Therapeutic hypothermia: applications in pediatric cardiac arrest

Therapeutic hypothermia in children: Which indications remain in 2018?

Experimental studies on therapeutic hypothermia in acute brain injury reported positive outcomes and identified two potential benefits, namely, reduction in seizure incidence and in intracranial pressure. Translating this evidence to humans is challenging, especially for conditions in pediatric patients, such as cardiac arrest, traumatic brain injury, and status epilepticus, among others. This narrative review aimed to discuss the current indications and benefits of therapeutic hypothermia in acute brain injury in the pediatric population (i.e., beyond the neonatal period) by analyzing the neurologic outcome and mortality data obtained from previous studies.

Infants Uniquely Express High Levels of RBM3 and Other Cold-Adaptive Neuroprotectant Proteins in the Human Brain

Neuroprotective cold-shock proteins (CSPs) are abundant in the normothermic neonatal rodent brain but decrease with advancing neurodevelopmental age and are low or absent in the adult brain. It has not been established if neurodevelopmental age alters the baseline expression of CSPs in the human brain. Here, we tested the hypothesis that protein levels of RNA-binding motif 3 (RBM3), reticulon-3 (RTN3), and cold-induced RNA-binding protein (CIRBP) are abundant in the normothermic developing human brain but low-to-absent in adults. We also tested if β-klotho (KLB) is expressed in the developing brain; KLB functions as a coreceptor that controls tissue-specific binding and activity of the systemically circulating thermogenic hormone fibroblast growth factor 21 (FGF21), and is predominantly expressed in the liver, pancreas, and in adipose cells. Methods: Hippocampi and anterior prefrontal cortices (aPFCs/BA10) from a total of 20 male and 20 female subjects were obtained from the NIH NeuroBioBank. CSP and KLB levels were measured in: infants < 1 year old (n = 8), toddlers aged 1-2 years (n = 8), children aged 3-5 years (n = 7), 18-year-old adolescents (n = 8), and adults aged 31-34 years (n = 8). An equal number of male and female (n = 4 each) samples were pooled into each age group, except in the 3- to 5-year-olds which comprised 3 male and 4 female specimens due to sample availability. In total, 78 whole-brain tissues were dissociated using a bead-based Precellys homogenizer to generate equivalent homogenates, and levels of protein targets subsequently analyzed by Western blotting. Results: Infants had the highest levels of RBM3 and other CSPs in the brain compared to all other ages. In the hippocampus, CSPs were detected predominantly in infants. In the aPFC, CSP levels were highest in infants, moderate-to-low in toddlers/children, and below assay detection limits in adolescents/adults. Germane to the thermogenic FGF21/KLB signaling axis, our results confirm that KLB is absent in the adult hippocampus/aPFC as reported by others. In contrast, we report for the first time that KLB is abundant in the early developing human brain; KLB levels were highest in the infant hippocampus/aPFC and moderately expressed in toddlers. RBM3 is a potent neuroprotective CSP. Thus, the impact of these findings on the observed efficacy of therapeutic hypothermia in neonatal brain injury merits further investigation.

From Hypothermia to Cephalosomatic Anastomoses: The Legacy of Robert White (1926-2010) at Case Western Reserve University of Cleveland

Dr. Robert J. White (1926-2010) was an eminent neurosurgeon and bioethicist, renowned for his classic work in hypothermia and pioneering mammalian head transplant experiments. He founded the Division of Neurosurgery at the Cleveland Metropolitan General Hospital (currently MetroHealth Medical Center, a level 1 trauma county hospital) and became the youngest full professor at the Case Western Reserve University in Cleveland, Ohio. With over 500 research articles to his credit, he founded the Brain Research Laboratory at what was then the Cleveland Metropolitan General Hospital, which was also home to future leaders in neurosurgery, neurosciences, and allied specialties. He transferred a healthy monkey head onto a surgically beheaded monkey body under deep hypothermic conditions drawing both laurels and criticisms alike. Despite a largely controversial neurosurgical research career, his original contributions to deep hypothermia have found profound clinical applications in modern trauma and vascular neurosurgery. The new fusogens and myelorrhaphy methods being tried in Europe hold promise for a future of reanastomosing 2 homologous or heterologous tracts in the neuraxis.

Cardiopulmonary Resuscitation in Children With In-Hospital and Out-of-Hospital Cardiopulmonary Arrest: Multicenter Study From Turkey

OBJECTIVES

The objectives of this study were to determine the causes, location of cardiopulmonary arrest (CPA) in children, and demographics of cardiopulmonary resuscitation (CPR) in Turkish pediatric emergency departments and pediatric intensive care units (PICUs) and to determine survival rates and morbidities for both in-hospital and out-of-hospital CPA.

METHODS

This multicenter descriptive study was conducted prospectively between January 15 and July 15, 2011, at 18 centers (15 PICUs, 3 pediatric emergency departments) in Turkey.

RESULTS

During the study period, 239 children had received CPR. Patients' average age was 42.4 (SD, 58.1) months. The most common cause of CPA was respiratory failure (119 patients [49.8%]). The location of CPA was the PICU in 168 (68.6%), hospital wards in 43 (18%), out-of-hospital in 24 (10%), and pediatric emergency department in 8 patients (3.3%). The CPR duration was 30.7 (SD, 23.6) minutes (range, 1-175 minutes) and return of spontaneous circulation was achieved in 107 patients (44.8%) after the first CPR. Finally, 58 patients (24.2%) were discharged from hospital; survival rates were 26% and 8% for in-hospital and out-of-hospital CPA, respectively (P = 0.001). Surviving patients' average length of hospital stay was 27.4 (SD, 39.2) days. In surviving patients, 19 (32.1%) had neurologic disability.

CONCLUSION

Pediatric CPA in both the in-hospital and out-of-hospital setting has a poor outcome.

Therapeutic hypothermia after out-of-hospital cardiac arrest in children

BACKGROUND

Therapeutic hypothermia is recommended for comatose adults after witnessed out-of-hospital cardiac arrest, but data about this intervention in children are limited.

METHODS

We conducted this trial of two targeted temperature interventions at 38 children's hospitals involving children who remained unconscious after out-of-hospital cardiac arrest. Within 6 hours after the return of circulation, comatose patients who were older than 2 days and younger than 18 years of age were randomly assigned to therapeutic hypothermia (target temperature, 33.0°C) or therapeutic normothermia (target temperature, 36.8°C). The primary efficacy outcome, survival at 12 months after cardiac arrest with a Vineland Adaptive Behavior Scales, second edition (VABS-II), score of 70 or higher (on a scale from 20 to 160, with higher scores indicating better function), was evaluated among patients with a VABS-II score of at least 70 before cardiac arrest.

RESULTS

A total of 295 patients underwent randomization. Among the 260 patients with data that could be evaluated and who had a VABS-II score of at least 70 before cardiac arrest, there was no significant difference in the primary outcome between the hypothermia group and the normothermia group (20% vs. 12%; relative likelihood, 1.54; 95% confidence interval [CI], 0.86 to 2.76; P=0.14). Among all the patients with data that could be evaluated, the change in the VABS-II score from baseline to 12 months was not significantly different (P=0.13) and 1-year survival was similar (38% in the hypothermia group vs. 29% in the normothermia group; relative likelihood, 1.29; 95% CI, 0.93 to 1.79; P=0.13). The groups had similar incidences of infection and serious arrhythmias, as well as similar use of blood products and 28-day mortality.

CONCLUSIONS

In comatose children who survived out-of-hospital cardiac arrest, therapeutic hypothermia, as compared with therapeutic normothermia, did not confer a significant benefit in survival with a good functional outcome at 1 year. (Funded by the National Heart, Lung, and Blood Institute and others; THAPCA-OH ClinicalTrials.gov number, NCT00878644.).

Therapeutic Hypothermia and Out-of-Hospital Cardiac Arrest in a Child with Hypertrophic Obstructive Cardiomyopathy

Neurologic outcomes following pediatric cardiac arrest are consistently poor. Early initiation of cardiopulmonary resuscitation has been shown to have positive effects on both survival to hospital discharge, and improved neurological outcomes after cardiac arrest. Additionally, the use of therapeutic hypothermia may improve survival in pediatric cardiac arrest patients admitted to the intensive care unit. We report a child with congenital hypertrophic obstructive cardiomyopathy and an out-of-hospital cardiac arrest, in whom the early initiation of effective prolonged cardiopulmonary resuscitation and subsequent administration of therapeutic hypothermia contributed to a positive outcome with no gross neurologic sequelae. Continuing efforts should be made to promote and employ high-quality cardiopulmonary resuscitation, which likely contributed to the positive outcome of this case. Further research will be necessary to develop and solidify national guidelines for the implementation of therapeutic hypothermia in selected subpopulations of children with OHCA.

Therapeutic hypothermia in children after cardiac arrest: a systematic review and meta-analysis

BACKGROUND

Therapeutic hypothermia (TH) has been shown to be effective in resuscitation of some adults following cardiac arrest and infants with hypoxic ischemic encephalopathy, but has not been well studied in children.

OBJECTIVES

The purpose of this systematic review/meta-analysis was to examine mortality, neurologic outcomes, and adverse events in children following use of TH.

RESULTS

A search of PubMed, the Cumulative Index to Nursing and Allied Health Literature, and the Institute for Scientific Information's Web of Knowledge from 1946 to 2014 yielded 6 studies (3 retrospective and 3 prospective cohort studies) that met our inclusion criteria. Quantitative synthesis of mortality following TH (136 subjects) was 44% (95% confidence interval, 32-57) with 28% (95% confidence interval, 11-53) of survivors (42 subjects) demonstrating poor neurologic outcome. The most frequently reported adverse events were electrolyte imbalances and pneumonia.

CONCLUSIONS

Evidence is insufficient to support the advantage of TH compared with normothermia in pediatric resuscitation. The adverse event profile appears to be different than that reported in adults. Further studies are needed before TH may be considered a standard protocol for children after cardiac arrest.

Targeted Temperature Management in Pediatric Central Nervous System Disease

Acute central nervous system conditions due to hypoxic-ischemic encephalopathy, traumatic brain injury (TBI), status epilepticus, and central nervous system infection/inflammation, are a leading cause of death and disability in childhood. There is a critical need for effective neuroprotective therapies to improve outcome targeting distinct disease pathology. Fever, defined as patient temperature > 38°C, has been clearly shown to exacerbate brain injury. Therapeutic hypothermia (HT) is an intervention using targeted temperature management that has multiple mechanisms of action and robust evidence of efficacy in multiple experimental models of brain injury. Prospective clinical evidence for its neuroprotective efficacy exists in narrowly-defined populations with hypoxic-ischemic injury outside of the pediatric age range while trials comparing hypothermia to normothermia after TBI have failed to demonstrate a benefit on outcome but consistently demonstrate potential use in decreasing refractory intracranial pressure. Data in children from prospective, randomized controlled trials using different strategies of targeted temperature management for various outcomes are few but a large study examining HT versus controlled normothermia to improve neurological outcome in cardiac arrest is underway.

Therapeutic hypothermia for febrile infection-related epilepsy syndrome in two patients

Despite advances in critical care, febrile infection-related epilepsy syndrome remains the most important cause of mortality and neurologic deficits during childhood. Only a few therapeutic agents were reported to shorten the acute phase and improve outcomes. Therapeutic hypothermia was reported effective in stabilizing immune activation, brain edema, and seizure activity, to protect the brain from ongoing functional, apoptotic neural, and glial damage and the systemic expansion of the cytokine storm. We present two pediatric cases of febrile infection-related epilepsy syndrome, refractory to conventional medical therapy. Moderate therapeutic hypothermia at 33°C resulted in fast, sustained control of refractory status epilepticus. After 3 months, both patients recovered with a Glasgow Outcome Scale score of 4. Therapeutic hypothermia may play an important role in children with febrile infection-related epilepsy syndrome.

Clinical report—Guidelines for the determination of brain death in infants and children: an update of the 1987 task force recommendations

OBJECTIVE

To review and revise the 1987 pediatric brain death guidelines.

METHODS

Relevant literature was reviewed. Recommendations were developed using the GRADE system.

CONCLUSIONS AND RECOMMENDATIONS

(1) Determination of brain death in term newborns, infants and children is a clinical diagnosis based on the absence of neurologic function with a known irreversible cause of coma. Because of insufficient data in the literature, recommendations for preterm infants less than 37 weeks gestational age are not included in this guideline. (2) Hypotension, hypothermia, and metabolic disturbances should be treated and corrected and medications that can interfere with the neurologic examination and apnea testing should be discontinued allowing for adequate clearance before proceeding with these evaluations. (3) Two examinations including apnea testing with each examination separated by an observation period are required. Examinations should be performed by different attending physicians. Apnea testing may be performed by the same physician. An observation period of 24 hours for term newborns (37 weeks gestational age) to 30 days of age, and 12 hours for infants and chi (> 30 days to 18 years) is recommended. The first examination determines the child has met the accepted neurologic examination criteria for brain death. The second examination confirms brain death based on an unchanged and irreversible condition. Assessment of neurologic function following cardiopulmonary resuscitation or other severe acute brain injuries should be deferred for 24 hours or longer if there are concerns or inconsistencies in the examination. (4) Apnea testing to support the diagnosis of brain death must be performed safely and requires documentation of an arterial Paco(2) 20 mm Hg above the baseline and ≥ 60 mm Hg with no respiratory effort during the testing period. If the apnea test cannot be safely completed, an ancillary study should be performed. (5) Ancillary studies (electroencephalogram and radionuclide cerebral blood flow) are not required to establish brain death and are not a substitute for the neurologic examination. Ancillary studies may be us d to assist the clinician in making the diagnosis of brain death (i) when components of the examination or apnea testing cannot be completed safely due to the underlying medical condition of the patient; (ii) if there is uncertainty about the results of the neurologic examination; (iii) if a medication effect may be present; or (iv) to reduce the inter-examination observation period. When ancillary studies are used, a second clinical examination and apnea test should be performed and components that can be completed must remain consistent with brain death. In this instance the observation interval may be shortened and the second neurologic examination and apnea test (or all components that are able to be completed safely) can be performed at any time thereafter. (6) Death is declared when the above criteria are fulfilled.

Hypothermia and pediatric cardiac arrest

The survival outcome following pediatric cardiac arrest still remains poor. Survival to hospital discharge ranges anywhere from 0 to 38% when considering both out-of-hospital and in-hospital arrests, with up to 50% of the survivors having neurologic injury. The use of mild induced hypothermia has not been definitively proven to improve outcomes following pediatric cardiac arrest. This may be due to the lack of consensus regarding target temperature, best method of cooling, optimal duration of cooling and identifying the patient population who will receive the greatest benefit. We review the current applications of induced hypothermia in pediatric patients following cardiac arrest after searching the current literature through Pubmed and Ovid journal databases. We put forth compiled recommendations/guidelines for initiating hypothermia therapy, its maintenance, associated monitoring and suggested adjunctive therapies to produce favorable neurologic and survival outcomes.

The effect of therapeutic hypothermia on drug metabolism and response: cellular mechanisms to organ function

INTRODUCTION

Therapeutic hypothermia is being employed clinically due to its neuro-protective benefits. Both critical illness and therapeutic hypothermia significantly affect drug disposition, potentially contributing to drug-therapy and drug-disease interactions. Currently, there is limited information on the known alterations in drug concentration and response during mild hypothermia treatment, and there is a limited understanding of the specific mechanisms that underlie alterations in drug concentrations and the potential clinical importance of these changes.

AREAS COVERED

A systemic review of the effect of therapeutic hypothermia on drug metabolism, disposition and response is provided. Specifically, the clinical and preclinical evidence of the effects of therapeutic hypothermia on blood flow, specific hepatic metabolism pathways, transporter function, renal excretion, pharmacodynamics and the effects during rewarming are reviewed.

EXPERT OPINION

Available evidence demonstrates that mild hypothermia decreases the clearance of a variety of drugs with apparently little change in drug-protein binding. Recent evidence suggests that the magnitude of the change is elimination route specific. Further research is needed to determine the impact of these alterations on both drug concentration and response in order to optimize the therapeutic hypothermia in this vulnerable patient population.