Association between cerebral oxygen saturation and brain injury in neonates receiving therapeutic hypothermia for neonatal encephalopathy

Electroencephalography and optical neuromonitoring predict short-term outcomes in neonates undergoing therapeutic hypothermia for hypoxic-ischemic encephalopathy

Electroencephalography (EEG) and optical neuromonitoring were used to predict short-term outcomes in neonates undergoing therapeutic hypothermia (TH) for hypoxic-ischemic encephalopathy (HIE). Fifty-two neonates undergoing TH for HIE were prospectively recruited. Continuous EEG monitoring was initiated within 24 h of life and a quantitative discontinuity index was calculated. Combined frequency-domain near infrared spectroscopy (FDNIRS) and diffuse correlation spectroscopy (DCS) were initiated within 48 h of life and used to measure cerebral hemoglobin oxygen saturation (SO2) and a cerebral blood flow index. Using these parameters and hemoglobin concentration measurements, cerebral oxygen extraction fraction (OEF), indices of cerebral oxygen delivery and metabolism (CMRO2i) as well as cerebral oxygen reserve (CRO2) were derived. Short-term outcome was classified based on brain injury pattern on magnetic resonance imaging and/or death; as normal-mild, moderate or severe outcome. Results showed that EEG discontinuity index, SO2 and CRO2 were higher and OEF lower in neonates with severe compared to normal-mild and moderate outcomes during TH. EEG discontinuity index was the most accurate and earliest parameter to identify moderate vs. severe outcomes while CMRO2i identified normal-mild vs. moderate outcomes as early as day 2 of TH. Combining EEG and FDNIRS-DCS parameters improved area-under-the-curve, sensitivity and specificity for most of the predictive models.

Updates in Neonatal Neuromonitoring: Electroencephalography, Near-Infrared Spectroscopy, and Transcranial Doppler in the Neonatal Intensive Care Unit

This article discusses advanced neuromonitoring techniques for neonates in intensive care, focusing on electroencephalography, near-infrared spectroscopy, and transcranial Doppler ultrasound. These noninvasive methods provide real-time data on brain function, oxygenation, and blood flow, allowing seizure detection, brain injury severity assessment, and outcome prediction. Technologies can guide personalized treatment strategies and identify infants at high risk for neurologic complications. While promising, challenges remain in translating these monitoring tools into standardized clinical practice. Future research should focus on developing evidence-based interventions to maximize benefits of these advanced neuromonitoring techniques in improving neonatal outcomes.

Association between cerebral oxygen saturation and neurological injury in asphyxiated neonates in a middle-income country: a retrospective cohort study

BACKGROUND

Neonatal outcomes following perinatal asphyxia vary significantly between low- and middle-income countries (LMICs) and high-income settings. Near-infrared spectroscopy is a non-invasive method for monitoring regional cerebral oxygen saturation (rScO2), providing real-time insights into brain oxygenation. In LMICs, where healthcare resources are limited, early rScO2 monitoring during therapeutic hypothermia (TH) may support neurological risk stratification. This study aimed to evaluate the association between early rScO2 levels and brain MRI abnormalities in asphyxiated neonates during their first week of life.

METHODS

A retrospective longitudinal study was conducted on term neonates with moderate-to-severe perinatal asphyxia undergoing TH at a high-complexity healthcare institution in an LMIC. Continuous rScO2 monitoring was performed for 72 hours during cooling and rewarming. Values were analysed at 6-hour intervals. The primary outcome was abnormal brain MRI findings during the first week, defined as radiological injury to the basal ganglia, thalami, cortical/watershed areas, white matter or vascular territories. Logistic regression was used to assess the association between rScO2 and MRI abnormalities, and receiver operating characteristic analysis was used to evaluate predictive performance.

RESULTS

88 neonates were included, of which 29 had abnormal MRI findings. All patients were referred from lower-complexity centres. Elevated rScO2 in the first 6 hours was significantly associated with abnormal MRI findings (adjusted OR, 1.10; 95% CI 1.02 to 1.18). The rScO2 threshold showed limited sensitivity and moderate specificity.

CONCLUSIONS

Higher rScO₂ values during the first 6 hours of TH were associated with abnormal brain MRI findings. Although not definitive, early rScO2 monitoring may aid in identifying neonates at risk of neurological injury in LMICs.

Complexin 2 contributes to the protective effect of NAD+ on neuronal survival following neonatal hypoxia-ischemia

Nicotinamide adenine dinucleotide (NAD) is a key coenzyme involved in cell metabolism associated with aging, cancer, neurodegenerative diseases and metabolic disorders. We recently showed that NAD+ therapy significantly improved neurobehavioral outcomes in neonatal mice after hypoxia-ischemia (HI), and bioinformatics analysis revealed that the expression of complexin 2 (CPLX2) in the injured cerebral cortex was significantly decreased 24 h after HI injury but could be reversed by NAD+ intervention. In this study we explored the role of CPLX2 in the survival and function of neonatal hypoxic-ischemic cortical neurons. HI models were established by permanent ligation of the left common carotid artery in mice. CPLX2-knockdown lentiviral vector was injected intraventricularly on postnatal day 1 (P1); CPLX2 knockout mice were also used. NAD+ (5 mg·kg-1·d-1, i.p.) was administered before HI surgery, thereafter once a day until sampling. We showed that NAD+ administration significantly ameliorated the morphological damages and neurobehavioral defects, and elevated the seizure thresholds in HI mice. All the beneficial effects of NAD+ were abolished by CPLX2 knockdown or knockout. In HT22 neuronal cells subjected to OGD/R, pretreated with NAD+ (100 μM) for 12 h significantly increased the cell viability, decreased the LDH levels, and inhibited the ferroptosis evidenced by the changes in redox-related parameters including concentrations of Fe2+, GSH, MDA, H2O2 as well as the expression of GPX4 and SLC7A11. CPLX2 knockdown in HT22 neuronal cells blocked the protective effects of NAD+ as in HI mice, whereas CPLX2 overexpression enhanced the inhibitory effects of NAD+ on ferroptosis in HT22 neuronal cells.

A narrative review of the clinical applications of renal NIRS and integration with cerebral NIRS in the NICU

Organ perfusion and regional tissue oxygen saturation (rSO2) can be measured non-invasively using near-infrared spectroscopy (NIRS). While cerebral NIRS monitoring in neonates has been widely used, the adoption of renal NIRS is still evolving. This narrative review explores the application of renal NIRS in neonates and proposes an algorithm for integrating renal and cerebral NIRS in the neonatal intensive care unit. Decreased renal regional oxygenation (RrSO2) suggests decreased renal O2 delivery/perfusion or increased O2 consumption, warranting evaluation for acute kidney injury, anemia, hemodynamically significant patent ductus arteriosus, or hypotension. Increased RrSO2 indicates increased renal O2 delivery/perfusion or decreased O2 consumption, necessitating assessment for hyperoxia or established kidney injury. Combining cerebral and renal NIRS provides a comprehensive evaluation, allowing for the detection of early clinical changes. This integrated monitoring approach holds promise for improving neonatal outcomes. However, further large-scale studies are needed to establish normal ranges and guide therapeutic interventions.

The predictive value of MRI scores for neurodevelopmental outcome in infants with neonatal encephalopathy

BACKGROUND

MRI scoring systems are utilized to quantify brain injury and predict outcome in infants with neonatal encephalopathy (NE). Our aim was to evaluate the predictive accuracy of total scores, white matter (WM) and grey matter (GM) subscores of Barkovich and Weeke scoring systems for neurodevelopmental outcome at 2 years of age in infants receiving therapeutic hypothermia for NE.

METHODS

Data of 162 infants were analyzed in this retrospective cohort study. DeLong tests were used to compare areas under the curve of corresponding items of the two scoring systems. LASSO logistic regression was carried out to evaluate the association between MRI scores and adverse composite (death or severe disabilities), motor and cognitive outcomes (Bayley developmental index <70).

RESULTS

Weeke scores predicted each outcome measure with greater accuracy than the corresponding items of Barkovich system (DeLong tests p < 0.03). Total scores, GM and cerebellum involvement were associated with increased odds for adverse outcomes, in contrast to WM injury, after adjustment to 5' Apgar score, first postnatal lactate and aEEG normalization within 48 h.

CONCLUSION

A more detailed scoring system had better predictive value for adverse outcome. GM injury graded on both scoring systems was an independent predictor of each outcome measure.

IMPACT STATEMENTS

A more detailed MRI scoring system had a better predictive value for motor, cognitive and composite outcomes. While hypoxic-ischemic brain injuries in the deep grey matter and cerebellum were predictive of adverse outcome, white matter injury including cortical involvement was not associated with any of the outcome measures at 2 years of age. Structured MRI evaluation based on validated scores may aid future clinical research, as well as inform parents and caregivers to optimize care beyond the neonatal period.

Impact of persistent pulmonary hypertension on cerebral oxygenation in infants with neonatal encephalopathy

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) affects systemic oxygenation and may worsen brain injury in infants with neonatal encephalopathy (NE). Evidence suggests that higher cerebral regional oxygenation (crSO2) indicates derangement in cerebral autoregulation, energy metabolism, and blood flow following NE. Our aim was to evaluate the impact of PPHN on crSO2, in infants with NE treated with therapeutic hypothermia (TH).

METHODS

We retrospectively evaluated infants with NE and PPHN vs without PPHN, between 2018-2022. Linear regression analysis was performed to evaluate the impact of PPHN on crSO2 and total MRI score, adjusted for perinatal factors.

RESULTS

164 infants were analyzed, including 19(12%) with PPHN and 145(88%) without. PPHN-infants had significantly higher crSO2 during rewarming and post-rewarming compared to non-PPHN infants (87 ± 6 vs 80 ± 6, p = 0.001; 87 ± 5 vs 80 ± 7, p = 0.008, respectively), and a significantly higher total MRI score [7(2-19) vs 1(0-3), p < 0.001]. PPHN was significantly associated with higher crSO2 during rewarming (b = 6.21, 95% CI 2.37-10.04, p = 0.002) and post-rewarming (b = 8.60, 95% CI 2.28-14.91, p = 0.009), and total MRI score (b = 7.42, 95% CI 4.88-9.95, p < 0.001).

CONCLUSIONS

PPHN was associated with higher crSO2 during and after rewarming, and worse brain MRI score, indicating a significant impact of PPHN on brain injury in infants with NE undergoing TH.

IMPACT

Cerebral oxygenation was significantly higher in infants with neonatal encephalopathy (NE) and persistent pulmonary hypertension (PPHN) compared to infants without PPHN, during the rewarming and post-rewarming periods of therapeutic hypothermia (TH). PPHN is associated with brain injury in infants with NE undergoing TH. In infants with NE and PPHN, monitoring of cerebral oxygenation would help detect infants at higher risk of adverse outcomes.

The role of endothelial frequency in the cerebral blood flow control during neonatal asphyxia: a retrospective longitudinal study

BACKGROUND

Cerebral blood flow dynamics can be explored through analysis of endothelial frequencies. Our hypothesis posits a disparity in endothelial activity among neonates with perinatal asphyxia, stratified by the presence or absence of neuronal lesions.

METHODS

We conducted a retrospective longitudinal study involving newborns treated with hypothermia for moderate to severe asphyxia. Participants were grouped based on the presence or absence of neuronal damage to investigate temporal endothelial involvement in cerebral blood flow regulation. Regional cerebral oxygen saturation (rScO2) was measured using near-infrared spectroscopy (NIRS), and temporal series were analyzed in the frequency domain, utilizing the original frequency of the INVOS™ device.

RESULTS

The study included 88 patients, with 53% (47/88) being male and 33% (29/88) demonstrating brain lesions on magnetic resonance imaging. Among them, 86% (76/88) had a gestational age exceeding 37 weeks according to the Ballard scale, and 81% (71/88) had a birth weight exceeding 2500 g. Cohen's d effect size was calculated to assess differences in endothelial frequency between groups, indicating a small effect size based on cerebral MRI findings (Cohen's d values for Day 2 = 0.2351 and Day 3 = 0.2325).

CONCLUSION

NIRS represents a valuable tool for monitoring cerebral autoregulation in neonates affected by perinatal asphyxia, underscoring the utility of assessing endothelial frequency or energy on rScO2 measured by NIRS using the original INVOS™ device frequency.

How do we reach the goal of personalized medicine for neuroprotection in neonatal hypoxic-ischemic encephalopathy?

Therapeutic hypothermia is now standard of care for neonates with hypoxic-ischemic encephalopathy (HIE) in high income countries (HIC). Conversely, compelling trial evidence suggests that hypothermia is ineffective, and may be deleterious, in low- and middle-income countries (LMIC), likely reflecting the lower proportion of infants who had sentinel events at birth, suggesting that injury had advanced to a stage when hypothermia is no longer effective. Although hypothermia significantly reduced the risk of death and disability in HICs, many infants survived with disability and in principle may benefit from targeted add-on neuroprotective or neurorestorative therapies. The present review will assess biomarkers that could be used to personalize treatment for babies with HIE - to determine first whether an individual infant is likely to respond to hypothermia, and second, whether additional treatments may be beneficial.

The Use of Cerebral Near-Infrared Spectroscopy in Neonatal Hypoxic-Ischemic Encephalopathy: A Systematic Review of the Literature

BACKGROUND

Cerebral near-infrared spectroscopy (cNIRS) is a noninvasive technology used to trend cerebral perfusion at the bedside. cNIRS has potential as a valuable tool in the evaluation of infants with suspected hypoxic-ischemic encephalopathy (HIE). Trending cerebral perfusion with cNIRS can provide information regarding cerebral metabolism as HIE is evolving, which may offer insight into the extent of brain injury.

PURPOSE

The purpose of this systematic review is to investigate the use of cNIRS as a neurocritical tool in the management of neonatal HIE by evaluating its ability to detect acute neurological compromise, including acute brain injury and seizure activity, as well as its potential to identify infants at high risk for long-term neurodevelopmental impairment.

METHODS

A literature search was conducted using PubMed, CINAHL, and Web of Science databases to review articles investigating cNIRS technology in the acute management of HIE.

RESULTS

Eight studies were identified and included in this systematic review. Correlations were observed between cNIRS trends and neurological outcomes as later detected by MRI. cNIRS has potential as a bedside neuromonitoring tool in the management of HIE to detect infants at high risk for brain injury.

IMPLICATIONS FOR PRACTICE

Existing research supports the value of trending cNIRS in HIE management. Documented normal cNIRS values for both term and preterm infants in the first few days of life is approximately 60% to 80%. A steadily increasing cNIRS reading above an infant's baseline and a value of more than 90% should prompt further evaluation and concern for significant neurological injury.

Comparison of the SenSmart™ and the INVOS™ neonatal cerebral near-infrared spectrometry devices

Objectives

To determine the correlation and agreement between the SenSmart™ and the INVOS™ devices of neonatal cerebral regional oxygen saturation (CrSO2) measurements using neonatal sensors. The secondary objective was to develop a regression model that predicts CrSO2-INVOS values using CrSO2-SenSmart indices and determine whether the values between the devices are interchangeable.

Methods

A prospective, cross-sectional study was conducted in infants during the first 4 weeks of life. Simultaneous, bilateral CrSO2 was measured using the SenSmart™X100 (CrSO2-SenSmart) or INVOS™ 5100C (CrSO2-INVOS) device in each frontoparietal area for 2 h. Five-minute CrSO2 values were extracted for analysis.

Results

Thirty infants were recruited with 720 pairwise measurements and 26 (84%) were evaluated in the first week of life. Mean gestational age of the preterm and term infants was [30.9 ± 2.8 (n = 14) and 38.8 ± 1.1 (n = 16)] weeks, respectively. Overall CrSO2- was 77.08 ± 9.70% and 71.45 ± 12.74% for the SenSmart and INVOS, respectively (p < 0.001). The correlation coefficient (r) between the CrSO2-SenSmart and INVOS was 0.20 (p < 0.001). The mean difference between the CrSO2-SenSmart and INVOS was 5.63 ± 13.87% with -21.6% to 32.8% limits of agreement. The r and mean difference was 0.39 (p < 0.001) and 8.87 ± 12.58% in preterm infants, and 0.06 (p = 0.27) and 2.79 ± 14.34 in term infants.

Conclusion

The CrSO2-SenSmart tended to read higher than the CrSO2-INVOS device. There was no correlation between the CrSO2-SenSmart and the CrSO2-INVOS in term infants and it was weak in preterms. Due to imprecise agreement, the CrSO2-SenSmart values are not interchangeable with those of the CrSO2-INVOS.

Optimal neuromonitoring techniques in neonates with hypoxic ischemic encephalopathy

Neonates with hypoxic ischemic encephalopathy (HIE) are at significant risk for adverse outcomes including death and neurodevelopmental impairment. Neuromonitoring provides critical diagnostic and prognostic information for these infants. Modalities providing continuous monitoring include continuous electroencephalography (cEEG), amplitude-integrated electroencephalography (aEEG), near-infrared spectroscopy (NIRS), and heart rate variability. Serial bedside neuromonitoring techniques include cranial ultrasound and somatic and visual evoked potentials but may be limited by discrete time points of assessment. EEG, aEEG, and NIRS provide distinct and complementary information about cerebral function and oxygen utilization. Integrated use of these neuromonitoring modalities in addition to other potential techniques such as heart rate variability may best predict imaging outcomes and longer-term neurodevelopment. This review examines available bedside neuromonitoring techniques for the neonate with HIE in the context of therapeutic hypothermia.

Neuromonitoring in neonatal critical care part I: neonatal encephalopathy and neonates with possible seizures

The blooming of neonatal neurocritical care over the last decade reflects substantial advances in neuromonitoring and neuroprotection. The most commonly used brain monitoring tools in the neonatal intensive care unit (NICU) are amplitude integrated EEG (aEEG), full multichannel continuous EEG (cEEG), and near-infrared spectroscopy (NIRS). While some published guidelines address individual tools, there is no consensus on consistent, efficient, and beneficial use of these modalities in common NICU scenarios. This work reviews current evidence to assist decision making for best utilization of neuromonitoring modalities in neonates with encephalopathy or with possible seizures. Neuromonitoring approaches in extremely premature and critically ill neonates are discussed separately in the companion paper. IMPACT: Neuromonitoring techniques hold promise for improving neonatal care. For neonatal encephalopathy, aEEG can assist in screening for eligibility for therapeutic hypothermia, though should not be used to exclude otherwise eligible neonates. Continuous cEEG, aEEG and NIRS through rewarming can assist in prognostication. For neonates with possible seizures, cEEG is the gold standard for detection and diagnosis. If not available, aEEG as a screening tool is superior to clinical assessment alone. The use of seizure detection algorithms can help with timely seizures detection at the bedside.

Comparative evaluation of approach to cardiovascular care in neonatal encephalopathy undergoing therapeutic hypothermia

OBJECTIVE

To analyze the association between cardiovascular care and adverse outcome in infants undergoing therapeutic hypothermia for neonatal encephalopathy (NE).

STUDY DESIGN

This was a retrospective cohort study of 176 infants with NE and hypotension, admitted to the SickKids Hospital (Center A, n = 86) or Semmelweis University (Center B, n = 90).

RESULT

The lowest systolic/diastolic blood pressures were comparable amongst centers; however, proportion of cardiovascular support was lower in Center A (51% vs 97% in Center B). Overall rate of death or abnormal MRI (adverse outcome) were comparable between centers, although pattern differed with more basal ganglia injury in Center B. A 24-hour longer duration of cardiovascular support increased the odds for adverse outcome by 14%.

CONCLUSION

We demonstrated that management of hemodynamic instability in infants with NE was markedly different in two high-volume NICUs and showed that longer duration of cardiovascular medication is an independent risk factor for adverse outcome.

Cerebral Oxygenation and Metabolism After Hypoxia-Ischemia

Perinatal hypoxia-ischemia (HI) is still a significant contributor to mortality and adverse neurodevelopmental outcomes in term and preterm infants. HI brain injury evolves over hours to days, and involves complex interactions between the endogenous protective and pathological processes. Understanding the timing of evolution of injury is vital to guide treatment. Post-HI recovery is associated with a typical neurophysiological profile, with stereotypic changes in cerebral perfusion and oxygenation. After the initial recovery, there is a delayed, prolonged reduction in cerebral perfusion related to metabolic suppression, followed by secondary deterioration with hyperperfusion and increased cerebral oxygenation, associated with altered neurovascular coupling and impaired cerebral autoregulation. These changes in cerebral perfusion are associated with the stages of evolution of injury and injury severity. Further, iatrogenic factors can also affect cerebral oxygenation during the early period of deranged metabolism, and improving clinical management may improve neuroprotection. We will review recent evidence that changes in cerebral oxygenation and metabolism after HI may be useful biomarkers of prognosis.

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.

Role of Optical Neuromonitoring in Neonatal Encephalopathy-Current State and Recent Advances

Neonatal encephalopathy (NE) in term and near-term infants is a significant global health problem; the worldwide burden of disease remains high despite the introduction of therapeutic hypothermia. Assessment of injury severity and effective management in the neonatal intensive care unit (NICU) relies on multiple monitoring modalities from systemic to brain-specific. Current neuromonitoring tools provide information utilized for seizure management, injury stratification, and prognostication, whilst systemic monitoring ensures multi-organ dysfunction is recognized early and supported wherever needed. The neuromonitoring technologies currently used in NE however, have limitations in either their availability during the active treatment window or their reliability to prognosticate and stratify injury confidently in the early period following insult. There is therefore a real need for a neuromonitoring tool that provides cot side, early and continuous monitoring of brain health which can reliably stratify injury severity, monitor response to current and emerging treatments, and prognosticate outcome. The clinical use of near-infrared spectroscopy (NIRS) technology has increased in recent years. Research studies within this population have also increased, alongside the development of both instrumentation and signal processing techniques. Increasing use of commercially available cerebral oximeters in the NICU, and the introduction of advanced optical measurements using broadband NIRS (BNIRS), frequency domain NIRS (FDNIRS), and diffuse correlation spectroscopy (DCS) have widened the scope by allowing the direct monitoring of oxygen metabolism and cerebral blood flow, both key to understanding pathophysiological changes and predicting outcome in NE. This review discusses the role of optical neuromonitoring in NE and why this modality may provide the next significant piece of the puzzle toward understanding the real time state of the injured newborn brain.