Development of the emergency preservation and resuscitation for cardiac arrest from trauma clinical trial

Approach to traumatic cardiac arrest in the emergency department: a narrative literature review for emergency providers

BACKGROUND

Traumatic cardiac arrest (TCA) is a major contributor to mortality and morbidity in all age groups and poses a significant burden on the healthcare system. Although there have been advances in treatment modalities, survival rates for TCA patients remain low. This narrative literature review critically examines the indications and effectiveness of current therapeutic approaches in treating TCA.

METHODS

We performed a literature search in the PubMed and Scopus databases for studies published before December 31, 2022. The search was refined by combining search terms, examining relevant study references, and restricting publications to the English language. Following the search, 943 articles were retrieved, and two independent reviewers conducted a screening process.

RESULTS

A review of various studies on pre- and intra-arrest prognostic factors showed that survival rates were higher when patients had an initial shockable rhythm. There were conflicting results regarding other prognostic factors, such as witnessed arrest, bystander cardiopulmonary resuscitation (CPR), and the use of prehospital or in-hospital epinephrine. Emergency thoracotomy was found to result in more favorable outcomes in cases of penetrating trauma than in those with blunt trauma. Resuscitative endovascular balloon occlusion of the aorta (REBOA) provides an advantage to emergency thoracotomy in terms of occupational safety for the operator as an alternative in managing hemorrhagic shock. When implemented in the setting of aortic occlusion, emergency thoracotomy and REBOA resulted in comparable mortality rates. Veno-venous extracorporeal life support (V-V ECLS) and veno-arterial extracorporeal life support (V-A ECLS) are viable options for treating respiratory failure and cardiogenic shock, respectively. In the context of traumatic injuries, V-V ECLS has been associated with higher rates of survival to discharge than V-A ECLS.

CONCLUSION

TCA remains a significant challenge for emergency medical services due to its high morbidity and mortality rates. Pre- and intra-arrest prognostic factors can help identify patients who are likely to benefit from aggressive and resource-intensive resuscitation measures. Further research is needed to enhance guidelines for the clinical use of established and emerging therapeutic approaches that can help optimize treatment efficacy and ameliorate survival outcomes.

Extracorporeal life support in trauma: Indications and techniques

BACKGROUND

Clarity about indications and techniques in extracorporeal life support (ECLS) in trauma is essential for timely and effective deployment, and to ensure good stewardship of an important resource. Extracorporeal life support deployments in a tertiary trauma center were reviewed to understand the indications, strategies, and tactics of ECLS in trauma.

METHODS

The provincial trauma registry was used to identify patients who received ECLS at a Level I trauma center and ECLS organization-accredited site between January 2014 and February 2021. Charts were reviewed for indications, technical factors, and outcomes following ECLS deployment. Based on this data, consensus around indications and techniques for ECLS in trauma was reached and refined by a multidisciplinary team discussion.

RESULTS

A total of 25 patients underwent ECLS as part of a comprehensive trauma resuscitation strategy. Eighteen patients underwent venovenous ECLS and seven received venoarterial ECLS. Nineteen patients survived the ECLS run, of which 15 survived to discharge. Four patients developed vascular injuries secondary to cannula insertion while four patients developed circuit clots. On multidisciplinary consensus, three broad indications for ECLS and their respective techniques were described: gas exchange for lung injury, extended damage control for severe injuries associated with the lethal triad, and circulatory support for cardiogenic shock or hypothermia.

CONCLUSION

The three broad indications for ECLS in trauma (gas exchange, extended damage control and circulatory support) require specific advanced planning and standardization of corresponding techniques (cannulation, circuit configuration, anticoagulation, and duration). When appropriately and effectively integrated into the trauma response, ECLS can extend the damage control paradigm to enable the management of complex multisystem injuries.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level IV.

Selective aortic arch perfusion: a first-in-human observational cadaveric study

BACKGROUND

Selective aortic arch perfusion (SAAP) is a novel endovascular technique that combines thoracic aortic occlusion with extracorporeal perfusion of the brain and heart. SAAP may have a role in both haemorrhagic shock and in cardiac arrest due to coronary ischaemia. Despite promising animal studies, no data is available that describes SAAP in humans. The primary aim of this study was to assess the feasibility of selective aortic arch perfusion in humans. The secondary aim of the study was to assess the feasibility of achieving direct coronary artery access via the SAAP catheter as a potential conduit for salvage percutaneous coronary intervention.

METHODS

Using perfused human cadavers, a prototype SAAP catheter was inserted into the descending aorta under fluoroscopic guidance via a standard femoral percutaneous access device. The catheter balloon was inflated and the aortic arch perfused with radio-opaque contrast. The coronary arteries were cannulated through the SAAP catheter.

RESULTS

The procedure was conducted four times. During the first two trials the SAAP catheter was passed rapidly and without incident to the intended descending aortic landing zone and aortic arch perfusion was successfully delivered via the device. The SAAP catheter balloon failed on the third trial. On the fourth trial the left coronary system was cannulated using a 5Fr coronary guiding catheter through the central SAAP catheter lumen.

CONCLUSIONS

For the first time using a perfused cadaveric model we have demonstrated that a SAAP catheter can be easily and safely inserted and SAAP can be achieved using conventional endovascular techniques. The SAAP catheter allowed successful access to the proximal aorta and permitted retrograde perfusion of the coronary and cerebral circulation.

Traumatic hemorrhage and chain of survival

Trauma is the number one cause of death among Americans between the ages of 1 and 46 years, costing more than $670 billion a year. Following death related to central nervous system injury, hemorrhage accounts for the majority of remaining traumatic fatalities. Among those with severe trauma that reach the hospital alive, many may survive if the hemorrhage and traumatic injuries are diagnosed and adequately treated in a timely fashion. This article aims to review the recent advances in pathophysiology management following a traumatic hemorrhage as well as the role of diagnostic imaging in identifying the source of hemorrhage. The principles of damage control resuscitation and damage control surgery are also discussed. The chain of survival for severe hemorrhage begins with primary prevention; however, once trauma has occurred, prehospital interventions and hospital care with early injury recognition, resuscitation, definitive hemostasis, and achieving endpoints of resuscitation become paramount. An algorithm is proposed for achieving these goals in a timely fashion as the median time from onset of hemorrhagic shock and death is 2 h.

Five Decades of Trauma Anesthesiology

We present a brief history of the scientific and educational development of trauma anesthesiology. Key milestones from the past 50 years are noted, as well as the current standing of the subspecialty and prospects for the future.

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

Myocardial Injury Is Associated with the Incidence of Major Adverse Cardiac Events in Patients with Severe Trauma

BACKGROUND

Severe trauma potentially results in end-organ damage such as myocardial injury. Data suggest that myocardial injury is associated with increased mortality in this cohort, but the association with the incidence of in-hospital major adverse cardiac events (MACE) remains undetermined.

METHODS

Retrospective cohort study including adult patients with severe trauma treated at the University Hospital Duesseldorf between January 2016 and December 2019. The main exposure was myocardial injury at presentation. Endpoints were in-hospital incidence of MACE and incidence of acute kidney injury (AKI) within 72 h. Discrimination of hsTnT for MACE and AKI was examined by the receiver operating characteristic curve (ROC) and the area under the curve (AUC). We conducted multivariate logistic regression analysis.

RESULTS

We included 353 patients in our final analysis (72.5% male (256/353), age: 55 ± 21 years). The AUC for hsTnT and MACE was 0.68 [95% confidence interval (CI): 0.59-0.78]. The AUC for hsTnT and AKI was 0.64 [95% (CI): 0.55-0.72]. The adjusted odds ratio (OR) for myocardial injury and MACE was 2.97 [95% (CI): 1.31-6.72], and it was 2.14 [95% (CI): 1.03-4.46] for myocardial injury and AKI.

CONCLUSION

Myocardial injury at presentation in patients with severe trauma is independently associated with the incidence of in-hospital MACE and AKI.

Protocol for a cluster randomised controlled feasibility study of Prehospital Optimal Shock Energy for Defibrillation (POSED)

Aims

The Prehospital Optimal Shock Energy for Defibrillation (POSED) study will assess the feasibility of conducting a cluster randomised controlled study of clinical effectiveness in UK ambulance services to identify the optimal shock energy for defibrillation.

Methods

POSED is a pragmatic, allocation concealed, open label, cluster randomised, controlled feasibility study. Defibrillators within a single UK ambulance service will be randomised in an equal ratio to deliver one of three shock strategies 120-150-200 J, 150-200-200 J, 200-200-200 J. Consecutive adults (≥18 years) presenting with out of hospital cardiac arrest requiring defibrillation will be eligible. The study plans to enrol 90 patients (30 in each group). Patients (or their relatives for non-survivors) will be informed about trial participation after the initial emergency has resolved. Survivors will be invited to consent to participate in follow-up (i.e., at 30 days or discharge).The primary feasibility outcome is the proportion of eligible patients who receive the randomised study intervention. Secondary feasibility outcomes will include recruitment rate, adherence to allocated treatment and data completeness. Clinical outcomes will include Return of an Organised Rhythm (ROOR) at 2 minutes post-shock, refibrillation rate, Return of Spontaneous Circulation (ROSC) at hospital handover, survival and neurological outcome at 30 days.

Conclusion

The POSED study will assess the feasibility of a large-scale trial and explore opportunities to optimise the trial protocol.Trial registration: ISRCTN16327029.

Increasing Solid Organ Donation: A Role for Emergency Physicians

BACKGROUND

More than 100,000 Americans with failing organs await transplantation, mostly from dead donors. Yet only a fraction of patients declared dead by neurological criteria (DNC) become organ donors.

DISCUSSION

Emergency physicians (EPs) can improve solid organ donation in the following ways: providing perimortem critical care support to potential organ donors, promptly notifying organ procurement organizations (OPOs), asking neurocritical care specialists to evaluate selected emergency department patients for death based on established neurologic criteria, participating in research to advance these developments, implementing automatic OPO notification technologies, and educating the professional and lay communities about organ donation and transplantation, including exploration of opt-out (presumed consent) organ recovery policies.

CONCLUSION

With future improvements in organ preservation and DNC assessment, EPs may become even more involved in the donation process. EPs should support and engage in efforts to promote organ donation and transplantation.

Development of a Modular Tissue Phantom for Evaluating Vascular Access Devices

Central vascular access (CVA) may be critical for trauma care and stabilizing the casualty. However, it requires skilled personnel, often unavailable during remote medical situations and combat casualty care scenarios. Automated CVA medical devices have the potential to make life-saving therapeutics available in these resource-limited scenarios, but they must be properly designed. Unfortunately, currently available tissue phantoms are inadequate for this use, resulting in delayed product development. Here, we present a tissue phantom that is modular in design, allowing for adjustable flow rate, circulating fluid pressure, vessel diameter, and vessel positions. The phantom consists of a gelatin cast using a 3D-printed mold with inserts representing vessels and bone locations. These removable inserts allow for tubing insertion which can mimic normal and hypovolemic flow, as well as pressure and vessel diameters. Trauma to the vessel wall is assessed using quantification of leak rates from the tubing after removal from the model. Lastly, the phantom can be adjusted to swine or human anatomy, including modeling the entire neurovascular bundle. Overall, this model can better recreate severe hypovolemic trauma cases and subject variability than commercial CVA trainers and may potentially accelerate automated CVA device development.

Time Limiting Boundaries of Reversible Clinical Death in Rats Subjected to Ultra-Deep Hypothermia

BACKGROUND

It is well known that body temperature maintenance between 20 and 35°C prevents hypoxic damage. However, data regarding the ideal duration and permissible temperature boundaries for ultra-deep hypothermia below 20°C are rather fragmentary. The aim of the present study was to determine the time limits of reversible clinical death in rats subjected to ultra-deep hypothermia at 1-8°C.

RESULTS

Rat survival rates were directly dependent on the duration of clinical death. If clinical death did not exceed 35 min, animal viability could be restored. Extending the duration of clinical death longer than 45 min led to rat death, and cardiac functioning in these animals was not recovered. The rewarming rate and the lowest temperature of hypothermia experienced did not directly influence survival rates.

CONCLUSIONS

In a rat model, reversible ultra-deep hypothermia as low as 1-8°C could be achieved without the application of hypercapnia or pharmacological support. The survival of animals was dependent on the duration of clinical death, which should not exceed 35 min.

Emergency preservation and resuscitation for cardiac arrest from trauma

Patients who suffer a cardiac arrest from trauma rarely survive. Surgical control of hemorrhage cannot be obtained in time to prevent irreversible organ damage. Emergency preservation and resuscitation (EPR) was developed to utilize hypothermia to buy time to achieve hemostasis and allow delayed resuscitation. Large animal studies have demonstrated that cooling to tympanic membrane temperature 10 °C during exsanguination cardiac arrest can allow up to 2 h of circulatory arrest and repair of simulated injuries with normal neurologic recovery. The Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT) trial is testing the feasibility and safety of initiating EPR. Study subjects include patients with penetrating trauma who lose a pulse within 5 minutes of hospital arrival and remain pulseless despite standard care. EPR is initiated via an intra-aortic flush of ice-cold saline solution. Following hemostasis, delayed resuscitation and rewarming are accomplished with cardiopulmonary bypass. The primary outcome is survival to hospital discharge without significant neurologic deficits. If trained team members are available, subjects can undergo EPR. If not, subjects can be enrolled as concurrent controls. Ten EPR and 10 control subjects will be enrolled. If successful, EPR could save the lives of trauma patients who are currently dying from exsanguinating hemorrhage.

Femoral vascular access for endovascular resuscitation

ABSTRACT

Endovascular resuscitation is an emerging area in the resuscitation of both severe traumatic hemorrhage and nontraumatic cardiac arrest. Vascular access is the critical first procedural step that must be accomplished to initiate endovascular resuscitation. The endovascular interventions presently available and emerging are routinely or potentially performed via the femoral vessels. This may require either femoral arterial access alone or access to both the femoral artery and vein. The time-critical nature of resuscitation necessitates that medical specialists performing endovascular resuscitation be well-trained in vascular access techniques. Keen knowledge of femoral vascular anatomy and skill with vascular access techniques are required to meet the needs of critically ill patients for whom endovascular resuscitation can prove lifesaving. This review article addresses the critical importance of femoral vascular access in endovascular resuscitation, focusing on the pertinent femoral vascular anatomy and technical aspects of ultrasound-guided percutaneous vascular access and femoral vessel cutdown that may prove helpful for successful endovascular resuscitation.

Diagnostic value of intravenous oxygen saturation compared with arterial and venous base excess to predict hemorrhagic shock in multiple trauma patients

Introduction:

In this study, with the help of peripheral vein sampling, Spvo2, and peripheral artery and vein sampling, we examined base excess (BE) in trauma patients and determined its diagnostic value for hemorrhagic shock.

Methods:

In this cross-sectional study, from 64 patients with abdominal, pelvic and chest Blunt trauma who have a score of 2 or higher trauma during treatment, blood samples were taken from peripheral vein to measure oxygen saturation and peripheral vein and artery for BE measurements and were compared in order to assess their diagnostic value in predicting the occurrence of hemorrhagic shock.

Results:

Out of 60 examined patients, 43 (71.67%) patients were diagnosed with hemorrhagic shock. The correlation for the percentage of oxygen saturation of the peripheral blood and the rate of arterial and venous BE for these r^2patients were 17.0 and 09.0, respectively, with a P value greater than 0.005. In the case of the percentage of oxygen saturation of the peripheral blood, the sensitivity and specificity were 93.03 and 11.76%, respectively. The positive and negative likelihood ratios were 1.05 and 0.59, respectively. The positive and negative predictive values were 72.73 and 40%, respectively.

Conclusion:

In general, the results of this study showed that arterial and venous excess base levels had a proper correlation, specificity and sensitivity for diagnosing and predicting hemorrhagic shock, while the percentage of oxygen saturation of peripheral blood and BE arterial and venous levels had not proper correlation to detect and predict hemorrhagic shock.

Cardiopulmonary Resuscitation and Rescue Therapies

The history of cardiopulmonary resuscitation and the Society of Critical Care Medicine have much in common, as many of the founders of the Society of Critical Care Medicine focused on understanding and improving outcomes from cardiac arrest. We review the history, the current, and future state of cardiopulmonary resuscitation.

State-of-the-art methods for the treatment of severe hemorrhagic trauma: selective aortic arch perfusion and emergency preservation and resuscitation-what is next?

Trauma is a primary cause of death globally, with non‐compressible torso hemorrhage constituting an important part of “potentially survivable trauma death.” Resuscitative endovascular balloon occlusion of the aorta has become a popular alternative to aortic cross‐clamping under emergent thoracotomy for non‐compressible torso hemorrhage in recent years, however, it alone does not improve the survival rate of patients with severe shock or traumatic cardiac arrest from non‐compressible torso hemorrhage. Development of novel advanced maneuvers is essential to improve these patients’ survival, and research on promising methods such as selective aortic arch perfusion and emergency preservation and resuscitation is ongoing. This review aimed to provide physicians in charge of severe trauma cases with a broad understanding of these novel therapeutic approaches to manage patients with severe hemorrhagic trauma, which may allow them to develop lifesaving strategies for exsanguinating trauma patients. Although there are still hurdles to overcome before their clinical application, promising research on these novel strategies is in progress, and ongoing development of synthetic red blood cells and techniques that reduce ischemia‐reperfusion injury may further maximize their effects. Both continuous proof‐of‐concept studies and translational clinical evaluations are necessary to clinically apply these hemostasis approaches to trauma patients.

State-of-the-Art Review-Endovascular Resuscitation

ABSTRACT

The emerging concept of endovascular resuscitation applies catheter-based techniques in the management of patients in shock to manipulate physiology, optimize hemodynamics, and bridge to definitive care. These interventions hope to address an unmet need in the care of severely injured patients, or those with refractory non-traumatic cardiac arrest, who were previously deemed non-survivable. These evolving techniques include Resuscitative Endovascular Balloon Occlusion of Aorta, Selective Aortic Arch Perfusion, and Extracorporeal Membrane Oxygenation and there is a growing literature base behind them. This review presents the up-to-date techniques and interventions, along with their application, evidence base, and controversy within the new era of endovascular resuscitation.

Emerging hemorrhage control and resuscitation strategies in trauma: Endovascular to extracorporeal

This article reviews four emerging endovascular hemorrhage control and extracorporeal perfusion techniques for management of trauma patients with profound hemorrhagic shock including hemorrhage-induced traumatic cardiac arrest: resuscitative endovascular balloon occlusion of the aorta, selective aortic arch perfusion, extracorporeal life support, and emergency preservation and resuscitation. The preclinical and clinical studies underpinning each of these techniques are summarized. We also present an integrated conceptual framework for how these emerging technologies may be used in the future care of trauma patients in both resource-rich and austere environments.

The impact of hypothermia on outcomes in massively transfused patients

BACKGROUND

Hypothermia is associated with poor outcomes after injury. The relationship between hypothermia during contemporary large volume resuscitation and blood product consumption is unknown. We evaluated this association, and the predictive value of hypothermia on mortality.

METHODS

Patients predicted to receive massive transfusion at 12 level 1 trauma centers were randomized in the Pragmatic Randomized Optimal Platelet and Plasma Ratios (PROPPR) trial and were grouped into those who were hypothermic (<36°C) or normothermic (36-38.5°C) within the first 6 hours of emergency department arrival. The impact of hypothermia or normothermia on the volume of blood product required during the first 24 hours was determined via negative binomial regression, adjusting for treatment arm, injury severity score, mechanism, demographics, pre-emergency department fluid volume, blood administered before becoming hypothermic, pulse and systolic blood pressure on arrival, and the time exposed to hypothermic or normothermic temperatures.

RESULTS

Of 680 patients, 590 had a temperature measured during the first 6 hours in hospital, and 399 experienced hypothermia. The mean number of red blood cell (RBC) units given to all patients in the first 24 hours of admission was 8.8 (95% confidence interval [CI], 7.9-9.6). In multivariable analysis, every 1°C decrease in temperature below 36.0°C was associated with a 10% increase (incidence rate ratio, 0.90; 95% CI, 0.89-0.92; p < 0.00) in consumption of RBCs during the first 24 hours of admission. There was no association between RBC administration and a temperature above 36°C. Hypothermia on arrival was an independent predictor of mortality, with an adjusted odds ratio of 2.7 (95% CI, 1.7-4.5; p < 0.00) for 24-hour mortality and 1.8 (95% CI, 1.3-2.4; p < 0.00) for 30-day mortality.

CONCLUSION

Hypothermia is associated with increase in blood product consumption and mortality. These findings support the maintenance of normothermia in trauma patients and suggest that further investigation on the impact of cooling or rewarming during massive transfusion is warranted.

LEVEL OF EVIDENCE

Prognostic, level III.

The Role of Tranexamic Acid in the Management of an Acutely Hemorrhaging Patient

Background: Acute hemorrhage, both traumatic and nontraumatic, leads to significant morbidity and mortality, both in the United States and globally. Traditional treatment of acute hemorrhage is focused on hemostasis and blood product replacement. Tranexamic acid is an antifibrinolytic agent that may reduce acute hemorrhage through inhibition of plasminogen. Newer research suggests that coagulopathy, specifically fibrinolysis, may contribute significantly to the pathology of acute hemorrhage. Methods: We searched the PubMed database for relevant articles from 2000 to 2018 for the terms "tranexamic acid," "TXA," "antifibrinolytic," "hyperfibrinolysis," and "coagulopathy." Our search was limited to studies published in the English language. Results: A total of 53 studies were included in this review. These articles suggest a potential role for tranexamic acid in the management of acute intracranial hemorrhage, epistaxis, hematuria, postpartum hemorrhage, gastrointestinal hemorrhage, and trauma-related hemorrhage. A theoretical risk of thrombotic events following tranexamic acid use exists, though large clinical trials suggest this risk remains exceedingly small. Conclusions: Recent studies suggest a mortality benefit with tranexamic acid following acute hemorrhage. First responders such as emergency medical technicians and emergency department clinicians should consider tranexamic acid as an adjunct therapy in the management of acute, severe traumatic and nontraumatic hemorrhage.

What's new for trauma haemorrhage management?

Uncontrolled haemorrhage is the leading cause of preventable death from injury and is a major contributor to the global burden of disease. The majority of deaths resulting from bleeding occur within the first 3 hours of hospital admission, and the window for meaningful intervention is therefore extremely small. Resuscitative efforts during active bleeding should focus on maintaining haemostatic function with blood product transfusion and early administration of tranexamic acid. Achieving control of haemorrhage is the overarching treatment priority and may require temporising measures before definitive surgical or radiological intervention. This review summarizes the contemporary approaches to resuscitation of bleeding trauma patients, options for achieving haemorrhage control, and current areas of active research including organ protective resuscitation and suspended animation.

Recent advances in personalizing cardiac arrest resuscitation

Cardiac arrest remains a significant cause of death and disability throughout the world. However, as our understanding of cardiac arrest and resuscitation physiology has developed, new technologies are fundamentally altering our potential to improve survival and neurologic sequela. Some advances are relatively simple, requiring only alterations in current basic life support measures or integration with pre-hospital organization, whereas others, such as extra-corporeal membrane oxygenation, require significant time and resource investments. When combined with consistent rescuer and patient-physiologic monitoring, these innovations allow an unprecedented capacity to personalize cardiac arrest resuscitation to patient-specific pathophysiology. However, as more extensive options are established, it can be difficult for providers to incorporate novel resuscitation techniques into a cardiac arrest protocol which can fit a wide variety of cases with varying complexity. This article will explore recent advances in our understanding of cardiac arrest physiology and resuscitation sciences, with particular focus on the metabolic phase after significant ischemia has been induced. To this end, we establish a practical consideration for providers seeking to integrate novel advances in cardiac arrest resuscitation into daily practice.

Annexin A1 Bioactive Peptide Promotes Resolution of Neuroinflammation in a Rat Model of Exsanguinating Cardiac Arrest Treated by Emergency Preservation and Resuscitation

Neuroinflammation initiated by damage-associated molecular patterns, including high mobility group box 1 protein (HMGB1), has been implicated in adverse neurological outcomes following lethal hemorrhagic shock and polytrauma. Emergency preservation and resuscitation (EPR) is a novel method of resuscitation for victims of exsanguinating cardiac arrest, shown in preclinical studies to improve survival with acceptable neurological recovery. Sirtuin 3 (SIRT3), the primary mitochondrial deacetylase, has emerged as a key regulator of metabolic and energy stress response pathways in the brain and a pharmacological target to induce a neuronal pro-survival phenotype. This study aims to examine whether systemic administration of an Annexin-A1 bioactive peptide (ANXA1sp) could resolve neuroinflammation and induce sirtuin-3 regulated cytoprotective pathways in a novel rat model of exsanguinating cardiac arrest and EPR. Adult male rats underwent hemorrhagic shock and ventricular fibrillation, induction of profound hypothermia, followed by resuscitation and rewarming using cardiopulmonary bypass (EPR). Animals randomly received ANXA1sp (3 mg/kg, in divided doses) or vehicle. Neuroinflammation (HMGB1, TNFα, IL-6, and IL-10 levels), cerebral cell death (TUNEL, caspase-3, pro and antiapoptotic protein levels), and neurologic scores were assessed to evaluate the inflammation resolving effects of ANXA1sp following EPR. Furthermore, western blot analysis and immunohistochemistry were used to interrogate the mechanisms involved. Compared to vehicle controls, ANXA1sp effectively reduced expression of cerebral HMGB1, IL-6, and TNFα and increased IL-10 expression, which were associated with improved neurological scores. ANXA1sp reversed EPR-induced increases in expression of proapoptotic protein Bax and reduction in antiapoptotic protein Bcl-2, with a corresponding decrease in cerebral levels of cleaved caspase-3. Furthermore, ANXA1sp induced autophagic flux (increased LC3II and reduced p62 expression) in the brain. Mechanistically, these findings were accompanied by upregulation of the mitochondrial protein deacetylase Sirtuin-3, and its downstream targets FOXO3a and MnSOD in ANXA1sp-treated animals. Our data provide new evidence that engaging pro-resolving pharmacological strategies such as Annexin-A1 biomimetic peptides can effectively attenuate neuroinflammation and enhance the neuroprotective effects of EPR after exsanguinating cardiac arrest.

Engineering Human Stasis for Long-Duration Spaceflight

Suspended animation for deep-space travelers is moving out of the realm of science fiction. Two approaches are considered: the first elaborates the current medical practice of therapeutic hypothermia; the second invokes the cascade of metabolic processes naturally employed by hibernators. We explore the basis and evidence behind each approach and argue that mimicry of natural hibernation will be critical to overcome the innate limitations of human physiology for long-duration space travel.

Past and present role of extracorporeal membrane oxygenation in combat casualty care: How far will we go?

Advanced extracorporeal therapies have been successfully applied in the austere environment of combat casualty care over the previous decade. In this review, we describe the historic underpinnings of extracorporeal membrane oxygenation, review the recent experience with both partial and full lung support during combat operations, and critically assess both the current status of the Department of Defense extracorporeal membrane oxygenation program and the way forward to establish long-range lung rescue therapy as a routine capability for combat casualty care.

Improved Long-term Survival with Remote Limb Ischemic Preconditioning in a Rat Fixed-Pressure Hemorrhagic Shock Model

PURPOSE

We investigated whether bilateral, lower limb remote ischemic preconditioning (RIPC) improved long-term survival using a rat model of hemorrhagic shock/resuscitation.

METHODS

Rats were anesthetized, intubated and ventilated, and randomly assigned to RIPC, induced by inflating bilateral pressure cuffs around the femoral arteries to 200 mmHg for 5 min, followed by 5-min release of the cuffs (repeated for 4 cycles), or control group (cuffs were inflated to 30 mmHg). Hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure of 30 mmHg for 30 min, followed by 30 min of resuscitation with shed blood. Rats remained anesthetized for 1 h during which hemodynamics were monitored then they were allowed to survive for 6 weeks.

RESULTS

The percentage of estimated total blood volume withdrawn to maintain a level of 30 mmHg was similar in both groups. RIPC significantly increased survival at 6 weeks: 5 of 27 (19%) rats in the control group and 13 of 26 (50%; p = 0.02) rats in the RIPC group survived. Blood pressure was higher in the RIPC group. The diastolic internal dimension of the left ventricle, an indicator of circulating intravascular blood volume, was significantly larger in the RIPC group at 1 h after initiation of resuscitation compared to the control group (p = 0.04). Left ventricular function assessed by fractional shortening was comparable in both groups at 1 h after initiation of resuscitation. Blood urea nitrogen (BUN) was within normal range in the RIPC group (17.3 ± 1.2 mg/dl) but elevated in the control group (22.0 ± 1.7 mg/dl) at 48 h after shock.

CONCLUSIONS

RIPC significantly improved short-term survival in rats that were subjected to hemorrhagic shock, and this benefit was maintained long term. RIPC led to greater circulating intravascular blood volume in the early phase of resuscitation and improved BUN.

Slow as Compared to Rapid Rewarming After Mild Hypothermia Improves Survival in Experimental Shock

BACKGROUND

Accidental hypothermia following trauma is an independent risk factor for mortality. However, in most experimental studies, hypothermia clearly improves outcome. We hypothesized that slow rewarming is beneficial over rapid rewarming following mild hypothermia in a rodent model of hemorrhagic shock.

MATERIALS AND METHODS

We subjected 32 male Wistar rats to severe hemorrhagic shock (25-30 mmHg for 30 min). Rats were assigned to four experimental groups (normothermia, hypothermia, rapid rewarming [RW], and slow RW). During induction of severe shock, all but the normothermia group were cooled to 34°C. After 60 min of shock, rats were resuscitated with Ringer's solution. The two RW groups were rewarmed at differing rates (6°C/h versus 2°C/h).

RESULTS

Slow RW animals exhibit a significantly prolonged survival compared with the rapid RW animals (P < 0.05). Nevertheless, hypothermic animals show a significant survival benefit as compared to all other experimental groups. Whereas seven animals of the hypothermia group survived to the end of the experiment, none of the other animals did (P < 0.001). No significant differences were found regarding acid base status, metabolism, parameters of organ injury, and coagulation.

CONCLUSIONS

The results indicate that even slow RW with 2°C/h may be still too fast in the setting of experimental hemorrhage. Too rapid rewarming may result in a loss of the protective effects of hypothermia. As rewarming is ultimately inevitable in patients with trauma, potential effects of rewarming on patient outcome should be further investigated in clinical studies.

Trauma care: Finding a better way

In a Perspective, Hasan Alam discusses emerging treatment approaches in trauma care.