Changes in hemodynamics, cerebral oxygenation and cerebrovascular reactivity during the early transitional circulation in preterm infants

Cerebral autoregulation in paediatric and neonatal intensive care: A scoping review

Deranged cerebral autoregulation (CA) is associated with worse outcome in adult brain injury. Strategies for monitoring CA and maintaining the brain at its 'best CA status' have been implemented, however, this approach has not yet developed for the paediatric population. This scoping review aims to find up-to-date evidence on CA assessment in children and neonates with a view to identify patient categories in which CA has been measured so far, CA monitoring methods and its relationship with clinical outcome if any. A literature search was conducted for studies published within 31st December 2022 in 3 bibliographic databases. Out of 494 papers screened, this review includes 135 studies. Our literature search reveals evidence for CA measurement in the paediatric population across different diagnostic categories and age groups. The techniques adopted, indices and thresholds used to assess and define CA are heterogeneous. We discuss the relevance of available evidence for CA assessment in the paediatric population. However, due to small number of studies and heterogeneity of methods used, there is no conclusive evidence to support universal adoption of CA monitoring, technique, and methodology. This calls for further work to understand the clinical impact of CA monitoring in paediatric and neonatal intensive care.

The Role of Oxidative Stress in the Progression of Secondary Brain Injury Following Germinal Matrix Hemorrhage

Germinal matrix hemorrhage (GMH) can be a fatal condition responsible for the death of 1.7% of all neonates in the USA. The majority of GMH survivors develop long-term sequalae with debilitating comorbidities. Higher grade GMH is associated with higher mortality rates and higher prevalence of comorbidities. The pathophysiology of GMH can be broken down into two main titles: faulty hemodynamic autoregulation and structural weakness at the level of tissues and cells. Prematurity is the most significant risk factor for GMH, and it predisposes to both major pathophysiological mechanisms of the condition. Secondary brain injury is an important determinant of survival and comorbidities following GMH. Mechanisms of brain injury secondary to GMH include apoptosis, necrosis, neuroinflammation, and oxidative stress. This review will have a special focus on the mechanisms of oxidative stress following GMH, including but not limited to inflammation, mitochondrial reactive oxygen species, glutamate toxicity, and hemoglobin metabolic products. In addition, this review will explore treatment options of GMH, especially targeted therapy.

Cardiovascular and cerebrovascular effects of caffeine maintenance in preterm infants during the transitional period

BACKGROUND AND AIM

Caffeine is routinely used for the prophylaxis of prematurity-related apnoeas. We aimed to evaluate the effect of caffeine maintenance on cardiovascular and cerebrovascular haemodynamics using a non-invasive multimodal monitoring in preterm infants during the transitional period.

METHODS

Infants <32 weeks' gestational age (GA) were enrolled in this observational prospective study. The following parameters were recorded before and after the administration of caffeine citrate 5 mg/kg using near-infrared spectroscopy, pulse oximetry and electrical velocimetry: heart rate, cardiac output, stroke volume, cardiac contractility, systemic vascular resistance (SVR), perfusion index, peripheral and cerebral oxygenation, cerebral fractional oxygen extraction, correlation index between cerebral oxygenation and heart rate (TOHRx, marker of cerebrovascular reactivity). Multilevel mixed-effects linear models were used to assess the impact of caffeine and of relevant clinical covariates on each parameter.

RESULTS

Seventy-seven infants (mean GA 29.3 ± 2.5 weeks, mean birthweight 1148 ± 353 g) were included. Caffeine administration was associated with increased SVR (B = 0.623, p = 0.004) and more negative TOHRx values (B = -0.036, p = 0.022), which suggest improved cerebrovascular reactivity.

CONCLUSIONS

Caffeine administration at maintenance dosage during postnatal transition is associated with increased systemic vascular tone and improved cerebrovascular reactivity. A possible role for caffeine-mediated inhibition of adenosine receptors may be hypothesized.

IMPACT

This study provides a thorough and comprehensive overview of multiple cerebrovascular and cardiovascular parameters, monitored non-invasively by combining near-infrared spectroscopy, electrical velocimetry and pulse oximetry, before and after the administration of caffeine at maintenance dosage in preterm infants during postnatal transition. Caffeine was associated with an improvement in cerebrovascular reactivity and with a slight but significant increase in systemic vascular resistance, with no additional effects on other cardiovascular and cerebrovascular parameters. Our results support the safety of caffeine treatment even during a phase at risk for haemodynamic instability such as postnatal transition and suggest potential beneficial effects on cerebral haemodynamics.

Relationship between cerebral oxygenation, cardiac output, and blood pressure during transitional period in extremely low gestational age neonates

Objective

To describe the relationship between cerebral oxygenation, cardiac output, arterial blood pressure (BP), and cerebral blood flow velocity in extremely low gestational age neonates (ELGANs) during transition.

Methods

This study comprises secondary analyses from a prospective observational study conducted at a tertiary Neonatal Intensive Care Unit. Recruited ELGANs underwent cerebral saturation (CrSO2) monitoring and serial echocardiography during 72 h from birth. Correlative analyses of CrSO2 and cerebral fractional tissue oxygen extraction (CFTOE) with left (LVO) and right ventricular output (RVO), superior vena cava (SVC) flow, middle cerebral artery blood flow mean velocity (MCA.MV), systolic (SBP), diastolic (DBP), and mean (MBP) BP were conducted.

Results

Fifty ELGANs with median (range) gestational age of 25.9 (23.1-27.9) weeks were recruited. Echocardiography was performed sequentially at a median (range) age 5.0 (3.8-6.6), 17.3 (15.4-19.4), 31.0 (27.0-34.1), and 53.7 (49.3-58.3) hours. RVO, LVO, CrSO2, and SBP increased over time but no changes in MBP, DBP, CFTOE, MCA.MV or SVC flow were noted. A weak correlation was identified between CrSO2 and SBP (r2 = 0.11, p = 0.047) and MBP (r2 = 0.12, p = 0.04) at 17.3 (15.4-19.4) hours. No correlation of either CrSO2 or CFTOE with any measures of blood flow was identified.

Conclusion

There is a weak correlation between measures of cardiac output, BP, and MCA.MV with both CrSO2 and CFTOE in ELGANs during transition. Whether this finding suggests intact cerebral autoregulation requires prospective evaluation in a cohort of sick ELGANs.

Insights into Neonatal Cerebral Autoregulation by Blood Pressure Monitoring and Cerebral Tissue Oxygenation: A Qualitative Systematic Review

OBJECTIVE

The aim of this qualitative systematic review was to identify publications on blood pressure monitoring in combination with cerebral tissue oxygenation monitoring during the first week after birth focusing on cerebral autoregulation.

METHODS

A systematic search was performed on PubMed. The following search terms were used: infants/newborn/neonates, blood pressure/systolic/diastolic/mean/MAP/SAP/DAP, near-infrared spectroscopy, oxygenation/saturation/oxygen, and brain/cerebral. Additional studies were identified by a manual search of references in the retrieved studies and reviews. Only human studies were included.

RESULTS

Thirty-one studies focused on preterm neonates, while five included preterm and term neonates. In stable term neonates, intact cerebral autoregulation was shown by combining cerebral tissue oxygenation and blood pressure during immediate transition, while impaired autoregulation was observed in preterm neonates with respiratory support. Within the first 24 h, stable preterm neonates had reduced cerebral tissue oxygenation with intact cerebral autoregulation, while sick neonates showed a higher prevalence of impaired autoregulation. Further cardio-circulatory treatment had a limited effect on cerebral autoregulation. Impaired autoregulation, with dependency on blood pressure and cerebral tissue oxygenation, increased the risk of intraventricular hemorrhage and abnormal neurodevelopmental outcomes.

CONCLUSIONS

Integrating blood pressure monitoring with cerebral tissue oxygenation measurements has the potential to improve treatment decisions and optimizes neurodevelopmental outcomes in high-risk neonates.

Cerebral Oximetry Monitoring in Extremely Preterm Infants

BACKGROUND

The use of cerebral oximetry monitoring in the care of extremely preterm infants is increasing. However, evidence that its use improves clinical outcomes is lacking.

METHODS

In this randomized, phase 3 trial conducted at 70 sites in 17 countries, we assigned extremely preterm infants (gestational age, <28 weeks), within 6 hours after birth, to receive treatment guided by cerebral oximetry monitoring for the first 72 hours after birth or to receive usual care. The primary outcome was a composite of death or severe brain injury on cerebral ultrasonography at 36 weeks' postmenstrual age. Serious adverse events that were assessed were death, severe brain injury, bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, and late-onset sepsis.

RESULTS

A total of 1601 infants underwent randomization and 1579 (98.6%) were evaluated for the primary outcome. At 36 weeks' postmenstrual age, death or severe brain injury had occurred in 272 of 772 infants (35.2%) in the cerebral oximetry group, as compared with 274 of 807 infants (34.0%) in the usual-care group (relative risk with cerebral oximetry, 1.03; 95% confidence interval, 0.90 to 1.18; P = 0.64). The incidence of serious adverse events did not differ between the two groups.

CONCLUSIONS

In extremely preterm infants, treatment guided by cerebral oximetry monitoring for the first 72 hours after birth was not associated with a lower incidence of death or severe brain injury at 36 weeks' postmenstrual age than usual care. (Funded by the Elsass Foundation and others; SafeBoosC-III ClinicalTrials.gov number, NCT03770741.).

Near-infrared spectroscopy monitoring of neonatal cerebrovascular reactivity: where are we now?

Cerebrovascular reactivity defines the ability of the cerebral vasculature to regulate its resistance in response to both local and systemic factors to ensure an adequate cerebral blood flow to meet the metabolic demands of the brain. The increasing adoption of near-infrared spectroscopy (NIRS) for non-invasive monitoring of cerebral oxygenation and perfusion allowed investigation of the mechanisms underlying cerebrovascular reactivity in the neonatal population, confirming important associations with pathological conditions including the development of brain injury and adverse neurodevelopmental outcomes. However, the current literature on neonatal cerebrovascular reactivity is mainly still based on small, observational studies and is characterised by methodological heterogeneity; this has hindered the routine application of NIRS-based monitoring of cerebrovascular reactivity to identify infants most at risk of brain injury. This review aims (1) to provide an updated review on neonatal cerebrovascular reactivity, assessed using NIRS; (2) to identify critical points that need to be addressed with targeted research; and (3) to propose feasibility trials in order to fill the current knowledge gaps and to possibly develop a preventive or curative approach for preterm brain injury. IMPACT: NIRS monitoring has been largely applied in neonatal research to assess cerebrovascular reactivity in response to blood pressure, PaCO₂ and other biochemical or metabolic factors, providing novel insights into the pathophysiological mechanisms underlying cerebral blood flow regulation. Despite these insights, the current literature shows important pitfalls that would benefit to be addressed in a series of targeted trials, proposed in the present review, in order to translate the assessment of cerebrovascular reactivity into routine monitoring in neonatal clinical practice.

Cerebral monitoring of very preterm infants with anterior cerebral artery resistive index and early NIRS

BACKGROUND

The prediction of adverse conditions in the preterm neonatal brain might be improved by cerebral monitoring using combined measures of cerebral function, including oxygenation and blood flow parameters. To perform the consecutive measurements of the resistive index (RI) from the anterior cerebral artery (ACA) within the first week of life and to evaluate the association of these measurements with cerebral oxygen saturation (Csat) detected by near-infrared spectroscopy (NIRS).

METHODS

This prospective cohort study enrolled very preterm infants, <32 weeks of gestational age, admitted to a tertiary neonatal intensive care unit. Csat levels were continuously monitored using NIRS for 72 h after birth. ACA RI measurements were obtained on the first, third, and seventh days of life by using transcranial Doppler ultrasound. These measurements were also compared between infants with and without unfavorable outcomes, including severe intraventricular hemorrhage (IVH) and early mortality.

RESULTS

A total of 96 preterm infants with Csat and ACA RI measurements were analyzed. Age at birth was 28.3 ± 1.9 weeks and birth weight was 1090 ± 305 g. The mean Csat of the infants was 77.1% ± 8.2% during the first 72 h of life. Mean ACA RI values were 0.76 ± 0.10, 0.75 ± 0.08, and 0.77 ± 0.08 on the first, third, and seventh days of life, respectively. RI on the first day of life was significantly higher in infants delivered by cesarian section than in those delivered vaginally (0.77 vs. 0.69; p = 0.017). Infants who died earlier had significantly higher ACA RI values on the first day than infants who survived beyond the first 7 postnatal days (0.83 vs. 0.76; p < 0.001).

DISCUSSION

There was no association between ACA RI and Csat in the early period of life. ACA RI values on the first postnatal day might be significant for predicting early mortality in very preterm infants.

Neuromonitoring in neonatal critical care part II: extremely premature infants and critically ill neonates

Neonatal intensive care has expanded from cardiorespiratory care to a holistic approach emphasizing brain health. To best understand and monitor brain function and physiology in the neonatal intensive care unit (NICU), the most commonly used tools are amplitude-integrated EEG, full multichannel continuous EEG, and near-infrared spectroscopy. Each of these modalities has unique characteristics and functions. While some of these tools have been the subject of expert consensus statements or guidelines, there is no overarching agreement on the optimal approach to neuromonitoring in the NICU. This work reviews current evidence to assist decision making for the best utilization of these neuromonitoring tools to promote neuroprotective care in extremely premature infants and in critically ill neonates. Neuromonitoring approaches in neonatal encephalopathy and neonates with possible seizures are discussed separately in the companion paper. IMPACT: For extremely premature infants, NIRS monitoring has a potential role in individualized brain-oriented care, and selective use of aEEG and cEEG can assist in seizure detection and prognostication. For critically ill neonates, NIRS can monitor cerebral perfusion, oxygen delivery, and extraction associated with disease processes as well as respiratory and hypodynamic management. Selective use of aEEG and cEEG is important in those with a high risk of seizures and brain injury. Continuous multimodal monitoring as well as monitoring of sleep, sleep-wake cycling, and autonomic nervous system have a promising role in neonatal neurocritical care.

[Influence of hypotension on the short-term prognosis of preterm infants with a gestational age of <32 weeks]

OBJECTIVES

To investigate the influence of early-stage hypotension defined as mean arterial pressure (MAP)<gestational age (weeks) or MAP<30 mmHg on the short-term prognosis of preterm infants with a gestational age of <32 weeks.

METHODS

A total of 320 preterm infants who were admitted to Maternal and Child Health Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology from April 2020 to August 2021 and met the inclusion criteria were enrolled in this prospective study. Blood pressure within 72 hours was monitored. The definition of hypotension and grouping were as follows: (1) Of the 320 preterm infants, those with MAP<gestational age in 2 consecutive measurements served as the hypotension group (n=104), and the others (n=216) served as the control group; (2) Of the 320 preterm infants, those with MAP<30 mmHg in 2 consecutive measurements served as the hypotension group (n=114), and the others served as the control group (n=206). Perinatal data and clinical data during hospitalization were collected.Poor short-term prognosis was defined as death during hospitalization and/or grade Ⅲ-Ⅳ periventricular-intraventricular hemorrhage identified within 1 week after birth. The multivariate logistic regression analysis was used to investigate the influence of hypotension based on the above two definitions on the short-term prognosis of preterm infants.

RESULTS

Compared with the control group, the hypotension group based on the above two definitions had higher incidence rates of the clinical manifestations of hypoperfusion, poor prognosis, hemodynamically significant patent ductus arteriosus, and pulmonary hemorrhage (P<0.05). In addition, compared with the control group, the hypotension group defined by MAP<30 mmHg had higher incidence rates of periventricular-intraventricular hemorrhage and bronchopulmonary dysplasia and mortality rate during hospitalization (P<0.05). The incidence of poor short-term prognosis in the hypotension group defined by MAP<30 mmHg was higher than that in the hypotension group defined by MAP<gestational age (18.4% vs 12.5%), but the difference was not statistically significant (P>0.05).The univariate analysis showed that the poor short-term prognosis was related to birth of cesarean section, gestational age, an Apgar score of ≤ 5 at 5 minutes, use of vasoactive drugs within 72 hours, mechanical ventilation within 72 hours, and hypotension under the two definitions (P<0.05).The multivariate logistic regression showed that hypotension based on either definition was not an independent risk factor for poor prognosis (P>0.05).

CONCLUSIONS

Hypotension based on either definition is not an independent risk factor for short-term poor prognosis in preterm infants with a gestational age of <32 weeks. Hypotension defined by MAP<30 mmHg might be more sensitive than that defined by MAP<gestational age in predicting short-term adverse outcomes, which needs further analysis by large sample studies.

Association of early cerebral oxygen saturation and brain injury in extremely preterm infants

OBJECTIVE

To assess the association between cerebral saturation (crSO2) using Near-Infrared Spectroscopy (NIRS) and brain injury in extremely preterm infants.

STUDY DESIGN

This retrospective study includes 62 infants (<28 weeks gestation) who underwent continuous NIRS monitoring in the first 5 days after birth. Median crSO2 were compared in 12 h increments between infants with and without germinal matrix/intraventricular hemorrhage (GM/IVH). crSO2 was also compared by IVH severity, onset, and by grade of injury on term equivalent MRI.

RESULTS

After 48 h of life (HOL), infants with GM/IVH had significantly lower crSO2 than those without GM/IVH in analysis adjusted for potential confounding e.g., at 49-60 HOL (69.5 (66.2, 72.8) vs. 74.7 (71.8, 77.6), p = 0.023). There were no significant differences in crSO2 by IVH subcategory or injury severity on MRI.

CONCLUSION

Clinical use of NIRS has the potential to identify crSO2 patterns associated with development of GM/IVH.

Pathogenesis and prevention of intraventricular hemorrhage

Despite improvements in the mortality rates of preterm infants, rates of germinal matrix intraventricular hemorrhage (IVH) have remained static with an overall incidence of 25% in infants less than 32 weeks. The importance of the lesion relates primarily to the underlying injury to the developing brain and the associated long-term neurodevelopmental consequences. This clinical-orientated review focuses on the pathogenesis of IVH and discusses the evidence behind proposed prevention strategies.

Clinical determinants of cerebrovascular reactivity in very preterm infants during the transitional period

BACKGROUND

Preterm infants are at enhanced risk of brain injury due to altered cerebral haemodynamics during postnatal transition. This observational study aimed to assess the clinical determinants of transitional cerebrovascular reactivity and its association with intraventricular haemorrhage (IVH).

METHODS

Preterm infants <32 weeks underwent continuous monitoring of cerebral oxygenation and heart rate over the first 72 h after birth. Serial cranial and cardiac ultrasound assessments were performed to evaluate the ductal status and to diagnose IVH onset. The moving correlation coefficient between cerebral oxygenation and heart rate (TOHRx) was calculated. Linear mixed-effect models were used to analyse the impact of relevant clinical variables on TOHRx. The association between TOHRx and IVH development was also assessed.

RESULTS

Seventy-seven infants were included. A haemodynamically significant patent ductus arteriosus (hsPDA) (β = 0.044, 95% CI: 0.007-0.081) and ongoing dopamine treatment (β = 0.096, 95% CI: 0.032-0.159) were associated with increasing TOHRx, indicating impaired cerebrovascular reactivity. A significant association between TOHRx, mean arterial blood pressure (β = -0.004, 95% CI: -0.007, -0.001) and CRIB-II score (β = 0.007, 95% CI: 0.001-0.015) was also observed. TOHRx was significantly higher in infants developing high-grade IVH compared to those without IVH.

CONCLUSIONS

Dopamine treatment, low blood pressure, hsPDA and high CRIB-II are associated with impaired cerebrovascular reactivity during postnatal transition, with potential implications on IVH development.

IMPACT

The correlation coefficient between cerebral oxygenation and heart rate (TOHRx) provides a non-invasive estimation of cerebrovascular reactivity, whose failure has a potential pathogenic role in the development of IVH in preterm infants. This study shows that cerebrovascular reactivity during the transitional period improves over time and is affected by specific clinical and therapeutic factors, whose knowledge could support the development of individualized neuroprotective strategies in at-risk preterm infants. The evidence of increased TOHRx in infants developing high-grade compared to low-grade or no IVH during the transitional period further supports the role of impaired cerebrovascular reactivity in IVH pathophysiology.

Association Analysis of the Cerebral Fractional Tissue Oxygen Extraction (cFTOE) and the Cerebral Oxygen Saturation (crSaO2) with Perinatal Factors in Preterm Neonates: A Single Centre Study

(1) Background: Near-infrared spectroscopy (NIRS) is a non-invasive, easily performed method of monitoring brain oxygenation. The regional cerebral oxygen saturation (crSaO2) and the cerebral fractional tissue oxygen extraction (cFTOE) evaluated by NIRS provide more accurate information on brain oxygenation than the blood oxygen saturation. We investigated the effect of perinatal factors on cerebral oxygenation of preterm newborns. (2) Methods: We conducted a longitudinal study with 48 preterm newborns <34 weeks of gestation who underwent NIRS registration during the first 72 h of life. crSaO2 was measured and cFTOE was calculated foreach patient. (3) Results: One-way ANOVA showed no significant main effect of IVH severity on crSaO2 and cFTOE (p > 0.05); there was a tendency toward statistical significance concerning the difference between the means of crSaO2 (p = 0.083) and cFTOE (p = 0.098). Patients with intraventricular haemorrhage (IVH) had a lower mean of crSaO2 and a higher mean of cFTOE (59.67 ± 10.37% vs. 64.92 ± 10.16% for crSaO2; 0.37 ± 0.11 vs. 0.32 ± 0.11 for cFTOE) compared to those with no IVH. Significantly lower values of crSaO2 and higher values of cFTOE were found in neonates receiving inotropic treatment (p < 0.0001). Episodes of apnoea also proved to influence the cerebral oxygen saturation of the study group (p = 0.0026). No significant association between the maternal hypertension treatment and the cerebral oxygenation of preterms was found. (4) Conclusions: This study showed a decreased cerebral oxygen saturation of preterms with IVH, inotrope support and apnoea episodes.

Intraventricular hemorrhage prediction in premature neonates in the era of hemodynamics monitoring: a prospective cohort study

Unstable hemodynamics and prematurity are the main players in intraventricular hemorrhage (IVH) development. Our objective was to study 8 the use of superior vena cava flow (SVCF), left ventricular output (LVO), and right ventricular output (RVO), and anterior cerebral artery (ACA) Doppler measures in prediction of IVH in the first week of life in preterm infant ≤ 32 weeks and birth weight ≤ 1500 g. This prospective cohort study was conducted in 55NICU of Alexandria University maternity hospital. Of 147 enrolled patients, 132 infants born ≤ 32 weeks GA and birth weight ≤ 1500 g were eligible for- the study. One hundred twenty-seven infants completed the study. Infants were scanned for ACA-RI using transfontanellar ultrasound, and SVCF, LVO, and RVO using functional echocardiography in the first 24 h after birth. Patients had another two scans on DOL3 and 7 to detect IVH development. Low SVCF and high ACA-RI significantly increased the risk of IVH using logistic regression models with OR, 3.16; 95%CI, 1.19-8.39; P = 0.02 and OR, 1.64; 95%Cl, 1.10-2.44; P = 0.02, respectively. Low SVCF and high ACA-RI significantly increased risk of catastrophic IVH P = 0.025 and 0.023, respectively. Combined use of low SVCF < 55 ml/kg/min and ACA-RI > 0.75 is predictor of IVH with sensitivity 40.8% and 82.1% specificity.

CONCLUSIONS

There are strong relations between both low SVCF and high ACA-RI, and IVH development in premature neonates ≤ 32 weeks and birth weight ≤ 1500 g, with more significance towards catastrophic IVH. Admission RSS and LVO are the strongest factors affecting SVCF. Maternal anemia, patent ductus arteriosus size (mm/kg), and capillary refill time were significantly associated with high ACA-RI. These findings help in more understanding of pathophysiological factors affecting central perfusion that might affect the longer term neurodeveopmental outcome.

TRIAL REGISTRATION

This work was registered in clinical trial.gv no NCT05050032.

WHAT IS KNOWN

•Whether SVCF and RI-ACA can predict IVH in preterm neonates is still debatable.

WHAT IS NEW

•Low SVC flow and high ACA-RI significantly increased risk of IVH, confirming the role of hypoperfusion-reperfusion cycle in IVH development. The most striking result that combined metrics using the cut-off value of < 41 ml/kg/min for SVCF and > 0.85 for ACA-RI "in the first day of life" can correctly reject the presence of IVH in 98% of patients "during the first week of life."

Three Physiological Components That Influence Regional Cerebral Tissue Oxygen Saturation

Near-infrared spectroscopy (NIRS) measurement of regional cerebral tissue oxygen saturation (rcStO2) has become a topic of high interest in neonatology. Multiple studies have demonstrated that rcStO2 measurements are feasible in the delivery room during immediate transition and resuscitation as well as after admission to the neonatal intensive care unit. Reference ranges for different gestational ages, modes of delivery, and devices have already been published. RcStO2 reflects a mixed tissue saturation, composed of arterial (A), venous (V), and capillary signals, derived from small vessels within the measurement compartment. The A:V signal ratio fluctuates based on changes in oxygen delivery and oxygen consumption, which enables a reliable trend monitoring of the balance between these two parameters. While the increasing research evidence supports its use, the interpretation of the absolute values of and trends in rcStO2 is still challenging, which halts its routine use in the delivery room and at the bedside. To visualize the influencing factors and improve the understanding of rcStO2 values, we have created a flowchart, which focuses on the three major physiological components that affect rcStO2: oxygen content, circulation, and oxygen extraction. Each of these has its defining parameters, which are discussed in detail in each section.

A neonatal neuroNICU collaborative approach to neuromonitoring of posthemorrhagic ventricular dilation in preterm infants

Morbidity and mortality in prematurely born infants have significantly improved due to advancement in perinatal care, development of NeuroNICU collaborative multidisciplinary approaches, and evidence-based management protocols that have resulted from a better understanding of perinatal risk factors and neuroprotective treatments. In premature infants with intraventricular hemorrhage (IVH), the detrimental secondary effect of posthemorrhagic ventricular dilation (PHVD) on the neurodevelopmental outcome can be mitigated by surgical intervention, though management varies considerably across institutions. Any benefit derived from the use of neuromonitoring to optimize surgical timing and technique stands to improve neurodevelopmental outcome. In this review, we summarize (1) the approaches to surgical management of PHVD in preterm infants and outcome data; (2) neuromonitoring modalities and the effect of neurosurgical intervention on this data; (3) our resultant protocol for the monitoring and management of PHVD. In particular, our protocol incorporates cerebral near-infrared spectroscopy (NIRS) and transcranial doppler ultrasound (TCD) to better understand cerebral physiology and to enable the hypothesis-driven study of the management of PHVD. IMPACT: Review of the published literature concerning the use of near-infrared spectroscopy (NIRS) and a cerebral Doppler ultrasound to study the effect of cerebrospinal fluid drainage on infants with posthemorrhagic ventricular dilation. Presentation of our institution's evidence-based protocol for the use of NIRS and cerebral Doppler ultrasound to study the optimal neurosurgical treatment of posthemorrhagic ventricular dilation, an as yet inadequately studied area.

Cerebral Oxygenation and Autoregulation in Preterm Infants (Early NIRS Study)

OBJECTIVE

To determine if decreased cerebral oxygenation or altered cerebral autoregulation as measured by near-infrared spectroscopy (NIRS) in the first 96 postnatal hours is associated with an increased risk of death or severe neuroradiographic abnormalities in very preterm infants.

STUDY DESIGN

The Early NIRS prospective, multicenter study enrolled very preterm infants with a birth weight of <1250 g from 6 tertiary neonatal intensive care units. Mean arterial blood pressure and cerebral oxygen saturation (Csat) were continuously monitored using a neonatal sensor until 96 hours of age. Moving window correlations between Csat and mean arterial blood pressure determined time periods with altered cerebral autoregulation, and percentiles of correlation were compared between infants with and without the adverse outcome of mortality or severe neuroradiographic abnormalities by early cranial ultrasound.

RESULTS

Of 103 subjects with mean gestational age of 26 weeks, 21 (20%) died or had severe neuroradiographic abnormalities. Infants with adverse outcomes had a lower mean Csat (67 ± 9%) compared with those without adverse outcomes (72 ± 7%; P = .02). A Csat of <50% was identified as a cut-point for identifying infants with adverse outcome (area under the curve, 0.76). Infants with adverse outcomes were more likely to have significant positive or negative correlations between Csat and mean arterial blood pressure, indicating impaired cerebral autoregulation (P = .006).

CONCLUSIONS

Early NIRS monitoring may detect periods of lower cerebral oxygenation and altered cerebral autoregulation, identifying preterm infants at risk for mortality or neuroradiographic injury. An improved understanding of the relationship between altered hemodynamics and cerebral oxygenation may inform future strategies to prevent brain injury.

Near-Infrared spectroscopy for perfusion assessment and neonatal management

Term and preterm infants often present with adverse conditions after birth resulting in abnormal vital functions and severe organ failure, which are associated or sometimes caused by low oxygen and/or blood supply. Brain injury may lead to substantial mortality and morbidity often affecting long-term outcome. Standard monitoring techniques in the NICU focus on arterial oxygen supply and hemodynamics and include respiratory rate, heart rate, blood pressure and arterial oxygen saturation as measured by pulse oximetry but provide only limited information on end organ oxygen delivery. Near-Infrared Spectroscopy can bridge this gap by displaying continuous measurements of tissue oxygen saturation, providing information on the balance of oxygen delivery and consumption in organs of interest. Future techniques using multi-wavelength devices may provide additional information on oxidative metabolism in real time adding important information.