Adding 5 h delayed xenon to delayed hypothermia treatment improves long-term function in neonatal rats surviving to adulthood.

BACKGROUND: We previously reported that combining immediate hypothermia with immediate or 2 h delayed inhalation of an inert gas, xenon, gave additive neuroprotection in rats after a hypoxic-ischemic insult, compared to hypothermia alone. Defining the therapeutic time window for this new combined intervention is crucial in clinical practice when immediate treatment is not always feasible. The aim of this study is to investigate whether combined hypothermia and xenon still provide neuroprotection in rats after a 5 h delay for both hypothermia and xenon. METHODS: Seven-day-old Wistar rat pups underwent a unilateral hypoxic-ischemic insult. Pups received 5 h of treatment starting 5 h after the insult randomized between normothermia, hypothermia, or hypothermia with 50% xenon. Surviving pups were tested for fine motor function through weeks 8-10 before being euthanized at week 11. Their hemispheric and hippocampal areas were assessed. RESULTS: Both delayed hypothermia-xenon and hypothermia-only treated groups had significantly less brain tissue loss than those which underwent normothermia. The functional performance after 1 wk and adulthood was significantly better after hypothermia-xenon treatment as compared to the hypothermia-only or normothermia groups. CONCLUSION: Adding 50% xenon to 5 h delayed hypothermia significantly improved functional outcome as compared to delayed hypothermia alone despite similar reductions in brain area.

Immediate hypothermia is not neuroprotective after severe hypoxia-ischemia and is deleterious when delayed by 12 hours in neonatal rats.

BACKGROUND AND PURPOSE: Hypothermia (HT) for neonatal hypoxic-ischemic encephalopathy is advised to start within the first 6 hours after birth. There is some clinical evidence that HT is more effective against moderate than against severe hypoxic-ischemic encephalopathy, but it is unknown whether delayed HT beyond 6 hours is effective or even injurious. METHODS: One-hundred seven 7-day-old rat pups underwent unilateral hypoxia-ischemia of moderate severity. Pups were randomized to receive 5 hours of normothermia (NT) or HT starting immediately, 3 hours, 6 hours, or 12 hours after the 90-minute hypoxic period. One-hundred five 7-day-old rat pups underwent severe hypoxia-ischemia lasting 150 minutes, followed by the same group design as mentioned. Relative area loss of the left/right hemisphere was measured after 1 week of survival. RESULTS: In the moderate NT group, the mean area loss of the left hemisphere was 40.5%. The area loss was significantly decreased to 24.8% with immediate HT (P<0.05) and increased linearly with the delay of HT by 1.788% per hour until at least 6 hours of delay (linear regression, P=0.026). After 12-hour delayed HT, the area loss was similar to the moderate NT group (41.1%). After severe NT, the mean area loss of the left hemisphere was 59.3%. Immediate HT, 3-hour delayed HT, and 6-hour delayed HT all resulted in similar area loss, whereas the 12-hour delayed-HT resulted in significantly increased area loss (69.5%; P=0.032). CONCLUSIONS: Immediate and delayed (≤6 hours) HT provides neuroprotection after moderate hypoxia-ischemia in neonatal rats. This neuroprotection decreases linearly with increasing delay. After severe insults, however, immediate or delayed HT≤6 hours provides no neuroprotection. Twelve-hour delayed hypothermia increased brain injury after severe hypoxia-ischemia, which is of clinical concern.

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).

Closed circuit xenon delivery for 72h in neonatal piglets following hypoxic insult using an ambient pressure automated control system: Development, technical evaluation and pulmonary effects.

BACKGROUND: Therapeutic hypothermia (TH) for 72h is the standard treatment following neonatal encephalopathy (NE). However, one-third do not benefit and adjunctive therapies are urgently needed. Xenon enhances neuroprotection with TH when administered at 50% concentration within 5hours of hypoxia in experimental studies. Delayed initiation (~10 hours of age) of 30% xenon for 24 hours during TH did not improve early adverse biomarkers in a clinical trial of Xenon+TH vs TH. After hypoxia-ischemia, excitotoxic injury via N-methyl-D-aspartate receptor overactivation lasts days. Since xenon partially inhibits this receptor, we hypothesised that giving 50% xenon throughout the entire 72h TH and rewarming periods would enhance neuroprotection. Xenon costs $30/litre, so a closed-circuit breathing system is desirable with automated fresh gas delivery. METHODS: Seven mechanically ventilated newborn pigs were randomized to receive 50% inhaled xenon for 72h during hypothermia (rectal-temperature 35°C) and subsequent rewarming following a global hypoxic-ischemic insult (XeHT, N = 4) or under normothermia for 72h (rectal-temperature 38.5°C) following sham insult (XeNT, N = 3). An automated fresh gas delivery system injected oxygen/air/xenon boluses into a closed-circuit based on measured gas concentrations. RESULTS AND DISCUSSION: Median (IQR) xenon consumption was 0.31 L/h (0.18, 0.50) and 0.34L/h (0.32, 0.49) for hypothermic and normothermic groups respectively, 0.34L/h (0.25, 0.53) overall. 92% of 9626 xenon and 69% of 9635 oxygen measurements were within 20% variation from targets. For xenon concentration, the median absolute performance errors for the XeHT and XeNT groups were 6.14% and 3.84% respectively and 4.31% overall. For oxygen these values were 13.42%, 15.05% and 12.4% respectively. There were no adverse pulmonary pathophysiology findings. Clinical problems over the total period included three related to sensors, seven breathing system leaks, ten partial and one complete tracheal tube occlusion episodes. CONCLUSION: The automated controller functioned as intended maintaining an inhaled xenon concentration close to the 50% target for 72-78h at a xenon cost of $11.1/h.

Fentanyl Induces Cerebellar Internal Granular Cell Layer Apoptosis in Healthy Newborn Pigs.

BACKGROUND: Opioids like fentanyl are regularly used in neonates for analgesia and sedation. So far, they have been reported to be safe and eligible to use. The cerebellum has become a focus of neurodevelopmental research within the last years, as it is known to play an important role in long-lasting motor, cognitive, and other behavioral changes. The cerebellar cortex is of major importance in the coordinative role of the cerebellum and highly vulnerable to injury and impaired growth. OBJECTIVE: This study was performed to evaluate the apoptotic effect of intravenous fentanyl infusion on the cerebellum in healthy newborn pigs. METHODS: Thirteen healthy pigs (

Xenon ventilation during therapeutic hypothermia in neonatal encephalopathy: a feasibility study.

BACKGROUND AND OBJECTIVES: Therapeutic hypothermia has become standard of care in newborns with moderate and severe neonatal encephalopathy; however, additional interventions are needed. In experimental models, breathing xenon gas during cooling offers long-term additive neuroprotection. This is the first xenon feasibility study in cooled infants. Xenon is expensive, requiring a closed-circuit delivery system. METHODS: Cooled newborns with neonatal encephalopathy were eligible for this single-arm, dose-escalation study if clinically stable, under 18 hours of age and requiring less than 35% oxygen. Xenon duration increased stepwise from 3 to 18 hours in 14 subjects; 1 received 25% xenon and 13 received 50%. Respiratory, cardiovascular, neurologic (ie, amplitude-integrated EEG, seizures), and inflammatory (C-reactive protein) effects were examined. The effects of starting or stopping xenon rapidly or slowly were studied. Three matched control subjects per xenon treated subject were selected from our cooling database. Follow-up was at 18 months using mental developmental and physical developmental indexes of the Bayley Scales of Infant Development II. RESULTS: No adverse respiratory or cardiovascular effects, including post-extubation stridor, were seen. Xenon increased sedation and suppressed seizures and background electroencephalographic activity. Seizures sometimes occurred during rapid weaning of xenon but not during slow weaning. C-reactive protein levels were similar between groups. Hourly xenon consumption was 0.52 L. Three died, and 7 of 11 survivors had mental and physical developmental index scores ≥70 at follow-up. CONCLUSIONS: Breathing 50% xenon for up to 18 hours with 72 hours of cooling was feasible, with no adverse effects seen with 18 months' follow-up.

Secretions from placenta, after hypoxia/reoxygenation, can damage developing neurones of brain under experimental conditions.

Some psychiatric diseases in children and young adults are thought to originate from adverse exposures during foetal life, including hypoxia and hypoxia/reoxygenation. The mechanism is not understood. Several authors have emphasised that the placenta is likely to play an important role as the key interface between mother and foetus. Here we have explored whether a first trimester human placenta or model barrier of primary human cytotrophoblasts might secrete factors, in response to hypoxia or hypoxia/reoxygenation, that could damage neurones. We find that the secretions in conditioned media caused an increase of [Ca(2+)]i and mitochondrial free radicals and a decrease of dendritic lengths, branching complexity, spine density and synaptic activity in dissociated neurones from embryonic rat cerebral cortex. There was altered staining of glutamate and GABA receptors. We identify glutamate as an active factor within the conditioned media and demonstrate a specific release of glutamate from the placenta/cytotrophoblast barriers invitro after hypoxia or hypoxia/reoxygenation. Injection of conditioned media into developing brains of P4 rats reduced the numerical density of parvalbumin-containing neurones in cortex, hippocampus and reticular nucleus, reduced immunostaining of glutamate receptors and altered cellular turnover. These results show that the placenta is able to release factors, in response to altered oxygen, that can damage developing neurones under experimental conditions.