated mortality, 188 deaths occurred out of a total of 4210 randomized patients, with 96 deaths occurring in 2098 patients (4.6%) randomized to RIPC and 92 deaths occurring in 2112 patients (4.4%) randomized to a sham control procedure, demonstrating no significant reduction in all‐cause mortality (risk ratio [RR], 0.987; 95% CI, 0.653–1.492, P=0.95). Twelve studies evaluated AKI in 4209 randomized patients. In these studies, AKI was observed in 516 of 2091 patients (24.7%) undergoing RIPC and in 577 of 2118 patients (27.2%) randomized to a sham procedure. RIPC did not result in a significant reduction in AKI (RR, 0.839; 95% CI, 0.703–1.001 [P=0.052]). In 6 studies consisting of 3799 randomized participants, myocardial infarction occurred in 237 of 1891 patients (12.5%) randomized to RIPC and in 282 of 1908 patients (14.8%) randomized to a sham procedure, resulting in no significant reduction in postoperative myocardial infarction (RR, 0.809; 95% CI, 0.615–1.064 [P=0.13]). A subgroup analysis was performed a priori based on previous studies suggesting that propofol may mitigate the protective benefits of RIPC. Three studies randomized patients undergoing cardiac surgery to RIPC or sham procedure in the absence of propofol anesthesia. Most of these patients were men (60.3%) and the mean or median age ranged from 57.0 to 70.6 years. In this propofol‐free subgroup of 434 randomized patients, 71 of 217 patients (32.7%) who underwent RIPC developed AKI compared with 103 of 217 patients (47.5%) treated with a sham procedure. In this cohort, RIPC resulted in a significant reduction in AKI (RR, 0.700; 95% CI, 0.527–0.930 [P=0.014]). In studies of patients who received propofol anesthesia, 445 of 1874 (23.7%) patients randomized to RIPC developed AKI compared with 474 of 1901 (24.9%) who underwent a sham procedure. The RR for AKI was 0.928 (95% CI, 0.781–1.102; P=0.39) for RIPC versus sham. There was no significant interaction between the two subgroups (P=0.098).

Conclusions

RIPC does not reduce morbidity or mortality in patients undergoing cardiac surgery with cardiopulmonary bypass. In the subgroup of studies in which propofol was not used, a reduction in AKI was seen, suggesting that propofol may interact with the protective effects of RIPC. Future studies should evaluate RIPC in the absence of propofol anesthesia.

[Cardioprotection via the arm? : How a blood pressure cuff decreases infarct sizes]

Cardiovascular diseases and especially myocardial infarctions are responsible for a high morbidity and mortality throughout Europe. An essential aspect of myocardial infarction is ischemia/reperfusion injury which represents the necrosis of myocytes following reperfusion. One possible option to counteract ischemia/reperfusion injury is the much researched process of remote ischemic conditioning (RIC), whereby a certain tissue (e.g. skeletal muscle) is subjected to several cycles of short periods (e.g. 5 min) of ischemia and reperfusion and leads to the protection of another organ (e.g. the heart). Despite substantial efforts to elucidate the underlying mechanisms during the last decades, this phenomenon is not yet completely understood. Clinical studies mainly concentrated on laboratory and radiological parameters, which led to better understanding of RIC; however, large clinical studies evaluating the possible influence on mortality are still lacking. This review article provides an introduction to RIC and summarizes the current understanding of known pathomechanisms and the results of important clinical studies.

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.

Novel Treatments in Neuroprotection for Aneurysmal Subarachnoid Hemorrhage

OPINION STATEMENT

New neuroprotective treatments aimed at preventing or minimizing "delayed brain injury" are attractive areas of investigation and hold the potential to have substantial beneficial effects on aneurysmal subarachnoid hemorrhage (aSAH) survivors. The underlying mechanisms for this "delayed brain injury" are multi-factorial and not fully understood. The most ideal treatment strategies would have the potential for a pleotropic effect positively modulating multiple implicated pathophysiological mechanisms at once. My personal management (RFJ) of patients with aneurysmal subarachnoid hemorrhage closely follows those treatment recommendations contained in modern published guidelines. However, over the last 5 years, I have also utilized a novel treatment strategy, originally developed at the University of Maryland, which consists of a 14-day continuous low-dose intravenous heparin infusion (LDIVH) beginning 12 h after securing the ruptured aneurysm. In addition to its well-known anti-coagulant properties, unfractionated heparin has potent anti-inflammatory effects and through multiple mechanisms may favorably modulate the neurotoxic and neuroinflammatory processes prominent in aneurysmal subarachnoid hemorrhage. In my personal series of patients treated with LDIVH, I have found significant preservation of neurocognitive function as measured by the Montreal Cognitive Assessment (MoCA) compared to a control cohort of my patients treated without LDIVH (RFJ unpublished data presented at the 2015 AHA/ASA International Stroke Conference symposium on neuroinflammation in aSAH and in abstract format at the 2015 AANS/CNS Joint Cerebrovascular Section Annual Meeting). It is important for academic physicians involved in the management of these complex patients to continue to explore new treatment options that may be protective against the potentially devastating "delayed brain injury" following cerebral aneurysm rupture. Several of the treatment options included in this review show promise and could be carefully adopted as the level of evidence for each improves. Other proposed neuroprotective treatments like statins and magnesium sulfate were previously thought to be very promising and to varying degrees were adopted at numerous institutions based on somewhat limited human evidence. Recent clinical trials and meta-analysis have shown no benefit for these treatments, and I currently no longer utilize either treatment as prophylaxis in my practice.

Protection of remote ischemic preconditioning against acute kidney injury: a systematic review and meta-analysis

Background

Remote ischemic preconditioning (RIPC) is a promising approach to preventing acute kidney injury (AKI), but its efficacy is controversial.

Methods

A systematic review of 30 randomized controlled trials was conducted to investigate the effects of RIPC on the incidence and outcomes of AKI. Random effects model meta-analyses and meta-regressions were used to generate summary estimates and explore sources of heterogeneity. The primary outcome was incidence of AKI and hospital mortality.

Results

The total pooled incidence of AKI in the RIPC group was 11.5 %, significantly less than the 23.3 % incidence in the control group (P = 0.009). Subgroup analyses indicated that RIPC significantly reduced the incidence of AKI in the contrast-induced AKI (CI-AKI) subgroup from 13.5 % to 6.5 % (P = 0.000), but not in the ischemia/reperfusion-induced AKI (IR-AKI) subgroup (from 29.5 % to 24.7 %, P = 0.173). Random effects meta-regression indicated that RIPC tended to strengthen its renoprotective effect (q = 3.95, df = 1, P = 0.047) in these trials with a higher percentage of diabetes mellitus. RIPC had no significant effect on the incidence of stages 1–3 AKI or renal replacement therapy, change in serum creatinine and estimated glomerular filtration rate (eGFR), hospital or 30-day mortality, or length of hospital stay. But RIPC significantly increased the minimum eGFR in the IR-AKI subgroup (P = 0.006) compared with the control group. In addition, the length of ICU stay in the RIPC group was significantly shorter than in the control group (2.6 vs 2.0 days, P = 0.003).

Conclusions

We found strong evidence to support the application of RIPC to prevent CI-AKI, but not IR-AKI.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1272-y) contains supplementary material, which is available to authorized users.

Effect of remote ischemic preconditioning on postoperative acute kidney injury among patients undergoing cardiac and vascular interventions: a meta-analysis

It is currently controversial whether remote ischemic preconditioning (RIPC) reduces the incidence of acute kidney injury (AKI) in patients undergoing cardiovascular interventions. The main objective of this meta-analysis was to investigate whether RIPC provides renal protection for patients undergoing cardiac or vascular surgery. We searched the PubMed database (1966-Oct 2015), Embase database (1966-Oct 2015), Google Scholar, Cochrane Library, ClinicalTrials Database and Open Grey. Then we conducted a meta-analysis of the randomized controlled trials that met the inclusion criteria of our study. The interventions included use of an inflatable tourniquet around the limbs or cross-clamping of the iliac arteries before surgery (RIPC groups) and general cardiovascular intervention (control groups). The main outcomes examined included the incidence of AKI; changes in acute kidney injury biomarkers; and use of renal replacement therapy. Other outcomes examined included in-hospital mortality and the lengths of hospital stay and intensive care unit (ICU) stay. Finally, we screened 26 eligible studies containing 6699 patients who underwent cardiac or vascular interventions with RIPC (n = 3343) or without RIPC (n = 3356). The AKI incidence was decreased in the RIPC group as was the length of ICU stay. There were no differences in the changes in AKI biomarkers, use of renal replacement therapy or in-hospital mortality between the two groups. Remote ischemic preconditioning may decrease the occurrence of AKI in cardiovascular surgery patients. Since studies included have a significant heterogeneity, meta-analyses using a stricter inclusion criteria are needed to clarify the renoprotection effect of RIPC.

Remote preconditioning and cardiac surgery: regrouping after Remote Ischemic Preconditioning for Heart Surgery (RIPHeart) and Effect of Remote Ischemic Preconditioning on Clinical Outcomes in Patients Undergoing Coronary Artery Bypass Surgery (ERICCA)

Remote ischaemic preconditioning (RIPC) is an attractive cardioprotective strategy. Although results from animal studies and phase II study on humans are convincing, it cannot have a role in clinical practice until benefits in clinical outcomes are proven in phase III study. Two phase III studies were recently published [Remote Ischemic Preconditioning for Heart Surgery (RIPHeart) and Effect of Remote Ischemic Preconditioning on Clinical Outcomes in Patients Undergoing Coronary Artery Bypass Surgery (ERICCA)] and this article discusses their design, results and implications.

[Neuroprotective and nephroprotective effects of remote postconditioning: Prospects for clinical use]

The results of experimental and clinical studies strongly suggest that remote ischemic preconditioning (RIP) has no neuroprotective effect during cardiac surgery performed under extracorporeal circulation. Remote preconditioning (RP) has no neuroprotective effect in hemorrhagic stroke. A randomized multicenter study is needed to evaluate the efficiency RIP in patients with ischemic stroke. RP reduces the severity of ischemia/reperfusion kidney injury during transplantation. RIP has been established to prevent contrast-induced nephropathy. There is a need for a multicenter trial to evaluate the efficiency of RIP in patients with abdominal aortic aneurysm repair. Analysis of the presented data indicates that RIP fails to prevent cardiorenal syndrome in infants and children during cardiac surgery. The data available in the literature on the capacity of RIP to provide nephroprotective effect in patients after coronary artery bypass surgery are discordant and indicative of the advisability of a multicenter study.

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.

Marked protection against acute renal and hepatic injury after nitrited myoglobin + tin protoporphyrin administration

The phenomenon known as renal "ischemic preconditioning," whereby an initial ischemic insult induces resistance against subsequent kidney damage, has been well established in the experimental literature. However, a clinically applicable way to safely recapitulate this state has not been defined. We hypothesized that a unique combination of agents (nitrited myoglobin [N-Mgb] + tin protoporphyrin [SnPP]) can achieve these ends safely and synergistically, increasing cytoprotective proteins (eg, heme oxygenase 1 [HO-1], interleukin 10 [IL-10], and haptoglobin) in kidney cells. To test this hypothesis, CD-1 mice received 1 mg of N-Mgb and 1 μmol of SnPP, either alone or in combination. Renal cortical HO-1, haptoglobin, and IL-10 gene expressions (messenger RNA [mRNA], protein levels) were determined 4 and 18 hours later. Cytoresistance to 3 forms of acute kidney injury (AKI; glycerol-induced rhabdomyolysis, maleate nephrotoxicity, and postischemic AKI progression to chronic kidney disease [CKD]) was assessed. To ascertain whether cytoresistance might emerge in extrarenal organs, hepatic HO-1, IL-10, and haptoglobin levels were also measured, and resistance to 25 minutes of hepatic ischemia-reperfusion injury and hepatotoxicity (intraperitoneal glycerol injection) was sought. N-Mgb + SnPP induced additive or synergistic increases in renal HO-1, haptoglobin, and IL-10 mRNA and protein levels (up to 20-fold) without inducing any apparent renal or extrarenal damage. After 18 hours of post-treatment, marked or complete protection against glycerol-induced AKI, maleate-induced AKI, and postischemic AKI progression to CKD had emerged. Combined N-Mgb + SnPP was more protective than either agent alone (assessed in glycerol model). N-Mgb + SnPP also upregulated cytoprotective pathways in liver and induced marked protection against both hepatic ischemia-reperfusion and toxic liver damage. In conclusion, we posit that "preconditioning" with combined administration of N-Mgb + SnPP represents a promising approach for protecting against diverse forms of renal and nonrenal (hepatic) forms of tissue damage.

Cardioprotection by remote ischemic conditioning: Mechanisms and clinical evidences

In remote ischemic conditioning (RIC), several cycles of ischemia and reperfusion render distant organ and tissues more resistant to the ischemia-reperfusion injury. The intermittent ischemia can be applied before the ischemic insult in the target site (remote ischemic preconditioning), during the ischemic insult (remote ischemic perconditioning) or at the onset of reperfusion (remote ischemic postconditioning). The mechanisms of RIC have not been completely defined yet; however, these mechanisms must be represented by the release of humoral mediators and/or the activation of a neural reflex. RIC has been discovered in the heart, and has been arising great enthusiasm in the cardiovascular field. Its efficacy has been evaluated in many clinical trials, which provided controversial results. Our incomplete comprehension of the mechanisms underlying the RIC could be impairing the design of clinical trials and the interpretation of their results. In the present review we summarize current knowledge about RIC pathophysiology and the data about its cardioprotective efficacy.

Renoprotective Mechanism of Remote Ischemic Preconditioning Based on Transcriptomic Analysis in a Porcine Renal Ischemia Reperfusion Injury Model

Ischemic preconditioning (IPC) is a well-known phenomenon in which tissues are exposed to a brief period of ischemia prior to a longer ischemic event. This technique produces tissue tolerance to ischemia reperfusion injury (IRI). Currently, IPC’s mechanism of action is poorly understood. Using a porcine single kidney model, we performed remote IPC with renal IRI and evaluated the IPC mechanism of action. Following left nephrectomy, 15 female Yorkshire pigs were divided into three groups: no IPC and 90 minutes of warm ischemia (control), remote IPC immediately followed by 90 minutes of warm ischemia (rIPCe), and remote IPC with 90 minutes of warm ischemia performed 24 hours later (rIPCl). Differential gene expression analysis was performed using a porcine-specific microarray. The microarray analysis of porcine renal tissues identified 1,053 differentially expressed probes in preconditioned pigs. Among these, 179 genes had altered expression in both the rIPCe and rIPCl groups. The genes were largely related to oxidation reduction, apoptosis, and inflammatory response. In the rIPCl group, an additional 848 genes had altered expression levels. These genes were primarily related to immune response and inflammation, including those coding for cytokines and cytokine receptors and those that play roles in the complement system and coagulation cascade. In the complement system, the membrane attack complex was determined to be sublytic, because it colocalized with phosphorylated extracellular signal-regulated kinase. Furthermore, alpha 2 macroglobulin, tissue plasminogen activator, uterine plasmin trypsin inhibitor, and arginase-1 mRNA levels were elevated in the rIPCl group. These findings indicate that remote IPC produces renoprotective effects through multiple mechanisms, and these effects develop over a long timeframe rather than immediately following IPC.

Remote Ischemic Preconditioning Fails to Benefit Pediatric Patients Undergoing Congenital Cardiac Surgery: A Meta-Analysis of Randomized Controlled Trials

Remote ischemic preconditioning (RIPC) has been proven to reduce the ischemia-reperfusion injury. However, its effect on children receiving congenital cardiac surgery (CCS) was inconsistent. We therefore performed the current meta-analysis of randomized controlled trials (RCTs) to comprehensively evaluate the effect of RIPC in pediatric patients undergoing CCS.PubMed, Embase, and Cochrane library were searched to identify RCTs assessing the effect of RIPC in pediatric patients undergoing CCS. The outcomes included the duration of mechanical ventilation (MV), intensive care unit (ICU) length of stay, postoperative cardiac troponin (cTnI) level, hospital length of stay (HLOS), postoperative inotropic score, and mortality. Subgroup and sensitivity analysis were also performed as predesigned. The meta-analysis was performed with random-effects model despite of heterogeneity. Sensitivity and subgroup analysis were predesigned to identify the robustness of the pooled estimate.Nine RCTs with 697 pediatric patients were included in the meta-analysis. Overall, RIPC failed to alter clinical outcomes of duration of MV (standard mean difference [SMD] -0.03, 95% confidence interval [CI] -0.23-0.17), ICU length of stay (SMD -0.22, 95% CI -0.47-0.04), or HLOS (SMD -0.14, 95% CI -0.55-0.26). Additionally, RIPC could not reduce postoperative cTnI (at 4-6 hours: SMD -0.25, 95% CI -0.73-0.23; P = 0.311; at 20-24 hours: SMD 0.09, 95% CI -0.51-0.68; P = 0.778) or postoperative inotropic score (at 4-6 hours: SMD -0.19, 95% CI -0.51-0.14; P = 0.264; at 24 hours: SMD -0.15, 95% CI -0.49-0.18; P = 0.365).RIPC may have no beneficial effects in children undergoing CCS. However, this finding should be interpreted with caution because of heterogeneity and large-scale RCTs are still needed.

Remote Ischemic Conditioning for Preventing Contrast-Induced Acute Kidney Injury in Patients Undergoing Percutaneous Coronary Interventions/Coronary Angiography: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

It is uncertain whether remote ischemic conditioning (RIC) has a protective effect on contrast-induced acute kidney injury (CI-AKI) after percutaneous coronary intervention (PCI)/coronary artery angiography (CAG). We performed a meta-analysis of randomized controlled trials (RCTs) to assess the effect of RIC on CI-AKI in such patients.

METHODS

PubMed, MEDLINE, EMBASE, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials databases were searched for RCTs that assessed the effect of RIC on CI-AKI in patients undergoing PCI/CAG.

RESULTS

Ten RCTs with 1389 patients (RIC group, 757 and control, 632) were included. The RIC group significantly exerted a lower risk of CI-AKI compared to the controls (odds ratio [OR] = 0.52, 95% confidence interval [CI] = 0.34-0.77, P = .001), and they had the similar effect on major adverse cardiovascular events within 1 year (OR = 0.36, 95% CI = 0.20-0.66, P < .001). The RIC reduced the rates of death within 30 days, but this was not significant (OR = 0.16, 95% CI = 0.02-1.34, P = .091). The RIC was associated with a significantly lower incidence of CI-AKI in patients following elective PCI/CAG (OR = 0.54, 95% CI = 0.33-0.87, P = .011). The RIC before not after the intervention was effective in reducing the occurrence of CI-AKI (OR: 0.37 vs 1.05, P = .022). The RIC of the upper arm has statistically significant effect on protecting CI-AKI but not that of the lower limb (OR: 0.41 vs 1.41, P = .004). The effect of RIC on CI-AKI was similar between patients with a mean estimated glomerular filtration rate <60 mL/min/1.73 m(2) and those with mean rates ≥60 (OR: 0.23 vs 0.41, P = .333).

CONCLUSION

The RIC reduced the incidence of CI-AKI in those receiving PCI/CAG. And RIC of the upper arm significantly reduced the risk of CI-AKI but not RIC of the lower limb in patients undergoing PCI/CAG.

Remote ischemic preconditioning (RIPC) modifies the plasma proteome in children undergoing repair of tetralogy of fallot: a randomized controlled trial

BACKGROUND

Remote ischemic preconditioning (RIPC) has been applied in paediatric cardiac surgery. We have demonstrated that RIPC induces a proteomic response in plasma of healthy volunteers. We tested the hypothesis that RIPC modifies the proteomic response in children undergoing Tetralogy of Fallot (TOF) repair.

METHODS AND RESULTS

Children (n=40) were randomized to RIPC and control groups. Blood was sampled at baseline, after cardiopulmonary bypass (CPB) and 6, 12 and 24h post-CPB. Plasma was analysed by liquid chromatography mass spectrometry (LC-MS) in an untargeted approach. Peptides demonstrating differential expression (p<0.01) were subjected to tandem LC-MS/MS and protein identification. Corresponding proteins were identified using the NCBI protein database. There was no difference in age (7.3±3.5vs6.8±3.6 months)(p=0.89), weight (7.7±1.8vs7.5±1.9 kg)(p=0.71), CPB time (104±7vs94±7 min)(p=0.98) or aortic cross-clamp time (83±22vs75±20 min)(p=0.36). No peptides were differentially expressed at baseline or immediately after CPB. There were 48 peptides with higher expression in the RIPC group 6h post-CPB. This was no longer evident at 12 or 24h, with one peptide down-regulated in the RIPC group. The proteins identified were: inter-alpha globulin inhibitor (42.0±11.8 vs 820.8±181.1, p=0.006), fibrinogen preproprotein (59.3±11.2 vs 1192.6±278.3, p=0.007), complement-C3 precursor (391.2±160.9 vs 5385.1±689.4, p=0.0005), complement C4B (151.5±17.8 vs 4587.8±799.2, p=0.003), apolipoprotein B100 (53.4±8.3 vs 1364.5±278.2, p=0.005) and urinary proteinase inhibitor (358.6±74.9 vs 5758.1±1343.1, p=0.009). These proteins are involved in metabolism, haemostasis, immunity and inflammation.

CONCLUSIONS

We provided the first comprehensive analysis of RIPC-induced proteomic changes in children undergoing surgery. The proteomic changes peak 6h post-CPB and return to baseline within 24h of surgery.

TRIAL REGISTRATION

ACTR.org.au ACTRN12610000496011.

Remote ischaemic preconditioning: is it a flag on the field?

Ischaemic preconditioning is one of several different techniques that have been proposed to render the heart more resistant to ischaemia/reperfusion injuries. A significant reduction of troponin release is ‘proof of concept’, however, whether ischaemic preconditioning leads to improved clinical outcomes is still to be proven. Moreover, the exact mechanism of action still remains unknown since very few studies have investigated the signal transmission in humans.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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