Topiramate concentrations in neonates treated with prolonged whole body hypothermia for hypoxic ischemic encephalopathy

Neonatal Hypoxic-Ischemic Encephalopathy: Perspectives of Neuroprotective and Neuroregenerative Treatments

Hypoxic-ischemic encephalopathy (HIE) is a serious condition that could have deleterious neurological outcomes, such as cerebral palsy, neuromotor disability, developmental disability, epilepsy, and sensitive or cognitive problems, and increase the risk of death in severe cases. Once HIE occurs, molecular cascades are triggered favoring the oxidative stress, excitotoxicity, and inflammation damage that promote cell death via apoptosis or necrosis. Currently, the therapeutic hypothermia is the standard of care in HIE; however, it has a small window of action and only can be used in children of more than 36 gestational weeks; for this reason, it is very important to develop new therapies to prevent the progression of the hypoxic-ischemic injury or to develop neuroregenerative therapies in severe HIE cases. The objective of this revision is to describe the emerging treatments for HIE, either preventing cell death for oxidative stress, excitotoxicity, or exacerbated inflammation, as well as describing a new therapeutic approach for neuroregeneration, such as mesenchymal stem cells, brain-derived neurotrophic factor, and gonadotropin realizing hormone agonists.

Topiramate Is Safe for Refractory Neonatal Seizures: A Multicenter Retrospective Cohort Study of Necrotizing Enterocolitis Risk

BACKGROUND

A previously published, single-institution, case series suggested an association between topiramate administration in neonates and subsequent development of necrotizing enterocolitis (NEC). This contradicted our more extensive experiences using topiramate in this population. We therefore studied safety and tolerability of topiramate for treating refractory neonatal seizures, hypothesizing that the risk of developing NEC following topiramate exposure was low and that most infants tolerate topiramate.

METHODS

This multicenter retrospective cohort study included seventy-five neonates who received topiramate to treat seizures from January 2011 to October 2019 at three geographically diverse level IV neonatal intensive care units affiliated with pediatric tertiary hospitals. Data included demographics, birth history, seizure etiology, treatment response, side effects, and occurrence and details of NEC.

RESULTS

Three of seventy-five infants (4%) developed NEC following topiramate exposure. These infants did not differ in gestational age, birth weight, seizure etiology, postmenstrual age, weight when topiramate was initiated, or dosing of topiramate. Topiramate was well tolerated. Only three infants (4%) discontinued due to side effects. The most common side effect (20%) was weight loss (typically <5%). Topiramate was felt to be efficacious (61%). Most infants (72%) continued topiramate when discharged.

CONCLUSIONS

Our multicenter, 75-infant study demonstrated that development of NEC after treatment with topiramate was rare (4%) and refutes prior literature suggesting an association. Topiramate was felt to be efficacious and was well tolerated. Although limited by retrospective design, study data are broadly applicable and support thoughtful use of topiramate as a safe, reasonable option for treating refractory neonatal seizures.

Neuroprotective Agents for Neonates with Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) remains a significant source of long-term neurodevelopmental impairment despite overall improvements in survival without disability in neonates who undergo therapeutic hypothermia. Each phase in the evolution of hypoxic-ischemic injury presents potential pharmacologic targets for neuroprotective agents. Melatonin is a promising emerging therapy for early phases of ischemic injury, but utility is currently limited by the lack of pharmaceutical-grade products. Magnesium has been extensively studied for its neuroprotective effects in the preterm population. Studies in neonates with HIE have produced mixed outcomes. Erythropoietin use in HIE with or without therapeutic hypothermia appears to be safe and may provide additional benefit. Dexmedetomidine, N-acetylcysteine, xenon, and topiramate all have promising animal data, but need additional human trials to elucidate what role they may play in HIE. Frequent review of existing literature is required to ensure provision of evidence-based pharmacologic agents for neuroprotection following HIE.

Pharmacokinetics during therapeutic hypothermia for neonatal hypoxic ischaemic encephalopathy: a literature review

BACKGROUND

Neonatal hypoxic ischaemic encephalopathy due to perinatal asphyxia, can result in severe neurodevelopmental disability or mortality. Hypothermia is at present the only proven neuroprotective intervention. During hypothermia, the neonate may need a variety of drugs with their specific pharmacokinetic profile. The aim of this paper is to determine the effect that hypothermia for neonates suffering from hypoxic ischaemic encephalopathy has on the pharmacokinetics and to what extent dosing regimens need adjustments.

METHOD

A systematic search was performed on PubMed, Embase and Cochrane Library of literature (2000-2020) using a combination of the following search terms: therapeutic hypothermia, neonate, hypoxic ischemic encephalopathy and pharmacokinetics. Titles and abstracts were screened, and inclusion/exclusion criteria were applied. Finally, relevant full texts were read, and secondary inclusion was applied on the identified articles.

RESULTS

A total of 380 articles were retrieved, and 34 articles included after application of inclusion/exclusion criteria and duplicate removal, two additional papers were included as suggested by the reviewers. Twelve out of 36 studies on 15 compounds demonstrated a significant decrease in clearance, be it that the extent differs between routes of elimination and compounds, most pronounced for renal elimination (phenobarbital no difference, midazolam metabolite -21%, lidocaine -24%; morphine -21% to -47%, gentamicin -25% to -35%, amikacin -40%) during hypothermia. The data as retrieved in literature were subsequent compared with the dosing regimen as stated in the Dutch paediatric formulary.

CONCLUSION

Depending on the drug-specific disposition characteristics, therapeutic hypothermia in neonates with hypoxic ischaemic encephalopathy affects pharmacokinetics.

A Physiology-Based Pharmacokinetic Framework to Support Drug Development and Dose Precision During Therapeutic Hypothermia in Neonates

Therapeutic hypothermia (TH) is standard treatment for neonates (≥36 weeks) with perinatal asphyxia (PA) and hypoxic-ischemic encephalopathy. TH reduces mortality and neurodevelopmental disability due to reduced metabolic rate and decreased neuronal apoptosis. Since both hypothermia and PA influence physiology, they are expected to alter pharmacokinetics (PK). Tools for personalized dosing in this setting are lacking. A neonatal hypothermia physiology-based PK (PBPK) framework would enable precision dosing in the clinic. In this literature review, the stepwise approach, benefits and challenges to develop such a PBPK framework are covered. It hereby contributes to explore the impact of non-maturational PK covariates. First, the current evidence as well as knowledge gaps on the impact of PA and TH on drug absorption, distribution, metabolism and excretion in neonates is summarized. While reduced renal drug elimination is well-documented in neonates with PA undergoing hypothermia, knowledge of the impact on drug metabolism is limited. Second, a multidisciplinary approach to develop a neonatal hypothermia PBPK framework is presented. Insights on the effect of hypothermia on hepatic drug elimination can partly be generated from in vitro (human/animal) profiling of hepatic drug metabolizing enzymes and transporters. Also, endogenous biomarkers may be evaluated as surrogate for metabolic activity. To distinguish the impact of PA versus hypothermia on drug metabolism, in vivo neonatal animal data are needed. The conventional pig is a well-established model for PA and the neonatal Göttingen minipig should be further explored for PA under hypothermia conditions, as it is the most commonly used pig strain in nonclinical drug development. Finally, a strategy is proposed for establishing and fine-tuning compound-specific PBPK models for this application. Besides improvement of clinical exposure predictions of drugs used during hypothermia, the developed PBPK models can be applied in drug development. Add-on pharmacotherapies to further improve outcome in neonates undergoing hypothermia are under investigation, all in need for dosing guidance. Furthermore, the hypothermia PBPK framework can be used to develop temperature-driven PBPK models for other populations or indications. The applicability of the proposed workflow and the challenges in the development of the PBPK framework are illustrated for midazolam as model drug.

Topiramate for hypoxic ischemic encephalopathy: A systematic review protocol

BACKGROUND

Hypoxic ischemic encephalopathy (HIE) is brain injury caused by different reasons and the most common diagnosed is neonatal HIE. Most of the existing treatments have their own shortcomings or there are still some unexplained mechanisms in it. Topiramate (TPM) is a new drug for the treatment for seizures in neonates with HIE, but is currently used off-label. Our protocol aims to access the efficiency and safety of TPM for HIE.

METHODS AND ANALYSIS

Eight databases will be searched by 2 independent researchers for the article on the topic of using TPM as treatment for HIE, including PubMed, the Cochrane Central Register of Controlled Trials (Cochrane Library), Embase, and Web of Science, China National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Database (CBM), Wang Fang Database and Chinese Science and Technology Periodical database (VIP). The included papers are those published from the established date of the databases to 2019. The therapeutic effects based on the grade of neonatal behavioral neurological assessment will be regarded as the primary outcomes. RevMan V5.3 will be used to compute the data synthesis and carry out meta-analysis. The risk of bias will be appraised by the Cochrane risk of bias tool. Rare ratio for dichotomous outcomes and mean different for continuous data will be expressed with 95% confidence intervals (CI) for analysis. A random effects model or a fixed effects model will be employed, when heterogeneity is found or not. Subgroup analysis and sensitivity analysis will be applied if the heterogeneity is obvious.

RESULTS

This study will provide the recent evidence of TPM for HIE from reducing seizure acticity.

CONCLUSION

The conclusion of this study will provide proof to evaluate if TPM is effective and safe in the treatment of HIE.PROSPERO registration number: PROSPERO CRD42018117981.

Topiramate pharmacokinetics in neonates undergoing therapeutic hypothermia and proposal of an optimised dosing schedule

AIM

The adequate dosing of topiramate in neonates undergoing therapeutic hypothermia has not been established. The aim of this study was to design a dosing schedule capable of providing topiramate serum concentrations within the accepted therapeutic range.

METHODS

Neonates (n = 52) with hypoxic ischaemic encephalopathy and subjected to therapeutic hypothermia were dosed with topiramate, 5 mg/kg on day one and 3 mg/kg on days two to five, to decrease seizure events. A total of 451 topiramate serum concentrations obtained in the patients were used to develop a population pharmacokinetic model using a non-linear mixed-effects modelling approach.

RESULTS

A one-compartment model with first-order absorption and two different clearance terms, one for the cooling period and another for the post-warming period, were used to describe the concentration-time topiramate data. The probability of no-seizure events could not be related to topiramate concentrations, which was attributed to excessively low topiramate concentrations. A modified dosage schedule was designed with the aim of obtaining more than 90% of patients with topiramate concentrations within the therapeutic range after the first dose.

CONCLUSION

The dosage schedule of topiramate in these patients should be modified with the aim of decreasing the frequency of seizure events.

Drug Disposition and Pharmacotherapy in Neonatal ECMO: From Fragmented Data to Integrated Knowledge

Extracorporeal membrane oxygenation (ECMO) is a lifesaving support technology for potentially reversible neonatal cardiac and/or respiratory failure. As the survival and the overall outcome of patients rely on the treatment and reversal of the underlying disease, effective and preferentially evidence-based pharmacotherapy is crucial to target recovery. Currently limited data exist to support the clinicians in their every-day intensive care prescribing practice with the contemporary ECMO technology. Indeed, drug dosing to optimize pharmacotherapy during neonatal ECMO is a major challenge. The impact of the maturational changes of the organ function on both pharmacokinetics (PK) and pharmacodynamics (PD) has been widely established over the last decades. Next to the developmental pharmacology, additional non-maturational factors have been recognized as key-determinants of PK/PD variability. The dynamically changing state of critical illness during the ECMO course impairs the achievement of optimal drug exposure, as a result of single or multi-organ failure, capillary leak, altered protein binding, and sometimes a hyperdynamic state, with a variable effect on both the volume of distribution (Vd) and the clearance (Cl) of drugs. Extracorporeal membrane oxygenation introduces further PK/PD perturbation due to drug sequestration and hemodilution, thus increasing the Vd and clearance (sequestration). Drug disposition depends on the characteristics of the compounds (hydrophilic vs. lipophilic, protein binding), patients (age, comorbidities, surgery, co-medications, genetic variations), and circuits (roller vs. centrifugal-based systems; silicone vs. hollow-fiber oxygenators; renal replacement therapy). Based on the potential combination of the above-mentioned drug PK/PD determinants, an integrated approach in clinical drug prescription is pivotal to limit the risks of over- and under-dosing. The understanding of the dose-exposure-response relationship in critically-ill neonates on ECMO will enable the optimization of dosing strategies to ensure safety and efficacy for the individual patient. Next to in vitro and clinical PK data collection, physiologically-based pharmacokinetic modeling (PBPK) are emerging as alternative approaches to provide bedside dosing guidance. This article provides an overview of the available evidence in the field of neonatal pharmacology during ECMO. We will identify the main determinants of altered PK and PD, elaborate on evidence-based recommendations on pharmacotherapy and highlight areas for further research.

Status Epilepticus in the Neonate: Updates in Treatment Strategies

PURPOSE OF REVIEW

The purpose of this review is to report recent advances in treatment of neonatal seizures, with a specific focus on new literature since a 2013 systematic review performed by this author (Slaughter) and others. There is a paucity of data with regard to well-defined status epilepticus (SE) in neonates, so treatment of recurrent seizures was also included in this inquiry. We aimed to summarize the efficacy and safety profiles of current therapeutic options as well as describe trends in medication selection in the neonatal intensive care unit (NICU) setting.

RECENT FINDINGS

Phenobarbital remains first-line therapy in practice, though there is increasing evidence of its neurotoxicity and long-term sequelae. Bumetanide failed an open-label trial for efficacy, demonstrated an increased risk for hearing loss, and has since fallen out of favor for use in this population. New agents, such as levetiracetam and topiramate, still have very limited data but appear to be as efficacious as older medications, with more favorable side effect profiles. There are limited high-level evidence-based data to guide treatment of neonatal seizures. Emerging research focusing on drug mechanisms and safety profiles may provide additional information to guide decisions; however, further research is needed.

Topiramate plus Cooling for Hypoxic-Ischemic Encephalopathy: A Randomized, Controlled, Multicenter, Double-Blinded Trial

BACKGROUND AND OBJECTIVES

Therapeutic interventions to improve the efficacy of whole-body cooling for hypoxic-ischemic encephalopathy (HIE) are desirable. Topiramate has been effective in reducing brain damage in experimental studies. However, in the clinical setting information is limited to a small number of feasibility trials. We launched a randomized controlled double-blinded topiramate/placebo multicenter trial with the primary objective being to reduce the antiepileptic activity in cooled neonates with HIE and assess if brain damage would be reduced as a consequence.

STUDY DESIGN

Neonates were randomly assigned to topiramate or placebo at the initiation of hypothermia. Topiramate was administered via a nasogastric tube. Brain electric activity was continuously monitored. Topiramate pharmacokinetics, energy-related and Krebs' cycle intermediates, and lipid peroxidation biomarkers were determined using liquid chromatography-mass spectrometry and MRI for assessing brain damage.

RESULTS

Out of 180 eligible patients 110 were randomized, 57 (51.8%) to topiramate and 53 (48.2%) to placebo. No differences in the perinatal or postnatal variables were found. The topiramate group exhibited less seizure burden in the first 24 h of hypothermia (topiramate, n = 14 [25.9%] vs. placebo, n = 22 [42%]); needed less additional medication, and had lower mortality (topiramate, n = 5 [9.2%] vs. placebo, n = 10 [19.2%]); however, these results did not achieve statistical significance. Topiramate achieved a therapeutic range in 37.5 and 75.5% of the patients at 24 and 48 h, respectively. A significant association between serum topiramate levels and seizure activity (p < 0.016) was established. No differences for oxidative stress, energy-related metabolites, or MRI were found.

CONCLUSIONS

Topiramate reduced seizures in patients achieving therapeutic levels in the first hours after treatment initiation; however, they represented only a part of the study population. Our results warrant further studies with higher loading and maintenance dosing of topiramate.

Targeted Temperature Management in Pediatric Neurocritical Care

Targeted temperature management encompasses a range of clinical interventions to regulate systemic temperature, and includes both induction of varying degrees of hypothermia and fever prevention ("targeted normothermia"). Targeted temperature management plays a key role in the contemporary management of critically ill neonates and children with acute brain injury. Yet, many unanswered questions remain regarding optimal temperature management in pediatric neurocritical care. The introduction highlights experimental studies that have evaluated the neuroprotective efficacy of therapeutic hypothermia and explored possible mechanisms of action in several brain injury models. The next section focuses on three major clinical conditions in which therapeutic hypothermia has been evaluated in randomized controlled trials in pediatric populations: neonatal hypoxic-ischemic encephalopathy, postcardiac arrest encephalopathy, and traumatic brain injury. Clinical implications of targeted temperature management in pediatric neurocritical care are also discussed. The final section examines some of the factors that may underlie the limited neuroprotective efficacy of hypothermia that has been observed in several major pediatric clinical trials, and outlines important directions for future research.

Severity of asphyxia is a covariate of phenobarbital clearance in newborns undergoing hypothermia

AIM

Phenobarbital (PB) pharmacokinetics (PK) in asphyxiated newborns show large variability, not only explained by hypothermia (HT). We evaluated potential relevant covariates of PK of PB in newborns treated with or without HT for hypoxic-ischemic encephalopathy (HIE).

METHODS

Clearance (CL), distribution volume (Vd) and elimination half-life (t_1/2) were calculated using one-compartment analysis. Covariates were clinical characteristics (weight, gestational age, hepatic, renal, and circulatory status), comedication and HIE severity [time to reach normal aEEG pattern (T_normaEEG), dichotomous, within 24 h] and asphyxia severity [severe aspyhxia = pH ≤7.1 + Apgar score ≤5 (5 min), dichotomous]. Student's t-test, two-way ANOVA, correlation and Pearson's chi-square test were used.

RESULTS

Forty newborns were included [14 non-HT; 26 HT with T_normaEEG <24 h in 14/26 (group_1-HT) and T_normaEEG ≥24 h in 12/26 (group_2-HT)]. Severe asphyxia was present in 26/40 [5/14 non-HT, 11/14 and 10/12 in both HT groups]. PB-CL, Vd and t_1/2 were similar between the non-HT and HT group. However, within the HT group, PB-CL was significantly different between group_1-HT and group_2-HT (p = .043). ANOVA showed that HT (p = .034) and severity of asphyxia (p = .038) reduced PB-CL (-50%).

CONCLUSION

The interaction of severity of asphyxia and HT is associated with a clinical relevant reduced PB-CL, suggesting the potential relevance of disease characteristics beyond HT itself.

Pharmacotherapy for Seizures in Neonates with Hypoxic Ischemic Encephalopathy

Seizures are common in neonates with moderate and severe hypoxic ischemic encephalopathy (HIE) and are associated with worse outcomes, independent of HIE severity. In contrast to adults and older children, no new drugs have been licensed for treatment of neonatal seizures over the last 50 years, because of a lack of controlled clinical trials. Hence, many antiseizure medications licensed in older children and adults are used off-label for neonatal seizure, which is associated with potential risks of adverse effects during a period when the brain is particularly vulnerable. Phenobarbital is worldwide the first-line drug and is considered standard of care, although there is a limited evidence base for its efficacy. Second-line agents include phenytoin, benzodiazepines, levetiracetam, and lidocaine. These drugs are discussed in more detail along with two emerging drugs (bumetanide and topiramate). More safety, pharmacokinetic, and efficacy data are needed from well-designed clinical trials to develop safe and effective antiseizure regimes for the treatment of neonatal seizures in HIE.

Safety and efficacy of topiramate in neonates with hypoxic ischemic encephalopathy treated with hypothermia (NeoNATI): a feasibility study

PURPOSE

To investigate the feasibility of a study based on treatment with topiramate (TPM) added to moderate hypothermia in newborns with hypoxic ischemic encephalopathy (HIE).

MATERIALS AND METHODS

Multicenter randomized controlled trial. Term newborns with precocious metabolic, clinical and electroencephalographic (EEG) signs of HIE were selected according to their amplified integrated EEG pattern and randomized to receive either TPM (10 mg/kg once a day for the first three days of life) plus moderate hypothermia or hypothermia alone. Safety was assessed by monitoring cardiorespiratory parameters and blood samples collected to check renal, liver, metabolic balance and TPM pharmacokinetics. Efficacy was evaluated by the combined frequency of mortality and severe neurological disability as primary outcome. Incidence of magnetic resonance injury, epilepsy, blindness, hearing loss, neurodevelopment at 18-24 months of life was assessed as secondary outcomes.

RESULTS

Forty-four asphyxiated newborns were enrolled in the study. Twenty one newborns (10 with moderate and 11 with severe HIE) were allocated to hypothermia plus TPM and 23 (12 moderate and 11 severe HIE) to hypothermia. No statistically or clinically significant differences were observed for safety, primary or secondary outcomes. However, a reduction in the prevalence of epilepsy was observed in newborns co-treated with TPM.

CONCLUSIONS

Results of this pilot trial suggest that administration of TPM in newborns with HIE is safe but does not reduce the combined frequency of mortality and severe neurological disability. The role of TPM co-treatment in preventing subsequent epilepsy deserves further studies.

Decreased Morphine Clearance in Neonates With Hypoxic Ischemic Encephalopathy Receiving Hypothermia

Morphine is commonly used in neonates with hypothermic ischemic encephalopathy (HIE) during therapeutic hypothermia to provide comfort and analgesia. However, pharmacokinetic data to support morphine dosing in this vulnerable population are lacking. A prospective, 2-center clinical pharmacokinetic study of morphine was conducted in 20 neonates (birthweight, 1.82-5.3 kg) with HIE receiving hypothermia. Morphine dosing was per standard of care at each center. Morphine and glucuronide metabolites (morphine-3-glucuronide and morphine-6-gluronide) were measured via a validated dried blood spot liquid chromatography-tandem mass spectrometry assay. From the available concentration data (n = 106 for morphine; n = 106 for each metabolite), a population pharmacokinetic model was developed using nonlinear mixed-effects modeling. The clearance of morphine and glucuronide metabolites was best predicted by birthweight allometrically scaled using an exponent of 1.23. In addition, the clearance of each glucuronide metabolite was influenced by serum creatinine. No other significant predictors of clearance or volume of distribution were found. For a 3.5-kg neonate, morphine clearance was 0.77 L/h (CV, 48%), and the steady-state volume of distribution was 8.0 L (CV, 49%). Compared with previous studies in full-term newborns without HIE, morphine clearance was markedly lower. Dosing strategies customized for this vulnerable population will be needed. Applying the final population pharmacokinetic model, repeated Monte Carlo simulations (n = 1000 per simulation) were performed to evaluate various morphine dosing strategies that optimized achievement of morphine concentrations between 10 and 40 ng/mL. An optimized morphine loading dose of 50 μg/kg followed by a continuous infusion of 5 μg/kg/h was predicted across birthweights.

Treating disorders of the neonatal central nervous system: pharmacokinetic and pharmacodynamic considerations with a focus on antiepileptics

A major consideration in the treatment of neonatal disorders is that the selected drug, dose and dosage frequency is safe, effective and appropriate for the intended patient population. Thus, a thorough knowledge of the pharmacokinetics and pharmacodynamics of the chosen drug within the patient population is essential. In paediatric and neonatal populations two additional challenges can often complicate drug treatment - the inherently greater physiological variability, and a lack of robust clinical evidence of therapeutic range. There has traditionally been an overreliance in paediatric medicine on extrapolating doses from adult values by adjusting for bodyweight or body surface area, but many other sources of variability exist which complicate the choice of dose in neonates. The lack of reliable drug dosage data in neonates has been highlighted by regulatory authorities, as only ~50% of the most commonly used paediatric medicines have been examined in a paediatric population. Moreover, there is a paucity of information on the pharmacokinetic parameters which affect drug concentrations in different body tissues, and pharmacodynamic responses to drugs in the neonate. Thus, in the present review, we draw attention to the main pharmacokinetic factors that influence the unbound brain concentration of neuroactive drugs. Moreover, the pharmacodynamic differences between neonates and adults that affect the activity of centrally-acting therapeutic agents are briefly examined, with a particular emphasis on antiepileptic drugs.

Seizures and hypothermia: importance of electroencephalographic monitoring and considerations for treatment

Hypoxic-ischemic encephalopathy is a common cause of seizures in neonates. Despite the introduction of therapeutic hypothermia, seizure rates are similar to those reported in the pre-therapeutic hypothermia era. However, the seizure profile has been altered resulting in a lower overall seizure burden, shorter individual seizure durations, and seizures that are harder to detect. Electroencephalographic (EEG) monitoring is the gold standard for detecting all seizures in neonates and this is even more critical in neonates who are cooled, as they are often sedated, making seizures more difficult to detect. Several studies have shown that the majority of seizures in neonates undergoing therapeutic hypothermia remain subclinical, thus requiring EEG monitoring for diagnosis. Amplitude-integrated EEG monitoring is useful but shorter duration seizures are more likely to be missed. Evidence is emerging about the pharmacokinetic profile of routinely used antiepileptic drugs during therapeutic hypothermia and some modifications have been suggested, particularly for lidocaine use.

A simple quantitative method analysing amikacin, gentamicin, and vancomycin levels in human newborn plasma using ion-pair liquid chromatography/tandem mass spectrometry and its applicability to a clinical study

Neuroprotective controlled therapeutic hypothermia is the standard of care for newborns suffering perinatal asphyxia. Antibiotic drugs, such as amikacin, gentamicin, and vancomycin are frequently administered during controlled hypothermia, which possibly alters their pharmacokinetic (PK) and pharmacodynamic (PD) profiles. In order to examine this effect an LC-MS/MS method for the simultaneous quantification of amikacin, the major gentamicin components (gentamicin C, C1a and C2), and vancomycin in plasma was developed. In 25μL plasma proteins were precipitated with trichloroacetic acid (TCA) and detection of the components was achieved using ion-pair reversed phase chromatography coupled with electrospray ionization tandem mass spectrometry. The chromatographic runtime was 7.5min per sample. Calibration standards were prepared over a range of 0.3-50mgL(-1) for amikacin and gentamicin and 1.0-100mgL(-1) for vancomycin. At LLOQ accuracy was between 103 and 120% and imprecision was less than 19%. For concentrations above LLOQ accuracy ranged from 98% to 102% and imprecision was less than 6%. Process efficiency, ionization efficiency, and recovery were acceptable. Samples and stock solutions were stable during the time periods and at the different temperatures examined. The applicability of the method was shown by analysing plasma samples from 3 neonatal patients. The developed method allows accurate and precise simultaneous quantification of amikacin, gentamicin, and vancomycin in a small volume (25μL) of plasma.

Clinical pharmacokinetics of new-generation antiepileptic drugs at the extremes of age: an update

Epilepsies occur across the entire age range, and their incidence peaks in the first years of life and in the elderly. Therefore, antiepileptic drugs (AEDs) are commonly used at the extremes of age. Rational prescribing in these age groups requires not only an understanding of the drugs' pharmacodynamic properties, but also careful consideration of potential age-related changes in their pharmacokinetic profile. The present article, which updates a review published in 2006 in this journal, focuses on recent findings on the pharmacokinetics of new-generation AEDs in neonates, infants, children, and the elderly. Significant new information on the pharmacokinetics of new AEDs in the perinatal period has been acquired, particularly for lamotrigine and levetiracetam. As a result of slow maturation of the enzymes involved in glucuronide conjugation, lamotrigine elimination occurs at a particularly slow rate in neonates, and becomes gradually more efficient during the first months of life. In the case of levetiracetam, elimination occurs primarily by renal excretion and is also slow at birth, but drug clearance increases rapidly thereafter and can even double within 1 week. In general, infants older than 2-3 months and children show higher drug clearance (normalized for body weight) than adults. This pattern was confirmed in recent studies that investigated the pediatric pharmacokinetics of several new AEDs, including levetiracetam, rufinamide, stiripentol, and eslicarbazepine acetate. At the other extreme of age, in the elderly, drug clearance is generally reduced compared with younger adults because of less efficient drug-metabolizing activity, decreased renal function, or both. This general pattern, described previously for several AEDs, was confirmed in recent studies on the effect of old age on the clearance of felbamate, levetiracetam, pregabalin, lacosamide, and retigabine. For those drugs which are predominantly eliminated by renal excretion, aging-related pharmacokinetic changes could be predicted by measuring creatinine clearance (CLCR). Overall, most recent findings confirm that age is a major factor influencing the pharmacokinetic profile of AEDs. However, pharmacokinetic variability at any age can be considerable, and the importance of other factors should not be disregarded. These include genetic factors, co-morbidities, and drug interactions, particularly those caused by concomitantly administered AEDs which induce or inhibit drug-metabolizing enzymes.

Dried blood spots and sparse sampling: a practical approach to estimating pharmacokinetic parameters of caffeine in preterm infants

AIMS

Dried blood spots (DBS) alongside micro-analytical techniques are a potential solution to the challenges of performing pharmacokinetic (PK) studies in children. However, DBS methods have received little formal evaluation in clinical settings relevant to children. The aim of the present study was to determine a PK model for caffeine using a 'DBS/microvolume platform' in preterm infants.

METHODS

DBS samples were collected prospectively from premature babies receiving caffeine for treatment of apnoea of prematurity. A non-linear mixed effects approach was used to develop a population PK model from measured DBS caffeine concentrations. Caffeine PK parameter estimates based on DBS data were then compared with plasma estimates for agreement.

RESULTS

Three hundred and thirty-eight DBS cards for caffeine measurement were collected from 67 preterm infants (birth weight 0.6-2.11 kg). 88% of cards obtained were of acceptable quality and no child had more than 10 DBS samples or more than 0.5 ml of blood taken over the study period. There was good agreement between PK parameters estimated using caffeine concentrations from DBS samples (CL = 7.3 ml h⁻¹  kg⁻¹; V = 593 ml kg⁻¹; t(½) = 57 h) and historical caffeine PK parameter estimates based on plasma samples (CL = 4.9-7.9 ml h⁻¹  kg⁻¹; V = 640-970 ml kg⁻¹; t(½) = 101-144 h). We also found that changes in blood haematocrit may significantly confound estimates of caffeine PK parameters based on DBS data.

CONCLUSIONS

This study demonstrates that DBS methods can be applied to PK studies in a vulnerable population group and are a practical alternative to wet matrix sampling techniques.

Newly emerging therapies for neonatal seizures

The treatment of neonatal seizures has not changed significantly over the last 50 years despite advances in antiepileptic drug (AED) development for older children and adults. Recently new drugs have emerged some of which address age-specific challenges or mechanisms and will be discussed in this review. The loop diuretic bumetanide blocks the neuronal NKCC1 co-transporter and is thought specifically to supress seizures in the immature brain. Levetiracetam has been used in children and infants with good efficacy, an excellent safety profile, and near-ideal pharmacokinetic characteristics. Randomised controlled trials are now underway to test the efficacy of some newer AEDs for neonatal seizures. Topiramate has been shown to have neuroprotective properties in addition to its antiepileptic action and trials in babies with hypoxic-ischaemic encephalopathy are now planned. There is an urgent need to develop age-specific AEDs for preterm and term babies. These drugs must be evaluated with multicentre, collaborative trials using innovative methods and high ethical standards to overcome age-specific challenges with the ultimate aim of improving the outcome for neonates with seizures.

Neonatal seizures therapy: we are still looking for the efficacious drug

Therapeutic options currently available for neonatal seizures are still unsatisfactory both in terms of efficacy and of risk for long-term neurotoxicity, even if there is growing recognition of their potential to worsen neurodevelopmental outcome. A recent paper by Slaughter and colleagues entitled “Pharmacological treatment of neonatal seizures: a systematic review” has been published with the aim to provide a treatment algorithm, but, due to the relative paucity of clinical studies, it relies mainly on traditional antiepileptic drugs and does not distinguish between different neonatal populations, especially preterm and hypothermic neonates, who might require a dedicated approach in order to improve seizure control and reduce side effects.

Hypoxic–ischemic brain injury and neuroprotection in the newborn infant

Recent clinical trials have confirmed that in term infants with moderate-to-severe hypoxic–ischemic encephalopathy, death and severe developmental disability can be reduced by early treatment with hypothermia. However, meta-analysis of these trials has confirmed that two-thirds of the survivors remain seriously impaired. The search for new neuroprotective interventions has therefore continued. Extensive research has identified the important biochemical pathways that result in neuronal loss, and the subsequent repair and regeneration processes. The most promising neuroprotective agents that limit the former, and promote the latter, are being tested in animal models of hypoxic–ischemic brain injury and are awaiting clinical trials. It is likely that a ‘cocktail’ of agents, affecting a number of pathways, will ultimately prove to be the most effective intervention. The latest additions to a long list of proposed substances are various stem cells that promote neurogenesis by releasing trophic substances into the injured brain. Future clinical trials are likely to employ early biomarkers, of which MRI and proton spectroscopy are probably the most predictive of long-term neurodevelopmental outcome. In conclusion, the exponential increase in knowledge in this field can be expected to provide many more neuroprotective agents within the next decade.

Heart Rate and Arterial Pressure Changes during Whole-Body Deep Hypothermia

Whole-body deep hypothermia (DH) could be a new therapeutic strategy for asphyxiated newborn. This retrospective study describes how DH modified the heart rate and arterial blood pressure if compared to mild hypothermia (MH). Fourteen in DH and 17 in MH were cooled within the first six hours of life and for the following 72 hours. Hypothermia criteria were gestational age ≥36 weeks; birth weight ≥1800 g; clinical signs of moderate/severe hypoxic-ischemic encephalopathy. Rewarming was obtained in the following 6-12 hours (0.5°C/h) after cooling. Heart rates were the same between the two groups; there was statistically significant difference at the beginning of hypothermia and during rewarming. Three babies in the DH group and 2 in the MH group showed HR < 80 bpm and QTc > 520 ms. Infant submitted to deep hypothermia had not bradycardia or Qtc elongation before cooling and after rewarming. Blood pressure was significantly lower in DH compared to MH during the cooling, and peculiar was the hypotension during rewarming in DH group. Conclusion. The deeper hypothermia is a safe and feasible, only if it is performed by a well-trained team. DH should only be associated with a clinical trial and prospective randomized trials to validate its use.

Plasma topiramate concentrations resulting from doses associated with neuroprotection against white matter injury and stroke in two strains of rat pups

BACKGROUND

Cerebral white matter (WM) injury and stroke are common neuropathological injuries in newborns with congenital heart defects (CHDs) requiring surgery. Previous investigations in Long Evans rat pups subjected to hypoxia-ischemia found that intraperitoneal (i.p.) topiramate (TPM) at 30 mg/kg, but not 50 mg/kg, conferred neuroprotection. In Sprague-Dawley pups, a dose of 30 mg/kg protected against stroke. Concentrations associated with neuroprotective doses were not measured. The aims of this investigation were to determine concentrations associated with neuroprotective doses and to investigate the pharmacokinetics (PK) of i.p. TPM.

METHODS

Concentration-time data following administration of 30 and 50 mg/kg doses were analyzed using nonlinear mixed-effect modeling.

RESULTS

Mean predicted steady-state maximum and average concentrations following 30 mg/kg TPM were 31.3 and 16.8 μg/ml in Long Evans and 39.9 and 24.4 μg/ml in Sprague-Dawley pups. Mean predicted steady-state maximum and average concentrations following 50 mg/kg TPM were 52.1 and 28.1 μg/ml in Long Evans and 66.5 and 40.6 μg/ml in Sprague-Dawley pups. The apparent clearance (CL/F) and apparent volume of distribution (V/F) were 0.0470 ml/min and 22.2 ml, respectively, for Long Evans and 0.0325 ml/min and 19.7 ml, respectively, for Sprague-Dawley pups.

CONCLUSION

TPM concentrations associated with neuroprotective doses were determined. Body size and strain were significant covariates on CL/F and V/F. Results provide targets for future neuroprotection studies.

Clinical management of seizures in newborns : diagnosis and treatment

Neonatal seizures can be classified as tonic, clonic, myoclonic, and subtle. A clinical diagnosis is not easy as seizures are usually subtle in neonates. In the majority of newborn infants seizures are subclinical. On the other hand, not all abnormal movements identified by clinicians as clinical seizures are accompanied by electroencephalographic seizure discharges in the EEG. Precise incidence is difficult to delineate and depends on study population and criteria used for diagnosis of seizures. Controversy exists as to whether neonatal seizures themselves cause damage to the developing brain, or if the damage is primarily due to the underlying cause of the seizures. As a result of this controversy there is ongoing discussion whether all seizures (both clinical and subclinical) should be treated. In addition, when (sub)clinical seizures are treated, there is no consensus about the most appropriate treatment for neonatal seizures and how to assess the efficacy of treatment. Current therapeutic options to treat neonatal seizures (i.e. primarily first-generation antiepileptic drugs [AEDs]) are relatively ineffective. In practice, phenobarbital still remains the drug of first choice for EEG confirmed or suspected seizures. Benzodiazepines are also used in (phenobarbital) refractory cases. Several (small) studies indicate that lidocaine is an effective drug for refractory seizures as second- or third-line treatment. Although data are scarce, some AEDs with a wide acceptance in adult and pediatric neurology practice are being used to treat neonatal seizures (i.e. second-generation AEDs). These drugs are chemically different from all first-generation AEDs and they have an effect on other pathways so they provide new pharmacological targets for controlling seizures in newborns. Levetiracetam, topiramate, felbamate, bumetanide, lamotrigine and vigabatrin are examples of these second-generation AEDs. There is an urgent need for prospective, randomized, controlled trials to assess the efficacy and safety of these second-generation AEDs in neonates. The aim of this review is to provide an overview of the current knowledge of diagnosis, the effect on brain injury, and the treatment of neonatal seizures.

Cooling for newborns with hypoxic ischaemic encephalopathy

BACKGROUND

Newborn animal studies and pilot studies in humans suggest that mild hypothermia following peripartum hypoxia-ischaemia in newborn infants may reduce neurological sequelae without adverse effects.

OBJECTIVES

To determine the effect of therapeutic hypothermia in encephalopathic asphyxiated newborn infants on mortality, long-term neurodevelopmental disability and clinically important side effects.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group as outlined in The Cochrane Library (Issue 2, 2007). Randomised controlled trials evaluating therapeutic hypothermia in term and late preterm newborns with hypoxic ischaemic encephalopathy were identified by searching the Oxford Database of Perinatal Trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2007, Issue 2), MEDLINE (1966 to June 2007), previous reviews including cross-references, abstracts, conferences, symposia proceedings, expert informants and journal handsearching. We updated this search in May 2012.

SELECTION CRITERIA

We included randomised controlled trials comparing the use of therapeutic hypothermia with standard care in encephalopathic term or late preterm infants with evidence of peripartum asphyxia and without recognisable major congenital anomalies. The primary outcome measure was death or long-term major neurodevelopmental disability. Other outcomes included adverse effects of cooling and 'early' indicators of neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

Four review authors independently selected, assessed the quality of and extracted data from the included studies. Study authors were contacted for further information. Meta-analyses were performed using risk ratios (RR) and risk differences (RD) for dichotomous data, and weighted mean difference for continuous data with 95% confidence intervals (CI).

MAIN RESULTS

We included 11 randomised controlled trials in this updated review, comprising 1505 term and late preterm infants with moderate/severe encephalopathy and evidence of intrapartum asphyxia. Therapeutic hypothermia resulted in a statistically significant and clinically important reduction in the combined outcome of mortality or major neurodevelopmental disability to 18 months of age (typical RR 0.75 (95% CI 0.68 to 0.83); typical RD -0.15, 95% CI -0.20 to -0.10); number needed to treat for an additional beneficial outcome (NNTB) 7 (95% CI 5 to 10) (8 studies, 1344 infants). Cooling also resulted in statistically significant reductions in mortality (typical RR 0.75 (95% CI 0.64 to 0.88), typical RD -0.09 (95% CI -0.13 to -0.04); NNTB 11 (95% CI 8 to 25) (11 studies, 1468 infants) and in neurodevelopmental disability in survivors (typical RR 0.77 (95% CI 0.63 to 0.94), typical RD -0.13 (95% CI -0.19 to -0.07); NNTB 8 (95% CI 5 to 14) (8 studies, 917 infants). Some adverse effects of hypothermia included an increase sinus bradycardia and a significant increase in thrombocytopenia.

AUTHORS' CONCLUSIONS

There is evidence from the 11 randomised controlled trials included in this systematic review (N = 1505 infants) that therapeutic hypothermia is beneficial in term and late preterm newborns with hypoxic ischaemic encephalopathy. Cooling reduces mortality without increasing major disability in survivors. The benefits of cooling on survival and neurodevelopment outweigh the short-term adverse effects. Hypothermia should be instituted in term and late preterm infants with moderate-to-severe hypoxic ischaemic encephalopathy if identified before six hours of age. Further trials to determine the appropriate techniques of cooling, including refinement of patient selection, duration of cooling and method of providing therapeutic hypothermia, will refine our understanding of this intervention.

A systematic review of the pharmacokinetics of antiepileptic drugs in neonates with refractory seizures

BACKGROUND

Neonatal seizures are associated with neurological sequelae and an increased risk of epilepsy later in life. Phenobarbital and phenytoin remain the antiepileptic drugs (AEDs) most commonly used to treat neonatal seizures, despite their suboptimal effectiveness and safety. As a result, other AEDs, such as levetiracetam and topiramate, are often used in neonates with refractory seizures, despite limited data and off-label use.

OBJECTIVES

To systematically review published pharmacokinetic data for second-line AEDs used in neonates with seizures and to provide dosing recommendations for these agents in the neonatal population.

METHODS

A literature search was conducted in PubMed (1949-May 2012), Medline (1950-May 2012), and Embase (1980-May 2012). Each study was ranked according to the quality of evidence it provided, based on the classification system developed by the US Preventive Services Task Force. Information extracted from each study included study design, number of subjects, gestational and postnatal age, AED dosage regimen, pharmacokinetic parameters, pharmacokinetic model, AED serum concentrations, and sampling times.

RESULTS

Nineteen relevant pharmacokinetic studies involving a total of 8 different drugs were identified. No prospective, randomized, controlled studies (level I evidence) or nonrandomized controlled studies (level II-I evidence) were identified; 2 studies were prospective, nonrandomized, uncontrolled (cohort) studies (level II-2 evidence), 11 studies obtained evidence from multiple time series (level II-3 evidence), and 6 studies were case reports or descriptive studies (level III evidence).

CONCLUSIONS

There are limited pharmacokinetic data for the use of carbamazepine, levetiracetam, lidocaine, paraldehyde, topiramate, valproic acid, and vigabatrin for neonates with seizures refractory to treatment with first-line antiepileptic agents. Further research is needed to elucidate target AED serum concentrations (if any) required to optimize effectiveness and minimize dose-related adverse effects in neonates.

The impact of extracorporeal life support and hypothermia on drug disposition in critically ill infants and children

Extracorporeal membrane oxygenation (ECMO) support is an established lifesaving therapy for potentially reversible respiratory or cardiac failure. In 10% of all pediatric patients receiving ECMO, ECMO therapy is initiated during or after cardiopulmonary resuscitation. Therapeutic hypothermia is frequently used in children after cardiac arrest, despite the lack of randomized controlled trials that show its efficacy. Hypothermia is frequently used in children and neonates during cardiopulmonary bypass (CPB). By combining data from pharmacokinetic studies in children on ECMO and CPB and during hypothermia, this review elucidates the possible effects of hypothermia during ECMO on drug disposition.

Safety and efficacy of topiramate in neonates with hypoxic ischemic encephalopathy treated with hypothermia (NeoNATI)

BACKGROUND

Despite progresses in neonatal care, the mortality and the incidence of neuro-motor disability after perinatal asphyxia have failed to show substantial improvements. In countries with a high level of perinatal care, the incidence of asphyxia responsible for moderate or severe encephalopathy is still 2-3 per 1000 term newborns. Recent trials have demonstrated that moderate hypothermia, started within 6 hours after birth and protracted for 72 hours, can significantly improve survival and reduce neurologic impairment in neonates with hypoxic-ischemic encephalopathy. It is not currently known whether neuroprotective drugs can further improve the beneficial effects of hypothermia. Topiramate has been proven to reduce brain injury in animal models of neonatal hypoxic ischemic encephalopathy. However, the association of mild hypothermia and topiramate treatment has never been studied in human newborns. The objective of this research project is to evaluate, through a multicenter randomized controlled trial, whether the efficacy of moderate hypothermia can be increased by concomitant topiramate treatment.

METHODS/DESIGN

Term newborns (gestational age ≥ 36 weeks and birth weight ≥ 1800 g) with precocious metabolic, clinical and electroencephalographic (EEG) signs of hypoxic-ischemic encephalopathy will be randomized, according to their EEG pattern, to receive topiramate added to standard treatment with moderate hypothermia or standard treatment alone. Topiramate will be administered at 10 mg/kg once a day for the first 3 days of life. Topiramate concentrations will be measured on serial dried blood spots. 64 participants will be recruited in the study. To evaluate the safety of topiramate administration, cardiac and respiratory parameters will be continuously monitored. Blood samplings will be performed to check renal, liver and metabolic balance. To evaluate the efficacy of topiramate, the neurologic outcome of enrolled newborns will be evaluated by serial neurologic and neuroradiologic examinations. Visual function will be evaluated by means of behavioural standardized tests.

DISCUSSION

This pilot study will explore the possible therapeutic role of topiramate in combination with moderate hypothermia. Any favourable results of this research might open new perspectives about the reduction of cerebral damage in asphyxiated newborns.

Pharmacokinetics and pharmacodynamics of medication in asphyxiated newborns during controlled hypothermia. The PharmaCool multicenter study

Background

In the Netherlands, perinatal asphyxia (severe perinatal oxygen shortage) necessitating newborn resuscitation occurs in at least 200 of the 180–185.000 newly born infants per year. International randomized controlled trials have demonstrated an improved neurological outcome with therapeutic hypothermia. During hypothermia neonates receive sedative, analgesic, anti-epileptic and antibiotic drugs. So far little information is available how the pharmacokinetics (PK) and pharmacodynamics (PD) of these drugs are influenced by post resuscitation multi organ failure and the metabolic effects of the cooling treatment itself. As a result, evidence based dosing guidelines are lacking. This multicenter observational cohort study was designed to answer the question how hypothermia influences the distribution, metabolism and elimination of commonly used drugs in neonatal intensive care.

Methods/Design

Multicenter cohort study. All term neonates treated with hypothermia for Hypoxic Ischemic Encephalopathy (HIE) resulting from perinatal asphyxia in all ten Dutch Neonatal Intensive Care Units (NICUs) will be eligible for this study. During hypothermia and rewarming blood samples will be taken from indwelling catheters to investigate blood concentrations of several antibiotics, analgesics, sedatives and anti-epileptic drugs. For each individual drug the population PK will be characterized using Nonlinear Mixed Effects Modelling (NONMEM). It will be investigated how clearance and volume of distribution are influenced by hypothermia also taking maturation of neonate into account. Similarly, integrated PK-PD models will be developed relating the time course of drug concentration to pharmacodynamic parameters such as successful seizure treatment; pain assessment and infection clearance.

Discussion

On basis of the derived population PK-PD models dosing guidelines will be developed for the application of drugs during neonatal hypothermia treatment. The results of this study will lead to an evidence based drug treatment of hypothermic neonatal patients. Results will be published in a national web based evidence based paediatric formulary, peer reviewed journals and international paediatric drug references.

Trial registration

NTR2529.

Pitfalls in the quest of neuroprotectants for the perinatal brain

Sick preterm and term newborns are highly vulnerable to neural injury, and thus there has been a major search for new, safe and efficacious neuroprotective interventions in recent decades. Preclinical studies are essential to select candidate drugs for clinical trials in humans. This article focuses on 'negative' preclinical studies, i.e. studies where significant differences cannot be detected. Such findings are critical to inform both clinical and preclinical investigators, but historically they have been difficult to publish. A significant amount of time and resources is lost when negative results or nonpromising therapeutics are replicated in separate laboratories because these negative results were not shared with the research community in an open and accessible format. In this article, we discuss approaches to strengthen conclusions from negative preclinical studies and, conversely, to reduce false-negative preclinical evaluations of potential therapeutic compounds. Without being exhaustive, we address three major issues in conducting and interpreting preclinical experiments, including: (a) the choice of animal models, (b) the experimental design, and (c) issues concerning statistical analyses of the experiments. This general introduction is followed by synopses of negative data obtained from studies of three potential therapeutics for perinatal brain injury: (1) the somatostatin analog octreotide, (2) an AMPA/kainate receptor antagonist, topiramate, and (3) a pyruvate derivative, ethyl pyruvate.

A new neurological focus in neonatal intensive care

Advances in the care of high-risk newborn babies have contributed to reduced mortality rates for premature and term births, but the surviving neonates often have increased neurological morbidity. Therapies aimed at reducing the neurological sequelae of birth asphyxia at term have brought hypothermia treatment into the realm of standard care. However, this therapy does not provide complete protection from neurological complications and a need to develop adjunctive therapies for improved neurological outcomes remains. In addition, the care of neurologically impaired neonates, regardless of their gestational age, clearly requires a focused approach to avoid further injury to the brain and to optimize the neurodevelopmental status of the newborn baby at discharge from hospital. This focused approach includes, but is not limited to, monitoring of the patient's brain with amplitude-integrated and continuous video EEG, prevention of infection, developmentally appropriate care, and family support. Provision of dedicated neurocritical care to newborn babies requires a collaborative effort between neonatologists and neurologists, training in neonatal neurology for nurses and future generations of care providers, and the recognition that common neonatal medical problems and intensive care have an effect on the developing brain.

Physiologic and pharmacologic considerations for hypothermia therapy in neonates

With mounting evidence that hypothermia is neuroprotective in newborns with hypoxic-ischemic encephalopathy (HIE), an increasing number of centers are offering this therapy. Hypothermia is associated with a wide range of physiologic changes affecting every organ system, and awareness of these effects is essential for optimum patient management. Lowering the core temperature also alters pharmacokinetic and pharmacodynamic properties of medications commonly used in asphyxiated neonates, necessitating close attention to drug efficacy and side effects. Rewarming introduces additional risks and challenges as the hypothermia-associated physiologic and pharmacologic changes are reversed. In this review we provide an organ system-based assessment of physiologic changes associated with hypothermia. We also summarize evidence from randomized controlled trials showing lack of serious adverse effects of moderate hypothermia therapy in term and near-term newborns with moderate-to-severe HIE. Finally, we review the effects of hypothermia on drug metabolism and clearance based on studies in animal models and human adults, and limited data from neonates.

Phenobarbital for neonatal seizures in hypoxic ischemic encephalopathy: a pharmacokinetic study during whole body hypothermia

PURPOSE

Therapeutic hypothermia has recently been introduced to treat term newborns with hypoxic-ischemic encephalopathy, of whom more than half have seizures. Phenobarbital is widely used to treat neonatal seizures, but it is unknown whether its pharmacokinetics is affected by hypothermia. We evaluated the influence of hypothermia on phenobarbital pharmacokinetics in asphyxiated newborns.

METHODS

Nineteen term asphyxiated newborns treated with mild whole body hypothermia, started within 6 h after birth and protracted for 72 h, received phenobarbital for clinical seizures. Treatment schedule consisted of a loading dose of 20 mg/kg, titrated to response, up to a maximum dose of 40 mg/kg, followed by a maintenance dose of 2.5 or 1.5 mg/kg every 12 h. Phenobarbital concentrations were measured on 28 dried blood spots in each newborn.

KEY FINDINGS

Eighteen newborns showed plasma concentrations within the reference range after receiving a loading dose of 20 mg/kg. In the remaining newborn, who had received a loading dose of 35 mg/kg, phenobarbital concentrations exceeded the upper reference limit. Phenobarbital concentrations reached a virtual steady state in all newborns. Pharmacokinetic parameters were then calculated. Minimum and maximum concentration (24.7 ± 8.8 and 30.63 ± 10.3 mg/L), average plasma concentration (27.37 ± 9.4 mg/L), and half-life (173.9 ± 62.5 h) were considerably higher than reported in literature for normothermic newborns. Pharmacokinetic parameters did not differ significantly between infants receiving different maintenance doses.

SIGNIFICANCE

Phenobarbital administered to newborns under whole body hypothermia results in higher plasma concentrations and longer half-lives than expected in normothermic newborns.

Hypothermia after perinatal asphyxia: selection for treatment and cooling protocol

Three large randomized controlled trials have demonstrated benefits from 3 days of cooling to 33-34°C after perinatal asphyxia. No serious adverse effects were documented. The trials excluded many infants for hypothermia (HT) therapy, including those of age >6 hours and those with prematurity of <36 weeks gestation, abnormal coagulation, persistent pulmonary hypertension, and congenital abnormalities. This article considers whether the foregoing trial exclusion criteria are feasible given current knowledge and evidence. HT affects the validity of some outcome predictors (eg, clinical examination, amplitude-integrated electroencephalography), but not of magnetic resonance imaging. HT is a time-critical emergency treatment after perinatal asphyxia that requires optimal collaboration among local hospitals, transport teams, and cooling centers.

Synergistic neuroprotective therapies with hypothermia

Neuroprotection is a major health care priority, given the enormous burden of human suffering and financial cost caused by perinatal brain damage. With the advent of hypothermia as therapy for term hypoxic-ischemic encephalopathy, there is hope for repair and protection of the brain after a profound neonatal insult. However, it is clear from the published clinical trials and animal studies that hypothermia alone will not provide complete protection or stimulate the repair that is necessary for normal neurodevelopmental outcome. This review critically discusses drugs used to treat seizures after hypoxia-ischemia in the neonate with attention to evidence of possible synergies for therapy. In addition, other agents such as xenon, N-acetylcysteine, erythropoietin, melatonin and cannabinoids are discussed as future potential therapeutic agents that might augment protection from hypothermia. Finally, compounds that might damage the developing brain or counteract the neuroprotective effects of hypothermia are discussed.