Twenty-four hours of mild hypothermia in unsedated newborn pigs starting after a severe global hypoxic-ischemic insult is not neuroprotective

The effects of anaesthesia on cell death in a porcine model of neonatal hypoxic-ischaemic brain injury

Background

Hypothermia is neuroprotective after neonatal hypoxic-ischaemic brain injury. However, systemic cooling to hypothermic temperatures is a stressor and may reduce neuroprotection in awake pigs. We compared two experiments of global hypoxic-ischaemic injury in newborn pigs, in which one group received propofol-remifentanil and the other remained awake during post-insult hypothermia treatment.

Methods

In both studies, newborn pigs were anaesthetised using halothane during a 45-min global hypoxic-ischaemic insult induced by reducing Fio2 and graded hypotension until a low-voltage <7 μV electroencephalogram was achieved. On reoxygenation, the pigs were randomly allocated to receive 24 h of normothermia or hypothermia. In the first study (n=18) anaesthesia was discontinued and the pigs' tracheas were extubated. In the second study (n=14) anaesthesia was continued using propofol and remifentanil. Brain injury was assessed after 72 h by classical global histopathology, Purkinje cell count, and apoptotic cell counts in the hippocampus and cerebellum.

Results

Global injury was nearly 10-fold greater in the awake group compared with the anaesthetised group (P=0.021). Hypothermia was neuroprotective in the anaesthetised pigs but not the awake pigs. In the hippocampus, the density of cleaved caspase-3-positive cells was increased in awake compared with anaesthetised pigs in normothermia. In the cerebellum, Purkinje cell density was reduced in the awake pigs irrespective of treatment, and the number of cleaved caspase-3-positive Purkinje cells was greatly increased in hypothermic awake pigs. We detected no difference in cleaved caspase-3 in the granular cell layer or microglial reactivity across the groups.

Conclusions

Our study provides novel insights into the significance of anaesthesia/sedation during hypothermia for achieving optimal neuroprotection.

Preclinical validation of NeoWarm, a low-cost infant warmer and carrier device, to ameliorate induced hypothermia in newborn piglets as models for human neonates

Introduction

Approximately 1.5 million neonatal deaths occur among premature and small (low birthweight or small-for gestational age) neonates annually, with a disproportionate amount of this mortality occurring in low- and middle-income countries (LMICs). Hypothermia, the inability of newborns to regulate their body temperature, is common among prematurely born and small babies, and often underlies high rates of mortality in this population. In high-resource settings, incubators and radiant warmers are the gold standard for hypothermia, but this equipment is often scarce in LMICs. Kangaroo Mother Care/Skin-to-skin care (KMC/STS) is an evidence-based intervention that has been targeted for scale-up among premature and small neonates. However, KMC/STS requires hours of daily contact between a neonate and an able adult caregiver, leaving little time for the caregiver to care for themselves. To address this, we created a novel self-warming biomedical device, NeoWarm, to augment KMC/STS. The present study aimed to validate the safety and efficacy of NeoWarm.

Methods

Sixteen, 0-to-5-day-old piglets were used as an animal model due to similarities in their thermoregulatory capabilities, circulatory systems, and approximate skin composition to human neonates. The piglets were placed in an engineered cooling box to drop their core temperature below 36.5°C, the World Health Organizations definition of hypothermia for human neonates. The piglets were then warmed in NeoWarm (n = 6) or placed in the ambient 17.8°C ± 0.6°C lab environment (n = 5) as a control to assess the efficacy of NeoWarm in regulating their core body temperature.

Results

All 6 piglets placed in NeoWarm recovered from hypothermia, while none of the 5 piglets in the ambient environment recovered. The piglets warmed in NeoWarm reached a significantly higher core body temperature (39.2°C ± 0.4°C, n = 6) than the piglets that were warmed in the ambient environment (37.9°C ± 0.4°C, n = 5) (p < 0.001). No piglet in the NeoWarm group suffered signs of burns or skin abrasions.

Discussion

Our results in this pilot study indicate that NeoWarm can safely and effectively warm hypothermic piglets to a normal core body temperature and, with additional validation, shows promise for potential use among human premature and small neonates.

Dexmedetomidine During Therapeutic Hypothermia: A Multicenter Quality Initiative

OBJECTIVES

Sedation is typically used during neonatal therapeutic hypothermia (TH). This report describes a quality improvement (QI) initiative with the aim of decreasing opioid exposure during TH by implementing dexmedetomidine as the primary sedative agent.

METHODS

This dual-center QI initiative used a multidisciplinary team to create a sedation algorithm for safe implementation of dexmedetomidine as first-line therapy during TH. The primary measure in this initiative was cumulative opioid exposure during TH; balancing measures included safety parameters, primarily the rate of dexmedetomidine discontinuation because of bradycardia. Baseline demographic and clinical data were collected retrospectively for the period before implementation and prospectively during the QI period. Data were analyzed using statistical process control charts to identify change over time.

RESULTS

One-hundred and fifty-four neonates in the 2-year pre-QI period were compared with 135 neonates in the 2 years after guideline implementation. Guideline compliance with dexmedetomidine initiation was 99% and compliance with initial dosing increased from 70% to 91% during the QI period. The cumulative dose of opioid during TH decreased by >90% by the end of the QI period. Dexmedetomidine was discontinued for transient bradycardia in 9.6% of the study population. No other adverse effects were observed.

CONCLUSIONS

Dexmedetomidine may be used as the primary sedative during neonatal TH with a low incidence of adverse effects. Clinical trials evaluating the impact of sedation during TH on neurologic outcomes are needed.

Analgesia and sedation strategies in neonates undergoing whole-body therapeutic hypothermia: A scoping review

BACKGROUND

Therapeutic hypothermia (TH) is a widely practiced neuroprotective strategy for neonates with hypoxic-ischemic encephalopathy. Induced hypothermia is associated with shivering, cold pain, agitation, and distress.

OBJECTIVE

This scoping review determines the breadth of research undertaken for pain and stress management in neonates undergoing hypothermia therapy, the pharmacokinetics of analgesic and sedative medications during hypothermia and the effect of such medication on short- and long-term neurological outcomes.

METHODS

We searched the following online databases namely, (i) MEDLINE, (ii) Web of Science, (iii) Cochrane Library, (iv) Scopus, (v) CINAHL, and (vi) EMBASE to identify published original articles between January 2005 and December 2022. We included only English full-text articles on neonates treated with TH and reported the sedation/analgesia strategy used. We excluded articles that reported TH on transport or extracorporeal membrane oxygenation, did not report the intervention strategies for sedation/analgesia, and reported hypoxic-ischemic encephalopathy in which hypothermia was not applied.

RESULTS

The eligible publications (n = 97) included cohort studies (n = 72), non-randomized experimental studies (n = 2), pharmacokinetic studies (n = 4), dose escalation feasibility trial (n = 1), cross-sectional surveys (n = 5), and randomized control trials (n = 13). Neonatal Pain, Agitation, and Sedation Scale (NPASS) is the most frequently used pain assessment tool in this cohort. The most frequently used pharmacological agents are opioids (Morphine, Fentanyl), benzodiazepine (Midazolam) and Alpha2 agonists (Dexmedetomidine). The proportion of neonates receiving routine sedation-analgesia during TH is center-specific and varies from 40-100% worldwide. TH alters most drugs' metabolic rate and clearance, except for Midazolam. Dexmedetomidine has additional benefits of thermal tolerance, neuroprotection, faster recovery, and less likelihood of seizures. There is a wide inter-individual variability in serum drug levels due to the impact of temperature, end-organ dysfunction, postnatal age, and body weight on drug metabolism.

CONCLUSIONS

No multidimensional pain scale has been tested for reliability and construct validity in hypothermic encephalopathic neonates. There is an increasing trend towards using routine sedation/analgesia during TH worldwide. Wide variability in the type of medication used, administration (bolus versus infusion), and dose ranges used emphasizes the urgent need for standardized practice recommendations and guidelines. There is insufficient data on the long-term neurological outcomes of exposure to these medications, adjusted for underlying brain injury and severity of encephalopathy. Future studies will need to develop framework tools to enable precise control of sedation/analgesia drug exposure customized to individual patient needs.

Continuous Fentanyl Infusion in Newborns with Hypoxic-Ischemic Encephalopathy Treated with Therapeutic Hypothermia: Background, Aims, and Study Protocol for Time-Concentration Profiles

Therapeutic hypothermia (TH) is the standard of care for newborns with moderate to severe hypoxic-ischemic encephalopathy (HIE). Discomfort and pain during treatment are common and may affect the therapeutic efficacy of TH. Opioid sedation and analgesia (SA) are generally used in clinical practice, and fentanyl is one of the most frequently administered drugs. However, although fentanyl's pharmacokinetics (PKs) may be altered by hypothermic treatment, the PK behavior of this opioid drug in cooled newborns with HIE has been poorly investigated. The aim of this phase 1 study protocol (Trial ID: FentanylTH; EUDRACT number: 2020-000836-23) is to evaluate the fentanyl time-concentration profiles of full-term newborns with HIE who have been treated with TH. Newborns undergoing TH receive a standard fentanyl regimen (2 mcg/Kg of fentanyl as a loading dose, followed by a continuous infusion-1 mcg/kg/h-during the 72 h of TH and subsequent rewarming). Fentanyl plasma concentrations before bolus administration, at the end of the loading dose, and 24-48-72-96 h after infusion are measured. The median, maximum, and minimum plasma concentrations, together with drug clearance, are determined. This study will explore the fentanyl time-concentration profiles of cooled, full-term newborns with HIE, thereby helping to optimize the fentanyl SA dosing regimen during TH.

Restraint stress during neonatal hypoxia-ischemia alters brain injury following normothermia and hypothermia

Rodent models of neonatal hypoxic-ischemic (HI) injury require a subset of animals to be immobilized for continuous temperature monitoring during the insult and subsequent treatment. Restrained animals are discarded from the analysis due to the effect of restraint on the brain injury as first demonstrated by Thoresen et al 1996. However, the effects of restraint on responses to hypothermic (HT) post-insult therapy are not well described. We examine the effects of restraint associated with different probe placements on HI brain injury. We have conducted a meta-analysis of 23 experiments comparing probe rats (skin n = 42, rectal n = 35) and free-moving matched non-probe controls (n = 80) that underwent HI injury (left common carotid artery ligation and 90 min 8% O₂ ) at postnatal day 7 (P7), followed by 5 h of NT (37°C) or HT (32°C). On P14, brain regions were analyzed for injury (by neuropathology and area loss), microglial reactivity and brain-derived neurotrophic factor (BDNF). HI injury was mitigated in NT skin and rectal probe rats, with greater neuroprotection among the rectal probe rats. Following HT, the skin probe rats maintained the restraint-associated neuroprotection, while brain injury was significantly exacerbated among the rectal probe rats. Microglial reactivity strongly correlated with the acquired injury, with no detectable difference between the groups. Likewise, we observed no differences in BDNF signal intensity. Our findings suggest a biphasic neuroprotection from restraint stress, which becomes detrimental in combination with HT and the presumed discomfort from the rectal probe. This finding is useful in highlighting unforeseen effects of common experimental designs or routine clinical management.

Adequacy of sedation analgesia to support the comfort of neonates undergoing therapeutic hypothermia and its impact on short-term neonatal outcomes

Objectives

We aimed to evaluate (1) whether sedation analgesia (SA) used during therapeutic hypothermia (TH) was efficient to support the wellbeing of neonates with hypoxic-ischemic encephalopathy, (2) the SA level and its adjustment to clinical pain scores, and (3) the impact of inadequate SA on short-term neonatal outcomes evaluated at discharge.

Methods

This was an observational retrospective study performed between 2011 and 2018 in two level III centers in Alsace, France. We analyzed the wellbeing of infants by using the COMFORT-Behavior (COMFORT-B) clinical score and SA level during TH, according to which we classified infants into four groups: those with excess SA, adequate SA, lack of SA, and variability of SA. We analyzed the variations in doses of SA and their justification. We also determined the impact of inadequate SA on neonatal outcomes at discharge by multivariate analyses with multinomial regression, with adequate SA as the reference.

Results

A total of 110 patients were included, 89 from Strasbourg university hospital and 21 from Mulhouse hospital. The COMFORT-B score was assessed 95.5% of the time. Lack of SA was mainly found on the first day of TH (15/110, 14%). In all, 62 of 110 (57%) infants were in excess of SA over the entire duration of TH. Most dose variations were related to clinical pain scores. Inadequate SA was associated with negative short-term consequences. Infants with excess of SA had a longer duration of mechanical ventilation [mean ratio 1.46, 95% confidence interval (CI), 1.13-1.89, p = 0.005] and higher incidence of abnormal neurological examination at discharge (odds ratio 2.61, 95% CI, 1.10-6.18, p = 0.029) than infants with adequate SA.

Discussion

Adequate SA was not easy to achieve during TH. Close and regular monitoring of SA level may help achieve adequate SA. Excess of SA can be harmful for newborns with hypoxic-ischemic encephalopathy who are undergoing TH.

Polygraphic EEG Can Identify Asphyxiated Infants for Therapeutic Hypothermia and Predict Neurodevelopmental Outcomes

Background: Neonatal encephalopathy due to perinatal asphyxia is one of the leading causes of neonatal death and morbidity worldwide. The neurodevelopmental outcomes of asphyxiated neonates have considerably improved after therapeutic hypothermia (TH). The current challenge is to identify all newborns with encephalopathy at risk of cerebral lesions and subsequent disability within 6 h of life and who may be within the window period for treatment with TH. This study evaluated the neurodevelopmental outcomes in surviving asphyxiated neonates who did and did not receive TH, based on clinical and polygraphic electroencephalographic (p-EEG) criteria. Methods: The study included 139 asphyxiated newborns divided into two groups: 82 who received TH and 57 who were not cooled. TH was administered to asphyxiated newborns (gestational age ≥ 35 weeks, birth weight ≥ 1800 g) with encephalopathy of any grade and moderate-to-severe p-EEG abnormalities or seizures. Neurodevelopmental outcomes between the groups at 24 months of life and the risk factors for severe outcomes were assessed. Results: Severe neurodevelopmental impairment occurred in 10 (7.2%) out of the 139 enrolled neonates. Nine out of the 82 cooled neonates (11.0%) had severe neurodevelopmental impairment. All but one neonate (98.2%) who did not receive TH had normal outcomes. The multivariate logistic regression analysis showed that abnormal p-EEG patterns (OR: 27.6; IC: 2.8-267.6) and general movements (OR: 3.2; IC: 1.0-10.0) were significantly associated with severe neurodevelopmental impairment (area under ROC curve: 92.7%). Conclusion: The combination of clinical and p-EEG evaluations in hypoxic-ischemic encephalopathy contributed to a more accurate selection of patients treated with therapeutic hypothermia. When administered to infants with moderate to severe p-EEG abnormalities, TH prevents approximately 90% of severe neurodevelopmental impairment after any grade of hypoxic-ischemic encephalopathy.

Opioid exposure during therapeutic hypothermia and short-term outcomes in neonatal encephalopathy

OBJECTIVE

To assess the association between opioid exposure during therapeutic hypothermia (TH) for perinatal hypoxic-ischemic encephalopathy (HIE) and in-hospital outcomes.

STUDY DESIGN

In this retrospective cohort study, linked data were accessed on infants ≥36 weeks gestation, who underwent TH for HIE, born from 2010-2016 in 23 Neonatal Intensive Care Units participating in Children's Hospitals Neonatal Consortium and Pediatric Health Information Systems. We excluded infants who received opioids for >5 days.

RESULTS

The cohort (n = 1484) was categorized as No opioid [240(16.2%)], Low opioid (1-2 days) [574 (38.7%)] and High opioid group (HOG, 3-5 days) [670 (45.2%)]. After adjusting for HIE severity, opioids were not associated with abnormal MRI, but were associated with decreased likelihood of complete oral feeds at discharge. HOG had increased likelihood of prolonged hospital stay and ventilation.

CONCLUSION

Opioid exposure during TH was not associated with abnormal MRI; its association with adverse short-term outcomes suggests need for cautious empiric use.

Opioid analgesia and temperature regulation are associated with EEG background activity and MRI outcomes in neonates with mild-to-moderate hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia

BACKGROUND

Therapeutic hypothermia (TH) without sedation may lead to discomfort, which may be associated with adverse consequences in neonates with hypoxic-ischemic encephalopathy (HIE). The aim of this study was to assess the association between level of exposure to opioids and temperature, with electroencephalography (EEG) background activity post-TH and magnetic resonance imaging (MRI) brain injury in neonates with HIE.

METHODS

Thirty-one neonates with mild-to-moderate HIE who underwent TH were identified. MRIs were reviewed for presence of brain injury. Quantitative EEG background features including EEG discontinuity index and spectral power densities were calculated during rewarming and post-rewarming periods. Dose of opioids administered during TH and temperatures were collected from the medical charts. Multivariable linear and logistic regression analyses were conducted to assess the associations between cumulative dose of opioids and temperature with EEG background and MRI while adjusting for markers of HIE severity.

RESULTS

Higher opioid doses (β = -0.21, p = 0.02) and reduced skin temperature (β = 0.14, p < 0.01) were associated with lower EEG discontinuity index recorded post-TH. Higher opioid doses (β = 0.75, p = 0.01) and reduced skin temperature (β = -0.39, p = 0.02) were also associated with higher EEG Delta power post-TH. MRI brain injury was observed in 14 patients (45%). In adjusted regression analyses, higher opioid doses (OR = 0.00; 95%CI: 0-0.19; p = 0.01), reduced skin temperature (OR = 41.19; 95%CI: 2.27-747.86; p = 0.01) and reduced cooling device output temperature (OR = 1.91; 95%CI: 1.05-3.48; p = 0.04) showed an association with lower odds of brain injury.

CONCLUSIONS

Higher level of exposure to opioids and reduced skin temperature during TH in mild-to-moderate HIE were associated with improved EEG background activity post-TH. Moreover, higher exposure to opioids, reduced skin temperature and reduced device output temperature were associated with lower odds of brain injury on MRI.

Adherence to hypothermia guidelines in newborns with hypoxic-ischemic encephalopathy

INTRODUCTION

We do not have population data in Spain on the application of therapeutic hypothermia (TH). The objective was to examine adherence to management standards during TH of infants with hypoxic-ischemic encephalopathy (HIE).

METHOD

Multicenter observational cohort study from the beginning of TH (year 2010) in 5 hospitals in a Spanish region, until year 2019.

RESULTS

133 patients were recruited, 72% diagnosed with moderate HIE and the rest of them with severe HIE. In 84% of infants, passive hypothermia was started at birth. Active TH was started at a median age of 5 h of life (IQR 3.3; 6.3), although the central targeted temperature (33-34 °C) was reached at a median age of 3.5 h (IQR 1; 6). Those born extramural, initiated active TH 3.3 h on average later than those born intramural, but without differences in the age at which the targeted temperature was reached. Sedoanalgesia was used in 97%. 100% were monitored with amplitude-integrated EEG and 59% with cerebral oxymetry. MRI was performed in 94% with moderate HIE vs. 65% with severe; P < .001. Neuron-specific enolase in cerebrospinal fluid was determined in 42%. The average duration of rewarming was median 10 h (IQR 8; 12), with no differences depending on the degree of HIE (P = .57).

CONCLUSIONS

The implementation of TH successfully met the standards. However, aspects of care that could be improved were detected. Auditing newborn care with HIE is crucial to achieving programs with a high quality of care in each region.

Dexmedetomidine Versus Fentanyl for Neonates With Hypoxic Ischemic Encephalopathy Undergoing Therapeutic Hypothermia

OBJECTIVE

Therapeutic hypothermia reduces the risk of death and major disability in neonates with moderate-to-severe hypoxic ischemic encephalopathy (HIE). Opioids and benzodiazepines are used to manage agitation but contribute to hemodynamic and respiratory instability. The objective of this study was to evaluate the safety and efficacy of dexmedetomidine (DEX) compared with fentanyl (FENT) in neonates with HIE undergoing therapeutic hypothermia.

METHODS

This was a retrospective, single-center study comparing outcomes in neonates with HIE undergoing therapeutic hypothermia who received FENT to those who received DEX.

RESULTS

A total of 45 neonates were included (FENT, n = 19; DEX, n = 26). The DEX group had a decreased need for sedative bolus doses during therapeutic hypothermia compared with the FENT group; however, there was no difference in number of uncontrolled agitation scores or need for additional scheduled sedatives. The DEX group had a shorter time to discontinuation of sedatives after rewarming compared with the FENT group (0.52 versus 5 days, respectively; p = 0.001), shorter time to extubation after birth (3.1 versus 11.3 days, respectively; p = 0.004), and earlier time to resumption of feeds (8.5 versus 13 days, respectively; p = 0.03). A non-statistically significant reduction in seizures was noted (3 versus 7 subjects, respectively; p = 0.07). There was no difference in baseline characteristics, mortality, or adverse effects.

CONCLUSIONS

The use of DEX during therapeutic hypothermia for HIE appears to provide comparable control of agitation to FENT with a reduced need for additional sedatives and may lead to an earlier time to extubation and discontinuation of sedatives.

Contemporary targeted temperature management: Clinical evidence and controversies

Advancements in cardiac arrest and post-cardiac arrest care have led to improved survival to hospital discharge. While survival to hospital discharge is an important clinical outcome, neurologic recovery is also a priority. With the advancement of targeted temperature management (TTM), the American Heart Association guidelines for post-cardiac arrest care recommend TTM in patients who remain comatose after return of spontaneous circulation (ROSC). Recently, the TTM2 randomized controlled trial found no significant difference in neurologic function and mortality at 6-months between traditional hypothermia to 33°C versus 37.5°C. While TTM has been evaluated for decades, current literature suggests that the use of TTM to 33° when compared to a protocol of targeted normothermia does not result in improved outcomes. Instead, perhaps active avoidance of fever may be most beneficial. Extracorporeal cardiopulmonary resuscitation and membrane oxygenation can provide a means of both hemodynamic support and TTM after ROSC. This review aims to describe the pathophysiology, physiologic aspects, clinical trial evidence, changes in post-cardiac arrest care, potential risks, as well as controversies of TTM.

Cooling to Hypothermic Circulatory Arrest by Immersion vs. Cardiopulmonary Bypass (CPB): Worse Outcome After Rewarming in Immersion Cooled Pigs

Introduction

Cooling by cardiopulmonary bypass (CPB) to deep hypothermic cardiac arrest (HCA) for cardiac surgical interventions, followed by CPB-rewarming is performed on a routine basis with relatively low mortality. In contrast, victims of deep accidental hypothermia rewarmed with CPB generally have a much worse prognosis. Thus, we have developed an intact pig model to compare effects on perfusion pressures and global oxygen delivery (DO₂) during immersion cooling versus cooling by CPB. Further, we compared the effects of CPB-rewarming between groups, to restitute cardiovascular function, brain blood flow, and brain metabolism.

Materials and Methods

Total sixteen healthy, anesthetized juvenile (2–3 months) castrated male pigs were randomized in a prospective, open placebo-controlled experimental study to immersion cooling (IMM_c, n = 8), or cooling by CPB (CPB_c, n = 8). After 75 minutes of deep HCA in both groups, pigs were rewarmed by CPB. After weaning from CPB surviving animals were observed for 2 h before euthanasia.

Results

Survival rates at 2 h after completed rewarming were 4 out of 8 in the IMM_c group, and 8 out of 8 in the CPB_c group. Compared with the CPB_c-group, IMM_c animals showed significant reduction in DO₂, mean arterial pressure (MAP), cerebral perfusion pressure, and blood flow during cooling below 25°C as well as after weaning from CPB after rewarming. After rewarming, brain blood flow returned to control in CPB_c animals only, and brain micro dialysate-data showed a significantly increase in the lactate/pyruvate ratio in IMM_c vs. CPB_c animals.

Conclusion

Our data indicate that, although global O₂ consumption was independent of DO₂, regional ischemic damage may have taken place during cooling in the brain of IMM_c animals below 25°C. The need for prolonged extracorporeal membrane oxygenation (ECMO) should be considered in all victims of accidental hypothermic arrest that cannot be weaned from CPB immediately after rewarming.

Clonidine for sedation in infants during therapeutic hypothermia with neonatal encephalopathy: pilot study

OBJECTIVE

To determine a safe dose of clonidine (CLON) to be used in infants with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH).

STUDY DESIGN

A pilot prospective study was performed to determine the effect of CLON on autonomic parameters, the pharmacokinetics (PK) of CLON, and the amount of morphine (MOR) given "as needed" for shivering and agitation in a cohort of infants (n = 12) with HIE undergoing TH compared to a historical control group (n = 28).

RESULTS

The CLON group received less "as needed" MOR than the MOR-only group for agitation/shivering (p < 0.001), and the CLON vs. MOR-only group spent 92% vs. 79% of cooling time at the target core body temperature (CBT; p = 0.03, CLON vs. MOR).

CONCLUSIONS

Intravenous CLON (1 mcg/kg Q8h) is well tolerated in infants treated with TH for HIE. CLON stabilizes CBT in the ideal range during cooling, which may be optimal for neuroprotection.

Effect of dexmedetomidine on heart rate in neonates with hypoxic ischemic encephalopathy undergoing therapeutic hypothermia

BACKGROUND

Sedation is recommended to optimize neuroprotection in neonates with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH). Dexmedetomidine is an alternative agent to opioids, which are commonly used but have adverse effects. Both TH and dexmedetomidine can cause bradycardia. In this study, we describe our experience with dexmedetomidine and fentanyl in neonates undergoing TH for HIE, with a focus on heart rate (HR).

METHODS

We performed a retrospective chart review from 2011-2019 at a level IV NICU comparing sedation with dexmedetomidine (n = 14), fentanyl (n = 120), or both (n = 32) during TH for HIE. HR trends were compared based on sedation and gestational age. Neonates were included if they underwent TH and received sedation and were excluded if cooling was initiated past 24hours (h) from birth or if they required ECMO.

RESULTS

Of the 166 neonates included, 46 received dexmedetomidine, 14 as monotherapy and 32 in combination with fentanyl. Mean hourly HR from 12-36 h after birth was significantly lower for infants on dexmedetomidine versus fentanyl monotherapy (91±9 vs. 103±11 bpm, p < 0.002). Dexmedetomidine was decreased or discontinued in 22 (47.8%) neonates, most commonly due to inadequate sedation with a low HR. Lower gestational age was associated with higher HR but no significant difference in dexmedetomidine-related HR trends.

CONCLUSIONS

Despite an association with lower HR, dexmedetomidine may be successfully used in neonates with HIE undergoing TH. Implementation of a standardized protocol may facilitate dexmedetomidine titration in this population.

Characterization of oxidative stress in animal model of neonatal hypoxia

Purpose

To evaluate the oxidative stress in swine neonates submitted to hypoxia.

Methods

Ten large white piglets, healthy newborns, of both sexes, were divided into two groups and submitted to an experimental hypoxia protocol with reduced inspired oxygen fraction. The hypoxia group, composed of six animals, was submitted to oxygen reduction for 180 min. The animals in the control group, n = 4, were handled and evaluated simultaneously, but without oxygen reduction.

Results

180 min after the start of the hypoxic insult, a significant difference was observed in the oximetry, and heart rate of the hypoxia group was compared to the control group (p<0.05). There was no significant difference in the oxidative stress analyses. Reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), lipid peroxidation (TBARS), protein carbonyl (PC), and myeloperoxidase (MPO) in the piglets’ brain tissue were analyzed.

Conclusions

Hypoxia causes adverse effects in swine neonates, although there is a natural physiological resistance of swine neonates to respond to this insult. Analyses of GSH, SOD, CAT, TBARS, MPO, and PC were tabulated and are presented as parameters for further studies to be carried out on an animal model of swine hypoxia.

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

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

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

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

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

Process variations between Swiss units treating neonates with hypoxic-ischemic encephalopathy and their effect on short-term outcome

OBJECTIVE

To compare therapeutic hypothermia (TH) treatment of term and near-term neonates with hypoxic-ischemic encephalopathy (HIE) between neonatal units.

STUDY DESIGN

Population-based, retrospective analysis of TH initiation and maintenance, and of diagnostic imaging. The comparison between units was based on crude data analysis, indirect standardization, and adjusted logistic regression.

RESULTS

TH was provided to 570 neonates with HIE between 2011 and 2018 in 10 Swiss units. We excluded 121 off-protocol cooled neonates to avoid selection bias. Of the remaining 449 neonates, the outcome was favorable to international benchmarks, but there were large unit-to-unit variations in baseline perinatal data and TH management. A total of 5% neonates did not reach target temperature within 7 h (3-10% between units), and 29% experienced over- or undercooling (0-38%).

CONCLUSION

Although the neonates had favorable short-term outcomes, areas for improvement remain for Swiss units in both process and outcome measures.

[Adherence to hypothermia guidelines in newborns with hypoxic-ischemic encephalopathy]

INTRODUCTION

We do not have population data in Spain on the application of therapeutic hypothermia (TH). The objective was to examine adherence to management standards during TH of infants with hypoxic-ischemic encephalopathy (HIE).

METHOD

Multicenter observational cohort study from the beginning of TH (year 2010) in 5 hospitals in a Spanish region, until year 2019.

RESULTS

133 patients were recruited, 72% diagnosed with moderate HIE and the rest of them with severe HIE. In 84% of infants, passive hypothermia was started at birth. Active TH was started at a median age of 5hours of life (IQR: 3.3-6.3), although the central targeted temperature (33-34°C) was reached at a median age of 3.5hours (IQR: 1-6). Those born extramural, initiated active TH 3.3hours on average later than those born intramural, but without differences in the age at which the targeted temperature was reached. Sedoanalgesia was used in 97%. The 100% were monitored with amplitude-integrated EEG and 59% with cerebral oxymetry. MRI was performed in 94% with moderate HIE vs. 65% with severe; P<.001. Neuron-specific enolase in cerebrospinal fluid was determined in 42%. The average duration of rewarming was median 10hours (IQR: 8-12), with no differences depending on the degree of HIE (P=.57).

CONCLUSIONS

The implementation of TH successfully met the standards. However, aspects of care that could be improved were detected. Auditing newborn care with HIE is crucial to achieving programs with a high quality of care in each region.

Fentanyl analgesia in asphyxiated newborns treated with therapeutic hypothermia

INTRODUCTION

Therapeutic hypothermia is the standard care for asphyxiated newborns. Discomfort and pain during treatment are common and may affect therapeutic efficacy of hypothermia. Opioid analgosedation is commonly used in the clinical setting, but its effects in the cooled newborns is poorly investigated.

OBJECTIVE

The aim of this study was to assess the safety of fentanyl analgosedation during therapeutic hypothermia, by evaluating severe adverse effects and possible correlation with the neurodevelopmental outcome.

METHODS

We analyzed asphyxiated newborns treated with hypothermia receiving fentanyl intravenous infusion (years 2013-2018). Severe neurodevelopmental outcome was defined as cerebral palsy or Griffith's developmental quotient <70 or major sensorineural deficit. Severe brain lesions were defined as cortical or/and basal ganglia extensive involvement.

RESULTS

Fentanyl cumulative dose was variable (61.7 ± 18.5 µg/kg; range 34.3-120.3 µg/kg) among 45 enrolled patients. Respiratory depression was recorded in 13.3% cases of 30 spontaneously breathing patients. Severe brain lesions and severe neurodevelopmental disability were found in 24.4 and 11.1% of all included cases, respectively. Higher cumulative fentanyl dose was not associated with poor outcome.

CONCLUSIONS

Fentanyl treatment during therapeutic hypothermia does not negatively affect the neurodevelopmental outcome, thus on the contrary, it may contribute to ameliorate neuroprotection in the asphyxiated cooled newborns.

Dexmedetomidine versus intermittent morphine for sedation of neonates with encephalopathy undergoing therapeutic hypothermia

OBJECTIVE

In March 2019, the sedative in the therapeutic hypothermia protocol at Bellevue Hospital Center and NYU Langone Health changed from morphine to dexmedetomidine. This study evaluated the impact of this change on efficacy and safety parameters.

STUDY DESIGN

This was a retrospective, observational cohort study including neonates with HIE undergoing therapeutic hypothermia (N = 70) at two regional perinatal medical centers.

RESULTS

Baseline demographics, pain scores, hemodynamics, and time to enteral feeds were similar between dexmedetomidine (N = 34) and morphine (N = 36) patients. Dexmedetomidine patients received more breakthrough morphine (0.13 ± 0.13 vs 0.04 ± 0.09 mg/kg, p = 0.001), but less cumulative morphine (0.13 ± 0.13 vs 1.79 ± 0.23 mg/kg, p < 0.0001). Morphine patients on invasive ventilation required increased support (0 vs 31.58%, p = 0.02).

CONCLUSION

Dexmedetomidine is effective and safe for sedation and analgesia during therapeutic hypothermia. It reduced total opioid usage, with no increased incidence of adverse events.

Challenges in respiratory management during therapeutic hypothermia for neonatal encephalopathy

Neonatal encephalopathy (NE) is a serious condition with devastating neurological outcomes that can impact oxygenation and ventilation. The currently recommended therapeutic hypothermia (TH) for these infants may also has several respiratory implications. It decreases metabolic rate and oxygen demands; however, it increases oxygen solubility in the blood and impacts its release to peripheral tissue including the brain. Respiratory management of infants treated with TH should aim for minimizing exposure to hypocapnia or hyperoxia. Inspiratory gas should be heated to 37 °C and humidified to prevent airway and alveolar injury. Blood gas values should be corrected to the core temperature during TH and the use of alkaline buffers is discouraged. While mild sedation/analgesia may ameliorate the discomfort related to cooling, paralytic agents/heavy sedation should be used with caution considering their side effects. Finally, the use of caffeine still needs careful investigation in this population.

Management of comfort and sedation in neonates with neonatal encephalopathy treated with therapeutic hypothermia

Ensuring comfort for neonates undergoing therapeutic hypothermia (TH) after neonatal encephalopathy (NE) exemplifies a vital facet of neonatal neurocritical care. Physiologic markers of stress are frequently present in these neonates. Non-pharmacologic comfort measures form the foundation of care, benefitting both the neonate and parents. Pharmacological sedatives may also be indicated, yet have the potential to both mitigate and intensify the neurotoxicity of a hypoxic-ischemic insult. Morphine represents current standard of care with a history of utilization and extensive pharmacokinetic data to guide safe and effective dosing. Dexmedetomidine, as an alternative to morphine, has several appealing characteristics, including neuroprotective effects in animal models; robust pharmacokinetic studies in neonates with NE treated with TH are required to ensure a safe and effective standard dosing approach. Future studies in neonates treated with TH must address comfort, adverse events, and long-term outcomes in the context of specific sedation practices.

Morphine and fentanyl exposure during therapeutic hypothermia does not impair neurodevelopment

BACKGROUND

Hypothermia-treated and intubated infants with moderate or severe hypoxic-ischemic encephalopathy (HIE) usually receive morphine for sedation and analgesia (SA) during therapeutic hypothermia (TH) and endotracheal ventilation. Altered drug pharmacokinetics in this population increases the risk of drug accumulation. Opioids are neurotoxic in preterm infants. In term infants undergoing TH, the long-term effects of morphine exposure are unknown. We examined the effect of opioid administration during TH on neurodevelopmental outcome and time to extubation after sedation ended.

METHODS

In this prospectively collected population-based cohort of 282 infants with HIE treated with TH (2007-2017), the cumulative opioid dose of morphine and equipotent fentanyl (10-60 µg/kg/h) administered during the first week of life was calculated. Clinical outcomes and concomitant medications were also collected. Of 258 survivors, 229 underwent Bayley-3 neurodevelopmental assessments of cognition, language and motor function at 18-24 months. Multivariate stepwise linear regression analysis was used to examine the relation between cumulative opioid dose and Bayley-3 scores. Three severity-groups (mild-moderate-severe) were stratified by early (<6 h) amplitude-integrated electroencephalography (aEEG) patterns.

FINDINGS

The cumulative dose of opioid administered as SA during TH was median (IQR) 2121 µg/kg (1343, 2741). Time to extubation was independent of SA dose (p > 0.2). There was no significant association between cumulative SA dose and any of the Bayley-3 domains when analysing the entire cohort or any of the aEEG severity groups.

INTERPRETATION

Higher cumulative opioid doses in TH-treated infants with HIE was not associated with worse Bayley-3 scores at 18-24 months of age.

FUNDING

The Bristol cooling program was funded by the Children's Medical Research Charity SPARKS managing donations for our research from the UK and US, the UK Moulton Foundation, the Lærdal Foundation for Acute Medicine in Norway and the Norwegian Research Council (JKG).

Emerging therapies and management for neonatal encephalopathy-controversies and current approaches

Neonatal encephalopathy (NE) continues to have a major impact on newborn survival and neurodevelopmental outcomes worldwide. In high-income settings, therapeutic hypothermia is the only established standard treatment for neonates with moderate-to-severe NE, with compelling evidence that cooling reduces mortality and major neurodevelopmental impairment in survivors. Despite therapeutic hypothermia, a significant proportion of cooled infants continue to suffer long-term disability from brain injury. Innovative therapies offer the possibility of further improving neurodevelopmental outcomes by working synergistically with therapeutic hypothermia to decrease hypoxia-ischemia-induced excitotoxicity, prevent progression to secondary energy failure, and in some cases, promote neuroregeneration in the developing neonatal brain. This review discusses emerging NE therapies currently under investigation, offers insight into controversies surrounding various approaches to clinical care during therapeutic hypothermia, and identifies ongoing knowledge deficits that hinder attainment of optimal outcomes for neonates with NE.

Practical approaches to sedation and analgesia in the newborn

The prevention, assessment, and treatment of neonatal pain and agitation continues to challenge clinicians and researchers. Substantial progress has been made in the past three decades, but numerous outstanding questions remain. In this setting, clinicians must establish safe and compassionate standardized practices that consider available efficacy data, long-term outcomes, and research gaps. Novel approaches with limited data must be carefully considered against historic standards of care with robust data suggesting limited benefit and clear adverse effects. This review summarizes available evidence while suggesting practical clinical approaches to pain assessment and avoidance, procedural analgesia, postoperative analgesia, sedation during mechanical ventilation and therapeutic hypothermia, and the issues of tolerance and withdrawal. Further research in all areas represents an urgent priority for optimal neonatal care. In the meantime, synthesis of available data offers clinicians challenging choices as they balance benefit and risk in vulnerable critically ill neonates.

Acute symptomatic neonatal seizures, brain injury, and long-term outcome: The role of neuroprotective strategies

INTRODUCTION

Neonatal seizures are frequent but underdiagnosed manifestations of acute brain dysfunction and an important contributor to unfavorable outcomes. Etiology and severity of brain injury are the single strongest outcome determinants.

AREAS COVERED

The authors will discuss the prognostic role of acute symptomatic seizures versus brain injury and the main neuroprotective and neurorestorative strategies for full-term and preterm infants.

EXPERT OPINION

Prolonged acute symptomatic seizures likely contribute to long-term outcomes by independently adding further brain injury to initial insults. Correct timing and dosing of therapeutic interventions, depending on etiology and gestational ages, need careful evaluation. Although promising strategies are under study, the only standard of care is whole-body therapeutic hypothermia in full-term newborns with hypoxic-ischemic encephalopathy.

Ten years since the introduction of therapeutic hypothermia in neonates with perinatal hypoxic-ischaemic encephalopathy in Spain

INTRODUCTION

More than a decade has passed since therapeutic hypothermia (TH) was introduced in Spain; this is the only neuroprotective intervention that has become standard practice in the treatment of perinatal hypoxic-ischaemic encephalopathy (HIE). This article aims to provide a current picture of the technique and to address the controversies surrounding its use.

DEVELOPMENT

In the last 10 years, TH has been successfully implemented in the vast majority of tertiary hospitals in Spain, and more than 85% of newborns with moderate or severe HIE currently receive the treatment. The factors that can improve the efficacy of TH include early treatment onset (first 6hours of life) and the control of comorbid factors associated with perinatal asphyxia. In patients with moderate HIE, treatment onset after 6hours seems to have some neuroprotective efficacy. TH duration longer than 72hours or deeper hypothermia do not offer greater neuroprotective efficacy, but instead increase the risk of adverse effects. Unclarified aspects are the sedation of patients during TH, the application of the treatment in infants with mild HIE, and its application in other scenarios. Prognostic information and time frame are one of the most challenging aspects.

CONCLUSIONS

TH is universal in countries with sufficient economic resources, although certain unresolved controversies remain. While the treatment is widespread in Spain, there is a need for cooling devices for the transfer of these patients and their centralisation.

Hypothermia and Cardiovascular Instability

Severely asphyxiated neonates have acute heart failure as part of their multiorgan dysfunction syndrome during the first days of life. Supporting the cardiovascular system during this phase is part of contemporary treatment and regarded as vital for limiting the neurodevelopmental injury. The decision to treat cardiovascular instability should be based on evaluation of end-organ function. Neonatologist-performed echocardiography in combination with other diagnostic modalities enables comprehensive real-time assessment. This review discusses associations between hemodynamics and adverse outcome, modalities for evaluating the hemodynamic state of the infant, and therapeutic approaches during intensive care.

Individual longitudinal neurodevelopmental trajectories of children treated with hypothermia for perinatal asphyxia from 3 months to 5 years of age

BACKGROUND

Hypothermia for perinatal asphyxia is a common treatment to decrease morbidity. This study aims to describe a) individual longitudinal neurodevelopmental trajectories over 5 years in children with perinatal asphyxia treated with hypothermia and b) the correlation between movement quality at 3 months and motor developmental outcomes at 5 years of age.

METHODS

In this longitudinal cohort study, 18 children (12 male) were assessed at 3 (t₁), 6 (t₂), 12 (t₃), and 24 (t₄) months, and at the age of 5 (t₅) years, with standardized norm-referenced tests.

RESULTS

Six children showed abnormal movement quality assessed with General Movements (t₁) and all showed severe neurodevelopmental disabilities at t₅. The 12 children without severe disabilities, showed a significant normalization of z-scores over the five assessment points (linear mixed model analysis). At t₅, four of these children scored mildly delayed motor or cognitive development.

CONCLUSION AND IMPLICATIONS

Children without anomalies on the MRI before hospital discharge and normal movement quality at 3 months of age showed normal neurodevelopment at the age of 5, however, individual motor trajectories showed variability over time. Presents of abnormal GMs tend to detect CP and developmental problems, advocating a developmental surveillance to determine need for early intervention.

Provision of Sedation and Treatment of Seizures During Neonatal Therapeutic Hypothermia

Hypoxic-ischemic encephalopathy (HIE) produces a high rate of long-term neurodevelopmental disability in survivors. Therapeutic hypothermia dramatically improves the incidence of intact survival, but does not eliminate adverse outcomes. The ideal provision of sedation and treatment of seizures during therapeutic hypothermia represent therapeutic targets requiring optimization in practice. Physiologic stress from therapeutic hypothermia may obviate some of the benefits of this therapy. Morphine is commonly utilized to provide comfort, despite limited empiric evidence supporting safety and efficacy. Dexmedetomidine represents an interesting alternative, with preclinical data suggesting direct efficacy against shivering during induced hypothermia and neuroprotection in the setting of HIE. Pharmacokinetic properties must be considered when utilizing either agent, with safety dependent on conservative dosing and careful monitoring. HIE is the leading cause of neonatal seizures. Traditional therapies, including phenobarbital, fosphenytoin, and benzodiazepines, control seizures in the vast majority of neonates. Concerns about the acute and long-term effects of these agents have led to the exploration of alternative anticonvulsants, including levetiracetam. Unfortunately, levetiracetam is inferior to phenobarbital as first-line therapy for neonatal seizures. Considering both the benefits and risks of traditional anticonvulsant agents, treatment should be limited to the shortest duration indicated, with maintenance therapy reserved for neonates at high risk for recurrent seizures.

Opioid and benzodiazepine use during therapeutic hypothermia in encephalopathic neonates

OBJECTIVES

To evaluate the use of sedatives and analgesics during therapeutic hypothermia in encephalopathic neonates and assess associations between medication exposure and hospital outcomes.

STUDY DESIGN

We identified neonates ≥35 weeks gestational age treated with therapeutic hypothermia at 125 neonatal intensive care units between 2007 and 2015. We compared characteristics and hospital outcomes between unexposed neonates and neonates exposed to opioids and/or benzodiazepines.

RESULTS

Opioids were administered to 1 677/2 621 (64%) neonates, and exposure increased from 38% in 2008 to 68% in 2015. Sedation/analgesia varied widely between centers. Opioid-exposed neonates experienced greater durations of respiratory support and were more likely to receive inotropes and inhaled nitric oxide. Mortality during postnatal days 0-3 was lower among opioid-exposed neonates (31/625 [5%]) than unexposed neonates (64/714 [9%]).

CONCLUSIONS

Sedation/analgesia during therapeutic hypothermia is prevalent but not uniform across centers. Prospective studies are needed to assess if exposure independently predicts intensity and duration of physiologic support.

Electroencephalogram studies of hypoxic ischemia in fetal and neonatal animal models

Alongside clinical achievements, experiments conducted on animal models (including primate or non-primate) have been effective in the understanding of various pathophysiological aspects of perinatal hypoxic/ischemic encephalopathy (HIE). Due to the reasonably fair degree of flexibility with experiments, most of the research around HIE in the literature has been largely concerned with the neurodevelopmental outcome or how the frequency and duration of HI seizures could relate to the severity of perinatal brain injury, following HI insult. This survey concentrates on how EEG experimental studies using asphyxiated animal models (in rodents, piglets, sheep and non-human primate monkeys) provide a unique opportunity to examine from the exact time of HI event to help gain insights into HIE where human studies become difficult.

Therapeutic hypothermia and N-PASS; results from implementation in a level 3 NICU

BACKGROUND

Neonates that have been subjected to perinatal asphyxia and fulfill criteria for therapeutic hypothermia are cooled to 33.5 °C for 72 h. There is no consensus regarding sedation and analgesic use during hypothermia, but there is evidence supporting the importance of pain relief and adequate sedation. There is a need for assessment of the neonates need for pain relief and sedation, and for adjustments of medication to ensure adequate treatment. There are many different scoring tools available. We found the N-PASS (Neonatal Pain, Agitation and Sedation Scale) scoring tool to be the most suitable for this patient group as it assesses both pain and sedation.

METHODS

We translated the scoring tool according to guidelines published by Wilder et al., and scored neonates treated with therapeutic hypothermia. Sedation and analgesia were adjusted according to scoring results. At the end of the study a questionnaire was filled out by the nurses in charge of this group of patients.

RESULTS

Both pain and sedation scores did not reach the desired levels until day 3. The nurses reported a high level of satisfaction (79.7% were extremely of very satisfied), and 96.7% of the nurses found the neonates to be better pain relieved after the initiation of the study.

CONCLUSION

The implementation of the N-PASS scoring tool in our unit has been successful, and has led to better pain relief and sedation than before the implementation.

Preemptive Morphine During Therapeutic Hypothermia After Neonatal Encephalopathy: A Secondary Analysis

Although therapeutic hypothermia (TH) improves outcomes after neonatal encephalopathy (NE), the safety and efficacy of preemptive opioid sedation during cooling therapy is unclear. We performed a secondary analysis of the data from a large multicountry prospective observational study (Magnetic Resonance Biomarkers in Neonatal Encephalopathy [MARBLE]) to examine the association of preemptive morphine infusion during TH on brain injury and neurodevelopmental outcomes after NE. All recruited infants had 3.0 Tesla magnetic resonance imaging and spectroscopy at 1 week, and neurodevelopmental outcome assessments at 22 months. Of 223 babies recruited to the MARBLE study, the data on sedation were available from 169 babies with moderate (n = 150) or severe NE (n = 19). Although the baseline characteristics and admission status were similar, the babies who received morphine infusion (n = 141) were more hypotensive (49% vs. 25%, p = 0.02) and had a significantly longer hospital stay (12 days vs. 9 days, p = 0.009) than those who did not (n = 28). Basal ganglia/thalamic injury (score ≥1) and cortical injury (score ≥1) was seen in 34/141 (24%) and 37/141 (26%), respectively, of the morphine group and 4/28 (14%) and 3/28 (11%) of the nonmorphine group (p > 0.05). On regression modeling adjusted for potential confounders, preemptive morphine was not associated with mean (standard deviation [SD]) thalamic N-acetylaspartate (NAA) concentration (6.9 ± 0.9 vs. 6.5 ± 1.5; p = 0.97), and median (interquartile range) lactate/NAA peak area ratios (0.16 [0.12-0.21] vs. 0.13 [0.11-0.18]; p = 0.20) at 1 week, and mean (SD) Bayley-III composite motor (92 ± 23 vs. 94 ± 10; p = 0.98), language (89 ± 22 vs. 93 ± 8; p = 0.53), and cognitive scores (95 ± 21 vs. 99 ± 13; p = 0.56) at 22 months. Adverse neurodevelopmental outcome (adjusted for severity of encephalopathy) was seen in 26 (18%) of the morphine group, and none of the nonmorphine group (p = 0.11). Preemptive morphine sedation during TH does not offer any neuroprotective benefits and may be associated with increased hospital stay. Optimal sedation during induced hypothermia requires further evaluation in clinical trials.

Pharmacokinetics of morphine in encephalopathic neonates treated with therapeutic hypothermia

OBJECTIVE

Morphine is a commonly used drug in encephalopathic neonates treated with therapeutic hypothermia after perinatal asphyxia. Pharmacokinetics and optimal dosing of morphine in this population are largely unknown. The objective of this study was to describe pharmacokinetics of morphine and its metabolites morphine-3-glucuronide and morphine-6-glucuronide in encephalopathic neonates treated with therapeutic hypothermia and to develop pharmacokinetics based dosing guidelines for this population.

STUDY DESIGN

Term and near-term encephalopathic neonates treated with therapeutic hypothermia and receiving morphine were included in two multicenter cohort studies between 2008-2010 (SHIVER) and 2010-2014 (PharmaCool). Data were collected during hypothermia and rewarming, including blood samples for quantification of morphine and its metabolites. Parental informed consent was obtained for all participants.

RESULTS

244 patients (GA mean (sd) 39.8 (1.6) weeks, BW mean (sd) 3,428 (613) g, male 61.5%) were included. Morphine clearance was reduced under hypothermia (33.5°C) by 6.89%/°C (95% CI 5.37%/°C- 8.41%/°C, p<0.001) and metabolite clearance by 4.91%/°C (95% CI 3.53%/°C- 6.22%/°C, p<0.001) compared to normothermia (36.5°C). Simulations showed that a loading dose of 50 μg/kg followed by continuous infusion of 5 μg/kg/h resulted in morphine plasma concentrations in the desired range (between 10 and 40 μg/L) during hypothermia.

CONCLUSIONS

Clearance of morphine and its metabolites in neonates is affected by therapeutic hypothermia. The regimen suggested by the simulations will be sufficient in the majority of patients. However, due to the large interpatient variability a higher dose might be necessary in individual patients to achieve the desired effect.

TRIAL REGISTRATION

www.trialregister.nl NTR2529.

Phenobarbital, Midazolam Pharmacokinetics, Effectiveness, and Drug-Drug Interaction in Asphyxiated Neonates Undergoing Therapeutic Hypothermia

BACKGROUND

Phenobarbital and midazolam are commonly used drugs in (near-)term neonates treated with therapeutic hypothermia for hypoxic-ischaemic encephalopathy, for sedation, and/or as anti-epileptic drug. Phenobarbital is an inducer of cytochrome P450 (CYP) 3A, while midazolam is a CYP3A substrate. Therefore, co-treatment with phenobarbital might impact midazolam clearance.

OBJECTIVES

To assess pharmacokinetics and clinical anti-epileptic effectiveness of phenobarbital and midazolam in asphyxiated neonates and to develop dosing guidelines.

METHODS

Data were collected in the prospective multicentre PharmaCool study. In the present study, neonates treated with therapeutic hypothermia and receiving midazolam and/or phenobarbital were included. Plasma concentrations of phenobarbital and midazolam including its metabolites were determined in blood samples drawn on days 2-5 after birth. Pharmacokinetic analyses were performed using non-linear mixed effects modelling; clinical effectiveness was defined as no use of additional anti-epileptic drugs.

RESULTS

Data were available from 113 (phenobarbital) and 118 (midazolam) neonates; 68 were treated with both medications. Only clearance of 1-hydroxy midazolam was influenced by hypothermia. Phenobarbital co-administration increased midazolam clearance by a factor 2.3 (95% CI 1.9-2.9, p < 0.05). Anticonvulsant effectiveness was 65.5% for phenobarbital and 37.1% for add-on midazolam.

CONCLUSIONS

Therapeutic hypothermia does not influence clearance of phenobarbital or midazolam in (near-)term neonates with hypoxic-ischaemic encephalopathy. A phenobarbital dose of 30 mg/kg is advised to reach therapeutic concentrations. Phenobarbital co-administration significantly increased midazolam clearance. Should phenobarbital be substituted by non-CYP3A inducers as first-line anticonvulsant, a 50% lower midazolam maintenance dose might be appropriate to avoid excessive exposure during the first days after birth.

Perinatal hypoxic-ischemic brain injury in large animal models: Relevance to human neonatal encephalopathy

Perinatal hypoxia-ischemia resulting in death or lifelong disabilities remains a major clinical disorder. Neonatal models of hypoxia-ischemia in rodents have enhanced our understanding of cellular mechanisms of neural injury in developing brain, but have limitations in simulating the range, accuracy, and physiology of clinical hypoxia-ischemia and the relevant systems neuropathology that contribute to the human brain injury pattern. Large animal models of perinatal hypoxia-ischemia, such as partial or complete asphyxia at the time of delivery of fetal monkeys, umbilical cord occlusion and cerebral hypoperfusion at different stages of gestation in fetal sheep, and severe hypoxia and hypoperfusion in newborn piglets, have largely overcome these limitations. In monkey, complete asphyxia produces preferential injury to cerebellum and primary sensory nuclei in brainstem and thalamus, whereas partial asphyxia produces preferential injury to somatosensory and motor cortex, basal ganglia, and thalamus. Mid-gestational fetal sheep provide a valuable model for studying vulnerability of progenitor oligodendrocytes. Hypoxia followed by asphyxia in newborn piglets replicates the systems injury seen in term newborns. Efficacy of post-insult hypothermia in animal models led to the success of clinical trials in term human neonates. Large animal models are now being used to explore adjunct therapy to augment hypothermic neuroprotection.

Predictive value of early EEG for seizures in neonates with hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia

OBJECTIVES

To assess the prognostic significance of an early normal/mildly abnormal conventional EEG (cEEG) on seizure risk in neonates undergoing therapeutic hypothermia.

METHODS

We reviewed the video-EEG recordings from a large cohort of neonates treated with therapeutic hypothermia for hypoxic-ischemic encephalopathy from 2008 to 2017 in a single tertiary center. Continuous video-EEG was started as soon as possible (median 8.2 h) and continued throughout hypothermia and rewarming. We studied those neonates with a normal/mildly abnormal EEG during the first 24 h of monitoring.

RESULTS

A total of 331 neonates were treated with hypothermia and 323 had cEEG recordings available for review; 99 were excluded because of a moderately/severely abnormal cEEG background and/or seizure during the first 24 h of recording, and an additional eight because of early rewarming. The remaining 216 had a normal/mildly abnormal cEEG in the first 24 h. None of these patients subsequently developed seizures.

CONCLUSION

A normal/mildly abnormal cEEG during the first 24 h indicates a very low risk of subsequent seizures. This suggests that cEEG monitoring can be safely discontinued after 24 h if it has remained normal or excessively discontinuous and no seizures are detected, limiting the need for this resource-intensive and expensive tool.

Association between sedation-analgesia and neurodevelopment outcomes in neonatal hypoxic-ischemic encephalopathy

OBJECTIVE

To evaluate the association between sedation-analgesia (SA) during initial 72 h and death/disability at 18 months of age in neonatal hypoxic-ischemic encephalopathy (HIE).

DESIGN

This was a secondary analysis of the NICHD therapeutic hypothermia (TH) randomized controlled trial in moderate or severe HIE. Receipt of SA and anticonvulsant medications at five time points were considered: prior to and at baseline, 24, 48, and 72 h of TH or normothermia. Disability was defined as mental developmental index <85, cerebral palsy, blindness, hearing impairment, or Gross Motor Function Classification System 2-5.

RESULTS

Of the 208 RCT participants, 38 (18%) infants had no exposure to SA or anticonvulsants at any of the five time points, 20 (10%) received SA agents only, 81 (39%) received anticonvulsants only, and 69 (33%) received both SA and anticonvulsants. SA category drugs were not administered in 57% of infants while 18% received SA at ≥3 time points; 72% infants received anticonvulsants during 72 h of intervention. At 18 months of age, disability among survivors and death/disability was more frequent in the groups receiving anticonvulsants, with (48 and 65%) or without (37 and 58%) SA, compared to groups with no exposure (14 and 34%) or SA (13 and 32%) alone. Severe HIE (aOR 3.60; 1.59-8.13), anticonvulsant receipt (aOR 2.48; 1.05-5.88), and mechanical ventilation (aOR 7.36; 3.15-17.20) were independently associated with 18-month death/disability, whereas TH (aOR 0.28; 0.13-0.60) was protective. SA exposure showed no association with outcome.

CONCLUSIONS

The risk benefits of SA in HIE need further investigation.

Dexmedetomidine for Sedation of Neonates with HIE Undergoing Therapeutic Hypothermia: A Single-Center Experience

Hypoxic-ischemic encephalopathy (HIE) is a significant cause of morbidity and mortality in neonates. Therapeutic hypothermia reduces the risk of death or disability. Providing optimal sedation while neonates are undergoing therapeutic hypothermia is likely beneficial but may present therapeutic challenges. There are limited data describing the use of dexmedetomidine for sedation in patients undergoing therapeutic hypothermia. The objective of this study is to evaluate the efficacy and short-term safety of dexmedetomidine infusion for sedation in term neonates undergoing therapeutic hypothermia for HIE.

Recent advances in preclinical and clinical multimodal MR in the newborn brain

Aside from injury identification, MRI of the newborn brain has given us insight into cortical and white matter development, identified windows of vulnerabilities, enabled the introduction of therapeutic hypothermia which has become the standard of care in neonatal asphyxia, and is fostering leapfrogging discoveries in the field of neuro-genetics. This article reviews the main advances in recent years in newborn brain imaging both in preclinical and clinical research.