Respiratory management during therapeutic hypothermia for hypoxic-ischemic encephalopathy

The Complex Interrelationship Between Mechanical Ventilation and Therapeutic Hypothermia in Asphyxiated Newborns. A Review

Asphyxiated newborns often require both therapeutic hypothermia (TH) and mechanical ventilation (MV) and the complex interrelationship between these two therapeutic interventions is very interesting, which could not only have several synergistic positive effects but also some risks. Perinatal asphyxia is the leading cause of neonatal hypoxic-ischemic encephalopathy (HIE) and TH is the only approved neuroprotective treatment to limit brain injury, improving the mortality rate and long-term neurological outcomes. HIE is often associated with severe respiratory failure, requiring MV, due to different lung diseases or an impairment of the respiratory drive. The respiratory support management of asphyxiated newborns is very difficult, considering (a) various pathophysiological contexts, (b) the strong impact of TH on gas metabolism and (c) on lung mechanics, and (d) complex TH-MV interactions. Therefore, it is necessary to evaluate the real indications of MV for cooled newborns, considering the risks of respiratory overassistance (hypocapnia/hyperoxia), as well as the adequate monitoring systems. To date, specific randomized studies about the optimal respiratory approach for cooled newborns are lacking, and strategies for MV support vary from center to center. Moreover, there are many open questions about the real effects of cooling on lung mechanics and on surfactant, most appropriate method of blood gas analysis, and clear indications for pharmacological sedation. The aim of this review is to propose a reasoned approach for respiratory management of cooled newborns, considering the pathophysiological context, multiple actions of TH, and consequences of TH-MV matched action and its related risks.

Expiratory braking defines the breathing patterns of asphyxiated neonates during therapeutic hypothermia

Introduction

Although neonatal breathing patterns vary after perinatal asphyxia, whether they change during therapeutic hypothermia (TH) remains unclear. We characterized breathing patterns in infants during TH for hypoxic-ischemic encephalopathy (HIE) and normothermia after rewarming.

Methods

In seventeen spontaneously breathing infants receiving TH for HIE and in three who did not receive TH, we analyzed respiratory flow and esophageal pressure tracings for respiratory timing variables, pulmonary mechanics and respiratory effort. Breaths were classified as braked (inspiratory:expiratory ratio ≥1.5) and unbraked (<1.5).

Results

According to the expiratory flow shape braked breaths were chategorized into early peak expiratory flow, late peak expiratory flow, slow flow, and post-inspiratory hold flow (PiHF). The most braked breaths had lower rates, larger tidal volume but lower minute ventilation, inspiratory airway resistance and respiratory effort, except for the PiHF, which had higher resistance and respiratory effort. The braked pattern predominated during TH, but not during normothermia or in the uncooled infants.

Conclusions

We speculate that during TH for HIE low respiratory rates favor neonatal braked breathing to preserve lung volume. Given the generally low respiratory effort, it seems reasonable to leave spontaneous breathing unassisted. However, if the PiHF pattern predominates, ventilatory support may be required.

Training in neonatal neurocritical care: A case-based interdisciplinary approach

Interdisciplinary fetal-neonatal neurology (FNN) training strengthens neonatal neurocritical care (NNCC) clinical decisions. Neonatal neurological phenotypes require immediate followed by sustained neuroprotective care path choices through discharge. Serial assessments during neonatal intensive care unit (NICU) rounds are supplemented by family conferences and didactic interactions. These encounters collectively contribute to optimal interventions yielding more accurate outcome predictions. Maternal-placental-fetal (MPF) triad disease pathways influence postnatal medical complications which potentially reduce effective interventions and negatively impact outcome. The science of uncertainty regarding each neonate's clinical status must consider timing and etiologies that are responsible for fetal and neonatal brain disorders. Shared clinical decisions among all stakeholders' balance "fast" (heuristic) and "slow" (analytic) thinking as more information is assessed regarding etiopathogenetic effects that impair the developmental neuroplasticity process. Two case vignettes stress the importance of FNN perspectives during NNCC that integrates this dual cognitive approach. Clinical care paths evaluations are discussed for an encephalopathic extremely preterm and full-term newborn. Recognition of cognitive errors followed by debiasing strategies can improve clinical decisions during NICU care. Re-evaluations with serial assessments of examination, imaging, placental-cord, and metabolic-genetic information improve clinical decisions that maintain accuracy for interventions and outcome predictions. Discharge planning includes shared decisions among all stakeholders when coordinating primary care, pediatric subspecialty, and early intervention participation. Prioritizing social determinants of healthcare during FNN training strengthens equitable career long NNCC clinical practice, education, and research goals. These perspectives contribute to a life course brain health capital strategy that will benefit all persons across each and successive lifespans.

Respiratory Distress Syndrome (RDS) in Newborns with Hypoxic-Ischemic Encephalopathy (HIE)

Respiratory distress syndrome (RDS) and hypoxic-ischemic encephalopathy (HIE) are frequent causes of death and disability in neonates. This study included newborns between January 2021 and July 2022 at the University Clinic for Gynecology and Obstetrics, Skopje. Up to date criteria for HIE/RDS for term and for preterm infants as well for the severity of HIE/RDS were used in a comprehensive analysis of cranial ultrasonography, neurological status, neonatal infections, Apgar score, bradycardia and hypotension, X-ray of the lungs, FiO2, acid-base status, assisted ventilation and use of surfactant. Three groups were created: HIE with RDS (42 babies), HIE without RDS (30 babies) and RDS without HIE in 38 neonates. All newborns with severe (third) degree of HIE died. Intracranial bleeding was found in 35.7% in the first group and 30% in the second group, and in the third group in 53.3%. The need for surfactant in the HIE group with RDS is 59.5%, and in the RDS group without HIE 84.2%. DIC associated with sepsis was found in 13.1-50% in those groups. In newborns with HIE and bradycardia, the probability of having RDS was on average 3.2 times higher than in those without bradycardia. The application of the surfactant significantly improved the pH, pO2, pCO2, BE and chest X-ray in children with RDS. An Apgar score less than 6 at the fifth minute increases the risk of RDS by 3 times. The metabolic acidosis in the first 24 hours increases the risk of death by 23.6 times. The combination of HIE/ RDS significantly worsens the disease outcome. The use of scoring systems improved the early detection of high risk babies and initiation of early treatment increased the chances for survival without disabilities.

pCO2 values in asphyxiated infants under therapeutic hypothermia after tailored respiratory management: a retrospective cohort study

Background

Hypoxic-ischemic encephalopathy (HIE) represents one of the major causes of neonatal death and long-term neurological disability. Both hypoxic-ischemic insults and therapeutic hypothermia (TH) can affect respiratory function. Currently, there is no evidence regarding optimal respiratory management in these infants.

Methods

This is a retrospective cohort study examining newborns with HIE treated with TH between January 2015 and September 2020. The study population was divided into two groups based on different respiratory assistance during TH: spontaneous breathing (Group A) or mechanical ventilation (Group B). The primary outcome of the study was the mean pCO2 ± SD evaluation during TH in ventilated and non-ventilated asphyxiated infants. The secondary outcome was the correlation between ventilation strategy and short-term neurologic outcome according to Rutherford et al.'s MRI scoring system.

Results

A total of 126 newborns were enrolled, 75 in Group A and 51 in Group B. Respiratory management was individualized, and volume guarantee (VG) ventilation was the first choice for ventilated infants. Group B infants showed more severe conditions at birth. During TH, ventilated infants showed optimal mean pCO2 comparable with those breathing spontaneously (40.6 mmHg vs. 42.3 mmHg, respectively, p 0.091), with no significant difference in pCO2 standard deviation between (7.7 mmHg vs. 8.1 mmHg, respectively, p 0.522). Mean pH, pH standard deviation, mean pO2, pO2 standard deviation, and mean respiratory rate also did not differ between groups. MRI patterns of brain injury predictive of abnormal neurodevelopmental outcomes were similar in both groups. Logistic regression analysis demonstrated that only umbilical cord arterial blood pH-affected MRI lesions were associated with poor neurodevelopmental outcomes (OR 1.505; CI 95% 1.069-2.117).

Conclusions

Infants cooled after HIE should receive individualized respiratory management, not necessarily involving intubation. In those infants requiring mechanical ventilation, a volume-targeted strategy appeared to be effective in maintaining stable blood gas levels. Short-term neurological outcomes appeared comparable in ventilated and non-ventilated infants.

Respiratory Changes in Ventilated and Not-Ventilated Neonates During and After Whole-Body Hypothermia: A Multicenter Retrospective Study

The aim of this study was to describe whether whole-body hypothermia induced different respiratory changes in both invasively and noninvasively ventilated newborns and spontaneously breathing asphyxiated newborns during the course and after therapeutic hypothermia (TH). Data of 44 asphyxiated newborns undergoing TH at five different neonatal intensive care units in southern Italy were collected retrospectively between January 2018 and January 2021. For each type of ventilation, patient data on pH, partial pressure of Carbon Dioxide (pCO2), base excess, lactate, and heart rate were recorded before cooling was started and at 24, 48, 72, and 96 hours from its initiation. Patients were later subgrouped into spontaneously breathing, noninvasively ventilated, and mechanically ventilated groups. The average trend of each parameter was reported, and a nonparametric statistical analysis of differences among groups before initiation and at 96 hours was performed using the Kruskal-Wallis test. Our results confirmed previous findings (supported by a small amount of literature) that no increase in requests for respiratory support is recorded in asphyxiated newborns undergoing TH during and after the rewarming phase. Furthermore, no statistically significant differences in the analyzed parameters were found among spontaneously breathing, noninvasively ventilated, and mechanically ventilated newborns, suggesting that changes in parameters might be attributable to TH itself rather than to an improvement in the respiratory condition over time; otherwise, a difference between spontaneously breathing patients, by definition "stable" from a respiratory point of view, and those requiring any type of respiratory support would have been expected.

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.

Hypocarbia is associated with adverse outcomes in hypoxic ischaemic encephalopathy (HIE)

AIM

Hypocarbia in the early postnatal period might exacerbate brain injury in babies with hypoxic ischaemic encephalopathy following birth asphyxia. This mini-review summarised studies on pCO2 values that were monitored periodically in term newborns with moderate/severe hypoxic-ischaemic encephalopathy and correlated with short or long-term outcomes.

METHODS

We searched the databases MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), web of science and the Cochrane Library and identified nine studies.

RESULTS

Among the nine included studies, therapeutic hypothermia was administered in seven studies. In most studies, blood pCO2 levels were measured from birth till 72 h of life or till the endpoint of therapeutic hypothermia. Eight studies showed that any hypocarbia (moderate or severe, or cumulative) was associated with an increased risk of adverse outcomes in the form of brain injury in MRI, death or neurodevelopmental disability.

CONCLUSION

Hypocarbia could lead to adverse short-term and long-term outcomes despite therapeutic hypothermia in neonates with HIE. Hence, it is vital to monitor pCO2 levels closely in these infants and consider strategies to maintain pCO2 levels in the normal range.

Brain-Oriented Strategies for Neuroprotection of Asphyxiated Newborns in the First Hours of Life

Perinatal asphyxia represents the first cause of severe neurological disabilities and the second cause of neonatal death in term-born babies. Currently, no treatment can prevent immediate cell death from necrosis, but some therapeutic interventions, such as therapeutic hypothermia (TH), can reduce delayed cell death from apoptosis. TH significantly improves the combined outcome of mortality or major neurodevelopmental disability, but the number of patients to be treated is 7 to get 1 child with no adverse neurological outcome. The aim of this educational review is to analyze the other care strategies to be implemented to improve the neurological outcome of children with hypoxic ischemic encephalopathy (HIE). Hypocapnia, hypoglycemia, pain control, and functional brain monitoring are recognized as appropriate approaches to improve outcome in critically ill infants with HIE. Pharmacologic neuroprotective adjuncts are currently under investigation. New drugs such as allopurinol and melatonin seem to provide positive effects although more randomized controlled trials are required to establish the effective therapeutic scheme. In the meantime, sustaining the respiratory, metabolic, and cardiovascular system during TH can be a valuable aid in managing and treating the patient with HIE in an optimal way.

Hypocapnia in early hours of life is associated with brain injury in moderate to severe neonatal encephalopathy

OBJECTIVE

To evaluate the association between hypocapnia within the first 24 h of life and brain injury assessed by a detailed MRI scoring system in infants receiving therapeutic hypothermia (TH) for neonatal encephalopathy (NE) stratified by the stage of NE.

STUDY DESIGN

This retrospective cohort study included infants who received TH for mild to severe NE.

RESULTS

188 infants were included in the study with 48% having mild and 52% moderate-severe NE. Infants with moderate-severe NE spent more time in hypocapnia (PCO₂ ≤ 35 mmHg) and presented with more severe brain injury on MRI compared to mild cases. The MRI injury score increased by 6% for each extra hour spent in hypocapnic range in infants with moderate-severe NE. There was no association between hypocapnia and injury scores in mild cases.

CONCLUSION

In infants with moderate-severe NE, the hours spent in hypocapnia was an independent predictor of brain injury.

New Horizons in Mild Hypoxic-ischemic Encephalopathy: A Standardized Algorithm to Move past Conundrum of Care

Hypoxic-ischemic encephalopathy (HIE) presents clinically with a neonatal encephalopathy (NE) whereby the mild spectrum is difficult to classify immediately after birth. For decades trials have focused exclusively on infants with moderate-severe HIE s, as these infants were easier to identify after birth and had the highest risk of adverse outcomes. Twenty years after those trials, the PRIME study finally solved the first part of the conundrum by providing a definition of mild HIE in the first 6 hours. There is strong biological plausibility and preclinical evidence supporting the efficacy of therapeutic hypothermia (TH) but there is a lack of comparative clinical data to establish the risk-benefit in mild HIE. The fundamental question of how best to manage mild HIE remains unanswered. This review will summarize (1) the evidence that neonates with mild HIE are at significant risk for adverse outcomes, (2) the gaps/controversies in management, and (3) an algorithm of care is proposed to ensure standardized management of mild HIE and the direction of future trials.

Opioid-free anesthesia with interfascial dexmedetomidine in a high-risk infant

Despite the advances in pediatric anesthesia, infants have higher mortality and critical incidents rates than children, especially ex-prematures and those with comorbidity. We present the case of a high-risk infant who underwent elective laparoscopic gastrostomy under opioid-free anesthesia (OFA) combined with transversus abdominis plane (TAP) block with Dexmedetomidine (DEX). Perioperative opioids were entirely avoided, and intraoperative anesthetics and postoperative analgesic were considerably reduced. The infant showed cardiorespiratory stability and optimal analgesia during the uneventful procedure and the postoperative period. We consider OFA and TAP block with DEX a safe and effective anesthetic combination for high-risk infants.

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.

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.

Cerebral blood volume increment after resuscitation measured by near-infrared time-resolved spectroscopy can estimate degree of hypoxic-ischemic insult in newborn piglets

Neonatal hypoxic–ischemic encephalopathy is a notable cause of neonatal death and developmental disabilities. To achieve better outcomes, it is important in treatment strategy selection to categorize the degree of hypoxia ischemia and evaluate dose response. In an asphyxia piglet model with histopathological brain injuries that we previously developed, animals survived 5 days after insult and showed changes in cerebral blood volume (CBV) that reflected the severity of injuries. However, little is known about the relationship between changes in CBV during and after insult. In this study, an HI event was induced by varying the amount and timing of inspired oxygen in 20 anesthetized piglets. CBV was measured using near-infrared time-resolved spectroscopy before, during, and 6 h after insult. Change in CBV was calculated as the difference between the peak CBV value during insult and the value at the end of insult. The decrease in CBV during insult was found to correlate with the increase in CBV within 6 h after insult. Heart rate exhibited a similar tendency to CBV, but blood pressure did not. Because the decrement in CBV was larger in severe HI, the CBV increment immediately after insult is considered useful for assessing degree of HI insult.

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).

Mechanical Ventilation, Partial Pressure of Carbon Dioxide, Increased Fraction of Inspired Oxygen and the Increased Risk for Adverse Short-Term Outcomes in Cooled Asphyxiated Newborns

Neonates treated with therapeutic hypothermia (TH) following perinatal asphyxia (PA) suffer a considerable rate of disability and mortality. Several risk factors associated with adverse outcomes have been identified. Mechanical ventilation might increase the risk for hyperoxia and hypocapnia in cooled newborns. We carried out a retrospective study in 71 asphyxiated cooled newborns. We analyzed the association of ventilation status and adverse short-term outcomes and investigated the effect of the former on pCO₂ and oxygen delivery before, during and after TH. Death, abnormal findings on magnetic resonance imaging, and pathological amplitude-integrated electroencephalography traces were used to define short-term outcomes. The need for mechanical ventilation was significantly higher in the newborns with adverse outcomes (38% vs. 5.6%, p = 0.001). Compared to spontaneously breathing neonates, intubated newborns suffered from significantly more severe asphyxia, had significantly lower levels of mean minimum pCO₂ over the first 6 and 72 h of life (HOL) (p = 0.03 and p = 0.01, respectively) and increased supply of inspired oxygen, which was, in turn, significantly higher in the newborns with adverse outcomes (p < 0.01). Intubated newborns with adverse short-term outcomes had lower levels of pCO₂ over the first 36 HOL. In conclusion, need for mechanical ventilation was significantly higher in newborns with more severe asphyxia. In ventilated newborns, level of encephalopathy, lower pCO₂ levels, and increased oxygen supplementation were significantly higher in the adverse short-term outcomes group. Ventilatory parameters need to be carefully monitored in cooled asphyxiated newborns.

Volume guarantee ventilation in neonates treated with hypothermia for hypoxic-ischemic encephalopathy during interhospital transport

OBJECTIVE

We investigated if volume guarantee (VG) ventilation in babies with hypoxic-ischemic encephalopathy (HIE) during interhospital transport decreases tidal volumes and prevents hypocapnia.

STUDY DESIGN

We computationally collected and analyzed ventilator data of babies ventilated with synchronized intermittent mandatory ventilation (SIMV) with VG (n = 28) or without VG (n = 8).

RESULT

The expiratory tidal volume of ventilator inflations was lower with SIMV-VG (median [IQR]: 4.9 [4.6-5.3] mL/kg) than with SIMV only (median [IQR]: 7.1 [5.3-8.0] mL/kg, p = 0.01). Babies receiving SIMV-VG had lower peak inflating pressures (median: 10.7 cmH₂O, versus 17.5 cmH₂O, p = 0.01). There was no significant difference in minute ventilation or in pCO₂. Babies with strong spontaneous breathing had a mean PIP < 10 cmH₂O but this did not result in adverse events or worsening of acidosis.

CONCLUSIONS

The use of VG ventilation in babies with HIE reduces tidal volumes and frequently results in very low inflating pressures without affecting pCO₂.

Endogenous brain-sparing responses in brain pH and PO2 in a rodent model of birth asphyxia

AIM

To study brain-sparing physiological responses in a rodent model of birth asphyxia which reproduces the asphyxia-defining systemic hypoxia and hypercapnia.

METHODS

Steady or intermittent asphyxia was induced for 15-45 minutes in anaesthetized 6- and 11-days old rats and neonatal guinea pigs using gases containing 5% or 9% O₂ plus 20% CO₂ (in N₂ ). Hypoxia and hypercapnia were induced with low O₂ and high CO₂ respectively. Oxygen partial pressure (PO₂ ) and pH were measured with microsensors within the brain and subcutaneous ("body") tissue. Blood lactate was measured after asphyxia.

RESULTS

Brain and body PO₂ fell to apparent zero with little recovery during 5% O₂ asphyxia and 5% or 9% O₂ hypoxia, and increased more than twofold during 20% CO₂ hypercapnia. Unlike body PO₂ , brain PO₂ recovered rapidly to control after a transient fall (rat), or was slightly higher than control (guinea pig) during 9% O₂ asphyxia. Asphyxia (5% O₂ ) induced a respiratory acidosis paralleled by a progressive metabolic (lact)acidosis that was much smaller within than outside the brain. Hypoxia (5% O₂ ) produced a brain-confined alkalosis. Hypercapnia outlasting asphyxia suppressed pH recovery and prolonged the post-asphyxia PO₂ overshoot. All pH changes were accompanied by consistent shifts in the blood-brain barrier potential.

CONCLUSION

Regardless of brain maturation stage, hypercapnia can restore brain PO₂ and protect the brain against metabolic acidosis despite compromised oxygen availability during asphyxia. This effect extends to the recovery phase if normocapnia is restored slowly, and it is absent during hypoxia, demonstrating that exposure to hypoxia does not mimic asphyxia.

Management of Multi Organ Dysfunction in Neonatal Encephalopathy

Neonatal Encephalopathy (NE) describes neonates with disturbed neurological function in the first post-natal days of life. NE is an overall term that does not specify the etiology of the encephalopathy although it often involves hypoxia-ischaemia. In NE, although neurological dysfunction is part of the injury and is most predictive of long-term outcome, these infants may also have multiorgan injury and compromise, which further contribute to neurological impairment and long-term morbidities. Therapeutic hypothermia (TH) is the standard of care for moderate to severe NE. Infants with NE may have co-existing immune, respiratory, endocrine, renal, hepatic, and cardiac dysfunction that require individualized management and can be impacted by TH. Non-neurological organ dysfunction not only has a negative effect on long term outcome but may also influence the efficacy of treatments in the acute phase. Post resuscitative care involves stabilization and decisions regarding TH and management of multi-organ dysfunction. This management includes detailed neurological assessment, cardio-respiratory stabilization, glycaemic and fluid control, sepsis evaluation and antibiotics, seizure identification, and monitoring and responding to biochemical and coagulation derangements. The emergence of new biomarkers of specific organ injury may have predictive value and improve the definition of organ injury and prognosis. Further evidence-based research is needed to optimize management of NE, prevent further organ dysfunction and reduce neurodevelopmental impairment.