Subcortical white matter differences according to presence of disorders of consciousness in hypoxic-ischemic brain injury: a tract-based spatial statistics study.

We investigated differences in subcortical white matter according to the presence disorders of consciousness (DOC) in patients with hypoxic-ischemic brain injury (HI-BI), using tract-based spatial statistics (TBSS). Thirty-two consecutive patients with HI-BI were recruited. The patients were assigned in group A [preserved consciousness (Glasgow Coma Scale: 15 and Coma Recovery Scale-revised (CRS-R): 23, 9 patients)] or group B [DOC present (Glasgow Coma Scale <15 and CRS-R < 23, 20 patients)]. Voxel-wise statistical analysis of fractional anisotropy data was performed by using TBSS as implemented in the FMRIB Software Library. We calculated mean fractional anisotropy values across the white matter skeleton and within 48 regions of interest (ROIs) based on intersections between the skeleton and the probabilistic Johns Hopkins University white matter atlases. Among the 48 ROIs examined, the fractional anisotropy values of two ROIs (the left superior corona radiata, and left tapetum) were significantly lower in group B than in group A ( P  < 0.05). No significant differences were observed, however, in the other 46 ROIs ( P  > 0.05). Our results suggest that abnormalities of the superior corona radiata and tapetum may be critical for DOC presence in patients with HI-BI.

A practical magnetic-resonance imaging score for outcome prediction in comatose cardiac arrest survivors.

AIM: Magnetic Resonance Imaging (MRI) is an important prognostic tool in cardiac arrest (CA) survivors given its sensitivity for detecting hypoxic-ischemic brain injury (HIBI), however, it is limited by poorly defined objective thresholds. To address this limitation, we evaluated a qualitative MRI score for predicting neurological outcome in CA survivors. METHODS: Adult comatose CA survivors who underwent MRI were retrospectively identified at a single academic medical center. Two blinded neurointensivists qualitatively scored HIBI amongst 12 MRI brain regions. Scores were summated to form four distinct score groups: cortex, deep grey nuclei (DGN), cortex-DGN combined, and total (cortex, DGN, brainstem, and cerebellum). Poor neurological outcome was defined as Cerebral Performance Category (CPC) score 3-5 at hospital discharge. Inter-rater reliability was tested using intra-class correlation (ICC) and discrimination of poor neurological outcome assessed using area under the receiver operating curve (AUC). RESULTS: Our cohort included 219 patients with median time to MRI of 96 (IQR 81-110) hours. ICC (95% CI) was good to excellent across all MRI scores: cortex 0.92 (0.89-0.94), DGN 0.88 (0.80-0.92), cortex-DGN 0.94 (0.92-0.95), and total 0.93 (0.91-0.95). AUC (95% CI) for poor outcome was good across all MRI scores: cortex 0.84 (0.78-0.90), DGN 0.83 (0.77-0.89), cortex-DGN 0.83 (0.77-0.89), and total 0.83 (0.77-0.88). CONCLUSION: A simplified, qualitative MRI score had excellent reliability and good discrimination for poor neurologic outcome. Further work is necessary to externally validate our findings in an independent, ideally prospective, cohort.

Persistent pulmonary hypertension and short-term neurological outcomes in infants with moderate to severe hypoxic ischemic encephalopathy.

BACKGROUND: Our aim was to investigate the relationship between persistent pulmonary hypertension of the newborn (PPHN), short-term brain injury or death, and clinical parameters in infants with moderate to severe hypoxic ischemic encephalopathy (HIE). METHODS: Retrospective single-center cohort study of 274 HIE infants, 230 underwent Therapeutic Hypothermia (TH). Primary outcome was severe HIE brain injury on MRI and/or death within the first month of life in relation to presence and severity of PPHN (clinical or echocardiographic). Secondary outcomes were HIE brain injury pattern, abnormal electroencephalogram (EEG), seizures, clinical, and laboratory differences. A logistic regression model was performed to evaluate PPHN presence and severity as risk factor for brain injury or death. RESULTS: The combined outcome of severe brain injury or death was higher in the clinical PPHN group vs non-PPHN (32.6 vs 22.8%, p = 0.014). There was no difference in brain injury, seizure burden or EEG abnormalities associated with PPHN, despite those with PPHN being sicker with higher ventilation needs and worse laboratory values than those without. Mortality had a strong correlation with echocardiographic PPHN with the highest incidence in severe (36%) vs moderate (7.7%) vs mild PPHN (10%, p = 0.002). Highest mortality had those with 'early exit' who did not complete 72 hours of TH (71.4%). CONCLUSIONS: In infants with HIE, PPHN was not associated with increased risk of brain injury as evident on MRI, nor seizure burden, despite being sicker with worse laboratory values. However, mortality rates were higher the worse the PPHN, especially with early exit from TH.

Successful treatment of cortical visual impairment in children using anti-amblyopia treatment despite the absence of amblyopia: a case report.

BACKGROUND: Cortical visual impairment (CVI) is a verifiable visual dysfunction that cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment. Given the limited knowledge on the most effective interventions for visual impairment resulting from CVI, this case report provides valuable insights into an example of successful implementation of anti-amblyopia therapy in a patient with CVI. CASE PRESENTATION: This case report presents a 5-year-old girl with CVI secondary to hypoxic-ischemic injury, resulting in visual impairment, dyspraxia, and abnormal visual evoked potential testing. The girl did not suffer from amblyopia, there was no evidence of relevant refractive errors or strabismus, so visual pathway damage was the cause of her visual deficit. Nevertheless, the patient underwent anti-amblyopia therapy and showed significant improvement in visual acuity after 12 months of treatment. The improvement, resulting from visual stimulation, was due to a good functional recovery by a better usage of the damaged visual pathways. The therapy included prescribing corrective glasses and implementing secondary occlusion of the better eye for 4 months, which was protracted for another 4 months, leading to further improvements in visual acuity. CONCLUSIONS: The case report shows that addressing even minor refractive errors and implementing anti-amblyopia therapy can significantly improve vision in children with CVI, even without co-existing amblyopia. It also highlights the importance of early intervention and multidisciplinary rehabilitation in children with CVI, focusing on motor and cognitive skills. Additionally, it emphasizes the need for further research to establish evidence-based practice standards for improving vision in children with CVI.

Positive outcome in a patient with severe hypoxic-ischaemic encephalopathy.

A male infant was born at 40 and 4/7 weeks of gestation via caesarean section for non-reassuring foetal heart tracing. The infant was non-responsive in the delivery room. with no heart rate detected until 40 min of life. The infant's physical examination and laboratory findings were consistent with severe hypoxic-ischaemic encephalopathy. Given the presumption of a very poor neurological prognosis, redirection to comfort care was recommended to the family. However, the family opted for intensive care. The infant underwent therapeutic hypothermia and management of multiorgan dysfunction. The infant survived with no findings of ischaemic injury on MRI and was discharged with no respiratory support and taking all feeds by mouth, with normal development at a year and a half of age. This case report demonstrates the imperative to understand family goals and to acknowledge the need for ongoing humility in providing prognostication for families.

Incidence and clinical analysis of asymptomatic intracranial hemorrhage in neonates with cerebral hypoxic-ischaemic risk based on multisequence MR images.

The incidence and clinical distribution of intracranial haemorrhage (ICH) in neonates at risk of cerebral hypoxia-ischaemia have not been reported in specific studies. Based on conventional magnetic resonance imaging (MRI) versus susceptibility weighted imaging (SWI), this study aimed to analyse the occurrence of asymptomatic ICH in newborns with or without risk of cerebral hypoxia-ischaemia and to accumulate objective data for clinical evaluations of high-risk neonates and corresponding response strategies. 317 newborns were included. MRI revealed that the overall incidence of ICH was 59.31%. The most common subtype was intracranial extracerebral haemorrhage (ICECH) which included subarachnoid haemorrhage (SAH) and subdural haemorrhage (SDH). ICECH accounted for 92.02% of ICH. The positive detection rate of ICECH by SWI was significantly higher than that by T1WI. The incidence of total ICH, ICECH and SAH was greater among children who were delivered vaginally than among those who underwent caesarean delivery. Asymptomatic neonatal ICH may be a common complication of the neonatal birth process, and SWI may improve the detection rate. Transvaginal delivery and a weight greater than 2500 g were associated with a high incidence of ICECH in neonates. The impact of neonatal cerebral hypoxia-ischaemia risk factors on the occurrence of asymptomatic ICH may be negligible.

Grey-to-White Matter Ratio Values in Early Head Computed Tomography (CT) as a Predictor of Neurologic Outcomes in Survivors of Out-of-Hospital Cardiac Arrest Based on Severity of Hypoxic-Ischemic Brain Injury.

BACKGROUND: Hypoxic-ischemic brain injury (HIBI) is a common complication of out-of-hospital cardiac arrest (OHCA). OBJECTIVES: We investigated whether grey-to-white matter ratio (GWR) values, measured using early head computed tomography (HCT), were associated with neurologic outcomes based on the severity of HIBI in survivors of OHCA. METHODS: This retrospective multicenter study included adult comatose OHCA survivors who underwent an HCT scan within 2 h after the return of spontaneous circulation. HIBI severity was assessed using the revised post-Cardiac Arrest Syndrome for Therapeutic hypothermia (rCAST) scale (low, moderate, and severe). Poor neurologic outcomes were defined as Cerebral Performance Categories 3 to 5 at 6 months after OHCA. RESULTS: Among 354 patients, 27% were women and 224 (63.3%) had poor neurologic outcomes. The distribution of severity was 19.5% low, 47.5% moderate, and 33.1% severe. The area under the receiver operating curves of the GWR values for predicting rCAST severity (low, moderate, and severe) were 0.52, 0.62, and 0.79, respectively. The severe group had significantly higher predictive performance than the moderate group (p = 0.02). Multivariate logistic regression analysis revealed a significant association between GWR values and poor neurologic outcomes in the moderate group (adjusted odds ratio = 0.012, 95% CI 0.0-0.54, p = 0.02). CONCLUSIONS: In this cohort study, GWR values measured using early HCT demonstrated variations in predicting neurologic outcomes based on HIBI severity. Furthermore, GWR in the moderate group was associated with poor neurologic outcomes.

Clinical-functional correlation with brain volumetry in severe perinatal asphyxia: a case report.

BACKGROUND: Hypoxic-ischemic encephalopathy (HIE) appears in neurological conditions where some brain areas are likely to be injured, such as deep grey matter, basal ganglia area, and white matter subcortical periventricular áreas. Moreover, modeling these brain areas in a newborn is challenging due to significant variability in the intensities associated with HIE conditions. This paper aims to evaluate functional measurements and 3D machine learning models of a given HIE case by correlating the affected brain areas with the pathophysiology and clinical neurodevelopmental. CASE PRESENTATION: A comprehensive analysis of a term infant with perinatal asphyxia using longitudinal 3D brain information from Machine Learning Models is presented. The clinical analysis revealed the perinatal asphyxia diagnosis with APGAR <5 at 5 and 10 minutes, umbilical arterial pH of 7.0 BE of -21.2 mmol / L), neonatal seizures, and invasive ventilation mechanics. Therapeutic interventions: physical, occupational, and language neurodevelopmental therapies. Epilepsy treatment: vagus nerve stimulation, levetiracetam, and phenobarbital. Furthermore, the 3D analysis showed how the volume decreases due to age, exhibiting an increasing asymmetry between hemispheres. The results of the basal ganglia area showed that thalamus asymmetry, caudate, and putamen increase over time while globus pallidus decreases. CLINICAL OUTCOMES: spastic cerebral palsy, microcephaly, treatment-refractory epilepsy. CONCLUSIONS: Slight changes in the basal ganglia and cerebellum require 3D volumetry for detection, as standard MRI examinations cannot fully reveal their complex shape variations. Quantifying these subtle neurodevelopmental changes helps in understanding their clinical implications. Besides, neurophysiological evaluations can boost neuroplasticity in children with neurological sequelae by stimulating new neuronal connections.

Genetic and Congenital Anomalies in Infants With Hypoxic-Ischemic Encephalopathy.

BACKGROUND: Infants with hypoxic ischemic encephalopathy (HIE) may have underlying conditions predisposing them to hypoxic-ischemic injury during labor and delivery. It is unclear how genetic and congenital anomalies impact outcomes of HIE. METHODS: Infants with HIE enrolled in a phase III trial underwent genetic testing when clinically indicated. Infants with known genetic or congenital anomalies were excluded. The primary outcome, i.e., death or neurodevelopmental impairment (NDI), was determined at age two years by a standardized neurological examination, Bayley Scales of Infant Development, Third Edition (BSID-III), and the Gross Motor Function Classification Scales. Secondary outcomes included cerebral palsy and BSID-III motor, cognitive, and language scores at age two years. RESULTS: Of 500 infants with HIE, 24 (5%, 95% confidence interval 3% to 7%) were diagnosed with a genetic (n = 15) or congenital (n = 14) anomaly. Infants with and without genetic or congenital anomalies had similar rates of severe encephalopathy and findings on brain magnetic resonance imaging. However, infants with genetic or congenital anomalies were more likely to have death or NDI (75% vs 50%, P = 0.02). Among survivors, those with a genetic or congenital anomaly were more likely to be diagnosed with cerebral palsy (32% vs 13%, P = 0.02), and had lower BSID-III scores in all three domains than HIE survivors without such anomalies. CONCLUSIONS: Among infants with HIE, 5% were diagnosed with a genetic or congenital anomaly. Despite similar clinical markers of HIE severity, infants with HIE and a genetic or congenital anomaly had worse neurodevelopmental outcomes than infants with HIE alone.

The effect of hypoxic ischemic encephalopathy towards multi-organ complications and its early outcome at a Malaysian district hospital.

INTRODUCTION: Hypoxic ischemic encephalopathy (HIE) is a clinically defined syndrome of disturbed neurologic function in the newborn with evidence of perinatal asphyxia. Stages of HIE are categorised into mild, moderate or severe based on the Sarnat classification. Neurological dysfunction constitutes a part of the wide spectrum of hypoxic ischemic insult as affected infants can have co-existing multi-organ dysfunction which further contributes to morbidities and mortality. This study aims to determine the relationship between the severity of HIE with multi-organ complications and early clinical outcomes. MATERIALS AND METHODS: All neonates who were admitted to the NICU at Hospital Sultan Abdul Halim between January 2018 to December 2022, who fulfilled the inclusion criteria were included. Demographic data, clinical course and investigation results were retrospectively obtained from the medical records. RESULTS: From a total of 90 infants (n = 90) who fulfilled our inclusion criteria, 31 (34%) were mild, 31 (34%) were moderate and 28 (31%) were severe HIE. The mean maternal age was 27 years. Common antenatal issues include diabetes mellitus (37.8%) and anaemia (22.2%). The Apgar scores at 1 and 5 minutes, initial resuscitation requiring intubation, chest compression and adrenaline were associated with higher severity of HIE (p < 0.05). Coagulation dysfunction was the most common complication (79.7%), followed by respiratory dysfunction (33.3%), cardiac dysfunction (28.9%), renal dysfunction (16.1%), haematological dysfunction (15.6%) and hepatic dysfunction (12%). Respiratory and haematological dysfunctions were significantly associated with higher mortality (p < 0.05). There was a significant longer hospital stay (p = 0.023), longer duration of ventilation (p < 0.001) and increase in frequency of seizures (p < 0.001) when comparing moderate and severe HIE patients to mild HIE patients. With increasing severity of HIE, there was also statistically significant higher mortality (p < 0.001). CONCLUSIONS: There is a significant relationship between multiorgan dysfunction, the severity of HIE and mortality. Early anticipation of multi-organ injury is crucial for optimal early management which would reduce the mortality and improve the neurological outcome of the patients.

Factors affecting early childhood growth in hypoxic-ischemic encephalopathy treated with hypothermia.

INTRODUCTION: There is an extensive body of research regarding neurological outcomes following neonatal hypoxic-ischemic encephalopathy (HIE) treated with therapeutic hypothermia (TH), with limited data on growth outcomes. We examined perinatal characteristics associated with postnatal growth in this population. METHODS: Convenience cohort of 66 infants with HIE who underwent TH and participated in follow-up at 24 months of age were included. Regression modeling including perinatal anthropomorphics, markers of HIE, and systemic injury was used to evaluate growth at 24 months. RESULTS: Birth head circumference was associated with weight (p = 0.036). MRI severity, pH at admission and birth head circumference were associated with height (p = 0.043, p = 0.015 and p = 0.043 respectively). MRI severity and length of intubation were associated with head circumference (p = 0.038 and p < 0.001 respectively). CONCLUSION: There was a significant association between specific early factors and growth at 24 months among infants with HIE treated with TH.

Acute kidney injury in neonates with hypoxic ischemic encephalopathy based on serum creatinine decline compared to KDIGO criteria.

BACKGROUND: Neonates with hypoxic ischemic encephalopathy receiving therapeutic hypothermia (HIE + TH) are at risk for acute kidney injury (AKI). The standardized Kidney Disease Improving Global Outcomes (KDIGO) criteria identifies AKI based on a rise in serum creatinine (SCr) or reduced urine output. This definition is challenging to apply in neonates given the physiologic decline in SCr during the first week of life. Gupta et al. proposed alternative neonatal criteria centered on rate of SCr decline. This study aimed to compare the rate of AKI based on KDIGO and Gupta in neonates with HIE and to examine associations with mortality and morbidity. METHODS: A retrospective review was performed of neonates with moderate to severe HIE + TH from 2008 to 2020 at a single center. AKI was assessed in the first 7 days after birth by KDIGO and Gupta criteria. Mortality, brain MRI severity of injury, length of stay, and duration of respiratory support were compared between AKI groups. RESULTS: Among 225 neonates, 64 (28%) met KDIGO, 69 (31%) neonates met Gupta but not KDIGO, and 92 (41%) did not meet either definition. Both KDIGO-AKI and GuptaOnly-AKI groups had an increased risk of the composite mortality and/or moderate/severe brain MRI injury along with longer length of stay and prolonged duration of respiratory support compared to those without AKI. CONCLUSIONS: AKI in neonates with HIE + TH was common and varied by definition. The Gupta definition based on rate of SCr decline identified additional neonates not captured by KDIGO criteria who are at increased risk for adverse outcomes. Incorporating the rate of SCr decline into the neonatal AKI definition may increase identification of clinically relevant kidney injury in neonates with HIE + TH.

Risk Factors and Outcomes for Cerebral Palsy With Hypoxic-Ischemic Brain Injury Patterns Without Documented Neonatal Encephalopathy.

BACKGROUND AND OBJECTIVES: Perinatal hypoxic-ischemic brain injury is a leading cause of term-born cerebral palsy, the most common lifelong physical disability. Diagnosis is commonly made in the neonatal period by the combination of neonatal encephalopathy (NE) and typical neuroimaging findings. However, children without a history of neonatal encephalopathy may present later in childhood with motor disability and neuroimaging findings consistent with perinatal hypoxic-ischemic injury. We sought to determine the prevalence of such presentations using the retrospective viewpoint of a large multiregional cerebral palsy registry. METHODS: Patient cases were extracted from the Canadian Cerebral Palsy Registry with gestational age >36 weeks, an MRI pattern consistent with hypoxic-ischemic injury (HII, acute total, partial prolonged, or combined), and an absence of postnatal cause for HII. Documentation of NE was noted. Maternal-fetal risk factors, labor and delivery, neonatal course, and clinical outcome were extracted. Comparisons were performed using χ2 tests and multivariable logistic regression with multiple imputation. Propensity scores were used to assess for bias. RESULTS: Of the 170 children with MRI findings typical for HII, 140 (82.4%, 95% confidence interval [CI] 75.7%-87.7%) had documented NE and 29 (17.0%, 95% CI 11.7%-23.6%) did not. The group without NE had more abnormalities of amniotic fluid volume (odds ratio [OR] 15.8, 95% CI 1.2-835), had fetal growth restriction (OR 4.7, 95% CI 1.0-19.9), had less resuscitation (OR 0.03, 95% CI 0.007-0.08), had higher 5-minute Apgar scores (OR 2.2, 95% CI 1.6-3.0), were less likely to have neonatal seizures (OR 0.004, 95% CI 0.00009-0.03), and did not receive therapeutic hypothermia. MRI was performed at a median 1.1 months (interquartile range [IQR] 0.67-12.8 months) for those with NE and 12.2 months (IQR 6.6-25.9) for those without (p = 0.011). Patterns of injury on MRI were seen in similar proportions. Hemiplegia was more common in those without documented NE (OR 5.1, 95% CI 1.5-16.1); rates of preserved ambulatory function were similar. DISCUSSION: Approximately one-sixth of term-born children with an eventual diagnosis of cerebral palsy and MRI findings consistent with perinatal hypoxic-ischemic brain injury do not have documented neonatal encephalopathy, which was associated with abnormalities of fetal growth and amniotic fluid volume, and a less complex neonatal course. Long-term outcomes seem comparable with their peers with encephalopathy. The absence of documented neonatal encephalopathy does not exclude perinatal hypoxic-ischemic injury, which may have occurred antenatally and must be carefully evaluated with MRI.

Catalpol alleviates hypoxia ischemia-induced brain damage by inhibiting ferroptosis through the PI3K/NRF2/system Xc-/GPX4 axis in neonatal rats.

Hypoxic-ischemic encephalopathy (HIE) is a brain damage caused by perinatal hypoxia and blood flow reduction. Severe HIE leads to death. Available treatments remain limited. Oxidative stress and nerve damage are major factors in brain injury caused by HIE. Catalpol, an iridoid glucoside found in the root of Rehmannia glutinosa, has antioxidant and neuroprotective effects. This study examined the neuroprotective effects of catalpol using a neonatal rat HIE model and found that catalpol might protect the brain through inhibiting neuronal ferroptosis and ameliorating oxidative stress. Behavior tests suggested that catalpol treatment improved functions of motor, learning, and memory abilities after hypoxic-ischemic injury. Catalpol treatment inhibited changes to several ferroptosis-related proteins, including p-PI3K, p-AKT, NRF2, GPX4, SLC7A11, SLC3A2, GCLC, and GSS in HIE neonatal rats. Catalpol also prevented changes to several ferroptosis-related proteins in PC12 cells after oxygen-glucose deprivation. The ferroptosis inducer erastin reversed the protective effects of catalpol both in vitro and in vivo. We concluded that catalpol protects against hypoxic-ischemic brain damage (HIBD) by inhibiting ferroptosis through the PI3K/NRF2/system Xc-/GPX4 axis.

Biochemical profiles and organ dysfunction in neonates with hypoxic-ischemic encephalopathy post-hoc analysis of the THIN trial.

BACKGROUND: Therapeutic hypothermia for infants with moderate to severe hypoxic-ischemic encephalopathy is well established as standard of care in high-income countries. Trials from low- and middle-income countries have shown contradictory results, and variations in the level of intensive care provided may partly explain these differences. We wished to evaluate biochemical profiles and clinical markers of organ dysfunction in cooled and non-cooled infants with moderate/severe hypoxic-ischemic encephalopathy. METHODS: This secondary analysis of the THIN (Therapeutic Hypothermia in India) study, a single center randomized controlled trial, included 50 infants with moderate to severe hypoxic-ischemic encephalopathy randomized to therapeutic hypothermia (n = 25) or standard care with normothermia (n = 25) between September 2013 and October 2015. Data were collected prospectively and compared by randomization groups. Main outcomes were metabolic acidosis, coagulopathies, renal function, and supportive treatments during the intervention. RESULTS: Cooled infants had lower pH than non-cooled infants at 6-12 h (median (IQR) 7.28 (7.20-7.32) vs 7.36 (7.31-7.40), respectively, p = 0.003) and 12-24 h (median (IQR) 7.30 (7.24-7.35) vs 7.41 (7.37-7.43), respectively, p < 0.001). Thrombocytopenia (< 100 000) was, though not statistically significant, twice as common in cooled compared to non-cooled infants (4/25 (16%) and 2/25 (8%), respectively, p = 0.67). No significant difference was found in the use of vasopressors (14/25 (56%) and 17/25 (68%), p = 0.38), intravenous bicarbonate (5/25 (20%) and 3/25 (12%), p = 0.70) or treatment with fresh frozen plasma (10/25 (40%) and 8/25 (32%), p = 0.56)) in cooled and non-cooled infants, respectively. Urine output < 1 ml/kg/h was less common in cooled infants compared to non-cooled infants at 0-24 h (7/25 (28%) vs. 16/23 (70%) respectively, p = 0.004). CONCLUSIONS: This post hoc analysis of the THIN study support that cooling of infants with hypoxic-ischemic encephalopathy in a level III neonatal intensive care unit in India was safe. Cooled infants had slightly lower pH, but better renal function during the first day compared to non-cooled infants. More research is needed to identify the necessary level of intensive care during cooling to guide further implementation of this neuroprotective treatment in low-resource settings. TRIAL REGISTRATION: Data from this article was collected during the THIN-study (Therapeutic Hypothermia in India; ref. CTRI/2013/05/003693 Clinical Trials Registry - India).

Early Hyperoxemia and 2-year Outcomes in Infants with Hypoxic-ischemic Encephalopathy: A Secondary Analysis of the Infant Cooling Evaluation Trial.

OBJECTIVE: To determine the causal relationship between exposure to early hyperoxemia and death or major disability in infants with hypoxic-ischemic encephalopathy (HIE). STUDY DESIGN: We analyzed data from the Infant Cooling Evaluation (ICE) trial that enrolled newborns ≥35 weeks' gestation with moderate-severe HIE, randomly allocated to hypothermia or normothermia. The primary outcome was death or major sensorineural disability at 2 years. We included infants with arterial pO2 measured within 2 hours of birth. Using a directed acyclic graph, we established that markers of severity of perinatal hypoxia-ischemia and pCO2 were a minimally sufficient set of variables for adjustment in a regression model to estimate the causal relationship between arterial pO2 and death/disability. RESULTS: Among 221 infants, 116 (56%) had arterial pO2 and primary outcome data. The unadjusted analysis revealed a U-shaped relationship between arterial pO2 and death or major disability. Among hyperoxemic infants (pO2 100-500 mmHg) the proportion with death or major disability was 40/58 (0.69), while the proportion in normoxemic infants (pO2 40-99 mmHg) was 20/48 (0.42). In the adjusted model, hyperoxemia increased the risk of death or major disability (adjusted risk ratio 1.61, 95% CI 1.07-2.00, P = .03) in relation to normoxemia. CONCLUSION: Early hyperoxemia increased the risk of death or major disability among infants who had an early arterial pO2 in the ICE trial. Limitations include the possibility of residual confounding and other causal biases. Further work is warranted to confirm this relationship in the era of routine therapeutic hypothermia.