Therapeutic hypothermia decreases phenytoin elimination in children with traumatic brain injury

Treating Seizures and Improving Newborn Outcomes for Infants with Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy is the most common cause of neonatal seizures. Continuous electroencephalographic monitoring is recommended given high rates of subclinical seizures. Prompt diagnosis and treatment of seizures may improve neurodevelopmental outcomes. International League Against Epilepsy guidelines indicate that (1) phenobarbital remains the first-line treatment of neonatal seizures and (2) early discontinuation of antiseizure medications following resolution of acute provoked seizures, and prior to discharge home, is recommended. Long-term follow-up of these infants is necessary to screen for postneonatal epilepsy and support neurodevelopment.

Personalized antiseizure medication therapy in critically ill adult patients

Precision medicine has the potential to have a significant impact on both drug development and patient care. It is crucial to not only provide prompt effective antiseizure treatment for critically ill patients after seizures start but also have a proactive mindset and concentrate on epileptogenesis and the underlying cause of the seizures or seizure disorders. Critical illness presents different treatment issues compared with the ambulatory population, which makes it challenging to choose the best antiseizure medications and to administer them at the right time and at the right dose. Since there is a paucity of information available on antiseizure medication dosing in critically ill patients, therapeutic drug monitoring is a useful tool for defining each patient's personal therapeutic range and assisting clinicians in decision-making. Use of pharmacogenomic information relating to pharmacokinetics, hepatic metabolism, and seizure etiology may improve safety and efficacy by individualizing therapy. Studies evaluating the clinical implementation of pharmacogenomic information at the point-of-care and identification of biomarkers are also needed. These studies may make it possible to avoid adverse drug reactions, maximize drug efficacy, reduce drug-drug interactions, and optimize medications for each individual patient. This review will discuss the available literature and provide future insights on precision medicine use with antiseizure therapy in critically ill adult patients.

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.

Evaluation of Two Fosphenytoin Loading Dose Regimens and Monitoring in Infants and Neonates Less Than Six Months of Age

OBJECTIVES

The objectives of the study were to compare the free serum concentrations after different fosphenytoin loading dose strategies in patients younger than 6 months old and to investigate the frequency of seizure cessation following a loading dose of fosphenytoin.

METHODS

This retrospective cohort study included neonates and infants admitted to a 150-bed children's hospital between August 1, 2014, and February 1, 2018. Patients were included if they were younger than 6 months old and had a postload free phenytoin serum concentration collected during the specified time frame. Patients were identified through a database query screening for the inclusion criteria. Patients were separated into 2 groups with the 15 mg/kg group as per protocol and the 20 mg/kg group as noted in common practice. Data collection included demographic information, fosphenytoin dose, time of administration of the fosphenytoin loading dose, time of sampling, free phenytoin serum concentration results, concomitant antiepileptic agents, albumin serum concentration, and total bilirubin serum concentration.

RESULTS

Forty-one patients were included for analysis, 12 in the 15 mg/kg group and 29 in the 20 mg/kg group. The average free phenytoin concentration after the loading dose was 2.45 ± 0.54 mg/L in the 15 mg/kg group and 2.52 ± 0.66 mg/L in the 20 mg/kg group. Seizure cessation after the fosphenytoin loading dose was achieved in 3 of 12 (25%) patients in the 15 mg/kg group and in 13 of 29 (45%) patients in the 20 mg/kg group (p = 0.305).

CONCLUSIONS

The study demonstrates that a traditional range of fosphenytoin loading dose (15-20 mg/kg) led to elevated postloading dose free phenytoin serum concentrations in the majority of patients with a seizure cessation rate of approximately 39%. The question remains as to what the optimal dose and target concentration should be in this patient population to achieve the best efficacy without risking associated toxicities.

Guidelines for the Management of Pediatric Severe Traumatic Brain Injury, Third Edition: Update of the Brain Trauma Foundation Guidelines, Executive Summary

The purpose of this work is to identify and synthesize research produced since the second edition of these Guidelines was published and incorporate new results into revised evidence-based recommendations for the treatment of severe traumatic brain injury in pediatric patients. This document provides an overview of our process, lists the new research added, and includes the revised recommendations. Recommendations are only provided when there is supporting evidence. This update includes 22 recommendations, 9 are new or revised from previous editions. New recommendations on neuroimaging, hyperosmolar therapy, analgesics and sedatives, seizure prophylaxis, temperature control/hypothermia, and nutrition are provided. None are level I, 3 are level II, and 19 are level III. The Clinical Investigators responsible for these Guidelines also created a companion algorithm that supplements the recommendations with expert consensus where evidence is not available and organizes possible interventions into first and second tier utilization. The complete guideline document and supplemental appendices are available electronically (https://doi.org/10.1097/PCC.0000000000001735). The online documents contain summaries and evaluations of all the studies considered, including those from prior editions, and more detailed information on our methodology. New level II and level III evidence-based recommendations and an algorithm provide additional guidance for the development of local protocols to treat pediatric patients with severe traumatic brain injury. Our intention is to identify and institute a sustainable process to update these Guidelines as new evidence becomes available.

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.

Traumatic Brain Injury: A Forensic Approach: A Literature Review

Traumatic brain injury (TBI) is the principal cause of invalidity and death in the population under 45 years of age worldwide. This mini-review aims to systematize the forensic approach in neuropathological studies, highlighting the proper elements to be noted during external, radiological, autoptical, and histological examinations with particular attention paid to immunohistochemistry and molecular biology. In the light of the results of this mini-review, an accurate forensic approach can be considered mandatory in the examination of suspected TBI with medico-legal importance, in order to gather all the possible evidence to corroborate the diagnosis of a lesion that may have caused, or contributed to, death. From this point of view, only the use of an evidence-based protocol can reach a suitable diagnosis, especially in those cases in which there are other neuropathological conditions (ischemia, neurodegeneration, neuro-inflammation, dementia) that may have played a role in death. This is even more relevant when corpses, in an advanced state of decomposition, are studied, where the radiological, macroscopic and histological analyses fail to give meaningful answers. In these cases, immune-histochemical and molecular biology diagnostics are of fundamental importance and a forensic neuropathologist has to know them. Particularly, MiRNAs are promising biomarkers for TBI both for brain damage identification and for medico-legal aspects, even if further investigations are required to validate the first experimental studies. In the same way, the genetic substrate should be examined during any forensic examination, considering its importance in the outcome of TBI.

The Evolution of Population Pharmacokinetic Model of Oral Phenytoin for Early Seizure Prophylaxis Post-Craniotomy

BACKGROUND

This study aimed to re-establish a Population Pharmacokinetic (PPK) model of oral phenytoin to further optimize the individualized medication regimen based on our previous research.

METHODS

Patients with intracranial malignant tumor requiring craniotomy were prospectively enrolled according to the inclusion criteria. Genotypes of CYP2C9*1 or *3 and CYP2C19*1, *2 or *3 were determined by real time PCR (TaqMan probe) method. Serum concentrations of phenytoin on the 4th and 7th day after oral administration were determined using fluorescence polarization immunoassay. The PPK parameters were estimated using Nonlinear Mixed Effects Models (NONMEM) and internal validation was performed using bootstraps. The predictive performance of the final model was evaluated by Normalized Predictive Distribution Errors (NPDEs) and diagnostic goodness- of-fit plots.

RESULTS

A total of 390 serum samples were collected from 170 patients in PPK model building group. The population typical values for Vm, Km and the apparent volume of distribution (V) in the final model were 17.5 mg/h, 6.41 mg/L and 54.8 L, respectively. Internal validation by bootstraps showed that the final model was stable and reliable. NPDEs with a normal distribution and a scatterplot with symmetrical distribution showed that the final model had good predictive capability. Individualized dose regimens of additional 40 patients in the external validation group were designed by the present final PPK model. The percentages of patients with serum concentrations within the therapeutic range were 61.53% (24/39) on the 4th day and 94.87% (37/39) on the 7th day, which were higher than the 39.33% (59/150) and 52.10% (87/167) of above 170 patients (P < 0.0001).

CONCLUSION

The present PPK final model for oral phenytoin may be used to further optimize phenytoin individualized dose regimen to prevent early seizure in patients after brain injury if patient characteristics meet those of the population studied.

Management of Pediatric Severe Traumatic Brain Injury: 2019 Consensus and Guidelines-Based Algorithm for First and Second Tier Therapies

OBJECTIVES

To produce a treatment algorithm for the ICU management of infants, children, and adolescents with severe traumatic brain injury.

DATA SOURCES

Studies included in the 2019 Guidelines for the Management of Pediatric Severe Traumatic Brain Injury (Glasgow Coma Scale score ≤ 8), consensus when evidence was insufficient to formulate a fully evidence-based approach, and selected protocols from included studies.

DATA SYNTHESIS

Baseline care germane to all pediatric patients with severe traumatic brain injury along with two tiers of therapy were formulated. An approach to emergent management of the crisis scenario of cerebral herniation was also included. The first tier of therapy focuses on three therapeutic targets, namely preventing and/or treating intracranial hypertension, optimizing cerebral perfusion pressure, and optimizing partial pressure of brain tissue oxygen (when monitored). The second tier of therapy focuses on decompressive craniectomy surgery, barbiturate infusion, late application of hypothermia, induced hyperventilation, and hyperosmolar therapies.

CONCLUSIONS

This article provides an algorithm of clinical practice for the bedside practitioner based on the available evidence, treatment protocols described in the articles included in the 2019 guidelines, and consensus that reflects a logical approach to mitigate intracranial hypertension, optimize cerebral perfusion, and improve outcomes in the setting of pediatric severe traumatic brain injury.

Guidelines for the Management of Pediatric Severe Traumatic Brain Injury, Third Edition: Update of the Brain Trauma Foundation Guidelines, Executive Summary

OBJECTIVES

The purpose of this work is to identify and synthesize research produced since the second edition of these Guidelines was published and incorporate new results into revised evidence-based recommendations for the treatment of severe traumatic brain injury in pediatric patients.

METHODS AND MAIN RESULTS

This document provides an overview of our process, lists the new research added, and includes the revised recommendations. Recommendations are only provided when there is supporting evidence. This update includes 22 recommendations, nine are new or revised from previous editions. New recommendations on neuroimaging, hyperosmolar therapy, analgesics and sedatives, seizure prophylaxis, temperature control/hypothermia, and nutrition are provided. None are level I, three are level II, and 19 are level III. The Clinical Investigators responsible for these Guidelines also created a companion algorithm that supplements the recommendations with expert consensus where evidence is not available and organizes possible interventions into first and second tier utilization. The purpose of publishing the algorithm as a separate document is to provide guidance for clinicians while maintaining a clear distinction between what is evidence based and what is consensus based. This approach allows, and is intended to encourage, continued creativity in treatment and research where evidence is lacking. Additionally, it allows for the use of the evidence-based recommendations as the foundation for other pathways, protocols, or algorithms specific to different organizations or environments. The complete guideline document and supplemental appendices are available electronically from this journal. These documents contain summaries and evaluations of all the studies considered, including those from prior editions, and more detailed information on our methodology.

CONCLUSIONS

New level II and level III evidence-based recommendations and an algorithm provide additional guidance for the development of local protocols to treat pediatric patients with severe traumatic brain injury. Our intention is to identify and institute a sustainable process to update these Guidelines as new evidence becomes available.

Phenytoin-induced hypothermia

A 60-year-old man with cerebral palsy and epilepsy was admitted with acute lethargy and deterioration in coordination. He was noted to be hypothermic at 35°C on admission. Routine work-up revealed toxic levels of phenytoin. No cause of hypothermia could be identified but as his phenytoin levels normalised, his body temperature also improved. There are three other reported cases of phenytoin- induced hypothermia in the literature. Could this be a rare cause of hypothermia?

Fosphenytoin Population Pharmacokinetics in the Acutely Ill Pediatric Population

OBJECTIVE

The purpose of this study is to describe the pharmacokinetics of phenytoin in pediatric patients receiving fosphenytoin.

DESIGN

Retrospective, population pharmacokinetic analysis.

SETTING

Emergency department or PICU of a large tertiary care children's hospital.

PATIENTS

Patients less than 19 years old who received fosphenytoin in the PICU or emergency center for treatment of seizures from January 2011 to June 2017 were included.

INTERVENTIONS

Population pharmacokinetic analysis was performed with NONMEM v7.3 (Icon Plc, Dublin, Ireland). Simulation was performed to determine optimal loading dose and maintenance dosing regimens.

MEASUREMENTS AND MAIN RESULTS

A total of 536 patients (55.4% male; median age, 3.4 yr [interquartile range, 0.92-8.5 yr]) met study criteria. Fosphenytoin was administered at median 15.1 mg/kg/dose (interquartile range, 6.3-20.7 mg/kg/dose). Mean serum concentrations of 17.5 ± 7.8 mg/L were at a median 4.2 hours (interquartile range, 2.5-7.8 hr) after a dose. A pharmacokinetic model with two compartments, allometrically scaled fat-free mass on all parameters, and serum creatinine and concomitant phenobarbital use on clearance had the best fit. Simulation demonstrated that a 20 mg/kg loading dose followed by 6 mg/kg/dose every 8 hours had the greatest percentage of concentrations in the 10-20 mg/L range, with reduced doses to achieve therapeutic in patients with reduced kidney function.

CONCLUSIONS

A loading dose of 20 mg/kg followed by 6 mg/kg/dose every 8 hours based on fat-free mass is a reasonable empiric strategy for attainment and maintenance of therapeutic trough concentrations. Concomitant phenobarbital use may increase clearance of phenytoin and fosphenytoin dose reductions should occur in patients with reduced kidney function.

The use of phenobarbital and other anti-seizure drugs in newborns

Neonatal seizures constitute the most frequent presenting neurologic sign encountered in the neonatal intensive care unit. Despite limited efficacy and safety data, phenobarbital continues to be used near-universally as the first-line anti-seizure drug (ASD) in neonates. The choice of second-line ASDs varies by provider and institution, and is still not supported by sufficient scientific evidence. In this review, we discuss the available evidence supporting the efficacy, mechanism of action, potential adverse effects, key pharmacokinetic characteristics such as interaction with therapeutic hypothermia, logistical issues, and rationale for use of neonatal ASDs. We describe the widely used neonatal ASDs, namely phenobarbital, phenytoin, midazolam, and levetiracetam, in addition to potential ASDs, including lidocaine, topiramate, and bumetanide.

Hypothermia for traumatic brain injury

BACKGROUND

Hypothermia has been used in the treatment of brain injury for many years. Encouraging results from small trials and laboratory studies led to renewed interest in the area and some larger trials.

OBJECTIVES

To determine the effect of mild hypothermia for traumatic brain injury (TBI) on mortality, long-term functional outcomes and complications.

SEARCH METHODS

We ran and incorporated studies from database searches to 21 March 2016. We searched the Cochrane Injuries Group's Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE (OvidSP), Embase Classic+Embase (OvidSP), PubMed, ISI Web of science (SCI-EXPANDED, SSCI, CPCI-S & CPSI-SSH), clinical trials registers, and screened reference lists. We also re-ran these searches pre-publication in June 2017; the result from this search is presented in 'Studies awaiting classification'.

SELECTION CRITERIA

We included randomised controlled trials of participants with closed TBI requiring hospitalisation who were treated with hypothermia to a maximum of 35 ºC for at least 12 consecutive hours. Treatment with hypothermia was compared to maintenance with normothermia (36.5 to 38 ºC).

DATA COLLECTION AND ANALYSIS

Two review authors assessed data on mortality, unfavourable outcomes according to the Glasgow Outcome Scale, and pneumonia.

MAIN RESULTS

We included 37 eligible trials with a total of 3110 randomised participants; nine of these were new studies since the last update (2009) and five studies had been previously excluded but were re-assessed and included during the 2017 update. We identified two ongoing studies from searches of clinical trials registers and database searches and two studies await classification.Studies included both adults and children with TBI. Most studies commenced treatment immediately on admission to hospital or after craniotomies and all treatment was maintained for at least 24 hours. Thirty-three studies reported data for mortality, 31 studies reported data for unfavourable outcomes (death, vegetative state or severe disability), and 14 studies reported pneumonia. Visual inspection of the results for these outcomes showed inconsistencies among studies, with differences in the direction of effect, and we did not pool these data for meta-analysis. We considered duration of hypothermia therapy and the length of follow-up in collected data for these subgroups; differences in study data remained such that we did not perform meta-analysis.Studies were generally poorly reported and we were unable to assess risk of bias adequately. Heterogeneity was evident both in the trial designs and participant inclusion. Inconsistencies in results may be explained by heterogeneity among study participants or bias introduced by individual study methodology but we did not explore this in detail in subgroup or sensitivity analyses. We used the GRADE approach to judge the quality of the evidence for each outcome and downgraded the evidence for mortality and unfavourable outcome to very low. We downgraded the evidence for the pneumonia outcome to low.

AUTHORS' CONCLUSIONS

Despite a large number studies, there remains no high-quality evidence that hypothermia is beneficial in the treatment of people with TBI. Further research, which is methodologically robust, is required in this field to establish the effect of hypothermia for people with TBI.

A Systematic Appraisal of Neurosurgical Seizure Prophylaxis: Guidance for Critical Care Management

Clinical decisions are often made in the presence of some uncertainty. Health care should be based on a combination of scientific evidence, clinical experience, economics, patient value judgments, and preferences. Seizures are not uncommon following brain injury, surgical trauma, hemorrhage, altered brain metabolism, hypoxia, or ischemic events. The impact of seizures in the immediate aftermath of injury may be a prolonged intensive care stay or compounding of the primary injury. The aim of brain injury management is to limit the consequences of the secondary damage. The original intention of seizure prophylaxis was to limit the incidence of early-onset seizures. However, clinical trials have been equivocal on this point, and there is concern about the adverse effects of antiepileptic drug therapy. This review of the literature raises concerns regarding the arbitrary division of seizures into early onset (7 d) and late onset (8 d and beyond). In many cases it would appear that seizures present within 24 hours of the injury or after 7 days, which would be outside of the scope of current seizure prophylaxis guidance. There also does not appear to be a pathophysiological reason to divide brain injury-related seizures into these timeframes. Therefore, a solution to the conundrum is to reevaluate current practice. Prophylaxis could be offered to those receiving intensive care for the primary brain injury, where the impact of seizure would be detrimental to the management of the brain injury, or other clinical judgments where prophylaxis is prudent. Neurosurgical seizure management can then focus attention on which agent has the best adverse effect profile and the duration of therapy. The evidence seems to support levetiracetam as the most appropriate agent. Although previous reviews have identified an increase cost associated with the use of levetiracetam, current cost comparisons with phenytoin demonstrate a marginal price differential. The aim of this review is to assimilate the applicable literature regarding seizure prophylaxis. The final guidance is a forum upon which further clinical research could evaluate a new seizure prophylaxis paradigm.

ABCB1 genotype is associated with fentanyl requirements in critically ill children

BackgroundThe gene ABCB1 encodes p-glycoprotein, a xenobiotic efflux pump capable of transporting certain opioids, including fentanyl. ABCB1 genotype has been previously associated with patient opioid requirements and may influence fentanyl dosing requirements in critically ill children.MethodsA diagnostically diverse cohort of 61 children who received a fentanyl infusion while admitted to the pediatric intensive care unit (PICU) were included in this study. We examined associations between fentanyl requirements, pain and sedation scores, serum fentanyl levels, and ABCB1 genotype.ResultsPatients with the AA allele at ABCB1 locus rs1045642 received less fentanyl compared with patients with the AG or GG allele. A multivariable model demonstrated that patients with the AA allele received 18.6 mcg/kg/day less fentanyl than patients with either the AG or GG allele (95% confidence interval -33.4 to -3.8 mcg/kg/day; P=0.014). Incorporating race in this model demonstrated a similar association, but did not reach the threshold for multiple testing.ConclusionABCB1 genotype rs1045642 AA is associated with fentanyl administration in this cohort of children admitted to the PICU, likely because of decreased expression and activity of p-glycoprotein. Prospective evaluation of the influence of ABCB1 in sedative-analgesia administration in critically ill children is warranted.

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

Targeted temperature management (TTM) has been shown to reduce mortality and improve neurological outcomes in out-of-hospital cardiac arrest (CA) patients and in neonates with hypoxic-ischemic encephalopathy (HIE). TTM has also been associated with adverse drug events in the critically ill patient due to its effect on drug pharmacokinetics (PKs) and pharmacodynamics (PDs). We aim to evaluate the current literature on the effect of TTM on drug PKs and PDs following CA. MEDLINE/PubMed databases were searched for publications, which include the MeSH terms hypothermia, drug metabolism, drug transport, P450, critical care, cardiac arrest, hypoxic-ischemic encephalopathy, pharmacokinetics, and pharmacodynamics between July 2006 and October 2015. Twenty-three studies were included in this review. The studies demonstrate that hypothermia impacts PK parameters and increases concentrations of cytochrome-P450-metabolized drugs in the cooling and rewarming phase. Furthermore, the current data demonstrate a combined effect of CA and hypothermia on drug PK. Importantly, these effects can last greater than 4-5 days post-treatment. Limited evidence suggests hypothermia-mediated changes in the Phase II metabolism and the Phase III transport of drugs. Hypothermia also has been shown to potentially decrease the effect of specific drugs at the receptor level. Therapeutic hypothermia, as commonly deployed/applied during TTM, alters PK, and elevates concentrations of several commonly used medications. Hypothermia-mediated effects are an important factor when dosing and monitoring patients undergoing TTM treatment.

Variability of Post-Cardiac Arrest Care Practices Among Cardiac Arrest Centers: United States and South Korean Dual Network Survey of Emergency Physician Research Principal Investigators

There is little consensus regarding many post-cardiac arrest care parameters. Variability in such practices could confound the results and generalizability of post-arrest care research. We sought to characterize the variability in post-cardiac arrest care practice in Korea and the United States. A 54-question survey was sent to investigators participating in one of two research groups in South Korea (Korean Hypothermia Network [KORHN]) and the United States (National Post-Arrest Research Consortium [NPARC]). Single investigators from each site were surveyed (N = 40). Participants answered questions based on local institutional protocols and practice. We calculated descriptive statistics for all variables. Forty surveys were completed during the study period with 30 having greater than 50% of questions completed (75% response rate; 24 KORHN and 6 NPARC). Most centers target either 33°C (N = 16) or vary the target based on patient characteristics (N = 13). Both bolus and continuous infusion dosing of sedation are employed. No single indication was unanimous for cardiac catheterization. Only six investigators reported having an institutional protocol for withdrawal of life-sustaining therapy (WLST). US patients with poor neurological prognosis tended to have WLST with subsequent expiration (N = 5), whereas Korean patients are transferred to a secondary care facility (N = 19). Both electroencephalography modality and duration vary between institutions. Serum biomarkers are commonly employed by Korean, but not US centers. We found significant variability in post-cardiac arrest care practices among US and Korean medical centers. These practice variations must be taken into account in future studies of post-arrest care.

Vancomycin pharmacokinetic parameters in patients with acute brain injury undergoing controlled normothermia, therapeutic hypothermia, or pentobarbital infusion

BACKGROUND

Therapeutic strategies that cause an alteration in patient temperature, such as controlled normothermia (CN), therapeutic hypothermia (TH), and pentobarbital infusion (PI), are often used to manage complications caused by acute brain injury. The purpose of this study was to evaluate pharmacokinetic (PK) parameters of vancomycin in patients with acute brain injury undergoing temperature modulation.

METHODS

This was a retrospective cohort study of adult patients with acute brain injury admitted between May 2010 and March 2014 who underwent CN, TH, or PI and received vancomycin. Predicted PK parameters based on population data were compared with calculated PK parameters based on serum concentrations.

RESULTS

Seventeen CN patients and 10 TH/PI patients met inclusion criteria. Traumatic brain injury and aneurysmal subarachnoid hemorrhage accounted for the majority of admitting diagnoses. In the CN group, the median dose was 16.7 (15.5-18.4) mg/kg. The median calculated elimination rate constant [0.155 (0.108-0.17) vs. 0.103 (0.08-0.142) hr(-1); p = 0.04] was significantly higher than the predicted value. The median measured trough concentration [8.9 (7.7-11.1) vs. 17.1 (10.8-22.3) υg/mL; p = 0.004] was significantly lower than predicted. In the TH/PI group, the median dose was 15.4 (14.7-17.2) mg/kg. No significant differences were found between the median calculated and predicted elimination rate constant [0.107 (0.097-0.109) vs. 0.112 (0.102-0.127) hr(-1); p = 0.41] and median measured and predicted trough concentration [14.2 (12.7-17.1) vs. 13.1 (11-17.8) υg/mL; p = 0.71].

CONCLUSION

Patients who underwent TH/PI did not exhibit PK alterations when compared to predicted PK parameters based on population data, while patients who underwent CN experienced PK alterations favoring an increased elimination of vancomycin.

Mild hypothermia decreases the total clearance of glibenclamide after low dose administration in rats

BACKGROUND AND PURPOSE

Low dose glibenclamide exhibits pleiotropic protective effects in different central nervous system diseases. Previously, we have shown that mild hypothermia enhanced the efficacy of glibenclamide in the cultured cortical neuronal cells. This study aims to evaluate the impact of mild hypothermia on the pharmacokinetics of low dose glibenclamide in rats via its cytochrome P450 2C9 (CYP2C9) metabolic pathway.

METHODS

Male Sprague-Dawley rats were maintained at 37°C (normothermic group) or cooled to 33°C (hypothermic group). Glibenclamide (33μg/kg) or diclofenac (10mg/kg, a probe drug for assessing the activity of CYP2C9 which involves in glibenclamide and diclofenac metabolism in liver) were intravenously administered at 10min after stabilization of temperature. Plasma samples were collected at 9 different time points. Glibenclamide and diclofenac in sera were separated by liquid chromatography and quantified with tandem mass spectrometry.

RESULTS

Compared with normothermia, mild hypothermia significantly decreased the total clearance of glibenclamide (16.00±4.1-6.72±2.1mL/min/kg; p<0.01), and there was a non-significant trend in a slightly higher half-life, (1.64±0.34-2.71±1.7h, p=0.157). Area under the plasma concentration versus time curve (AUClast) in the hypothermic group was increased (33.2±11-77.8±18hng/mL, p<0.01). Moreover, mild hypothermia reduced the total clearance of diclofenac (10.33±1.53-7.20±1.66mL/min/kg, p<0.01), indicating that the CYP2C9 activity was compromised in reduced temperature.

CONCLUSION

Mild hypothermia reduced the total clearance of glibenclamide, probably via mediating the activity of CYP2C9. The impact of hypothermia in clinical application of glibenclamide should be considered.

Approach to Modeling, Therapy Evaluation, Drug Selection, and Biomarker Assessments for a Multicenter Pre-Clinical Drug Screening Consortium for Acute Therapies in Severe Traumatic Brain Injury: Operation Brain Trauma Therapy

Traumatic brain injury (TBI) was the signature injury in both the Iraq and Afghan wars and the magnitude of its importance in the civilian setting is finally being recognized. Given the scope of the problem, new therapies are needed across the continuum of care. Few therapies have been shown to be successful. In severe TBI, current guidelines-based acute therapies are focused on the reduction of intracranial hypertension and optimization of cerebral perfusion. One factor considered important to the failure of drug development and translation in TBI relates to the recognition that TBI is extremely heterogeneous and presents with multiple phenotypes even within the category of severe injury. To address this possibility and attempt to bring the most promising therapies to clinical trials, we developed Operation Brain Trauma Therapy (OBTT), a multicenter, pre-clinical drug screening consortium for acute therapies in severe TBI. OBTT was developed to include a spectrum of established TBI models at experienced centers and assess the effect of promising therapies on both conventional outcomes and serum biomarker levels. In this review, we outline the approach to TBI modeling, evaluation of therapies, drug selection, and biomarker assessments for OBTT, and provide a framework for reports in this issue on the first five therapies evaluated by the consortium.

Combination Therapies for Traumatic Brain Injury: Retrospective Considerations

Patients enrolled in clinical trials for traumatic brain injury (TBI) may present with heterogeneous features over a range of injury severity, such as diffuse axonal injury, ischemia, edema, hemorrhage, oxidative damage, mitochondrial and metabolic dysfunction, excitotoxicity, inflammation, and other pathophysiological processes. To determine whether combination therapies might be more effective than monotherapy at attenuating moderate TBI or promoting recovery, the National Institutes of Health funded six preclinical studies in adult and immature male rats to evaluate promising acute treatments alone and in combination. Each of the studies had a solid rationale for its approach based on previous research, but only one reported significant improvements in long-term outcomes across a battery of behavioral tests. Four studies had equivocal results because of a lack of sensitivity of the outcome assessments. One study demonstrated worse results with the combination in comparison with monotherapies. While specific research findings are reported elsewhere, this article provides an overview of the study designs, insights, and recommendations for future research aimed at therapy development for TBI.

Prolonged cooling duration mitigates myocardial and cerebral damage in cardiac arrest

BACKGROUND

The purpose of this study was to investigate the effect of prolonged cooling on cardiac and cerebral injury in animals under cardiac arrest.

METHODS

Adult male Wistar rats were equally randomized to normothermia, 5H1, 5H2, 7H1, 7H2, and 7H4 groups. The first number in the group name indicated ventricular fibrillation duration (minutes), the middle H indicated hypothermia, and the last number signified hypothermia duration (hours). Ventricular fibrillation was induced and untreated for 5 minutes (normothermia, 5H1, and 5H2) or 7 minutes (7H1, 7H2, and 7H4) followed by 1 minute of cardiopulmonary resuscitation followed by electric shocks. Hypothermia was initiated simultaneously with cardiopulmonary resuscitation initiation and maintained for 1 hour (5H1 and 7H1), 2 hours (5H2 and 7H2) or 4 hours (7H4).

RESULTS

There were 12 rats in each group. Compared with the 7H1 group, the 7H4 group had significantly better systolic function (dp/dt40) and cardiac output within the early postcardiac arrest period. Histologic examination disclosed less myocardial and hippocampal damage in the 7H4 group than the 7H1 group and in the 5H2 group than the 5H1 group. Plasma troponin I, fatty acid-binding protein, and S-100β concentrations were significantly lower in the 7H4 and 5H2 groups. The 7H4 and 5H2 groups survived statistically longer than the groups with shorter cooling duration.

CONCLUSION

Slightly prolonging hypothermia may mitigate myocardial and cerebral damage and improve survival and neurologic outcomes in a rat model of ventricular fibrillation cardiac arrest.

Treatment of Generalized Convulsive Status Epilepticus in Pediatric Patients

Generalized convulsive status epilepticus (GCSE) is one of the most common neurologic emergencies and can be associated with significant morbidity and mortality if not treated promptly and aggressively. Management of GCSE is staged and generally involves the use of life support measures, identification and management of underlying causes, and rapid initiation of anticonvulsants. The purpose of this article is to review and evaluate published reports regarding the treatment of impending, established, refractory, and super-refractory GCSE in pediatric patients.

Effect of administration of neuromuscular blocking agents in children with severe traumatic brain injury on acute complication rates and outcomes: a secondary analysis from a randomized, controlled trial of therapeutic hypothermia

OBJECTIVE

To evaluate the association between neuromuscular blocking agents and outcome, intracranial pressure, and medical complications in children with severe traumatic brain injury.

DESIGN

A secondary analysis of a randomized, controlled trial of therapeutic hypothermia.

SETTING

Seventeen hospitals in the United States, Australia, and New Zealand.

PATIENTS

Children (< 18 yr) with severe traumatic brain injury.

INTERVENTIONS

None for this secondary analysis.

MEASUREMENTS AND MAIN RESULTS

Children received neuromuscular blocking agent on the majority of days of the study (69.6%), and the modified Pediatric Intensity Level of Therapy scores (modified by removing neuromuscular blocking agent administration from the score) were increased on days when neuromuscular blocking agents were used (9.67 ± 0.21 vs 5.48 ± 0.26; p < 0.001). Children were stratified into groups based on exposure to neuromuscular blocking agents (group 1 received neuromuscular blocking agents each study day; group 2 did not). Group 1 had increased number of daily intracranial pressure readings more than 20 mm Hg (4.4 ± 1.1 vs 2.4 ± 0.5;p = 0.015) and longer ICU and hospital length of stay (p = 0.003 and 0.07, respectively, Kaplan-Meier). The Glasgow Outcome Score-Extended for Pediatrics at hospital discharge and 3, 6, and 12 months after traumatic brain injury and medical complications observed during the acute hospitalization were similar between groups.

CONCLUSIONS

Administration of neuromuscular blocking agents was ubiquitous and daily administration of neuromuscular blocking agents was associated with intracranial hypertension but not outcomes-likely indicating that increased injury severity prompted their use. Despite this, neuromuscular blocking agent use was not associated with complications. A different study design-perhaps using randomization or methodologies-of a larger cohort will be required to determine if neuromuscular blocking agent use is helpful after severe traumatic brain injury in children.

Pediatric head injury: a pain for the emergency physician?

The prompt diagnosis and initial management of pediatric traumatic brain injury poses many challenges to the emergency department (ED) physician. In this review, we aim to appraise the literature on specific management issues faced in the ED, specifically: indications for neuroimaging, choice of sedatives, applicability of hyperventilation, utility of hyperosmolar agents, prophylactic anti-epileptics, and effect of hypothermia in traumatic brain injury. A comprehensive literature search of PubMed and Embase was performed in each specific area of focus corresponding to the relevant questions. The majority of the head injured patients presenting to the ED are mild and can be observed. Clinical prediction rules assist the ED physician in deciding if neuroimaging is warranted. In cases of major head injury, prompt airway control and careful use of sedation are necessary to minimize the chance of hypoxia, while avoiding hyperventilation. Hyperosmolar agents should be started in these cases and normothermia maintained. The majority of the evidence is derived from adult studies, and most treatment modalities are still controversial. Recent multicenter trials have highlighted the need to establish common platforms for further collaboration.

Drug metabolism for the paediatrician

Drug metabolism importantly determines drug concentrations. The efficacy and safety of many drugs prescribed for children are, therefore, dependent on intraindividual and interindividual variation in drug-metabolising enzyme activity. During growth and development, changes in drug-metabolising enzyme activity result in age-related differences in drug disposition, most pronounced in preterm infants and young infants. The shape of the developmental trajectory is unique to the drug-metabolising enzyme involved in the metabolism of individual drugs. Other factors impacting drug metabolism are underlying disease, drug-drug interactions and genetic variation. The interplay of age with these other factors may result in unexpected variation in drug metabolism in children of different ages. Extrapolation of adult data to guide drug dosing in children should be done with caution. The younger the child, the less reliable is the extrapolation. This review aims to identify the primary sources of variability of drug metabolism in children, the knowledge of which can ultimately guide the practitioner towards effective and safe drug therapy.

Therapeutic Hypothermia in Children and Adults with Severe Traumatic Brain Injury

Great expectations have been raised about neuroprotection of therapeutic hypothermia in patients with traumatic brain injury (TBI) by analogy with its effects after heart arrest, neonatal asphyxia, and drowning in cold water. The aim of this study is to review our present knowledge of the effect of therapeutic hypothermia on outcome in children and adults with severe TBI. A literature search for relevant articles in English published from year 2000 up to December 2013 found 19 studies. No signs of improvement in outcome from hypothermia were seen in the five pediatric studies. Varied results were reported in 14 studies on adult patients, 2 of which reported a tendency of higher mortality and worse neurological outcome, 4 reported lower mortality, and 9 reported favorable neurological outcome with hypothermia. The quality of several trials was low. The best-performed randomized studies showed no improvement in outcome by hypothermia-some even indicated worse outcome. TBI patients may suffer from hypothermia-induced pulmonary and coagulation side effects, from side effects of vasopressors when re-establishing the hypothermia-induced lowered blood pressure, and from a rebound increase in intracranial pressure (ICP) during and after rewarming. The difference between body temperature and temperature set by the biological thermostat may cause stress-induced worsening of the circulation and oxygenation in injured areas of the brain. These mechanisms may counteract neuroprotective effects of therapeutic hypothermia. We conclude that we still lack scientific support as a first-tier therapy for the use of therapeutic hypothermia in TBI patients for both adults and children, but it may still be an option as a second-tier therapy for refractory intracranial hypertension.

Traumatic Brain Injury pathophysiology and treatments: early, intermediate, and late phases post-injury

Traumatic Brain Injury (TBI) affects a large proportion and extensive array of individuals in the population. While precise pathological mechanisms are lacking, the growing base of knowledge concerning TBI has put increased emphasis on its understanding and treatment. Most treatments of TBI are aimed at ameliorating secondary insults arising from the injury; these insults can be characterized with respect to time post-injury, including early, intermediate, and late pathological changes. Early pathological responses are due to energy depletion and cell death secondary to excitotoxicity, the intermediate phase is characterized by neuroinflammation and the late stage by increased susceptibility to seizures and epilepsy. Current treatments of TBI have been tailored to these distinct pathological stages with some overlap. Many prophylactic, pharmacologic, and surgical treatments are used post-TBI to halt the progression of these pathologic reactions. In the present review, we discuss the mechanisms of the pathological hallmarks of TBI and both current and novel treatments which target the respective pathways.