Effect of Hypothermia and Targeted Temperature Management on Drug Disposition and Response Following Cardiac Arrest: A Comprehensive Review of Preclinical and Clinical Investigations

An Update on Brain Death/Death by Neurologic Criteria since the World Brain Death Project

The World Brain Death Project (WBDP) is a 2020 international consensus statement that provides historical background and recommendations on brain death/death by neurologic criteria (BD/DNC) determination. It addresses 13 topics including: (1) worldwide variance in BD/DNC, (2) the science of BD/DNC, (3) the concept of BD/DNC, (4) minimum clinical criteria for BD/DNC determination, (5) beyond minimum clinical BD/DNC determination, (6) pediatric and neonatal BD/DNC determination, (7) BD/DNC determination in patients on ECMO, (8) BD/DNC determination after treatment with targeted temperature management, (9) BD/DNC documentation, (10) qualification for and education on BD/DNC determination, (11) somatic support after BD/DNC for organ donation and other special circumstances, (12) religion and BD/DNC: managing requests to forego a BD/DNC evaluation or continue somatic support after BD/DNC, and (13) BD/DNC and the law. This review summarizes the WBDP content on each of these topics and highlights relevant work published from 2020 to 2023, including both the 192 citing publications and other publications on BD/DNC. Finally, it reviews questions for future research related to BD/DNC and emphasizes the need for national efforts to ensure the minimum standards for BD/DNC determination described in the WBDP are included in national BD/DNC guidelines and due consideration is given to the recommendations about social and legal aspects of BD/DNC determination.

Soluble Urokinase-Type Plasminogen Activator Receptor in Comatose Survivors After Out-of-Hospital Cardiac Arrest Treated with Targeted Temperature Management

Exposure to whole-body ischemia/reperfusion after out-of-hospital cardiac arrest (OHCA) triggers a systemic inflammatory response where soluble urokinase plasminogen activator receptor (suPAR) is released. This study investigated serial levels of suPAR in differentiated target temperature management and the associations with mortality and 6-month neurological outcome. This is a single-center substudy of the randomized Targeted Temperature Management (TTM) for 24-hour versus 48-hour trial. In this analysis, we included 82 patients and measured serial levels of suPAR at 24, 48, and 72 hours after achievement of target temperature (32-34°C). We assessed all-cause mortality and neurological function evaluated by the Cerebral Performance Categories (CPC) at 6 months after OHCA. Levels of suPAR between TTH groups were evaluated in repeated measures mixed models. Mortality was assessed by the Kaplan-Meier method and serial measurements of suPAR (log2 transformed) were investigated by Cox proportional-hazards models. Good neurological outcome at 6 months was assessed by logistic regression analyses. Levels of suPAR were significantly different between TTH groups (pinteraction = 0.04) with the highest difference at 48 hours, 4.7 ng/mL (95% CI: 4.1-5.4 ng/mL) in the TTH24 group compared to 2.8 ng/mL (95% CI: 2.2-3.5 ng/mL) in the TTH48 group, p < 0.0001. Levels of suPAR above the median value were significantly associated with increased all-cause mortality at any time point (plog-rank<0.05). The interaction of suPAR levels and TTH group was not significant (pinteraction = NS). A twofold increase in levels of suPAR was significantly associated with a decreased odds ratio of a good neurological outcome in both unadjusted and adjusted analyses without interaction of TTH group (pinteraction = NS). Prolonged TTM of 48 hours versus 24 hours was associated with lower levels of suPAR. High levels of suPAR were associated with increased mortality and lower odds for good neurological outcome at 6 months with no significant interaction of TTH group.

Time-course relationship between cerebrospinal fluid and serum concentrations of midazolam and albumin in patients with cardiac arrest undergoing targeted temperature management

AIM

To understand the serum and cerebrospinal fluid (CSF) distribution of midazolam is important for proper timing of neurological prognostication of targeted temperature management(TTM) patients. Midazolam binds extensively to albumin in serum although non protein bound form exist in CSF. We investigated the time-course of CSF, serum concentrations of midazolam and albumin in patients with cardiac arrest who underwent TTM.

METHODS

This prospective, single-center, observational study was conducted between May 2020 and April 2022. Midazolam and albumin concentrations in CSF and serum were quantified 0, 24, 48, and 72 h after the return of spontaneous circulation for comparison between the good (Cerebral Performance Category (CPC) 1 and 2) and poor (CPC 3, 4, and 5) neurologic outcome groups. The CSF/serum (C/S) ratios of midazolam and albumin concentrations were determined, along with their correlation coefficients.

RESULTS

Of the 19 enrolled patients, 13 experienced poor outcomes. At 0 h, serum midazolam concentrations were the lowest, whereas serum albumin levels were the highest; in the CSF, the concentrations of both peaked at 24 h. There were no significant inter-group differences in midazolam concentrations in CSF or serum. The C/S ratios of midazolam and albumin significantly differed between the groups. Moderate to strong positive correlations were observed between the midazolam and albumin C/S ratios.

CONCLUSION

In CSF, midazolam and albumin concentrations peaked 24 h post-cardiac arrest. Midazolam and albumin C/S ratios were significantly higher in the poor outcome group and positively correlated with each other, suggesting blood-brain barrier disruption 24 h post-cardiac arrest.

Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest; The effect on post-intervention serum concentrations of sedatives and analgesics and time to awakening

BACKGROUND

This study investigated the association of two levels of targeted temperature management (TTM) after out-of-hospital cardiac arrest (OHCA) with administered doses of sedative and analgesic drugs, serum concentrations, and the effect on time to awakening.

METHODS

This substudy of the TTM2-trial was conducted at three centers in Sweden, with patients randomized to either hypothermia or normothermia. Deep sedation was mandatory during the 40-hour intervention. Blood samples were collected at the end of TTM and end of protocolized fever prevention (72 hours). Samples were analysed for concentrations of propofol, midazolam, clonidine, dexmedetomidine, morphine, oxycodone, ketamine and esketamine. Cumulative doses of administered sedative and analgesic drugs were recorded.

RESULTS

Seventy-one patients were alive at 40 hours and had received the TTM-intervention according to protocol. 33 patients were treated at hypothermia and 38 at normothermia. There were no differences between cumulative doses and concentration and of sedatives/analgesics between the intervention groups at any timepoint. Time until awakening was 53 hours in the hypothermia group compared to 46 hours in the normothermia group (p=0.09).

CONCLUSION

This study of OHCA patients treated at normothermia versus hypothermia found no significant differences in dosing or concentration of sedatives or analgesic drugs in blood samples drawn at the end of the TTM intervention, or at end of protocolized fever prevention, nor the time to awakening.

The influence of temperature on the metabolic activity of CYP2C9, CYP2C19, and CYP3A4 genetic variants in vitro

1. Temperature is considered to affect the activity of drug-metabolizing enzymes; however, no previous studies have compared temperature dependency among cytochrome P450 genetic variants. This study aimed to analyse warfarin 7-hydroxylation by CYP2C9 variants; omeprazole 5-hydroxylation by CYP2C19 variants; and midazolam 1-hydroxylation by CYP3A4 variants at 34 °C, 37 °C, and 40 °C.2. Compared with that seen at 37 °C, the intrinsic clearance rates (Vmax/Km) of CYP2C9.1 and .2 were decreased (76 ∼ 82%), while that of CYP2C9.3 was unchanged at 34 °C. At 40 °C, CYP2C9.1, .2, and .3 exhibited increased (121%), unchanged and decreased (87%) intrinsic clearance rates, respectively. At 34 °C, the clearance rates of CYP2C19.1A and .10 were decreased (71 ∼ 86%), that of CYP2C19.1B was unchanged, and those of CYP2C19.8 and .23 were increased (130 ∼ 134%). At 40 °C, the clearance rates of CYP2C19.1A, .1B, .10, and .23 remained unaffected, while that of CYP2C19.8 was decreased (74%). At 34 °C, the clearance rates of CYP3A4.1 and .16 were decreased (79 ∼ 84%), those of CYP3A4.2 and .7 were unchanged, and that of CYP3A4.18 was slightly increased (112%). At 40 °C, the clearance rate of CYP3A4.1 remained unaffected, while those of CYP3A4.2, .7, .16, and .18 were decreased (58 ∼ 82%).3. These findings may be clinically useful for dose optimisation in patients with hypothermia or hyperthermia.

The influence of cardiopulmonary bypass on pediatric pharmacokinetics

INTRODUCTION

Every year thousands of children undergo surgery for congenital heart disease. Cardiac surgery requires the use of cardiopulmonary bypass, which can have unexpected consequences for pharmacokinetic parameters.

AREAS COVERED

We describe the pathophysiological properties of cardiopulmonary bypass that may influence pharmacokinetic parameters, with a focus on literature published in the last 10 years. We performed a PubMed database search with the keywords 'Cardiopulmonary bypass' AND 'Pediatric' AND 'Pharmacokinetics'. We searched related articles on PubMed and checked the references of articles for relevant studies.

EXPERT OPINION

Interest in the influence of cardiopulmonary bypass on pharmacokinetics has increased over the last 10 years, especially due to the use of population pharmacokinetic modeling. Unfortunately, study design usually limits the amount of information that can be obtained with sufficient power and the best way to model cardiopulmonary bypass is yet unknown. More information is needed on the pathophysiology of pediatric heart disease and cardiopulmonary bypass. Once adequately validated, PK models should be integrated in the patient electronic database integrating covariates and biomarkers influencing PK, making it possible to predict real-time drug concentrations and guide further clinical management for the individual patient at the bedside.

Withdrawal of life-sustaining therapy in intensive care unit patients following out-of-hospital cardiac arrest: An Australian metropolitan ICU experience

BACKGROUND

Withdrawal of life-sustaining therapy is a common phenomenon following out-of-hospital cardiac arrest. The clinical practices surrounding withdrawal of life-sustaining therapy remain unclear and warrant further inspection due to their reported impact on post-cardiac arrest mortality.

OBJECTIVES

To determine factors associated with withdrawal of life-sustaining therapy (WLST) in intensive care unit (ICU) patients following out-of-hospital cardiac arrest (OHCA).

METHODS

A retrospective review of ICU patients' clinical records following OHCA was conducted from January 2010 to December 2015. Demographic features, cardiac arrest characteristics, and targeted temperature management practices were compared between patients with and without WLST. We dichotomised WLST into early (ICU length of stay <72 h) and late (ICU length of stay ≥72 h). Factors independently associated with WLST were determined by multivariable binary logistic regression.

RESULTS

The study cohort included 260 post-OHCA ICU patients. The mean age was 58 years, and majority were males (178, 68%); 145 (56%) underwent WLST, with the majority undergoing early WLST (89, 61%). Status myoclonus was the strongest independent factor associated with early WLST (OR 42.53, 95% CI 4.97-363.60; p < 0.001). Glasgow Coma Scale (GCS) motor response of <4 on day three post-OHCA was the strongest factor associated with delayed WLST (OR 48.76, 95% CI 11.87-200.27; p < 0.0001).

CONCLUSION

The majority of deaths in ICU patients post-OHCA occurred following early WLST. Status myoclonus and a GCS motor response of <4 on day three post-OHCA are independently associated with WLST.

Targeted temperature management after cardiac arrest is associated with reduced metabolism of pantoprazole - A probe drug of CYP2C19 metabolism

OBJECTIVE

Targeted temperature management (TTM) is part of standard post-resuscitation care. TTM may downregulate cytochrome enzyme activity and thus impact drug metabolism. This study compared the pharmacokinetics (PK) of pantoprazole, a probe drug of CYP2C19-dependent metabolism, at different stages of TTM following cardiac arrest.

METHODS

This prospective controlled study was performed at the Medical University of Vienna and enrolled 16 patients following cardiac arrest. The patients completed up to three study periods (each lasting 24 h) in which plasma concentrations of pantoprazole were quantified: (P1) hypothermia (33 °C) after admission, (P2) normothermia after rewarming (36 °C, intensive care), and (P3) normothermia during recovery (normal ward, control group). PK was analysed using non-compartmental analysis and nonlinear mixed-effects modelling.

RESULTS

16 patients completed periods P1 and P2; ten completed P3. The median half-life of pantoprazole was 2.4 h (quartiles: 1.8-4.8 h) in P1, 2.8 h (2.1-6.8 h, p = 0.046 vs. P1, p = 0.005 vs. P3) in P2 and 1.2 h (0.9 - 2.3 h, p = 0.007 vs. P1) in P3. A two-compartment model described the PK data best. Typical values for clearance were estimated separately for each study period, indicating 40% and 29% reductions during P1 and P2, respectively, compared to P3. The central volume of distribution was estimated separately for P2, indicating a 64% increase compared to P1 and P3.

CONCLUSION

CYP2C19-dependent drug metabolism is downregulated during TTM following cardiac arrest. These results may influence drug choice and dosing of similarly metabolized drugs and may be helpful for designing studies in similar clinical situations.

Dexmedetomidine Use in Infants Undergoing Cooling Due to Neonatal Encephalopathy (DICE Trial): A Randomized Controlled Trial: Background, Aims and Study Protocol

Background: Neonatal hypoxia-ischemia encephalopathy (HIE) is the leading cause of neonatal death and poor neurodevelopmental outcomes worldwide. Therapeutic hypothermia (TH), while beneficial, still leaves many HIE treated infants with lifelong disabilities. Furthermore, infants undergoing TH often require treatment for pain and agitation which may lead to further brain injury. For instance, morphine use in animal models has been shown to induce neuronal apoptosis. Dexmedetomidine is a potent α₂-adrenergic receptor agonist that may be a better alternative to morphine for newborns with HIE treated with TH. Dexmedetomidine provides sedation, analgesia, and prevents shivering but does not suppress ventilation. Importantly, there is increasing evidence that dexmedetomidine has neuroprotective properties. Even though there are limited data on pharmacokinetics (PK), safety and efficacy of dexmedetomidine in infants with HIE, it has been increasingly administered in many centers.

Objectives: To review the current approach to treatment of pain, sedation and shivering in infants with HIE undergoing TH, and to describe a new phase II safety and pharmacokinetics randomized controlled trial that proposes the use of dexmedetomidine vs. morphine in this population.

Methods: This article presents an overview of the current management of pain and sedation in critically ill infants diagnosed with HIE and undergoing TH for 72 h. The article describes the design and methodology of a randomized, controlled, unmasked multicenter trial of dexmedetomidine vs. morphine administration enrolling 50 (25 per arm) neonates ≥36 weeks of gestation with moderate or severe HIE undergoing TH and that require pain/sedation treatment.

Results and Conclusions: Dexmedetomidine may be a better alternative to morphine for the treatment of pain and sedation in newborns with HIE treated with TH. There is increasing evidence that dexmedetomidine has neuroprotective properties in several preclinical studies of injury models including ischemia-reperfusion, inflammation, and traumatic brain injury as well as adult clinical trials of brain trauma. The Dexmedetomidine Use in Infants undergoing Cooling due to Neonatal Encephalopathy (DICE) trial will evaluate whether administration of dexmedetomidine vs. morphine is safe, establish dexmedetomidine optimal dosing by collecting opportunistic PK data, and obtain preliminary neurodevelopmental data to inform a large Phase III efficacy trial with long term neurodevelopment impairment as the primary outcome.

Opioid-Associated Out-of-Hospital Cardiac Arrest: Distinctive Clinical Features and Implications for Health Care and Public Responses: A Scientific Statement From the American Heart Association

Opioid overdose is the leading cause of death for Americans 25 to 64 years of age, and opioid use disorder affects >2 million Americans. The epidemiology of opioid-associated out-of-hospital cardiac arrest in the United States is changing rapidly, with exponential increases in death resulting from synthetic opioids and linear increases in heroin deaths more than offsetting modest reductions in deaths from prescription opioids. The pathophysiology of polysubstance toxidromes involving opioids, asphyxial death, and prolonged hypoxemia leading to global ischemia (cardiac arrest) differs from that of sudden cardiac arrest. People who use opioids may also develop bacteremia, central nervous system vasculitis and leukoencephalopathy, torsades de pointes, pulmonary vasculopathy, and pulmonary edema. Emergency management of opioid poisoning requires recognition by the lay public or emergency dispatchers, prompt emergency response, and effective ventilation coupled to compressions in the setting of opioid-associated out-of-hospital cardiac arrest. Effective ventilation is challenging to teach, whereas naloxone, an opioid antagonist, can be administered by emergency medical personnel, trained laypeople, and the general public with dispatcher instruction to prevent cardiac arrest. Opioid education and naloxone distributions programs have been developed to teach people who are likely to encounter a person with opioid poisoning how to administer naloxone, deliver high-quality compressions, and perform rescue breathing. Current American Heart Association recommendations call for laypeople and others who cannot reliably establish the presence of a pulse to initiate cardiopulmonary resuscitation in any individual who is unconscious and not breathing normally; if opioid overdose is suspected, naloxone should also be administered. Secondary prevention, including counseling, opioid overdose education with take-home naloxone, and medication for opioid use disorder, is important to prevent recurrent opioid overdose.

Rationale and Strategies for Development of an Optimal Bundle of Management for Cardiac Arrest

Objectives

To construct a highly detailed yet practical, attainable roadmap for enhancing the likelihood of neurologically intact survival following sudden cardiac arrest.

Design Setting and Patients

Population-based outcomes following out-of-hospital cardiac arrest were collated for 10 U.S. counties in Alaska, California, Florida, Ohio, Minnesota, Utah, and Washington. The 10 identified emergency medical services systems were those that had recently reported significant improvements in neurologically intact survival after introducing a more comprehensive approach involving citizens, hospitals, and evolving strategies for incorporating technology-based, highly choreographed care and training. Detailed inventories of in-common elements were collated from the ten 9-1-1 agencies and assimilated. For reference, combined averaged outcomes for out-of-hospital cardiac arrest occurring January 1, 2017, to February 28, 2018, were compared with concurrent U.S. outcomes reported by the well-established Cardiac Arrest Registry to Enhance Survival.

Interventions

Most commonly, interventions and components from the ten 9-1-1 systems consistently included extensive public cardiopulmonary resuscitation training, 9-1-1 system-connected smart phone applications, expedited dispatcher procedures, cardiopulmonary resuscitation quality monitoring, mechanical cardiopulmonary resuscitation, devices for enhancing negative intrathoracic pressure regulation, extracorporeal membrane oxygenation protocols, body temperature management procedures, rapid cardiac angiography, and intensive involvement of medical directors, operational and quality assurance officers, and training staff.

Measurements and Main Results

Compared with Cardiac Arrest Registry to Enhance Survival (n = 78,704), the cohorts from the 10 emergency medical services agencies examined (n = 2,911) demonstrated significantly increased likelihoods of return of spontaneous circulation (mean 37.4% vs 31.5%; p < 0.001) and neurologically favorable hospital discharge, particularly after witnessed collapses involving bystander cardiopulmonary resuscitation and shockable cardiac rhythms (mean 10.7% vs 8.4%; p < 0.001; and 41.6% vs 29.2%; p < 0.001, respectively).

Conclusions

The likelihood of neurologically favorable survival following out-of-hospital cardiac arrest can improve substantially in communities that conscientiously and meticulously introduce a well-sequenced, highly choreographed, system-wide portfolio of both traditional and nonconventional approaches to training, technologies, and physiologic management. The commonalities found in the analyzed systems create a compelling case that other communities can also improve out-of-hospital cardiac arrest outcomes significantly by conscientiously exploring and adopting similar bundles of system organization and care.

Early risk stratification after resuscitation from cardiac arrest

Emergency clinicians often resuscitate cardiac arrest patients, and after acute resuscitation, clinicians face multiple decisions regarding disposition. Recent evidence suggests that out-of-hospital cardiac arrest patients with return of spontaneous circulation have higher odds of survival to hospital discharge, long-term survival, and improved functional outcomes when treated at centers that can provide advanced multidisciplinary care. For community clinicians, a high volume cardiac arrest center may be hours away. While current guidelines recommend against neurological prognostication in the first hours or days after return of spontaneous circulation, there are early findings suggestive of irrecoverable brain injury in which the patient would receive no benefit from transfer. In this Concepts article, we describe a simplified approach to quickly evaluate neurological status in cardiac arrest patients and identify findings concerning for irrecoverable brain injury. Characteristics of the arrest and resuscitation, initial neurological assessment, and brain computed tomography together can identify patients with high likelihood of irrecoverable anoxic injury. Patients who may benefit from centers with access to continuous electroencephalography are discussed. This approach can be used to identify patients who may benefit from rapid transfer to cardiac arrest centers versus those who may benefit from care close to home. Risk stratification also can provide realistic expectations for recovery to families.

Management of temperature control in post-cardiac arrest care: an expert report

Targeted temperature management (TTM) through induced hypothermia (between 32-36 ^oC) is currently regarded as a first-line treatment during the management of post-cardiac arrest patients admitted to the Intensive Care Unit (ICU). The aim of TTM is to afford neuroprotection and reduce secondary neurological damage caused by anoxia. Despite the large body of evidence on its benefits, the TTM is still little used in Spain. There are controversial issues referred to its implementation, such as the optimal target body temperature, timing, duration and the rewarming process. The present study reviews the best available scientific evidence and the current recommendations contained in the international guidelines. In addition, the study focuses on the practical implementation of TTM in post-cardiac arrest patients in general and cardiological ICUs, with a discussion of the implementation strategies, protocols, management of complications and assessment of the neurological prognosis.

Unsupervised learning of early post-arrest brain injury phenotypes

INTRODUCTION

Trials may be neutral when they do not appropriately target the experimental intervention. We speculated multimodality assessment of early hypoxic-ischemic brain injury would identify phenotypes likely to benefit from therapeutic interventions.

METHODS

We performed a retrospective study including comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA) by one of 126 emergency medical services or in-hospital arrest at one of 26 hospitals from 2011 to 2019. All patients were ultimately transported to a single tertiary center for care including standardized initial neurological examination, brain imaging and electroencephalography; targeted temperature management (TTM); hemodynamic optimization targeting mean arterial pressure (MAP) >80 mmHg; and, coronary angiography for clinical suspicion for acute coronary syndrome. We used unsupervised learning to identify brain injury phenotypes defined by admission neurodiagnostics. We tested for interactions between phenotype and TTM, hemodynamic management and cardiac catheterization in models predicting recovery.

RESULTS

We included 1086 patients with mean (SD) age 58 (17) years of whom 955 (88%) were resuscitated from OHCA. Survival to hospital discharge was 27%, and 248 (23%) were discharged with Cerebral Performance Category (CPC) 1-3. We identified 5 clusters defining distinct brain injury phenotypes, each comprising 14% to 30% of the cohort with discharge CPC 1-3 in 59% to <1%. We found significant interactions between cluster and TTM strategy (P = 0.01), MAP (P < 0.001) and coronary angiography (P = 0.04) in models predicting outcomes.

CONCLUSIONS

We identified patterns of early hypoxic-ischemic injury based on multiple diagnostic modalities that predict responsiveness to several therapeutic interventions recently tested in neutral clinical trials.

Dynamic determination of functional liver capacity with the LiMAx test in post-cardiac arrest patients undergoing targeted temperature management-A prospective trial

BACKGROUND

Transiently increased transaminases is a common finding after cardiac arrest but little is known about the functional liver capacity (LiMAx) during the post-cardiac arrest syndrome and treatment in the intensive care unit (ICU). The aim of this trial was to evaluate liver function capacity in post-cardiac arrest survivors undergoing targeted temperature management (TTM) in ICU.

METHODS

Thirty-two post-cardiac arrest survivors were prospectively included with all patients undergoing TTM at 33°C for 24 hours. Blood samples were collected, and LiMAx testing was performed at days 1, 2, 5, and 10 post-cardiac arrest. LiMAx is a non-invasive, in vivo, dynamic breath test determining cytochrome P450 1A2 (CYP1A2) capacity using intravenous (IV) ¹³ C-methacetin, thus reflecting maximum liver function capacity. Static liver parameters were determined and compared to LiMAx values.

RESULTS

A typical pattern of transiently, mildly increased transaminases was demonstrated without fulfilling the criteria for hypoxic hepatitis (HH). CYP1A2 activity was reduced with slow normalization over 10 days (lowest median 48 hours after cardiac arrest: 228.5 (25-75 percentile 105.2-301.7 μg/kg/h, P < .05). Parameters reflecting the liver synthetic function were not impaired, as assessed by, in standard laboratory testing.

CONCLUSION

Liver functional capacity is impaired in patients after cardiac arrest undergoing TTM at 33°C. More data are needed to determine if liver functional capacity may add relevant information, especially in the context of pharmacotherapy, to individualize post-cardiac arrest care.

Standards for Studies of Neurological Prognostication in Comatose Survivors of Cardiac Arrest: A Scientific Statement From the American Heart Association

Significant improvements have been achieved in cardiac arrest resuscitation and postarrest resuscitation care, but mortality remains high. Most of the poor outcomes and deaths of cardiac arrest survivors have been attributed to widespread brain injury. This brain injury, commonly manifested as a comatose state, is a marker of poor outcome and a major basis for unfavorable neurological prognostication. Accurate prognostication is important to avoid pursuing futile treatments when poor outcome is inevitable but also to avoid an inappropriate withdrawal of life-sustaining treatment in patients who may otherwise have a chance of achieving meaningful neurological recovery. Inaccurate neurological prognostication leading to withdrawal of life-sustaining treatment and deaths may significantly bias clinical studies, leading to failure in detecting the true study outcomes. The American Heart Association Emergency Cardiovascular Care Science Subcommittee organized a writing group composed of adult and pediatric experts from neurology, cardiology, emergency medicine, intensive care medicine, and nursing to review existing neurological prognostication studies, the practice of neurological prognostication, and withdrawal of life-sustaining treatment. The writing group determined that the overall quality of existing neurological prognostication studies is low. As a consequence, the degree of confidence in the predictors and the subsequent outcomes is also low. Therefore, the writing group suggests that neurological prognostication parameters need to be approached as index tests based on relevant neurological functions that are directly related to the functional outcome and contribute to the quality of life of cardiac arrest survivors. Suggestions to improve the quality of adult and pediatric neurological prognostication studies are provided.

Studies on long term behavioural changes in group-housed rat models of brain and spinal cord injury using an automated home cage recording system

BACKGROUND

Neurotrauma patients face major neurological sequelae. The failure in the preclinical-to-clinical translation of candidate therapies could be due to poor evaluation of rodent behaviours after neurotrauma.

NEW METHOD

A home cage automated system was used to study the long term behaviour of individual rats with traumatic brain injury (TBI), spinal cord injury (SCI) and non-CNS injured controls, whilst group-housed in their home cages. Naïve rats were used as baseline controls. Automated locomotor activity and body temperature recordings were carried out 24 h /day for 3 days/week during 12 weeks post-injury. Behavioural patterns, including aggression, rearing, grooming, feeding and drinking were analysed from automated video recordings during week 1, 6 and 12.

RESULTS

SCI animals showed a lower locomotor activity compared to TBI or control animals during light and dark phases. TBI animals showed a higher aggression during the dark phase in the first week post-injury compared to SCI or control animals. Individual grooming and rearing were reduced in SCI animals compared to TBI and control animals in the first week post-injury during the dark phase. No differences in drinking or feeding were detected between groups. Locomotor activity did not differ between naïve male and female rats, but body temperature differ between light and dark phases for both.

STANDARD METHODS

Injury severity was compared to standard SCI and TBI behaviour scores (BBB and mNSS, respectively) and histological analysis.

CONCLUSIONS

This study demonstrates the practical benefits of using a non-intrusive automated home cage recording system to observe long term individual behaviour of group-housed SCI and TBI rats.

Neuroprotection by cannabidiol and hypothermia in a piglet model of newborn hypoxic-ischemic brain damage

OBJECTIVE

Hypothermia, the gold standard after a hypoxic-ischemic insult, is not beneficial in all treated newborns. Cannabidiol is neuroprotective in animal models of newborn hypoxic-ischemic encephalopathy. This study compared the relative efficacies of cannabidiol and hypothermia in newborn hypoxic-ischemic piglets and assessed whether addition of cannabidiol augments hypothermic neuroprotection.

METHODS

One day-old HI (carotid clamp and FiO₂ 10% for 20 min) piglets were randomized to vehicle or cannabidiol 1 mg/kg i.v. u.i.d. for three doses after being submitted to normothermia or 48 h-long hypothermia with a subsequent rewarming period of 6 h. Non-manipulated piglets (naïve) served as controls. Hemodynamic or respiratory parameters as well as brain activity (aEEG amplitude) were monitored throughout the experiment. Following termination, brains were obtained for histological (TUNEL staining, apoptosis; immunohistochemistry for Iba-1, microglia), biochemical (protein carbonylation, oxidative stress; and TNFα concentration, neuroinflammation) or proton magnetic resonance spectroscopy (Lac/NAA: metabolic derangement; Glu/NAA: excitotoxicity).

RESULTS

HI led to sustained depressed brain activity and increased microglial activation, which was significantly improved by cannabidiol alone or with hypothermia but not by hypothermia alone. Hypoxic-ischemic-induced increases in Lac/NAA, Glu/NAA, TNFα or apoptosis were not reversed by either hypothermia or cannabidiol alone, but combination of the therapies did. No treatment modified the effects of HI on oxidative stress or astroglial activation. Cannabidiol treatment was well tolerated.

CONCLUSIONS

cannabidiol administration after hypoxia-ischemia in piglets offers some neuroprotective effects but the combination of cannabidiol and hypothermia shows some additive effect leading to more complete neuroprotection than cannabidiol or hypothermia alone.

Impact of Targeted Temperature Management on ED Patients with Drug Overdose-Related Cardiac Arrest

INTRODUCTION

Drug overdose is the leading cause of non-traumatic out-of-hospital cardiac arrest (OHCA) among young adults. This study investigates whether targeted temperature management (TTM) improves hospital survival from presumed overdose-related cardiac arrest.

METHODS

Retrospective chart review of consecutive cardiac arrests presenting to an urban tertiary care hospital ED from 2011 to 2015. ED patients with cardiac arrest were included if < 50 years old, and excluded if there was a non-overdose etiology (e.g., trauma, ST-elevation myocardial infarction, subarachnoid hemorrhage). The main intervention was TTM, carried out with a combination of the Arctic Sun device and refrigerated crystalloid/antipyretics (goal temperature 33-36 °C). The primary outcome was survival to hospital discharge; neurologically intact survival was the secondary outcome.

RESULTS

Of 923 patients with cardiac arrest, 802 (86.9%) met exclusion criteria, leaving 121 patients for final analysis. There were 29 patients in the TTM group (24.0%) vs 92 patients in the non-TTM group (76.0%). Eleven patients (9.1%) survived to hospital discharge. TTM was associated with increased odds of survival to hospital discharge (OR 11.3, 95% CI 2.8-46.3, p < 0.001), which increased substantially when palliative outcomes were excluded from the cohort (OR 117.3, 95% CI 17.0-808.4, p < 0.001). Despite achieving statistical significance (OR 1.1, 95% CI 1.0-1.3), TTM had no clinically significant effect on neurologically intact survival.

CONCLUSIONS

TTM was associated with improved survival in ED patients with presumed drug overdose-related cardiac arrest. The impact of TTM on neurologically intact survival among these patients requires further study.

Therapeutic hypothermia after paediatric cardiac arrest: Pooled randomized controlled trials

BACKGROUND

Separate trials to evaluate therapeutic hypothermia after paediatric cardiac arrest for out-of-hospital and in-hospital settings reported no statistically significant differences in survival with favourable neurobehavioral outcome or safety compared to therapeutic normothermia. However, larger sample sizes might detect smaller clinical effects. Our aim was to pool data from identically conducted trials to approximately double the sample size of the individual trials yielding greater statistical power to compare outcomes.

METHODS

Combine individual patient data from two clinical trials set in forty-one paediatric intensive care units in USA, Canada and UK. Children aged at least 48 h up to 18 years old, who remained comatose after resuscitation, were randomized within 6 h of return of circulation to hypothermia or normothermia (target 33.0 °C or 36.8 °C). The primary outcome, survival 12 months post-arrest with Vineland Adaptive Behaviour Scales, Second Edition (VABS-II) score at least 70 (scored from 20 to 160, higher scores reflecting better function, population mean = 100, SD = 15), was evaluated among patients with pre-arrest scores ≥70.

RESULTS

624 patients were randomized. Among 517 with pre-arrest VABS-II scores ≥70, the primary outcome did not significantly differ between hypothermia and normothermia groups (28% [75/271] and 26% [63/246], respectively; relative risk, 1.08; 95% confidence interval [CI], 0.81 to 1.42; p = 0.61). Among 602 evaluable patients, the change in VABS-II score from baseline to 12 months did not differ significantly between groups (p = 0.20), nor did, proportion of cases with declines no more than 15 points or improvement from baseline [22% (hypothermia) and 21% (normothermia)]. One-year survival did not differ significantly between hypothermia and normothermia groups (44% [138/317] and 38% [113/ 297], respectively; relative risk, 1.15; 95% CI, 0.95 to 1.38; p = 0.15). Incidences of blood-product use, infection, and serious cardiac arrhythmia adverse events, and 28-day mortality, did not differ between groups.

CONCLUSIONS

Analysis of combined data from two paediatric cardiac arrest targeted temperature management trials including both in-hospital and out-of-hospital cases revealed that hypothermia, as compared with normothermia, did not confer a significant benefit in survival with favourable functional outcome at one year.

COOL-ARREST: Results from a Pilot Multicenter, Prospective, Single-Arm Observational Trial to Assess Intravascular Temperature Management in the Treatment of Cardiac Arrest

Targeted temperature management (TTM) is recommended postcardiac arrest. The cooling method with the highest safety and efficacy is unknown. The COOL-ARREST pilot trial aimed to evaluate the safety and efficacy of the most contemporary ZOLL Thermogard XP Intravascular Temperature Management (IVTM) system for providing mild TTM postcardiac arrest. This multicenter, prospective, single-arm, observational pilot trial enrolled patients at eight U.S. hospitals between July 28, 2014, and July 24, 2015. Adult (≥18 years old), out-of-hospital cardiac arrest subjects of presumed cardiac etiology who achieved return of spontaneous circulation (ROSC) were considered for inclusion. Patients were excluded if (1) awake or consistently following commands after ROSC, (2) significant prearrest neurological dysfunction, (3) terminal illness or advanced directives precluding aggressive care, and (4) severe hemodynamic instability or shock. Patient temperature was maintained at 33.0°C ± 0.3°C for a total of 24 hours followed by controlled rewarming (0.1-0.2°C/h). Logistic regressions were used to assess association of good functional outcome (modified Rankin Scale ≤3) measured at the time of hospital discharge with shockable rhythm (yes/no), age, gender, race/ethnicity, lay-rescuer cardiopulmonary resuscitation, time to basic life support (minutes), time to ROSC (minutes), lactate (mg/dL), and pH on admission. The ZOLL IVTM system was effective at inducing TTM (median time to target temperature from initiation, 89 minutes [interquartile range 42-155]). Adverse events most often included electrolyte abnormalities and dysrhythmias. Of patients surviving to hospital discharge, 16/20 patients had a good functional outcome. A total of 18 patients survived through 90-day follow-up, at which time 94% (17/18) of patients had good functional outcome. The COOL-ARREST pilot trial demonstrates high safety and efficacy of the ZOLL Thermogard XP IVTM system in the application of mild TTM postcardiac arrest. This observational trial also revealed noteworthy variability in the management of postcardiac arrest patients, particularly with the use of early withdrawal of life-sustaining therapy.

ILCOR Scientific Knowledge Gaps and Clinical Research Priorities for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: A Consensus Statement

Despite significant advances in the field of resuscitation science, important knowledge gaps persist. Current guidelines for resuscitation are based on the International Liaison Committee on Resuscitation 2015 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations, which includes treatment recommendations supported by the available evidence. The writing group developed this consensus statement with the goal of focusing future research by addressing the knowledge gaps identified during and after the 2015 International Liaison Committee on Resuscitation evidence evaluation process. Key publications since the 2015 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations are referenced, along with known ongoing clinical trials that are likely to affect future guidelines.

Comparison of two sedation regimens during targeted temperature management after cardiac arrest

PURPOSE

Although guidelines on post-resuscitation care recommend the use of short-acting agents for sedation during targeted temperature management (TTM) after cardiac arrest (CA), the potential advantages of this strategy have not been clinically demonstrated.

METHODS

We compared two sedation regimens (propofol-remifentanil, period P2, vs midazolam-fentanyl, period P1) among comatose TTM-treated CA survivors. Management protocol, apart from sedation and neuromuscular blockers use, did not change between the two periods. Baseline severity was assessed with Cardiac-Arrest-Hospital-Prognosis (CAHP) score. Time to awakening was measured starting from discontinuation of sedation at the end of rewarming. Awakening was defined as delayed when it occurred after more than 48 h.

RESULTS

460 patients (134 in P2, 326 in P1) were included. CAHP score did not significantly differ between P2 and P1 (P = 0.93). Sixty percent of patients awoke in both periods (81/134 vs. 194/326, P = 0.85). Median time to awakening was 2.5 (IQR 1-9) hours in P2 vs. 17 (IQR 7-60) hours in P1. Awakening was delayed in 6% of patients in P2 vs. 29% in P1 (p < 0.001). After adjustment, P2 was associated with significantly lower odds of delayed awakening (OR 0.08, 95% CI 0.03-0.2; P < 0.001). Patients in P2 had significantly more ventilator-free days (25 vs. 24 days; P = 0.007), and lower catecholamine-free days within day 28. Survival and favorable neurologic outcome at discharge did not differ across periods.

CONCLUSIONS

During TTM following resuscitation from CA, sedation with propofol-remifentanil was associated with significantly earlier awakening and more ventilator-free days as compared with midazolam-fentanyl.

2-Iminobiotin Superimposed on Hypothermia Protects Human Neuronal Cells from Hypoxia-Induced Cell Damage: An in Vitro Study

Perinatal asphyxia represents one of the major causes of neonatal morbidity and mortality. Hypothermia is currently the only established treatment for hypoxic-ischemic encephalopathy (HIE), but additional pharmacological strategies are being explored to further reduce the damage after perinatal asphyxia. The aim of this study was to evaluate whether 2-iminobiotin (2-IB) superimposed on hypothermia has the potential to attenuate hypoxia-induced injury of neuronal cells. In vitro hypoxia was induced for 7 h in neuronal IMR-32 cell cultures. Afterwards, all cultures were subjected to 25 h of hypothermia (33.5°C), and incubated with vehicle or 2-IB (10, 30, 50, 100, and 300 ng/ml). Cell morphology was evaluated by brightfield microscopy. Cell damage was analyzed by LDH assays. Production of reactive oxygen species (ROS) was measured using fluorometric assays. Western blotting for PARP, Caspase-3, and the phosphorylated forms of akt and erk1/2 was conducted. To evaluate early apoptotic events and signaling, cell protein was isolated 4 h post-hypoxia and human apoptosis proteome profiler arrays were performed. Twenty-five hour after the hypoxic insult, clear morphological signs of cell damage were visible and significant LDH release as well as ROS production were observed even under hypothermic conditions. Post-hypoxic application of 2-IB (10 and 30 ng/ml) reduced the hypoxia-induced LDH release but not ROS production. Phosphorylation of erk1/2 was significantly increased after hypoxia, while phosphorylation of akt, protein expression of Caspase-3 and cleavage of PARP were only slightly increased. Addition of 2-IB did not affect any of the investigated proteins. Apoptosis proteome profiler arrays performed with cellular protein obtained 4 h after hypoxia revealed that post-hypoxic application of 2-IB resulted in a ≥ 25% down regulation of 10/35 apoptosis-related proteins: Bad, Bax, Bcl-2, cleaved Caspase-3, TRAILR1, TRAILR2, PON2, p21, p27, and phospho Rad17. In summary, addition of 2-IB during hypothermia is able to attenuate hypoxia-induced neuronal cell damage in vitro. Combination treatment of hypothermia with 2-IB could be a promising strategy to reduce hypoxia-induced neuronal cell damage and should be considered in further animal and clinical studies.

Automated recording of home cage activity and temperature of individual rats housed in social groups: The Rodent Big Brother project

Measuring the activity and temperature of rats is commonly required in biomedical research. Conventional approaches necessitate single housing, which affects their behavior and wellbeing. We have used a subcutaneous radiofrequency identification (RFID) transponder to measure ambulatory activity and temperature of individual rats when group-housed in conventional, rack-mounted home cages. The transponder location and temperature is detected by a matrix of antennae in a baseplate under the cage. An infrared high-definition camera acquires side-view video of the cage and also enables automated detection of vertical activity. Validation studies showed that baseplate-derived ambulatory activity correlated well with manual tracking and with side-view whole-cage video pixel movement. This technology enables individual behavioral and temperature data to be acquired continuously from group-housed rats in their familiar, home cage environment. We demonstrate its ability to reliably detect naturally occurring behavioral effects, extending beyond the capabilities of routine observational tests and conventional monitoring equipment. It has numerous potential applications including safety pharmacology, toxicology, circadian biology, disease models and drug discovery.

Prasugrel in critically ill patients

While prasugrel is indicated for the treatment of myocardial infarction, its effects in the most severely affected patients requiring intensive care is unknown, so that we measured the antiplatelet effects and sparse pharmacokinetics of prasugrel in critically ill patients. Twenty-three patients admitted to medical intensive care units, who were treated with 10 mg prasugrel once daily, were included in this prospective trial. Critically ill patients responded poorly to daily prasugrel treatment: adenosine diphosphate (ADP)-induced aggregation in whole blood classified 65 % (95 % confidence intervals (CI) 43-84 %) of patients as having high on treatment platelet reactivity, platelet function under high shear rates even 74 % (95 %CI 52-90 %). There was only limited additional inhibition provided 2 hours after the next dose of prasugrel. In contrast, insufficient inhibition of the target was only seen in 26 % (95 %CI 10-48 %) of patients as measured by the vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) assay. Low effective plasma levels of prasugrel active metabolite were measured at trough [0.5 (quartiles 0.5-1.1) ng/ml at baseline], and 2 hours after intake [5.7 (3.8-9.8) ng/ml], but showed coefficients of variation of ~70 %. In sum, inhibition of platelet aggregation by prasugrel is not uniform but highly variable in critically ill patients, similar to clopidogrel in a general population. The pharmacokinetic measurements indicate that poor absorption/metabolism of prasugrel may partly contribute while inflammation induced heightened intrinsic platelet reactivity may also play a role.