Failure of remote ischemic preconditioning to reduce the risk of postoperative acute kidney injury in children undergoing operation for complex congenital heart disease: a randomized single-center study

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.

Clinical usage of ischemic tolerance-where are its limits?

Ischemic tolerance is a robust internal defense mechanism of all living organisms. The effectiveness of this mechanism has been repeatedly demonstrated in experiments, but a comprehensive review of the clinical applicability of this phenomenon in practice has not yet been published. The results in clinical practice sound ambiguous and unconvincing in comparison with the results of experimental studies. Also, in many localities, the effect of ischemic tolerance was not clinically proven. For the reasons mentioned, the authors analyze the possible causes of the mentioned discrepancies and provide a comprehensive insight into the possible relevant clinical use of this phenomenon in practice for different groups of patients.

Randomized controlled trial of remote ischemic preconditioning in children having cardiac surgery

BACKGROUND

Children undergoing cardiac surgery are at risk for acute kidney injury (AKI) and cardiac dysfunction. Opportunity exists in protecting end organ function with remote ischemic preconditioning. We hypothesize this intervention lessens kidney and myocardial injury.

METHODS

We conducted a randomized, double blind, placebo controlled trial of remote ischemic preconditioning in children undergoing cardiac surgery. Pre-specified end points are change in creatinine, estimated glomerular filtration rate, development of AKI, B-type natriuretic peptide and troponin I at 6, 12, 24, 48, 72 h post separation from bypass.

RESULTS

There were 45 in the treatment and 39 patients in the control group, median age of 3.5 and 3.8 years, respectively. There were no differences between groups in creatinine, cystatin C, eGFR at each time point. There was a trend for a larger rate of decrease, especially for cystatin C (p = 0.042) in the treatment group but the magnitude was small. AKI was observed in 21 (54%) of control and 16 (36%) of treatment group (p = 0.094). Adjusting for baseline creatinine, the odds ratio for AKI in treatment versus control was 0.31 (p = 0.037); adjusting for clinical characteristics, the odds ratio was 0.34 (p = 0.056). There were no differences in natriuretic peptide or troponin levels between groups. All secondary end points of clinical outcomes were not different.

CONCLUSIONS

There is suggestion of RIPC delivering some kidney protection in an at-risk pediatric population. Larger, higher risk population studies will be required to determine its efficacy. Trial registration and date: Clinicaltrials.gov NCT01260259; 2021.

Acute Microcirculatory Effects of Remote Ischemic Conditioning in Superficial Partial Thickness Burn Wounds

Microcirculation is a critical factor in burn wound healing. Remote ischemic conditioning (RIC) has been shown to improve microcirculation in healthy skin and demonstrated ischemic protective effects on heart, kidney, and liver cells. Therefore, we examined microcirculatory effects of RIC in partial thickness burn wounds. The hypothesis of this study is that RIC improves cutaneous microcirculation in partial thickness burn wounds. Twenty patients with partial thickness burn wounds within 48 hours after trauma were included in this study. RIC was performed with an upper arm blood pressure cuff on a healthy upper arm using three ischemia cycles (5 min inflation to 200 mm Hg) followed by 10-minute reperfusion phases. The third and final reperfusion phase lasted 20 minutes. Microcirculation of the remote (lower/upper extremities or torso) burn wound was continuously quantified, using a combined Laser Doppler and white light spectrometry. The capillary blood flow in the burn wounds increased by a maximum of 9.6% after RIC (percentage change from baseline; P < .01). Relative hemoglobin was increased by a maximum of 2.8% (vs. baseline; P < .01), while cutaneous tissue oxygen saturation remained constant (P > .05). RIC improves microcirculation in partial thickness burn wounds by improving blood flow and elevating relative hemoglobin.

Is Renal Ischemic Preconditioning an Alternative to Ameliorate the Short- and Long-Term Consequences of Acute Kidney Injury?

Acute kidney injury (AKI) is a global health problem and has recently been recognized as a risk factor for developing chronic kidney disease (CKD). Unfortunately, there are no effective treatments to reduce or prevent AKI, which results in high morbidity and mortality rates. Ischemic preconditioning (IPC) has emerged as a promising strategy to prevent, to the extent possible, renal tissue from AKI. Several studies have used this strategy, which involves short or long cycles of ischemia/reperfusion (IR) prior to a potential fatal ischemic injury. In most of these studies, IPC was effective at reducing renal damage. Since the first study that showed renoprotection due to IPC, several studies have focused on finding the best strategy to activate correctly and efficiently reparative mechanisms, generating different modalities with promising results. In addition, the studies performing remote IPC, by inducing an ischemic process in distant tissues before a renal IR, are also addressed. Here, we review in detail existing studies on IPC strategies for AKI pathophysiology and the proposed triggering mechanisms that have a positive impact on renal function and structure in animal models of AKI and in humans, as well as the prospects and challenges for its clinical application.

Remote ischemic preconditioning and clinical outcomes after pediatric cardiac surgery: a systematic review and meta-analysis

BACKGROUND

The benefit of remote ischemia preconditioning (RIPreC) in pediatric cardiac surgery is unclear. The objective of this systematic review and meta-analysis was to examine the effectiveness of RIPreC in reducing the duration of mechanical ventilation and intensive care unit (ICU) length of stay after pediatric cardiac surgery.

METHODS

We searched PubMed, EMBASE and the Cochrane Library from inception to December 31, 2022. Randomized controlled trials comparing RIPreC versus control in children undergoing cardiac surgery were included. The risk of bias of included studies was assessed using the Risk of Bias 2 (RoB 2) tool. The outcomes of interest were postoperative duration of mechanical ventilation and ICU length of stay. We conducted random-effects meta-analysis to calculate weighted mean difference (WMD) with 95% confidence interval (CI) for the outcomes of interest. We performed sensitivity analysis to examine the influence of intraoperative propofol use.

RESULTS

Thirteen trials enrolling 1,352 children were included. Meta-analyses of all trials showed that RIPreC did not reduce postoperative duration of mechanical ventilation (WMD -5.35 h, 95% CI -12.12-1.42) but reduced postoperative ICU length of stay (WMD -11.48 h, 95% CI -20.96- -2.01). When only trials using propofol-free anesthesia were included, both mechanical ventilation duration (WMD -2.16 h, 95% CI -3.87- -0.45) and ICU length of stay (WMD -7.41 h, 95% CI -14.77- -0.05) were reduced by RIPreC. The overall quality of evidence was moderate to low.

CONCLUSIONS

The effects of RIPreC on clinical outcomes after pediatric cardiac surgery were inconsistent, but both postoperative mechanical ventilation duration and ICU length of stay were reduced in the subgroup of children not exposed to propofol. These results suggested a possible interaction effect of propofol. More studies with adequate sample size and without intraoperative propofol use are needed to define the role of RIPreC in pediatric cardiac surgery.

Remote ischaemic conditioning in necrotising enterocolitis: a phase I feasibility and safety study

OBJECTIVE

Remote ischaemic conditioning (RIC) improves the outcome of experimental necrotising enterocolitis (NEC) by preserving intestinal microcirculation. The feasibility and safety of RIC in preterm infants with NEC are unknown. The study aimed to assess the feasibility and safety of RIC in preterm infants with suspected or confirmed NEC.

DESIGN

Phase I non-randomised pilot study conducted in three steps: step A to determine the safe duration of limb ischaemia (up to 4 min); step B to assess the safety of 4 repeated cycles of ischaemia-reperfusion at the maximum tolerated duration of ischaemia determined in step A; step C to assess the safety of applying 4 cycles of ischaemia-reperfusion on two consecutive days.

SETTING

Level III neonatal intensive care unit, The Hospital for Sick Children (Toronto, Canada).

PATIENTS

Fifteen preterm infants born between 22 and 33 weeks gestational age.

INTERVENTION

Four cycles of ischaemia (varying duration) applied to the limb via a manual sphygmomanometer, followed by reperfusion (4 min) and rest (5 min), repeated on two consecutive days.

OUTCOMES

The primary outcomes were (1) feasibility defined as RIC being performed as planned in the protocol, and (2) safety defined as perfusion returning to baseline within 4 min after cuff deflation.

RESULTS

Four cycles/day of limb ischaemia (4 min) followed by reperfusion (4 min) and a 5 min gap, repeated on two consecutive days was feasible and safe in all neonates with suspected or confirmed NEC.

CONCLUSIONS

This study is pivotal for designing a future randomised controlled trial to assess the efficacy of RIC in preterm infants with NEC.

TRIAL REGISTRATION NUMBER

NCT03860701.

Advances in Neonatal Acute Kidney Injury

In this state-of-the-art review, we highlight the major advances over the last 5 years in neonatal acute kidney injury (AKI). Large multicenter studies reveal that neonatal AKI is common and independently associated with increased morbidity and mortality. The natural course of neonatal AKI, along with the risk factors, mitigation strategies, and the role of AKI on short- and long-term outcomes, is becoming clearer. Specific progress has been made in identifying potential preventive strategies for AKI, such as the use of caffeine in premature neonates, theophylline in neonates with hypoxic-ischemic encephalopathy, and nephrotoxic medication monitoring programs. New evidence highlights the importance of the kidney in "crosstalk" between other organs and how AKI likely plays a critical role in other organ development and injury, such as intraventricular hemorrhage and lung disease. New technology has resulted in advancement in prevention and improvements in the current management in neonates with severe AKI. With specific continuous renal replacement therapy machines designed for neonates, this therapy is now available and is being used with increasing frequency in NICUs. Moving forward, biomarkers, such as urinary neutrophil gelatinase-associated lipocalin, and other new technologies, such as monitoring of renal tissue oxygenation and nephron counting, will likely play an increased role in identification of AKI and those most vulnerable for chronic kidney disease. Future research needs to be focused on determining the optimal follow-up strategy for neonates with a history of AKI to detect chronic kidney disease.

Strategies to Prevent Acute Kidney Injury after Pediatric Cardiac Surgery: A Network Meta-Analysis

BACKGROUND AND OBJECTIVES

AKI is a common complication after pediatric cardiac surgery and has been associated with higher morbidity and mortality. We aimed to compare the efficacy of available pharmacologic and nonpharmacologic strategies to prevent AKI after pediatric cardiac surgery.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

PubMed/MEDLINE, Embase, Cochrane Controlled Trials Register, and reference lists of relevant articles were searched for randomized controlled trials from inception until August 2020. Random effects traditional pairwise, Bayesian network meta-analyses, and trial sequential analyses were performed.

RESULTS

Twenty randomized controlled trials including 2339 patients and 11 preventive strategies met the eligibility criteria. No overall significant differences were observed compared with control for corticosteroids, fenoldopam, hydroxyethyl starch, or remote ischemic preconditioning in traditional pairwise meta-analysis. In contrast, trial sequential analysis suggested a 80% relative risk reduction with dexmedetomidine and evidence of <57% relative risk reduction with remote ischemic preconditioning. Nonetheless, the network meta-analysis was unable to demonstrate any significant differences among the examined treatments, including also acetaminophen, aminophylline, levosimendan, milrinone, and normothermic cardiopulmonary bypass. Surface under the cumulative ranking curve probabilities showed that milrinone (76%) was most likely to result in the lowest risk of AKI, followed by dexmedetomidine (70%), levosimendan (70%), aminophylline (59%), normothermic cardiopulmonary bypass (57%), and remote ischemic preconditioning (55%), although all showing important overlap.

CONCLUSIONS

Current evidence from randomized controlled trials does not support the efficacy of most strategies to prevent AKI in the pediatric population, apart from limited evidence for dexmedetomidine and remote ischemic preconditioning.

Which remote ischemic preconditioning protocol is favorable in renal ischemia-reperfusion injury in the rat?

BACKGROUND

The optimal timing of remote ischemic preconditioning (RIPC) in renal ischemia-reperfusion (I/R) injury is still unclear. We aimed to compare early- and delayed-effect RIPC with hematological, microcirculatory and histomorphological parameters.

METHODS

In anesthetized male CrI:WI Control rats (n = 7) laparotomy and femoral artery cannulation were performed. In I/R group (n = 7) additionally a 45-minute unilateral renal ischemia with 120-minute reperfusion was induced. The right hind-limb was strangulated for 3×10 minutes (10-minute intermittent reperfusion) 1 hour (RIPC-1 group, n = 7) or 24 hour (RIPC-24 group, n = 6) prior to the I/R. Hemodynamic, hematological parameters and organs' surface microcirculation were measured.

RESULTS

Control and I/R group had the highest heart rate (p < 0.05 vs base), while the lowest mean arterial pressure (p < 0.05 vs RIPC-1) were found in the RIPC-24 group. The highest microcirculation values were measured in the I/R group (liver: p < 0.05 vs Control). The leukocyte count increased in I/R group (base: p < 0.05 vs Control), also this group's histological score was the highest (p < 0.05 vs Control). The RIPC-24 group had a significantly lower score than the RIPC-1 (p = 0.0025 vs RIPC-1).

CONCLUSION

Renal I/R caused significant functional and morphological, also in the RIPC groups. According to the histological examination the delayed-effect RIPC method was more effective.

Cardiac protective effects of remote ischaemic preconditioning in children undergoing tetralogy of fallot repair surgery: a randomized controlled trial

Aims

Remote ischaemic preconditioning (RIPC) by inducing brief ischaemia in distant tissues protects the heart against myocardial ischaemia-reperfusion injury (IRI) in children undergoing open-heart surgery, although its effectiveness in adults with comorbidities is controversial. The effectiveness and mechanism of RIPC with respect to myocardial IRI in children with tetralogy of Fallot (ToF), a severe cyanotic congenital cardiac disease, undergoing open heart surgery are unclear. We hypothesized that RIPC can confer cardioprotection in children undergoing ToF repair surgery.

Methods and results

Overall, 112 ToF children undergoing radical open cardiac surgery using cardiopulmonary bypass (CPB) were randomized to either a RIPC group (n = 55) or a control group (n = 57). The RIPC protocol consisted of three cycles of 5-min lower limb occlusion and 5-min reperfusion using a cuff-inflator. Serum inflammatory cytokines and cardiac injury markers were measured before surgery and after CPB. Right ventricle outflow tract (RVOT) tissues were collected during the surgery to assess hypoxia-inducible factor (Hif)-1α and other signalling proteins. Cardiac mitochondrial injury was assessed by electron microscopy. The primary results showed that the length of stay in the intensive care unit (ICU) was longer in the control group than in the RIPC group (52.30 ± 13.43 h vs. 47.55 ± 10.34 h, respectively, P = 0.039). Patients in the control group needed longer post-operative ventilation time compared to the RIPC group (35.02 ± 6.56 h vs. 31.96 ± 6.60 h, respectively, P = 0.016). The levels of post-operative serum troponin-T at 12 and 18 h, CK-MB at 24 h, as well as the serum h-FABP levels at 6 h, after CPB were significantly lower, which was coincident with significantly higher protein expression of cardiac Hif-1α, p-Akt, p-STAT3, p-STAT5, and p-eNOS and less vacuolization of mitochondria in the RIPC group compared to the control group.

Conclusion

In ToF children undergoing open heart surgery, RIPC attenuates myocardial IRI and improves the short-term prognosis.

Acute kidney injury after pediatric cardiac surgery

Acute kidney injury (AKI) is a common complication of pediatric cardiac surgery and is associated with increased morbidity and mortality. Literature of AKI after pediatric cardiac surgery is comprehensively reviewed in terms of incidence, risk factors, biomarkers, treatment and prognosis. The novel RIFLE (pediatric RIFLE for pediatrics), Acute Kidney Injury Network (AKIN) and Kidney Disease Improving Global Outcomes (KDIGO) criteria have brought about unified diagnostic standards and comparable results for AKI after cardiac surgery. Numerous risk factors, either renal or extrarenal, can be responsible for the development of AKI after cardiac surgery, with low cardiac output syndrome being the most pronounced predictor. Early fluid overload is also crucial for the occurrence of AKI and prognosis in pediatric patients. Three sensitive biomarkers, neutrophil gelatinase-associated lipocalin, cystatin C (CysC) and liver fatty acid-binding protein, are regarded as the earliest (increase at 2-4 h), and another two, kidney injury molecule-1 and interleukin-18 represent the intermediate respondents (increase at 6-12 h after surgery). To ameliorate the cardiopulmonary bypass techniques, improve renal perfusion and eradicate the causative risk factors are imperative for the prevention of AKI in pediatric patients. The early and intermediate biomarkers are helpful for an early judgment of occurrence of postoperative AKI. Improved survival has been achieved by prevention, renal support and modifications of hemofiltration techniques. Further development is anticipated in small children.

Prevention of Acute Kidney Injury in Children Undergoing Cardiac Surgery: A Narrative Review

Children undergoing cardiac surgery are at risk of developing acute kidney injury (AKI). Preventing cardiac surgery-associated AKI (CS-AKI) is important as it is associated with increased early- and long-term mortality and morbidity. Targeting modifiable risk factors (eg, avoiding poor renal perfusion, nephrotoxic drugs, and fluid overload) reduces the risk of CS-AKI. There is currently no strong evidence for the routine use of pharmacological approaches (eg, aminophylline, dexmedetomidine, fenoldopam, and steroids) to prevent CS-AKI. There is robust evidence to support the role of early peritoneal dialysis as a nonpharmacologic approach to prevent CS-AKI.

Differences in acute kidney injury ascertainment for clinical and preclinical studies

Background

Acute kidney injury (AKI) is a common clinical condition directly associated with adverse outcomes. Several AKI biomarkers have been discovered, but their use in clinical and preclinical studies has not been well examined. This study aims to investigate the differences between clinical and preclinical studies on AKI biomarkers.

Methods

We performed a systematic review of clinical and preclinical interventional studies that considered AKI biomarkers in enrollment criteria and/or outcome assessment and described the main differences according to their setting, the inclusion of biomarkers in the definition of AKI and the use of biomarkers as primary or secondary end points.

Results

In the 151 included studies (76 clinical, 75 preclinical), clinical studies have prevalently focused on cardiac surgery (38.1%) and contrast-associated AKI (17.1%), while the majority of preclinical studies have focused on ether ischemia-reperfusion injury or drug-induced AKI (42.6% each). A total of 57.8% of clinical studies defined AKI using the standard criteria and only 19.7% of these studies used AKI biomarkers in the definition of renal injury. Conversely, the majority of preclinical studies defined AKI according to the increase in serum creatinine and blood urea nitrogen, and 32% included biomarkers in that definition. The percentage of both clinical and preclinical studies with biomarkers as a primary end point has not significantly increased in the last 10 years; however, preclinical studies are more likely to use AKI biomarkers as a primary end point compared with clinical studies [odds ratio 2.31 (95% confidence interval 1.17-4.59); P  =  0.016].

Conclusion

Differences between clinical and preclinical studies are evident and may affect the translation of preclinical findings in the clinical setting.

Remote Ischemic Preconditioning Does Not Prevent White Matter Injury in Neonates

BACKGROUND

Remote ischemic preconditioning (RIPC) is a mechanism to protect tissues from injury during ischemia and reperfusion. We investigated the neuroprotective effects of RIPC in neonates undergoing cardiac surgery.

METHODS

The outcome was white matter injury (WMI), assessed by the change in volume of WMI from preoperative to postoperative brain magnetic resonance imaging (MRI). Patients were randomized to RIPC or SHAM. RIPC was induced prior to cardiopulmonary bypass by four 5-minute cycles of blood pressure cuff inflation to produce ischemia of the lower extremity. For patients randomized to SHAM, the cuff was positioned, but not inflated.

RESULTS

The study included 67 patients, with 33 randomized to RIPC and 34 randomized to SHAM. Preoperative and postoperative MRIs were available in 50 patients, including 26 of the 33 RIPC patients and 24 of the 34 SHAM patients. There were no differences in baseline and operative characteristics for either the overall study group or the group with evaluable MRIs. WMI was identified in 28% of the patients preoperatively and in 62% postoperatively. There was no difference in the prevalence of WMI by treatment group (p > 0.5). RIPC patients had an average change in WMI of 600 mL³, and SHAM subjects had an average WMI change of 107 mL³. There was no significant difference in the mean value of WMI change between patients who received RIPC and those who received SHAM treatments (p = 0.178).

CONCLUSIONS

In this randomized, blinded clinical trial, there was no evidence that use of RIPC provides neuroprotection in neonates undergoing repair of congenital heart defects with cardiopulmonary bypass.

Remote Ischemic Preconditioning has a Cardioprotective Effect in Children in the Early Postoperative Phase: A Meta-Analysis of Randomized Controlled Trials

In this updated meta-analysis, we assessed the cardioprotective effect of remote ischemic preconditioning (RIPC) in pediatric patients undergoing congenital heart surgery. A total of 9 randomized controlled trials (RCTs) involving 793 pediatric patients under 18 years old were identified. RIPC obviously reduced the release of troponin I at 6 h after surgery [standard mean difference (SMD) -0.59, 95% confidence interval (CI) -1.14 to -0.04; p = 0.03], mitigated the inotropic scores within 4-6 h (SMD -0.43, 95% CI -0.72 to -0.14; p = 0.004) and within 12 h (SMD -0.26, 95% CI -0.50 to -0.02; p = 0.03) and shortened the ventilator support time (SMD -0.28, 95% CI -0.49 to -0.07; p = 0.01) as well as the duration of intensive care unit (ICU) stay (SMD -0.21, 95% CI -0.35 to -0.06; p = 0.004). Our meta-analysis determined that RIPC had cardioprotective effects in the early postoperative phase. Additional RCTs focused on the cardiac benefits from RIPC in pediatric patients are warranted.

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.

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.

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.

Adenosine Receptor Activation in the "Trigger" Limb of Remote Pre-Conditioning Mediates Human Endothelial Conditioning and Release of Circulating Cardioprotective Factor(s)

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Pre-conditioning has emerged as a potentially powerful means of reducing ischemia-reperfusion injury.

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Several animal models have implicated adenosine in pre-conditioning pathways, but its role in human physiology is unknown.

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In human volunteers, the authors demonstrate that adenosine receptor activation in “trigger” tissue is an important step in initiating a pre-conditioning signal, but adenosine receptor blockade in “target” tissue does not block the protection afforded by pre-conditioning.

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The authors also demonstrate that pre-conditioning elaborates a transferrable cardioprotective factor(s) into the serum. This elaboration is prevented by adenosine receptor blockade but can be mirrored by the infusion of exogenous adenosine.

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An improved understanding of the physiological effectors of pre-conditioning may allow for better targeted clinical studies of pre-conditioning and pre-conditioning mimetics in the future.

Remote ischemic pre-conditioning (rIPC) has emerged as a potential mechanism to reduce ischemia-reperfusion injury. Clinical data, however, have been mixed, and its physiological basis remains unclear, although it appears to involve release of circulating factor(s) and/or neural pathways. Here, the authors demonstrate that adenosine receptor activation is an important step in initiating human pre-conditioning; that pre-conditioning liberates circulating cardioprotective factor(s); and that exogenous adenosine infusion is able to recapitulate release of this factor. However, blockade of adenosine receptors in ischemic tissue does not block the protection afforded by pre-conditioning. These data have important implications for defining the physiology of human pre-conditioning and its translation to future clinical trials.

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

OBJECTIVE

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

DATA SOURCES

We searched the PubMed database for relevant literature.

STUDY SELECTION AND DATA EXTRACTION

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

DATA SYNTHESIS AND CONCLUSIONS

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

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 ischemic conditioning for kidney protection: A meta-analysis

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Urinary apolipoprotein M as a biomarker of acute kidney injury in children undergoing heart surgery

Aim: To investigate whether apoM is excreted in urine of children undergoing heart surgery and the potential of apoM as early biomarker of acute kidney injury (AKI). Materials & methods: Urine was collected in children undergoing heart surgery. ApoM was measured with ELISA. U-apoM was characterized by gel filtration chromatography and western blotting. Results: ApoM was excreted into the urine 0–4 h postoperatively as the full-length apoM in particles smaller than plasma HDL. At 0 h, U-apoM predicted AKI with an area under the receiver-operating characteristics curve of 0.70 (p < 0.018). Sensitivity was 0.71 and specificity was 0.68 at a cutoff level at 1.45 nmol/l. Conclusion: ApoM is excreted in the urine of children after cardiac surgery. Its potential as biomarker of AKI deserves exploration.

[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.

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

AIM

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Molecular Mechanisms of Renal Ischemic Conditioning Strategies

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

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

INTRODUCTION

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

METHODS AND ANALYSIS

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

ETHICS AND DISSEMINATION

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

TRIAL REGISTRATION NUMBER

NCT01395719.

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

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

Multiorgan protection of remote ischemic perconditioning in valve replacement surgery

BACKGROUND

Remote ischemic perconditioning (RIPerc) is a new alternative of remote ischemic conditioning and has not been well studied. RIPerc attenuates myocardial injury when applied during cardiac surgery. However, its protective effects on other organs remain unknown.

MATERIALS AND METHODS

Patients with rheumatic heart disease undergoing valve replacement surgery were randomized into the RIPerc group (n = 101) or the control group (n = 100). RIPerc was achieved by three cycles of 5-min ischemia-5-min reperfusion in the right thigh during surgery. Clinical data and the levels of injury biomarkers for the heart, lungs, liver, and kidneys within 48 h after surgery were compared using one-way or repeated measurement analysis of variance.

RESULTS

In the RIPerc group, the release of serum cardiac troponin I (128.68 ± 102.56 versus 172.33 ± 184.38, P = 0.04) and the inotropic score (96.4 ± 73.8 versus 121.5 ± 89.6, P = 0.032) decreased compared with that of the control; postoperative drainage (458.2 ± 264.2 versus 545.1 ± 349.0 ml, P = 0.048) and the incidence of acute lung injury was reduced (36.6% versus 51%, P = 0.04), and the extent of hyperbilirubinemia was also attenuated. No significant difference was observed in the levels of biomarkers for renal injury and systemic inflammation response.

CONCLUSIONS

RIPerc applied during the valve replacement surgery induced multiple beneficial effects postoperatively including reduced drainage and myocardial damage, lower incidence of acute lung injury, and attenuated hyperbilirubinemia.

Remote ischemic preconditioning in children undergoing cardiac surgery with cardiopulmonary bypass: a single-center double-blinded randomized trial

Background

Remote ischemic preconditioning (RIPC) harnesses an innate defensive mechanism that protects against inflammatory activation and ischemia‐reperfusion injury, known sequelae of cardiac surgery with cardiopulmonary bypass. We sought to determine the impact of RIPC on clinical outcomes and physiological markers related to ischemia‐reperfusion injury and inflammatory activation after cardiac surgery in children.

Methods and Results

Overall, 299 children (aged neonate to 17 years) were randomized to receive an RIPC stimulus (inflation of a blood pressure cuff on the left thigh to 15 mm Hg above systolic for four 5‐minute intervals) versus a blinded sham stimulus during induction with a standardized anesthesia protocol. Primary outcome was duration of postoperative hospital stay, with serial clinical and laboratory measurements for the first 48 postoperative hours and clinical follow‐up to discharge. There were no significant baseline differences between RIPC (n=148) and sham (n=151). There were no in‐hospital deaths. No significant difference in length of postoperative hospital stay was noted (sham 5.4 versus RIPC 5.6 days; difference +0.2; adjusted P=0.91), with the 95% confidence interval (−0.7 to +0.9) excluding a prespecified minimal clinically significant differences of 1 or 1.5 days. There were few significant differences in other clinical outcomes or values at time points or trends in physiological markers. Benefit was not observed in specific subgroups when explored through interactions with categories of age, sex, surgery type, Aristotle score, or first versus second half of recruitment. Adverse events were similar (sham 5%, RIPC 6%; P=0.68).

Conclusions

RIPC is not associated with important improvements in clinical outcomes and physiological markers after cardiac surgery in children.

Clinical Trial Registration

URL: clinicaltrials.gov. Unique identifier: NCT00650507.

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

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

The Delay Phenomenon: A Compilation of Knowledge across Specialties

Objective The purpose of this article is to review and integrate the available literature in different fields to gain a better understanding of the basic physiology and optimize vascular delay as a reconstructive surgery technique. Methods A broad search of the literature was performed using the Medline database. Two queries were performed using "vascular delay," a search expected to yield perspectives from the field of plastic and reconstructive surgery, and "ischemic preconditioning," (IPC) which was expected to yield research on the same topic in other fields. Results The combined searches yielded a total of 1824 abstracts. The "vascular delay" query yielded 76 articles from 1984 to 2011. The "ischemic preconditioning" query yielded 6534 articles, ranging from 1980 to 2012. The abstracts were screened for those from other specialties in addition to reconstructive surgery, analyzed potential or current uses of vascular delay in practice, or provided developments in understanding the pathophysiology of vascular delay. 70 articles were identified that met inclusion criteria and were applicable to vascular delay or ischemic preconditioning. Conclusion An understanding of IPC's implementation and mechanisms in other fields has beneficial implications for the field of reconstructive surgery in the context of the delay phenomenon. Despite an incomplete model of IPC's pathways, the anti-oxidative, anti-apoptotic and anti-inflammatory benefits of IPC are well recognized. The activation of angiogenic genes through IPC could allow for complex flap design, even in poorly vascularized regions. IPC's promotion of angiogenesis and reduction of endothelial dysfunction remain most applicable to reconstructive surgery in reducing graft-related complications and flap failure.

Neutrophil gelatinase associated lipocalin in acute kidney injury

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Radiographic contrast-media-induced acute kidney injury: pathophysiology and prophylactic strategies

Contrast-induced acute kidney injury (CI-AKI) is one of the most widely discussed and debated topics in cardiovascular medicine. With increasing number of contrast-media- (CM-) enhanced imaging studies being performed and growing octogenarian population with significant comorbidities, incidence of CI-AKI remains high. In this review, pathophysiology of CI-AKI, its relationship with different types of CM, role of serum and urinary biomarkers for diagnosing CI-AKI, and various prophylactic strategies used for nephroprotection against CI-AKI are discussed in detail.