Controlled reperfusion after ischemia may be the unifying recovery denominator

Protection of multiple ischemic organs by controlled reperfusion

Reperfusion injury (RI) is a harmful complication that takes place during recanalization treatment of ischemic organs. Currently, there are no efficacious treatments for protecting the organs against RI. Therefore, it is necessary to discover new strategies to prevent RI. As a novel intervention technique, controlled reperfusion has promising effects on protecting multiple organs from RI, and it is done by adjusting physical parameters of blood flow or chemical compositions of the reperfusion liquid. In this brief review, the status of various controlled reperfusion methods is presented, as well as their application in the protection of ischemic organs.

Controlling Reperfusion Injury With Controlled Reperfusion: Historical Perspectives and New Paradigms

Cardiac reperfusion injury is a well-established outcome following treatment of acute myocardial infarction and other types of ischemic heart conditions. Numerous cardioprotection protocols and therapies have been pursued with success in pre-clinical models. Unfortunately, there has been lack of successful large-scale clinical translation, perhaps in part due to the multiple pathways that reperfusion can contribute to cell death. The search continues for new cardioprotection protocols based on what has been learned from past results. One class of cardioprotection protocols that remain under active investigation is that of controlled reperfusion. This class consists of those approaches that modify, in a controlled manner, the content of the reperfusate or the mechanical properties of the reperfusate (e.g., pressure and flow). This review article first provides a basic overview of the primary pathways to cell death that have the potential to be addressed by various forms of controlled reperfusion, including no-reflow phenomenon, ion imbalances (particularly calcium overload), and oxidative stress. Descriptions of various controlled reperfusion approaches are described, along with summaries of both mechanistic and outcome-oriented studies at the pre-clinical and clinical phases. This review will constrain itself to approaches that modify endogenously-occurring blood components. These approaches include ischemic postconditioning, gentle reperfusion, controlled hypoxic reperfusion, controlled hyperoxic reperfusion, controlled acidotic reperfusion, and controlled ionic reperfusion. This review concludes with a discussion of the limitations of past approaches and how they point to potential directions of investigation for the future.

Donor Heart Preservation with Hydrogen Sulfide: A Systematic Review and Meta-Analysis

Preclinical studies have shown that postconditioning with hydrogen sulfide (H2S) exerts cardioprotective effects against myocardial ischemia-reperfusion injury (IRI). The aim of this study was to appraise the current evidence of the cardioprotective effects of H2S against IRI in order to explore the future implementation of H2S in clinical cardiac transplantation. The current literature on H2S postconditioning in the setting of global myocardial ischemia was systematically reviewed and analyzed, performing meta-analyses. A literature search of the electronic databases Medline, Embase and Cinahl identified 1835 studies that were subjected to our pre-defined inclusion criteria. Sixteen studies were considered eligible for inclusion. Postconditioning with H2S showed significant robust effects with regard to limiting infarct size (standardized mean difference (SMD) = -4.12, 95% CI [-5.53--2.71], p < 0.00001). Furthermore, H2S postconditioning consistently resulted in a significantly lower release of cardiac injury markers, lower levels of oxidative stress and improved cardiac function. Postconditioning with slow-releasing H2S donors offers a valuable opportunity for novel therapies within cardiac preservation for transplantation. Before clinical implication, studies evaluating the long-term effects of H2S treatment and effects of H2S treatment in large animal studies are warranted.

Acute Aortic Occlusion and Its Sequelae: Metabolic, Pathologic Etiology, and Management

Acute occlusion of the abdominal aorta is a catastrophic occurrence that results in high risk of limb loss and death. The etiology has historically been either acute embolism obstructing the aortic bifurcation in 8% to 75% of patients, or thrombosis of existing aorta-iliac occlusive disease in 35% to 84% of patients. Other etiologies include thrombosis of either a previously placed endograft or aortic graft or acute dissection. The most common symptoms are severe pain in almost 100% of patients or lower extremity paralysis/paresis in up to 80% of patients. Evaluation in the past was by angiography, but presently, computed tomography angiography is the preferred imaging study. Treatment is dependent on the etiology and includes embolectomy, aorta femoral bypass, axillary femoral bypass, and endovascular techniques. The aim of intervention is to restore flow in the shortest time period. Mortality rates vary widely from 17% to 52%, amputation occurs in up to 30% of patients. Paraplegia can occur in 40% of patients, renal insufficiency in 40% to 70%, and visceral ischemia in 6% to 14%. Both mortality and morbidity are affected by the duration of ischemia and the local and systemic complications of reperfusion injury. Complications of acute aortic occlusion can be reduced by a more prompt diagnosis, rapid intervention, and a more rapid and complete reestablishment of perfusion.

Effect of Mean Blood Pressure During Extracorporeal Life Support on Outcome After Out-of-Hospital Cardiac Arrest

Objective

Extracorporeal Life Support (ECLS) can help to improve the outcome of refractory cardiac arrest (CA). ECLS allows to maintain blood pressure and tissue perfusion until the cause of CA is treated. The aim of the present study was to describe the mean blood pressure (MBP) during the first 24 h of ECLS for out-of-hospital CA (OHCA).

Methods

We performed a retrospective analysis of consecutive refractory OHCA requiring ECLS admitted to the intensive care unit. MBP was examined after starting ECLS (H0) and every 6 h during the first 24 h (H6, H12, H18 and H24).

Results

Forty patients were analysed. MBP significantly differs between survivors and non-survivors since 6 h: 77 vs 44 mm Hg (p=0.002), 51 vs 87 mm Hg at H12 (p=0.008), 57 vs 75 mm Hg at H18 (p=0.015) and 79 vs 53 mm Hg at H24 (p=0.004), whereas no difference was observed at H0: 69 vs 55 mm Hg (p=0.06). An MBP lower than 65 mm Hg since 6 h is associated with a poor outcome (sensitivity and specificity of death of 87% and 66% at H6, 80% and 75% at H12, 100% and 75% at H18 and 70% and 80% at H24, respectively).

Conclusion

Despite high levels of catecholamine, the inability to maintain MBP higher than 60 mm Hg after starting ECLS for OHCA is associated with a poor outcome.

Differential Effects of Normoxic and Hyperoxic Reperfusion on Global Myocardial Ischemia-Reperfusion Injury

The objectives were to investigate if after hypoxia or ischemia, normoxic reperfusion is associated with less oxidant stress (OS), inflammation, and myocardial injury than hyperoxic reperfusion. In this study, cardiomyocytes (H9c2 cells) were cultured in hypoxia, followed by reoxygenation in normoxia or hyperoxia. Cardiomyocyte OS, inflammation, and apoptosis were measured. In parallel experiments, rabbits were cannulated for cardiopulmonary bypass (CPB). Following cardioplegic arrest and aortic cross-clamp removal, hearts were reperfused under normoxic or hyperoxic conditions. Left ventricular developed pressure and contractility (LV +dP/dt) were recorded, and blood samples and heart tissues were collected for measurement of OS, inflammation, and cardiac injury. Results showed that H9c2 cells exposed to hyperoxic reoxygenation showed significant increases in OS, inflammation, and apoptosis compared to normoxic reoxygenation. Following CPB and 2-hour hyperoxic reperfusion, LV +dP/dt and left ventricular developed pressure were significantly decreased compared with pre-CPB values (to 36 ± 21%, P = 0.002; and 53 ± 20%, P = 0.02, respectively), associated with significant increases in all plasma and tissue biomarkers for OS, inflammation, and myocardial injury. In contrast, LV +dP/dt was relatively well preserved under normoxic reperfusion conditions (to 70 ± 14% after 2-hour reperfusion), and was associated with an attenuated myocardial OS, inflammatory, apoptotic, and injury response compared to the hyperoxia group (eg, cTn-I: 5.9 ± 1.5 vs 20.2 ± 7.6 ng/mL, respectively, P < 0.0001). Overall, in both in vitro and in vivo experiments, normoxic reperfusion/reoxygenation was associated with less robust OS, inflammation, apoptosis, and myocardial injury compared with hyperoxic reperfusion/reoxygenation. These results suggest that hyperoxia should be avoided to minimize myocardial OS, inflammation, and ventricular dysfunction after CPB.

Extracorporeal Life Support Increases Survival After Prolonged Ventricular Fibrillation Cardiac Arrest in the Rat

Background:

Extracorporeal life support (ECLS) for cardiopulmonary resuscitation (CPR) may increase end organ perfusion and thus survival when conventional CPR fails. The aim was to investigate, if after ventricular fibrillation cardiac arrest in rodents ECLS improves outcome compared with conventional CPR.

Methods:

In 24 adult male Sprague–Dawley rats (460–510 g) resuscitation was started after 10 min of no-flow with ECLS (consisting of an open reservoir, roller pump, and membrane oxygenator, connected to cannulas in the jugular vein and femoral artery, n = 8) or CPR (mechanical chest compressions plus ventilations, n = 8) and compared with a sham group (n = 8). After return of spontaneous circulation (ROSC), all rats were maintained at 33°C for 12 h. Survival to 14 days, neurologic deficit scores and overall performance categories were assessed.

Results:

ECLS leads to sustained ROSC in 8 of 8 (100%) and neurological intact survival to 14 days in 7 of 8 rats (88%), compared with 5 of 8 (63%) and 1 of 8 CPR rats. The median survival time was 14 days (IQR: 14–14) in the ECLS and 1 day (IQR: 0 to 5) for the CPR group (P = 0.004).

Conclusion:

In a rat model of prolonged ventricular fibrillation cardiac arrest, ECLS with mild hypothermia produces 100% resuscitability and 88% long-term survival, significantly better than conventional CPR.

Ischemia Reperfusion Injury after Gradual versus Rapid Flow Restoration for Middle Cerebral Artery Occlusion Rats

Ischemia-reperfusion injury (IRI) is an important cause of adverse prognosis after recanalization in patients with acute occlusion of major intracranial artery (AOMIA). Here, we provided data indicating that gradual flow restoration (GFR) would be superior to rapid flow restoration (RFR) in alleviating cerebral IRIs in middle cerebral artery occlusion (MCAO) rats. A total of 94 MCAO rats with 15, 30 and 60-minute occlusion were randomly assigned to receive either GFR or RFR intervention. There were significant differences between GFR and RFR group in mean neurological severity score (1.02 versus 1.28; p < 0.05), median infarct ratio (0.016 versus 0.12; p < 0.001), median neuronal apoptosis ratio (1.81 versus 14.46; p < 0.001), and mean histopathological abnormality score (0.92 versus 1.66; p < 0.001). In addition, these differences were mainly distributed in 30-minute and 60-minute occlusion rats, not in 15-minute occlusion rats. These results indicated that GFR rather than RFR could effectively alleviate cerebral IRIs in MCAO rats, especially in rats with longer occlusion duration, suggesting that GFR may be particularly applicable to AOMIA patients who are presented to neurointerventionalists in the later-time of recanalization therapy window.

Controlled automated reperfusion of the whole body after 120 minutes of Cardiopulmonary resuscitation: first clinical report

BACKGROUND

Cardiopulmonary resuscitation (CPR) is associated with a high mortality rate. Furthermore, the few survivors often have severe, persistent cerebral dysfunction. A potential cause for this unsatisfactory outcome after CPR is the combination of cardiac arrest (ischemia) and the inability to restore adequate hemodynamics during conventional CPR (reperfusion), resulting in ischemia/reperfusion injury of the whole body. Therefore we developed a concept counteracting this ischemia/reperfusion injury during the process of CPR.

CASE PRESENTATION

We present data from a patient, in whom the concept of a novel controlled automated reperfusion of the whole body (CARL) was applied after 120 min of CPR under normothermic conditions. The patient survived without cerebral deficits and showed full recovery of all organs after prolonged cardiac arrest (CA) except for the spinal cord, where a defect at the level of the 11th thoracic vertebra caused partial loss of motoric function of the legs.

CONCLUSION

This is the first reported clinical application of CARL after CA. The implementation of CARL resulted in unexpected survival and recovery after prolonged normothermic CA and CPR. In synopsis with the preclinical experience in pigs this case shows, that the new concept of CARL treating ischemia/reperfusion during the CPR may be an important element within the future treatment of CA.

TRIAL REGISTRATION

Trial was retrospectively registered in the "German Clinical Trials Register" ( www.germanctr.de ) under No.: DRKS00005773 on July 28th, 2015.

Delayed low pressure at reperfusion: A new approach for cardioprotection

OBJECTIVES

The aims of this study were to evaluate whether the delayed application of low-pressure reperfusion could reduce lethal reperfusion injury and whether the inhibition of the opening of the mitochondrial permeability transition pore is involved in this protection.

METHODS

Isolated rat hearts (n = 120) underwent 40 minutes of global ischemia followed by 60 minutes of reperfusion. Hearts were randomly assigned to the following groups: control, postconditioning (comprising 2 episodes of 30 seconds of ischemia and 30 seconds of reperfusion), and low-pressure reperfusion (using a reduction of perfusion pressure at 70 cm H2O for 10 minutes). In additional groups, postconditioning and low-pressure reperfusion were applied after a delay of 3, 10, and 20 minutes after the initial 40-minute ischemic insult.

RESULTS

As expected, infarct size (triphenyltetrazolium chloride staining) and lactate dehydrogenase release were significantly reduced in low-pressure reperfusion and postconditioning versus controls (P < .01), whereas functional parameters (coronary flow, rate pressure product) were improved (P < .01). Although delaying postconditioning by more than 3 minutes resulted in a loss of protection, low-pressure reperfusion still significantly reduced infarct size when applied as late as 20 minutes after reperfusion. This delayed low-pressure reperfusion protection was associated with an improved mitochondrial respiration, lower reactive oxygen species production, and enhanced calcium retention capacity, related to inhibition of permeability transition pore opening.

CONCLUSIONS

We demonstrated for the first time that low-pressure reperfusion can reduce lethal myocardial reperfusion injury even when performed 10 to 20 minutes after the initiation of reperfusion.

Cardiac arrest: resuscitation and reperfusion

The modern treatment of cardiac arrest is an increasingly complex medical procedure with a rapidly changing array of therapeutic approaches designed to restore life to victims of sudden death. The 2 primary goals of providing artificial circulation and defibrillation to halt ventricular fibrillation remain of paramount importance for saving lives. They have undergone significant improvements in technology and dissemination into the community subsequent to their establishment 60 years ago. The evolution of artificial circulation includes efforts to optimize manual cardiopulmonary resuscitation, external mechanical cardiopulmonary resuscitation devices designed to augment circulation, and may soon advance further into the rapid deployment of specially designed internal emergency cardiopulmonary bypass devices. The development of defibrillation technologies has progressed from bulky internal defibrillators paddles applied directly to the heart, to manually controlled external defibrillators, to automatic external defibrillators that can now be obtained over-the-counter for widespread use in the community or home. But the modern treatment of cardiac arrest now involves more than merely providing circulation and defibrillation. As suggested by a 3-phase model of treatment, newer approaches targeting patients who have had a more prolonged cardiac arrest include treatment of the metabolic phase of cardiac arrest with therapeutic hypothermia, agents to treat or prevent reperfusion injury, new strategies specifically focused on pulseless electric activity, which is the presenting rhythm in at least one third of cardiac arrests, and aggressive post resuscitation care. There are discoveries at the cellular and molecular level about ischemia and reperfusion pathobiology that may be translated into future new therapies. On the near horizon is the combination of advanced cardiopulmonary bypass plus a cocktail of multiple agents targeted at restoration of normal metabolism and prevention of reperfusion injury, as this holds the promise of restoring life to many patients for whom our current therapies fail.

Effects of antegrade versus integrated blood cardioplegia on left ventricular function evaluated by echocardiographic real-time 3-dimensional speckle tracking

OBJECTIVE

The objective of this study was to evaluate left ventricular free wall and interventricular septal function by 2-dimensional transthoracic echocardiography and live/real-time 3-dimensional transthoracic speckle tracking echocardiography before and after on-pump cardiac surgery and to assess the effect of mode of cardioplegia delivery.

METHODS

A total of 22 patients were studied 1 day before and 4 to 5 days after surgery. Cold blood cardioplegia was delivered by intermittent antegrade infusion or by the integrated method. The latter includes a combination of intermittent antegrade and retrograde cardioplegia with a terminal warm amino acid-enriched reperfusion.

RESULTS

The overall group displayed significant deterioration of septal function after surgery by 2-dimensional transthoracic echocardiography, as assessed by wall motion score index, yet subgroup analysis by 3-dimensional transthoracic speckle tracking echocardiography permitted distinction of outcomes achieved by antegrade or integrated delivery methods. Analysis after surgery showed that only the antegrade group displayed statistically significant deterioration in the strain parameters of some of the segments of the septum and free wall when strain was measured in the free wall and septum in the longitudinal, circumferential, and radial modes of deformation (P < .05). In contrast, only the integrated group displayed significant improvement in global radial, circumferential, and longitudinal strain (P < .05).

CONCLUSIONS

These findings by 3-dimensional transthoracic speckle tracking echocardiography indicate that integrated cardioplegia offers superior myocardial protection of the left ventricular free wall and septum compared with the antegrade mode of cardioplegia delivery.

Primary endpoints of the biventricular pacing after cardiac surgery trial

BACKGROUND

This study sought to determine whether optimized biventricular pacing increases cardiac index in patients at risk of left ventricular dysfunction after cardiopulmonary bypass. Procedures included coronary artery bypass, aortic or mitral surgery and combinations. This trial was approved by the Columbia University Institutional Review Board and was conducted under an Investigational Device Exemption.

METHODS

Screening of 6,346 patients yielded 47 endpoints. With informed consent, 61 patients were randomized to pacing or control groups. Atrioventricular and interventricular delays were optimized 1 (phase I), 2 (phase II), and 12 to 24 hours (phase III) after bypass in all patients. Cardiac index was measured by thermal dilution in triplicate. A 2-sample t test assessed differences between groups and subgroups.

RESULTS

Cardiac index was 12% higher (2.83±0.16 [standard error of the mean] vs 2.52±0.13 liters/minute/square meter) in the paced group, less than predicted and not statistically significant (p=0.14). However, when aortic and aortic-mitral surgery groups were combined, cardiac index increased 29% in the paced group (2.90±0.19, n=14) versus controls (2.24±0.15, n=11) (p=0.0138). Using a linear mixed effects model, t-test revealed that mean arterial pressure increased with pacing versus no pacing at all optimization points (phase I 79.2±1.7 vs 74.5±1.6 mm Hg, p=0.008; phase II 75.9±1.5 vs 73.6±1.8, p=0.006; phase III 81.9±2.8 vs 79.5±2.7, p=0.002).

CONCLUSIONS

Cardiac index did not increase significantly overall but increased 29% after aortic valve surgery. Mean arterial pressure increased with pacing at 3 time points. Additional studies are needed to distinguish rate from resynchronization effects, emphasize atrioventricular delay optimization, and examine clinical benefits of temporary postoperative pacing.