Pragmatic evaluation of events and benefits of lipid lowering in older adults (PREVENTABLE): Trial design and rationale

Whether initiation of statins could increase survival free of dementia and disability in adults aged ≥75 years is unknown. PREVENTABLE, a double-blind, placebo-controlled randomized pragmatic clinical trial, will compare high-intensity statin therapy (atorvastatin 40 mg) with placebo in 20,000 community-dwelling adults aged ≥75 years without cardiovascular disease, disability, or dementia at baseline. Exclusion criteria include statin use in the prior year or for >5 years and inability to take a statin. Potential participants are identified using computable phenotypes derived from the electronic health record and local referrals from the community. Participants will undergo baseline cognitive testing, with physical testing and a blinded lipid panel if feasible. Cognitive testing and disability screening will be conducted annually. Multiple data sources will be queried for cardiovascular events, dementia, and disability; survival is site-reported and supplemented by a National Death Index search. The primary outcome is survival free of new dementia or persisting disability. Co-secondary outcomes are a composite of cardiovascular death, hospitalization for unstable angina or myocardial infarction, heart failure, stroke, or coronary revascularization; and a composite of mild cognitive impairment or dementia. Ancillary studies will offer mechanistic insights into the effects of statins on key outcomes. Biorepository samples are obtained and stored for future study. These results will inform the benefit of statins for increasing survival free of dementia and disability among older adults. This is a pioneering pragmatic study testing important questions with low participant burden to align with the needs of the growing population of older adults.

Enhanced Oxygen Utilization Efficiency With Concomitant Activation of AMPK-TBC1D1 Signaling Nexus in Cyclophilin-D Conditional Knockout Mice

We have previously reported in HEK 293 T cells and in constitutive cyclophilin-D (Cyp-D) knockout (KO) mice that Cyp-D ablation downregulates oxygen consumption (VO₂) and triggers an adaptive response that manifest in higher exercise endurance with less VO₂. This adaptive response involves a metabolic switch toward preferential utilization of glucose via AMPK-TBC1D1 signaling nexus. We now investigated whether a similar response could be triggered in mice after acute ablation of Cyp-D using tamoxifen-induced ROSA26-Cre-mediated (i.e., conditional KO, CKO) by subjecting them to treadmill exercise involving five running sessions. At their first treadmill running session, CKO mice and controls had comparable VO₂ (208.4 ± 17.9 vs. 209.1 ± 16.8 ml/kg min⁻¹), VCO₂ (183.6 ± 17.2 vs. 184.8 ± 16.9 ml/kg min⁻¹), and RER (0.88 ± 0.043 vs. 0.88 ± 0.042). With subsequent sessions, CKO mice displayed more prominent reduction in VO₂ (genotype & session interaction p = 0.000) with less prominent reduction in VCO₂ resulting in significantly increased RER (genotype and session interaction p = 0.013). The increase in RER was consistent with preferential utilization of glucose as respiratory substrate (4.6 ± 0.8 vs. 4.0 ± 0.9 mg/min, p = 0.003). CKO mice also performed a significantly higher treadmill work for given VO₂ expressed as a power/VO₂ ratio (7.4 ± 0.2 × 10⁻³ vs. 6.7 ± 0.2 10⁻³ ratio, p = 0.025). Analysis of CKO skeletal muscle tissue after completion of five treadmill running sessions showed enhanced AMPK activation (0.669 ± 0.06 vs. 0.409 ± 0.11 pAMPK/β-tubulin ratio, p = 0.005) and TBC1D1 inactivation (0.877 ± 0.16 vs. 0.565 ± 0.09 pTBC1D1/β-tubulin ratio, p < 0.05) accompanied by increased glucose transporter-4 levels consistent with activation of the AMPK-TBC1D1 signaling nexus enabling increased glucose utilization. Taken together, our study demonstrates that like constitutive Cyp-D ablation, acute Cyp-D ablation also induces a state of increased O₂ utilization efficiency, paving the way for exploring the use of pharmacological approach to elicit the same response, which could be beneficial under O₂ limiting conditions.

Targeted Delivery of Electrical Shocks and Epinephrine, Guided by Ventricular Fibrillation Amplitude Spectral Area, Reduces Electrical and Adrenergic Myocardial Burden, Improving Survival in Swine

Background

We previously reported that resuscitation delivering electrical shocks guided by real‐time ventricular fibrillation amplitude spectral area (AMSA) enabled return of spontaneous circulation (ROSC) with fewer shocks, resulting in less myocardial dysfunction. We now hypothesized that AMSA could also guide delivery of epinephrine, expecting further outcome improvement consequent to less electrical and adrenergic burdens.

Methods and Results

A swine model of ventricular fibrillation was used to compare after 10 minutes of untreated ventricular fibrillation a guidelines‐driven (n=8) resuscitation protocol, delivering shocks every 2 minutes and epinephrine every 4 minutes, with an AMSA‐driven shocks (n=8) protocol, delivering epinephrine every 4 minutes, and with an AMSA‐driven shocks and epinephrine (ADSE; n=8) protocol. For guidelines‐driven, AMSA‐driven shocks, and ADSE protocols, the time to ROSC (mean±SD) was 569±164, 410±111, and 400±80 seconds (P=0.045); the number of shocks (mean±SD) was 5±2, 3±1, and 3±2 (P=0.024) with ADSE fewer than guidelines‐driven (P=0.03); and the doses of epinephrine (median [interquartile range]) were 2.0 (1.3–3.0), 1.0 (1.0–2.8), and 1.0 (0.3–3.0) (P=0.419). The ROSC rate was similar, yet survival after ROSC favored AMSA‐driven protocols (guidelines‐driven, 3/6; AMSA‐driven shocks, 6/6; and ADSE, 7/7; P=0.019 by log‐rank test). Left ventricular function and survival after ROSC correlated inversely with electrical burden (ie, cumulative unsuccessful shocks, J/kg; P=0.020 and P=0.046) and adrenergic burden (ie, total epinephrine doses, mg/kg; P=0.042 and P=0.002).

Conclusions

Despite similar ROSC rates achieved with all 3 protocols, AMSA‐driven shocks and ADSE resulted in less postresuscitation myocardial dysfunction and better survival, attributed to attaining ROSC with less electrical and adrenergic myocardial burdens.

Constitutive cyclophilin-D ablation in mice increases exercise and cognitive-behavioral performance under normoxic and hypoxic conditions

We recently reported that constitutive ablation of cyclophilin-D (Cyp-D) in mice reduces oxygen consumption (VO2) while paradoxically increasing exercise endurance, thereby demonstrating increased O2 utilization efficiency. This response was associated with augmented glucose uptake and glucose utilization, in part mediated through adenosine monophosphate-activated kinase signaling. We now hypothesized that Cyp-D knock-out (KO) mice might also exhibit improved cognitive-behavioral performance and that these favorable adaptive responses may persist under hypoxic conditions. We therefore assessed under normoxic (20.9% O2, simulating ground O2 levels) and hypoxic (8% O2, simulating 7600 m altitude O2 levels) conditions exercise capacity and cognitive-behavioral performance. We used a treadmill test to assess exercise capacity, a pole-test to assess agility, an elevated-plus-maze test to assess anti-anxiety, and a passive avoidance test to assess learning and memory retention. Compared to wild type, Cyp-D KO mice showed comparable treadmill work under normoxia (48 ± 12 vs 47 ± 9 Joules) but increased treadmill work (12 ± 1 vs 8 ± 1 Joules; p = 0.02) under hypoxia. Cyp-D KO mice displayed increased pole-descending time (17 ± 3 vs 8 ± 2 s; p ≤ 0.05) under normoxia but shorter pole-descending time (21 ± 3 vs 37 ± 4 s; p ≤ 0.01) under hypoxia. In addition, the Cyp-D KO mice demonstrated increased elevated plus-maze open arm time (91 ± 31 vs 23 ± 12 s; p ≤ 0.05) under hypoxia and increased latency to enter dark chamber (261 ± 23 vs 185 ± 42 s; p ≤ 0.05) under normoxia. Thus, our experiments showed that under normoxia Cyp-D KO mice displayed anti-anxiety behavior and improved learning and memory retention. Under hypoxia, Cyp-D KO mice displayed increased exercise capacity, increased agility, and increased anti-anxiety consistent with our previously reported findings of increased O2 utilization efficiency. Identifying interventions to elicit these effects could be beneficial in a myriad of physiological and clinical conditions in which increasing O2 utilization efficiency would be advantageous.

From a pressure-guided to a perfusion-centered resuscitation strategy in septic shock: Critical literature review and illustrative case

PURPOSE

To support a paradigm shift in the management of septic shock from pressure-guided to perfusion-centered, expected to improve outcome while reducing adverse effects from vasopressor therapy and aggressive fluid resuscitation.

MATERIAL AND METHODS

Critical review of the literature cited in support of vasopressor use to achieve a predefined mean arterial pressure (MAP) of 65 mmHg and review of pertinent clinical trials and studies enabling deeper understanding of the hemodynamic pathophysiology supportive of a perfusion-centered approach, accompanied by an illustrative case.

RESULTS

Review of the literature cited by the Surviving Sepsis Campaign revealed lack of controlled clinical trials supporting outcome benefits from vasopressors. Additional literature review revealed adverse effects associated with vasopressors and worsened outcome in some studies. Vasopressors increase MAP primarily by peripheral vasoconstriction and in occasions by a modest increase in cardiac output when using norepinephrine. Thus, achieving the recommended MAP of 65 mmHg using vasopressors should not be presumed indicative that organ perfusion has been restored. It may instead create a false sense of hemodynamic stability hampering shock resolution.

CONCLUSIONS

We propose focusing the hemodynamic management of septic shock on reversing organ hypoperfusion instead of attaining a predefined MAP target as the key strategy for improving outcome.

2019 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations: Summary From the Basic Life Support; Advanced Life Support; Pediatric Life Support; Neonatal Life Support; Education, Implementation, and Teams; and First Aid Task Forces

The International Liaison Committee on Resuscitation has initiated a continuous review of new, peer-reviewed, published cardiopulmonary resuscitation science. This is the third annual summary of the International Liaison Committee on Resuscitation International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. It addresses the most recent published resuscitation evidence reviewed by International Liaison Committee on Resuscitation Task Force science experts. This summary addresses the role of cardiac arrest centers and dispatcher-assisted cardiopulmonary resuscitation, the role of extracorporeal cardiopulmonary resuscitation in adults and children, vasopressors in adults, advanced airway interventions in adults and children, targeted temperature management in children after cardiac arrest, initial oxygen concentration during resuscitation of newborns, and interventions for presyncope by first aid providers. Members from 6 International Liaison Committee on Resuscitation task forces have assessed, discussed, and debated the certainty of the evidence on the basis of the Grading of Recommendations, Assessment, Development, and Evaluation criteria, and their statements include consensus treatment recommendations. Insights into the deliberations of the task forces are provided in the Justification and Evidence to Decision Framework Highlights sections. The task forces also listed priority knowledge gaps for further research.

Improved exercise capacity in cyclophilin-D knockout mice associated with enhanced oxygen utilization efficiency and augmented glucose uptake via AMPK-TBC1D1 signaling nexus

We previously reported in HEK 293T cells that silencing the mitochondrial peptidyl prolyl isomerase cyclophilin-D (Cyp-D) reduces Vo2. We now report that in vivo Cyp-D ablation using constitutive Cyp-D knockout (KO) mice also reduces Vo2 both at rest (∼15%) and during treadmill exercise (∼12%). Yet, despite Vo2 reduction, these Cyp-D KO mice ran longer (1071 ± 77 vs. 785 ± 79 m; P = 0.002), for longer time (43 ± 3 vs. 34 ± 3 min; P = 0.004), and at higher speed (34 ± 1 vs. 29 ± 1 m/s; P ≤ 0.001), resulting in increased work (87 ± 6 vs. 58 ± 6 J; P ≤ 0.001). There were parallel reductions in carbon dioxide production, but of lesser magnitude, yielding a 2.3% increase in the respiratory exchange ratio consistent with increased glucose utilization as respiratory substrate. In addition, primary skeletal muscle cells of Cyp-D KO mice subjected to electrical stimulation exhibited higher glucose uptake (4.4 ± 0.55 vs. 2.6 ± 0.04 pmol/mg/min; P ≤ 0.001) with enhanced AMPK activation (0.58 ± 0.06 vs. 0.38 ± 0.03 pAMPK/β-tubulin ratio; P ≤ 0.01) and TBC1 (Tre-2/USP6, BUB2, Cdc16) domain family, member 1 (TBC1D1) inactivation. Likewise, pharmacological activation of AMPK also increased glucose uptake (3.2 ± 0.3 vs. 2.3 ± 0.2 pmol/mg/min; P ≤ 0.001). Moreover, lactate and ATP levels were increased in these cells. Taken together, Cyp-D ablation triggered an adaptive response resulting in increased exercise capacity despite less oxygen utilization associated with increased glucose uptake and utilization involving AMPK-TBC1D1 signaling nexus.-Radhakrishnan, J., Baetiong, A., Kaufman, H., Huynh, M., Leschinsky, A., Fresquez, A., White, C., DiMario, J. X., Gazmuri, R. J. Improved exercise capacity in cyclophilin-D knockout mice associated with enhanced oxygen utilization efficiency and augmented glucose uptake via AMPK-TBC1D1 signaling nexus.

Chest compression components (rate, depth, chest wall recoil and leaning): A scoping review

AIM

To understand whether the science to date has focused on single or multiple chest compression components and identify the evidence related to chest compression components to determine the need for a full systematic review.

METHODS

This review was undertaken by members of the International Liaison Committee on Resuscitation and guided by a specific methodological framework and the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR). Studies were eligible for inclusion if they were peer-reviewed human studies that examined the effect of different chest compression depths or rates, or chest wall or leaning, on physiological or clinical outcomes. The databases searched were MEDLINE complete, Embase, and Cochrane.

RESULTS

Twenty-two clinical studies were included in this review: five observational studies involving 879 patients examined both chest compression rate and depth; eight studies involving 14,285 patients examined chest compression rate only; seven studies involving 12001 patients examined chest compression depth only, and two studies involving 1848 patients examined chest wall recoil. No studies were identified that examined chest wall leaning. Three studies reported an inverse relationship between chest compression rate and depth.

CONCLUSION

This scoping review did not identify sufficient new evidence that would justify conducting new systematic reviews or reconsideration of current resuscitation guidelines. This scoping review does highlight significant gaps in the research evidence related to chest compression components, namely a lack of high-level evidence, paucity of studies of in-hospital cardiac arrest, and failure to account for the possibility of interactions between chest compression components.

Plasma Cytochrome c Detection Using a Highly Sensitive Electrochemiluminescence Enzyme-Linked Immunosorbent Assay

Background

Cytochrome c is an intermembrane mitochondrial protein that is released to the bloodstream following mitochondrial injury.

Methods and results

We developed an electrochemiluminescence immunoassay to measure cytochrome c in human and rat plasma, which showed high sensitivity with broad dynamic range (2-1200 ng/mL in humans and 5-500 ng/mL in rat) and high assay reproducibility (inter-assay coefficient <6% in humans and <10% in rat). In patients after blunt trauma, plasma cytochrome c directly correlated with injury severity. In rats after cardiac resuscitation, plasma cytochrome c inversely correlated with survival and responsiveness to mitochondrial protective interventions.

Conclusions

The cytochrome c assays herein presented have high sensitivity, wide dynamic range, and high reproducibility well suited for biomarker of mitochondrial injury.

2017 American Heart Association Focused Update on Adult Basic Life Support and Cardiopulmonary Resuscitation Quality: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

Cardiopulmonary resuscitation is a lifesaving technique for victims of sudden cardiac arrest. Despite advances in resuscitation science, basic life support remains a critical factor in determining outcomes. The American Heart Association recommendations for adult basic life support incorporate the most recently published evidence and serve as the basis for education and training for laypeople and healthcare providers who perform cardiopulmonary resuscitation.

2017 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations Summary

The International Liaison Committee on Resuscitation has initiated a near-continuous review of cardiopulmonary resuscitation science that replaces the previous 5-year cyclic batch-and-queue approach process. This is the first of an annual series of International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations summary articles that will include the cardiopulmonary resuscitation science reviewed by the International Liaison Committee on Resuscitation in the previous year. The review this year includes 5 basic life support and 1 pediatric Consensuses on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Each of these includes a summary of the science and its quality based on Grading of Recommendations, Assessment, Development, and Evaluation criteria and treatment recommendations. Insights into the deliberations of the International Liaison Committee on Resuscitation task force members are provided in Values and Preferences sections. Finally, the task force members have prioritized and listed the top 3 knowledge gaps for each population, intervention, comparator, and outcome question.

Real-Time Ventricular Fibrillation Amplitude-Spectral Area Analysis to Guide Timing of Shock Delivery Improves Defibrillation Efficacy During Cardiopulmonary Resuscitation in Swine

Background

The ventricular fibrillation amplitude spectral area (AMSA) predicts whether an electrical shock could terminate ventricular fibrillation and prompt return of spontaneous circulation. We hypothesized that AMSA can guide more precise timing for effective shock delivery during cardiopulmonary resuscitation.

Methods and Results

Three shock delivery protocols were compared in 12 pigs each after electrically induced ventricular fibrillation, with the duration of untreated ventricular fibrillation evenly stratified into 6, 9, and 12 minutes: AMSA‐Driven (AD), guided by an AMSA algorithm; Guidelines‐Driven (GD), according to cardiopulmonary resuscitation guidelines; and Guidelines‐Driven/AMSA‐Enabled (GDAE), as per GD but allowing earlier shocks upon exceeding an AMSA threshold. Shocks delivered using the AD, GD, and GDAE protocols were 21, 40, and 62, with GDAE delivering only 2 AMSA‐enabled shocks. The corresponding 240‐minute survival was 8/12, 6/12, and 2/12 (log‐rank test, P=0.035) with AD exceeding GDAE (P=0.026). The time to first shock (seconds) was (median [Q1–Q3]) 272 (161–356), 124 (124–125), and 125 (124–125) (P<0.001) with AD exceeding GD and GDAE (P<0.05); the average coronary perfusion pressure before first shock (mm Hg) was 16 (9–30), 10 (6–12), and 3 (−1 to 9) (P=0.002) with AD exceeding GDAE (P<0.05); and AMSA preceding the first shock (mV·Hz, mean±SD) was 13.3±2.2, 9.0±1.6, and 8.6±2.0 (P<0.001) with AD exceeding GD and GDAE (P<0.001). The AD protocol delivered fewer unsuccessful shocks (ie, less shock burden) yielding less postresuscitation myocardial dysfunction and higher 240‐minute survival.

Conclusions

The AD protocol improved the time precision for shock delivery, resulting in less shock burden and less postresuscitation myocardial dysfunction, potentially improving survival compared with time‐fixed, guidelines‐driven, shock delivery protocols.

In vivo opening of the mitochondrial permeability transition pore in a rat model of ventricular fibrillation and closed-chest resuscitation

Opening of the mitochondrial permeability transition pore (mPTP) is considered central to reperfusion injury. Yet, most of our knowledge comes from observations in isolated mitochondria, cells, and organs. We used a rat model of ventricular fibrillation (VF) and closed-chest resuscitation to examine whether the mPTP opens in vivo and whether cyclosporine A (CsA) attenuates the associated myocardial injury. Two series of 26 and 18 rats each underwent 10 minutes of untreated VF before attempting resuscitation. In series-1, rats received 50 µCi of tritium-labeled 2-deoxyglucose ([³H]DOG) harvesting their hearts at baseline (n=5), during VF (n=5), during resuscitation (n=6), and at post-resuscitation 60 minutes (n=5) and 240 minutes (n=5). mPTP opening was estimated measuring the ratio of mitochondria to left ventricular intracellular [³H]. In series-2, rats received 10 mg/kg of CsA or vehicle before resuscitation, measuring mitochondrial NAD⁺ content to indirectly assess mPTP opening. In Series-1, the mPTP opening ratio vs baseline (10.4 ± 1.9) increased during VF (16.8 ± 2.4, NS), closed-chest resuscitation (20.8 ± 6.3, P<0.05), and at post-resuscitation 60 minutes (20.9 ± 4.7, P<0.05) and 240 minutes (25.7 ± 11.0, P<0.01). In series 2, CsA failed to attenuate reductions in mitochondrial NAD⁺ and did not affect plasma cytochrome c, plasma cardiac troponin I, myocardial function, and survival. We report for the first time in an intact rat model of VF that mPTP opens during closed-chest resuscitation consistent with previous observations in mitochondria, cells, and organs of mPTP opening upon reperfusion. CsA, at the dose of 10 mg/kg neither prevented mPTP opening nor attenuated post-resuscitation myocardial injury.

Early and sustained vasopressin infusion augments the hemodynamic efficacy of restrictive fluid resuscitation and improves survival in a liver laceration model of hemorrhagic shock

BACKGROUND

Current management of hemorrhagic shock favors restrictive fluid resuscitation before control of the bleeding source. We investigated the additional effects of early and sustained vasopressin infusion in a swine model of hemorrhagic shock produced by liver laceration.

METHODS

Forty male domestic pigs (32-40 kg) had a liver laceration inflicted with an X-shaped blade clamp, 32 received a second laceration at minute 7.5, and 24 received two additional lacerations at minute 15. Using a two-by-two factorial design, animals were randomized 1:1 to receive vasopressin infusion (0.04 U/kg per minute) or vehicle intraosseously from minute 7 until minute 240 and 1:1 to receive isotonic sodium chloride solution (12 mL/kg) intravenously at minute 30 or no fluids.

RESULTS

Kaplan-Meier curves showed greater survival after vasopressin with isotonic sodium chloride solution (8/10) compared to vasopressin without isotonic sodium chloride solution (4/10), vehicle with isotonic sodium chloride solution (3/10), or vehicle without isotonic sodium chloride solution (3/10), but the differences were not statistically significant (p = 0.095 by log-rank test). However, logistic regression showed vasopressin to elicit a statistically significant benefit on survival (p = 0.042). Vasopressin augmented mean aortic pressure between 10 and 20 mm Hg without intensifying the rate of bleeding from liver laceration, which was virtually identical to that of vehicle-treated animals (33.9 ± 5.1 and 33.8 ± 4.8 mL/kg). Vasopressin increased systemic vascular resistance and reduced transcapillary fluid extravasation, augmenting the volume of isotonic sodium chloride solution retained (6.5 ± 2.7 vs 2.4 ± 2.0 mL/kg by minute 60). The cardiac output and blood flow to the myocardium, liver, spleen, kidney, small bowel, and skeletal muscle at minute 120 and minute 180 were comparable or higher in the vasopressin group.

CONCLUSIONS

Early and sustained vasopressin infusion provided critical hemodynamic stability during hemorrhagic shock induced by liver laceration and increased the hemodynamic efficacy of restrictive fluid resuscitation without intensifying bleeding or compromising organ blood flow resulting in improved 240-minute survival.

Adherence to Evidence-Base Endotracheal Intubation Practice Patterns by Intensivists and Emergency Department Physicians

BACKGROUND

Endotracheal intubation outside the operating room (OR) is mainly performed by intensive care (IC) physicians and emergency department (ED) physicians. We hypothesized that difference in practice patterns exists between these two groups of physicians.

METHODS

A retrospective chart review was performed on all endotracheal intubations that were performed out of OR over a fi ve year period at our health care facility. Practice patterns of IC and ED physicians were compared regarding use of (a) video laryngoscopy, (b) paralytic agents, (c) waveform capnography, and (d) use of larger size of endotracheal tube (internal diameter ≥ 8 mm).

RESULTS

A total of 201 patients underwent out of OR intubations over a 5 year period. IC physicians used more often than ED physicians video laryngoscopy (67% vs. 49%; p = 0.008), waveform capnography (99% vs. 86%; p = 0.001) and larger size endotracheal tubes (95% vs. 60%; p < 0.001). Conversely, paralytic agents were used less frequently by IC than ED physicians (12% vs. 51%; p < 0.001). The success of fi rst intubation attempt was higher by IC than ED physicians (82% vs. 67%; p = 0.018).

CONCLUSIONS

IC physicians more often adhered to currently considered preferable practices for endotracheal intubation than ED physicians in this single center retrospective study. Although larger scale studies are needed to unveil the effects of different practice patterns on short and long term outcomes, the present study identifi es opportunity to bridge practice gaps that could lead to improved outcomes.

Characterization of mitochondrial injury after cardiac arrest (COMICA)

INTRODUCTION

Mitochondrial injury post-cardiac arrest has been described in pre-clinical settings but the extent to which this injury occurs in humans remains largely unknown. We hypothesized that increased levels of mitochondrial biomarkers would be associated with mortality and neurological morbidity in post-cardiac arrest subjects.

METHODS

We performed a prospective multicenter study of post-cardiac arrest subjects. Inclusion criteria were comatose adults who suffered an out-of-hospital cardiac arrest. Mitochondrial biomarkers were measured at 0, 12, 24, 36 and 48h after return of spontaneous circulation as well as in healthy controls.

RESULTS

Out of 111 subjects enrolled, 102 had evaluable samples at 0h. Cardiac arrest subjects had higher baseline cytochrome c levels compared to controls (2.18ng/mL [0.74, 7.74] vs. 0.16ng/mL [0.03, 0.91], p<0.001), and subjects who died had higher 0h cytochrome c levels compared to survivors (3.66ng/mL [1.40, 14.9] vs. 1.27ng/mL [0.16, 2.37], p<0.001). There were significantly higher Ribonuclease P (RNaseP) (3.3 [1.2, 5.7] vs. 1.2 [0.8, 1.2], p<0.001) and Beta-2microglobulin (B2M) (12.0 [1.0, 22.9], vs. 0.6 [0.6, 1.3], p<0.001) levels in cardiac arrest subjects at baseline compared to the control subjects. There were no differences between survivors and non-survivors for mitochondrial DNA, nuclear DNA, or cell free DNA.

CONCLUSIONS

Cytochrome c was increased in post- cardiac arrest subjects compared to controls, and in post-cardiac arrest non-survivors compared to survivors. Nuclear DNA and cell free DNA was increased in plasma of post-cardiac arrest subjects. There were no differences in mitochondrial DNA, nuclear DNA, or cell free DNA between survivors and non-survivors. Mitochondrial injury markers showed mixed results in the post-cardiac arrest period. Future research needs to investigate these differences.

Circulatory collapse, right ventricular dilatation, and alveolar dead space: A triad for the rapid diagnosis of massive pulmonary embolism

A triad of circulatory collapse, right ventricular dilatation, and large alveolar dead space is proposed for the rapid diagnosis and treatment of massive pulmonary embolism. A 17year-old female on oral contraceptives collapsed at home becoming incoherent with shallow breathing. Paramedics initiated mechanical chest compression and transported the patient to our emergency department, arriving minimally responsive with undetectable blood pressure but having positive corneal reflexes and bradycardia with wide QRS. The trachea was intubated and goal-directed echocardiography revealed marked right ventricular dilatation with septal flattening. The arterial PCO₂ was 40mmHg with an end-tidal PCO₂ of 8mmHg, revealing a large alveolar dead space. Persistent hypotension, bradycardia, and fading alertness despite epinephrine and norepinephrine infusions prompted resumption of chest compression. Intravenous alteplase (10mg bolus over 10min followed by 90mg over 110min) begun 125min after collapse improved hemodynamic function within 10min allowing discontinuation of chest compression. Five and a half hours after starting alteplase, the patient was hemodynamically stable and had normal end-tidal PCO₂. A CT-angiogram showed the pulmonary arteries free of emboli but a thrombus in the right common iliac vein. The patient recovered fully and was discharged home on warfarin 8days later. Based on this and other reports, we propose a triad of circulatory collapse, right ventricular dilatation, and large alveolar dead space for the rapid diagnosis and treatment of massive pulmonary embolism, with systemic fibrinolysis as the first-line intervention.

Adverse postresuscitation myocardial effects elicited by buffer-induced alkalemia ameliorated by NHE-1 inhibition in a rat model of ventricular fibrillation

Major myocardial abnormalities occur during cardiac arrest and resuscitation including intracellular acidosis-partly caused by CO₂ accumulation-and activation of the Na⁺-H⁺ exchanger isoform-1 (NHE-1). We hypothesized that a favorable interaction may result from NHE-1 inhibition during cardiac resuscitation followed by administration of a CO₂-consuming buffer upon return of spontaneous circulation (ROSC). Ventricular fibrillation was electrically induced in 24 male rats and left untreated for 8 min followed by defibrillation after 8 min of cardiopulmonary resuscitation (CPR). Rats were randomized 1:1:1 to the NHE-1 inhibitor zoniporide or vehicle during CPR and disodium carbonate/sodium bicarbonate buffer or normal saline (30 ml/kg) after ROSC. Survival at 240 min declined from 100% with Zoniporide/Saline to 50% with Zoniporide/Buffer and 25% with Vehicle/Buffer (P = 0.004), explained by worsening postresuscitation myocardial dysfunction. Marked alkalemia occurred after buffer administration along with lactatemia that was maximal after Vehicle/Buffer, attenuated by Zoniporide/Buffer, and minimal with Zoniporide/Saline [13.3 ± 4.8 (SD), 9.2 ± 4.6, and 2.7 ± 1.0 mmol/l; P ≤ 0.001]. We attributed the intense postresuscitation lactatemia to enhanced glycolysis consequent to severe buffer-induced alkalemia transmitted intracellularly by an active NHE-1. We attributed the worsened postresuscitation myocardial dysfunction also to severe alkalemia intensifying Na⁺ entry via NHE-1 with consequent Ca²⁺ overload injuring mitochondria, evidenced by increased plasma cytochrome c Both buffer-induced effects were ameliorated by zoniporide. Accordingly, buffer-induced alkalemia after ROSC worsened myocardial function and survival, likely through enhancing NHE-1 activity. Zoniporide attenuated these effects and uncovered a complex postresuscitation acid-base physiology whereby blood pH drives NHE-1 activity and compromises mitochondrial function and integrity along with myocardial function and survival.

Ubiquinol (reduced Coenzyme Q10) in patients with severe sepsis or septic shock: a randomized, double-blind, placebo-controlled, pilot trial

Introduction

We previously found decreased levels of Coenzyme Q10 (CoQ10) in patients with septic shock. The objective of the current study was to assess whether the provision of exogenous ubiquinol (the reduced form of CoQ10) could increase plasma CoQ10 levels and improve mitochondrial function.

Methods

We performed a randomized, double-blind, pilot trial at a single, tertiary care hospital. Adults (age ≥18 years) with severe sepsis or septic shock between November 2012 and January 2014 were included. Patients received 200 mg enteral ubiquinol or placebo twice a day for up to seven days. Blood draws were obtained at baseline (0 h), 12, 24, 48, and 72 h. The primary outcome of the study was change in plasma CoQ10 parameters (total CoQ10 levels, CoQ10 levels relative to cholesterol levels, and levels of oxidized and reduced CoQ10). Secondary outcomes included assessment of: 1) vascular endothelial biomarkers, 2) inflammatory biomarkers, 3) biomarkers related to mitochondrial injury including cytochrome c levels, and 4) clinical outcomes. CoQ10 levels and biomarkers were compared between groups using repeated measures models.

Results

We enrolled 38 patients: 19 in the CoQ10 group and 19 in the placebo group. The mean patient age was 62 ± 16 years and 47 % were female. Baseline characteristics and CoQ10 levels were similar for both groups. There was a significant increase in total CoQ10 levels, CoQ10 levels relative to cholesterol levels, and levels of oxidized and reduced CoQ10 in the ubiquinol group compared to the placebo group. We found no difference between the two groups in any of the secondary outcomes.

Conclusions

In this pilot trial we showed that plasma CoQ10 levels could be increased in patients with severe sepsis or septic shock, with the administration of oral ubiquinol. Further research is needed to address whether ubiquinol administration can result in improved clinical outcomes in this patient population.

Trial registration

Clinicaltrials.gov identifier NCT01948063. Registered on 18 February 2013.

Vasopressin Infusion with Small-Volume Fluid Resuscitation during Hemorrhagic Shock Promotes Hemodynamic Stability and Survival in Swine

Introduction

Current management of hemorrhagic shock (HS) in the battlefield and civilian settings favors small-volume fluid resuscitation before controlling the source of bleeding. We investigated in a swine model of HS the effects of vasopressin infusion along with small-volume fluid resuscitation; with erythropoietin (EPO) and HS severity as additional factors.

Methods

HS was induced in 24 male domestic pigs (36 to 41 kg) by blood withdrawal (BW) through a right atrial cannula modeling spontaneous bleeding by a mono-exponential decay function. The initial 12 pigs received no fluids; the last 12 pigs received normal saline (NS) half the BW volume. Pigs were randomized 2:1 to receive intraosseously vasopressin (0.04 U/kg·min^-1) or vehicle control from minute 7 to minute 210. Pigs assigned to vasopressin were further randomized 1:1 to receive EPO (1,200 U/kg) or vehicle control and 1:1 to have 65% or 75% BW of their blood volume. Shed blood was reinfused at 210 minutes and the pigs recovered from anesthesia.

Results

Survival at 72 hours was influenced by vasopressin and NS but not by EPO or % BW. Vasopressin with NS promoted the highest survival (8/8) followed by vasopressin without NS (3/8), NS without vasopressin (1/4), and neither treatment (0/4) with overall statistical significance (log-rank test, p = 0.009) and each subset different from vasopressin with NS by Holm-Sidak test. Vasopressin increased systemic vascular resistance whereas NS increased cardiac output.

Conclusion

Vasopressin infusion with small-volume fluid resuscitation during severe HS was highly effective enabling critical hemodynamic stabilization and improved 72 hour survival.

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes - but is not limited to - hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.

Cyclophilin-D: a resident regulator of mitochondrial gene expression

Cyclophilin-D (Cyp-D) is a mitochondrial matrix peptidyl-prolyl isomerase. Because cyclophilins can regulate nuclear gene expression, we examined whether Cyp-D could regulate mitochondrial gene expression. We demonstrated in HEK 293T cells that transfected Cyp-D interacts with mitochondrial transcription factors B1 and B2 (TFB2M) but not with mitochondrial transcription factor A. We also demonstrated that Cyp-D interacts in vivo with TFB2M. Genetic silencing of Cyp-D and pharmacologic inhibition of Cyp-D markedly reduced mitochondrial transcription to 18 ± 5% (P < 0.05) and 24 ± 3% (P < 0.05) of respective controls. The level of interaction between Cyp-D and TFB2M correlated with the level of nascent mitochondrial RNA intensity (r = 0.896; P = 0.0156). Cyp-D silencing down-regulated mitochondrial transcripts initiated from the heavy strand promoter 2 [i.e., NADH dehydrogenase 1 (ND1) by 11-fold, P < 0.005; cytochrome oxidase 1 (COX1) by 4-fold, P < 0.001; and ATP synthase subunit 6 (ATP6) by 6.5-fold, P < 0.005); but not NADH dehydrogenase 6 (ND6)], which is initiated from the light strand promoter. Cyp-D silencing reduced mitochondrial membrane potential and cellular oxygen consumption (from 59 ± 5 to 34 ± 1 µmol oxygen/min/10(6) cells, P < 0.001); the latter without a statistically significant reversal after uncoupling electron transport from ATP synthesis, consistent with down-regulation of electron transport complexes. Accordingly, these studies provide novel evidence that Cyp-D could play a key role in regulating mitochondrial gene expression.

Estrogen fails to facilitate resuscitation from ventricular fibrillation in male rats

Administration of 17β-estradiol has been shown to exert myocardial protective effects in hemorrhagic shock. We hypothesized that similar protective effects could help improve resuscitation from cardiac arrest. Three series of 18, 40, and 12 rats each, underwent ventricular fibrillation for 8 minutes followed by 8 minutes of chest compression and delivery of electrical shocks. In series-1, rats were randomized 1:1 to receive a bolus dose of 17β-estradiol (1 mg/kg) or 0.9% NaCl before chest compression; in series-2, rats were randomized 1:1:1:1 to receive a continuous infusion of 0.9% NaCl or a 17β-estradiol solution designed to attain a plasma level of 10(0), 10(2), or 10(4) nM during chest compression; and in series-3, rats were randomized 1:1 to receive a continuous infusion of 17β-estradiol to attain a plasma level of 10(2) nM or 0.9% NaCl during chest compression, providing inotropic support during the post-resuscitation interval using dobutamine infusion. 17β-estradiol failed to facilitate resuscitation in each of the 3 series. In series-1 and series-2, resuscitability and short-term survival was reduced in 17β-estradiol groups attaining statistical significance in series-2 when the three 17β-estradiol groups were combined (p = 0.035). In series-3, all rats were resuscitated and survived for 180 minutes aided by dobutamine which partially reversed post-resuscitation myocardial dysfunction but without additional benefits on myocardial function in the 17β-estradiol group. The present study failed to support a beneficial effect of 17β-estradiol for resuscitation from cardiac arrest and raised the possibility of detrimental cardiac effects compromising initial resuscitability and subsequent survival in a male rat model of ventricular fibrillation and closed chest resuscitation.

Effects of intraosseous erythropoietin during hemorrhagic shock in swine

Objective

To determine whether erythropoietin given during hemorrhagic shock (HS) ameliorates organ injury while improving resuscitation and survival.

Methods

Three series of 24 pigs each were studied. In an initial series, 50% of the blood volume (BV) was removed in 30 minutes and normal saline (threefold the blood removed) started at minute 90 infusing each third in 30, 60, and 150 minutes with shed blood reinfused at minute 330 (HS-50_BV). In a second series, the same HS-50_BV protocol was used but removing an additional 15% of BV from minute 30 to 60 (HS-65_BV). In a final series, blood was removed as in HS-65_BV and intraosseous vasopressin given from minute 30 (0.04 U/kg min⁻¹) until start of shed blood reinfusion at minute 150 (HS-65_BV+VP). Normal saline was reduced to half the blood removed and given from minute 90 to 120 in half of the animals. In each series, animals were randomized 1∶1 to receive erythropoietin (1,200 U/kg) or control solution intraosseously after removing 10% of the BV.

Results

In HS-50_BV, O₂ consumption remained near baseline yielding minimal lactate increases, 88% resuscitability, and 60% survival at 72 hours. In HS-65_BV, O₂ consumption was reduced and lactate increased yielding 25% resuscitability. In HS-65_BV+VP, vasopressin promoted hemodynamic stability yielding 92% resuscitability and 83% survival at 72 hours. Erythropoietin did not affect resuscitability or subsequent survival in any of the series but increased interleukin-10, attenuated lactate increases, and ameliorated organ injury based on lesser troponin I, AST, and ALT increases and lesser neurological deficits in the HS-65_BV+VP series.

Conclusions

Erythropoietin given during HS in swine failed to alter resuscitability and 72 hour survival regardless of HS severity and concomitant treatment with fluids and vasopressin but attenuated acute organ injury. The studies also showed the efficacy of vasopressin and restrictive fluid resuscitation for hemodynamic stabilization and survival.

Erythropoietin facilitates resuscitation from ventricular fibrillation by signaling protection of mitochondrial bioenergetic function in rats

OBJECTIVE

We previously reported beneficial myocardial effects during chest compression after administration of high-dose erythropoietin. We hypothesized that erythropoietin also elicits post-resuscitation myocardial benefits partly linked to protection of mitochondrial bioenergetic function.

METHODS

Two series of 10 rats each underwent ventricular fibrillation for 10 minutes (series-1) and 8 minutes (series-2) and were randomized to erythropoietin (5,000 U/kg) or 0.9% NaCl before chest compression. Dobutamine was infused post-resuscitation in series-2 harvesting their hearts at 120 minutes.

RESULTS

During chest compression, a statistically insignificant trend showing progressively higher coronary perfusion pressure in the erythropoietin group was observed consistent with previously reported preservation of left ventricular distensibility. Post-resuscitation, in the absence of dobutamine (series-1) erythropoietin failed to improve post-resuscitation myocardial function or survival; in the presence of dobutamine (series-2) all rats survived and those treated with erythropoietin reversed post-resuscitation myocardial dysfunction yielding higher cardiac work index (CWI; 39±3 vs 25±10 mmHg·ml/kg, p<0.01) and higher mean aortic pressure (MAP; 99±4 vs 83±16, p<0.01) at 120 minutes post-resuscitation. Better myocardial function was associated with lesser increases in plasma cytochrome c, attaining levels which inversely correlated with CWI (p=0.026) and MAP (p=0.025). Hearts from erythropoietin-treated rats had higher phosphorylation levels of cytosolic Akt and higher phosphorylation levels of cytosolic and mitochondrial PKCε and maintained cytochrome c oxidase activity.

CONCLUSION

Erythropoietin activated mitochondrial protective mechanisms that helped maintain bioenergetic function enabling reversal of post-resuscitation myocardial dysfunction in the presence of dobutamine.

AVE4454B--a novel sodium-hydrogen exchanger isoform-1 inhibitor--compared less effective than cariporide for resuscitation from cardiac arrest

We compared the efficacy of the novel sodium-hydrogen exchanger (NHE-1) inhibitor AVE4454B with cariporide for resuscitation from ventricular fibrillation (VF) assessing the effects on left ventricular myocardial distensibility during chest compression, myocardial function after the return of spontaneous circulation, and survival. Three groups of 10 rats each were subjected to 10 min of untreated VF and resuscitation attempted by providing chest compression for up to 8 min with the depth of compression adjusted to attain an aortic diastolic pressure between 26 and 28 mmHg (to secure a coronary perfusion pressure above 20 mmHg) followed by electrical shocks. Rats received AVE4454B (1 mg/kg), cariporide (1 mg/kg), or vehicle control immediately before chest compression. We observed that NHE-1 inhibition (NHEI) preserved left ventricular myocardial distensibility during chest compression evidenced by less depth of compression required to attain the target aortic diastolic pressure corresponding to (mean ± standard deviation) 14.1 ± 1.1 mm in the AVE4454B group (P < 0.001 versus control), 15.0 ± 1.4 mm in the cariporide group (P < 0.01 versus control), and 17.0 ± 1.2 mm in controls. When the depth of compression was related to the coronary perfusion pressure generated-an index of left ventricular distensibility-only the cariporide group attained statistical significance. Postresuscitation, both compounds ameliorated myocardial dysfunction evidenced by lesser reductions in mean aortic pressure and the maximal rate of left ventricular pressure increase as well as earlier normalization of left ventricular end-diastolic pressure increases. This effect was associated with improved survival corresponding to 55% in the AVE4454B group (not significant) and 70% in the cariporide group (P < 0.01 versus control by Gehan-Breslow analysis) at 240 min postresuscitation. An inverse correlation was found between plasma cytochrome c and indices of left ventricular function at 240 min postresuscitation suggesting that NHEI exerts beneficial effects in part by attenuating mitochondrial injury. We conclude that cariporide is more effective than AVE4454B for resuscitation from cardiac arrest given its more prominent effect on preserving left ventricular myocardial distensibility and promoting survival.

Cariporide given during resuscitation promotes return of electrically stable and mechanically competent cardiac activity

Episodes of ventricular fibrillation (VF) and myocardial dysfunction commonly occur after cardiac resuscitation compromising the return of stable circulation. We investigated in a pig model of VF whether limiting Na(+)-induced cytosolic Ca(2+) overload using the sarcolemmal sodium-hydrogen exchanger isoform-1 (NHE-1) inhibitor cariporide promotes resuscitation with stable circulation.

METHODS

VF was electrically induced in 20 male pigs and left untreated for 6 min after which CPR was initiated and continued for 8 min before attempting defibrillation. Pigs were randomized to receive 3-mg/kg cariporide (n=10) or 0.9%-NaCl (n=10) before chest compression.

RESULTS

Seven of 10 pigs in each group were successfully resuscitated and survived 2h. Cariporide ameliorated post-resuscitation ventricular ectopic activity such that fewer singlets (5+/-5 vs. 26+/-21; p<0.05) and fewer bigemini (1+/-3 vs. 33+/-25; p<0.05) were observed during the initial 5 min post-resuscitation. Additionally, cariporide-treated pigs did not require additional post-resuscitation shocks for ventricular tachycardia or recurrent VF (0.0+/-0.0 vs. 5.3+/-7.8 shocks; p=0.073). During the initial 60 min cariporide-treated pigs had higher, cardiac index (6.1+/-0.7 vs. 4.4+/-1.1L/min/m(2); p<0.01), left ventricular stroke work index (45+/-9 vs. 36+/-10 gmm/beat/m(2); p<0.05), and numerically higher mean aortic pressure (104+/-11 vs. 91+/-12 mmHg; p=0.054).

CONCLUSION

Cariporide administered at the start of chest compression may help restore electrically and mechanically stable circulation after resuscitation from cardiac arrest.

Erythropoietin facilitates the return of spontaneous circulation and survival in victims of out-of-hospital cardiac arrest

BACKGROUND

Erythropoietin activates potent protective mechanisms in non-hematopoietic tissues including the myocardium. In a rat model of ventricular fibrillation, erythropoietin preserved myocardial compliance enabling hemodynamically more effective CPR.

OBJECTIVE

To investigate whether intravenous erythropoietin given within 2 min of physician-led CPR improves outcome from out-of-hospital cardiac arrest.

METHODS

Erythropoietin (90,000 IU of beta-epoetin, n=24) was compared prospectively with 0.9% NaCl (concurrent controls=30) and retrospectively with a preceding group treated with similar protocol (matched controls=48).

RESULTS

Compared with concurrent controls, the erythropoietin group had higher rates of ICU admission (92% vs 50%, p=0.004), return of spontaneous circulation (ROSC) (92% vs 53%, p=0.006), 24-h survival (83% vs 47%, p=0.008), and hospital survival (54% vs 20%, p=0.011). However, after adjusting for pretreatment covariates only ICU admission and ROSC remained statistically significant. Compared with matched controls, the erythropoietin group had higher rates of ICU admission (92% vs 65%, p=0.024) and 24-h survival (83% vs 52%, p=0.014) with statistically insignificant higher ROSC (92% vs 71%, p=0.060) and hospital survival (54% vs 31%, p=0.063). However, after adjusting for pretreatment covariates all four outcomes were statistically significant. End-tidal PCO(2) (an estimate of blood flow during chest compression) was higher in the erythropoietin group.

CONCLUSIONS

Erythropoietin given during CPR facilitates ROSC, ICU admission, 24-h survival, and hospital survival. This effect was consistent with myocardial protection leading to hemodynamically more effective CPR (Trial registration: http://isrctn.org. Identifier: ISRCTN67856342).

Activation of caspase-3 may not contribute to postresuscitation myocardial dysfunction

We have previously reported that postresuscitation myocardial dysfunction is accompanied by the release of cytochrome c and caspase-3 activation. We now investigated the role of caspase-3 activation by examining whether such process prompts apoptotic DNA fragmentation, whether caspase-3 inhibition attenuates myocardial dysfunction, and whether myocardial protective effects of sodium-hydrogen exchanger isoform-1 (NHE-1) inhibition involve caspase-3 inhibition using a rat model of ventricular fibrillation (VF) of closed-chest resuscitation. Resuscitation after 4 or 8 min of untreated VF caused significant reductions in left ventricular stroke work index averaging 23% of sham control rats at 4 h postresuscitation. Left ventricular dysfunction was accompanied by increases in cytosolic cytochrome c, decreases in pro- and cleaved caspase-9 fragments, increases in 17-kDa caspase-3 fragments, and increases in caspase-3 activity indicating the activation of the mitochondrial apoptotic pathway but without evidence of apoptotic DNA fragmentation. In addition, levels of heat shock protein 70 were increased and levels of X-linked inhibitor of apoptosis protein and alphabeta-crystallin were preserved, all of which can exert antiapoptotic effects. In a separate series, the caspase-3 inhibitor z-Asp-Glu-Val-Asp chloromethyl ketone given before the induction of VF failed to prevent postresuscitation myocardial dysfunction despite reductions in caspase-3 activity (2.3 +/- 0.5 vs. 1.3 +/- 0.5 pmol fluorophore AFC released.mg protein(-1).min-1; P < 0.03). Treatment with the NHE-1 inhibitor cariporide had no effect on caspase-3 activity. Accordingly, in this rat model of VF and severe postresuscitation myocardial dysfunction, activation of caspase-3 did not lead to DNA fragmentation or contribute to myocardial dysfunction. Concomitant activation of intrinsic antiapoptotic mechanisms could play a protective role downstream to caspase-3 activation.

Targeting mitochondria for resuscitation from cardiac arrest

Reversal of cardiac arrest requires reestablishment of aerobic metabolism by reperfusion with oxygenated blood of tissues that have been ischemic for variable periods of time. However, reperfusion concomitantly activates a myriad of pathogenic mechanisms causing what is known as reperfusion injury. At the center of reperfusion injury are mitochondria, playing a critical role as effectors and targets of injury. Studies in animal models of ventricular fibrillation have shown that limiting myocardial cytosolic Na+ overload attenuates mitochondrial Ca2+ overload and maintains oxidative phosphorylation, which is the main bioenergetic function of mitochondria. This effect is associated with functional myocardial benefits such as preservation of myocardial compliance during chest compression and attenuation of myocardial dysfunction after return of spontaneous circulation. Additional studies in similar animal models of ventricular fibrillation have shown that mitochondrial injury leads to activation of the mitochondrial apoptotic pathway, characterized by the release of cytochrome c to the cytosol, reduction of caspase-9 levels, and activation of caspase-3 coincident with marked reduction in left ventricular function. Cytochrome c also "leaks" into the bloodstream attaining levels that are inversely proportional to survival. These data indicate that mitochondria play a key role during cardiac resuscitation by modulating energy metabolism and signaling apoptotic cascades and that targeting mitochondria could represent a promising strategy for cardiac resuscitation.

Myocardial protection by erythropoietin during resuscitation from ventricular fibrillation

Human recombinant erythropoietin (rhEPO) can protect the myocardium during ischemia and reperfusion. We investigated whether rhEPO could ameliorate previously identified functional myocardial abnormalities that develop during resuscitation from cardiac arrest, using a rat model of ventricular fibrillation (VF) and closed-chest resuscitation. VF was electrically induced and maintained, untreated, for 10 minutes. Chest compression and ventilation were then started and electrical defibrillation was attempted 8 minutes later. Rats were randomized to receive rhEPO (5000 U/kg) in the right atrium at baseline, 15 minutes before induction of VF (rhEPOBL -15-min), or at 10 minutes of VF, immediately before the start of chest compression (rhEPOVF 10-min), or to receive 0.9% NaCl solution instead (control). rhEPO given at the time of resuscitation (rhEPOVF 10-min group) -- but not at baseline -- prompted more effective chest compression, yielding higher coronary perfusion pressures for a given compression depth (1.95 +/- 0.27 mm Hg/mm; P < 0.05 in comparison with rhEPOBL -15-min [1.63 +/- 0.23 mm Hg/mm] and control [1.62 +/- 0.26 mm Hg/mm], by Dunnett's multicomparison method). Post-resuscitation, rats in the rhEPOVF 10-min group displayed higher mean aortic pressure associated with numerically higher cardiac index, stroke work index, and systemic vascular resistance index. rhEPO may rapidly induce myocardial protection during resuscitation from cardiac arrest.

Limiting sarcolemmal Na+ entry during resuscitation from ventricular fibrillation prevents excess mitochondrial Ca2+ accumulation and attenuates myocardial injury

BACKGROUND

intracellular Na+ accumulation during ischemia and reperfusion leads to cytosolic Ca2+ overload through reverse-mode operation of the sarcolemmal Na+ -Ca2+ exchanger. Cytosolic Ca2+ accumulation promotes mitochondrial Ca2+ (Ca2+ m) overload, leading to mitochondrial injury. We investigated whether limiting sarcolemmal Na+ entry during resuscitation from ventricular fibrillation (VF) attenuates Ca2+ m overload and lessens myocardial dysfunction in a rat model of VF and closed-chest resuscitation.

METHODS

hearts were harvested from 10 groups of 6 rats each representing baseline, 15 min of untreated VF, 15 min of VF with chest compression given for the last 5 min (VF/CC), and 60 min postresuscitation (PR). VF/CC and PR included four groups each randomized to receive before starting chest compression the new NHE-1 inhibitor AVE4454B (1.0 mg/kg), the Na+ channel blocker lidocaine (5.0 mg/kg), their combination, or vehicle control. The left ventricle was processed for intracellular Na+ and Ca2+ m measurements.

RESULTS

limiting sarcolemmal Na+ entry attenuated cytosolic Na+ increase during VF/CC and the PR phase and prevented Ca2+ m overload yielding levels that corresponded to 77% and 71% of control hearts at VF/CC and PR, without differences among specific Na+ -limiting interventions. Limiting sarcolemmal Na+ entry attenuated reductions in left ventricular compliance during VF and prompted higher mean aortic pressure (110 +/- 7 vs. 95 +/- 11 mmHg, P < 0.001) and higher cardiac work index (159 +/- 34 vs. 126 +/- 29 g x m x min(-1) x kg(-1), P < 0.05) with lesser increases in circulating cardiac troponin I at 60 min PR.

CONCLUSIONS

Na+ -limiting interventions prevented excess Ca2+ m accumulation induced by ischemia and reperfusion and ameliorated myocardial injury and dysfunction.

Circulating levels of cytochrome c after resuscitation from cardiac arrest: a marker of mitochondrial injury and predictor of survival

Ca(2+) overload and reactive oxygen species can injure mitochondria during ischemia and reperfusion. We hypothesized that mitochondrial injury occurs during cardiac resuscitation, causing release of cytochrome c to the cytosol and bloodstream while activating apoptotic pathways. Plasma cytochrome c was measured using reverse-phase HPLC and Western immunoblotting in rats subjected to 4 or 8 min of untreated ventricular fibrillation and 8 min of closed-chest resuscitation followed by 240 min of postresuscitation hemodynamic observation. A sham group served as control. Plasma cytochrome c rose progressively to levels 10-fold higher than in sham rats 240 min after resuscitation (P < 0.01), despite reversal of whole body ischemia (decreases in arterial lactate). Cytochrome c levels were inversely correlated with left ventricular stroke work (r = -0.40, P = 0.02). Western immunoblotting of left ventricular tissue demonstrated increased levels of 17-kDa cleaved caspase-3 fragments in the cytosol. Plasma cytochrome c was then serially measured in 12 resuscitated rats until the rat died or cytochrome c returned to baseline. In three survivors, cytochrome c rose slightly to <or=2 microg/ml and returned to baseline within 96 h. In nine nonsurvivors, cytochrome c rose progressively to significantly higher maximal levels [4.6 (SD 2.0) vs. 1.6 (SD 0.3) microg/ml, P = 0.029] and at faster rates [0.7 (SD 0.5) vs. 0.1 (SD 0.1) microg.ml(-1).h(-1), P = 0.046] than in survivors. Plasma cytochrome c may represent a novel in vivo marker of mitochondrial injury after resuscitation from cardiac arrest that relates inversely with survival outcome.

Cariporide minimizes adverse myocardial effects of epinephrine during resuscitation from ventricular fibrillation

OBJECTIVE

Epinephrine given during closed-chest resuscitation increases blood flow across the coronary and cerebral circuits. However, epinephrine worsens reperfusion arrhythmias and intensifies postresuscitation myocardial dysfunction. We investigated whether cariporide-a selective sodium-hydrogen exchanger isoform-1 inhibitor-could ameliorate such adverse effects without diminishing its vasopressor actions.

DESIGN

Randomized animal study.

SETTING

University-based animal laboratory.

SUBJECTS

Twenty-four anesthetized male domestic pigs (29-43 kg).

INTERVENTIONS

Ventricular fibrillation was electrically induced and left untreated for 8 mins. Pigs were randomized to receive after 2 mins of chest compression a 3 mg/kg bolus of cariporide (n = 8), a 0.02 mg/kg bolus of epinephrine (n = 8), or a combination of cariporide and epinephrine (n = 8). Additional doses of epinephrine were given if the coronary perfusion pressure decreased below 15 mm Hg. Successfully resuscitated pigs were observed for 72 hrs.

MEASUREMENTS AND MAIN RESULTS

The averaged coronary perfusion pressure was higher in the epinephrine (34 +/- 11 mm Hg, p = .001) and cariporide/epinephrine (35 +/- 10 mm Hg, p < .001) groups compared with the cariporide group (15 +/- 6 mm Hg). All pigs in the epinephrine and cariporide/epinephrine groups but only six in the cariporide group were successfully resuscitated and survived 72 hrs. During the immediate postresuscitation period, four of eight pigs in the epinephrine group had episodes of recurrent ventricular fibrillation or pulseless ventricular tachycardia requiring additional electrical shocks (7.0 +/- 6.4) but none in the cariporide and cariporide/epinephrine groups (chi-square, p = .008). Myocardial dysfunction occurred early after return of spontaneous circulation but only in the epinephrine group.

CONCLUSIONS

The combined administration of cariporide and epinephrine prompted adequate pressor effects during chest compression and facilitated reestablishment of cardiac activity without episodes of recurrent ventricular fibrillation or transient myocardial dysfunction as with epinephrine alone.