Current research suggests that the future looks brighter for cerebral oxygenation monitoring in preterm infants

Effect of the change of mechanical ventilation mode on cerebral oxygen saturation level in neonates

BACKGROUND

This study aimed to apply near-infrared spectroscopy (NIRS) to monitor cerebral oxygen saturation (SrO2) level in neonates before and after the change of mechanical ventilation mode, and thus, the effects of the change of mechanical ventilator mode on SrO2 level in neonates were assessed.

METHODS

This trial was designed as an observational study .A total of 70 neonates who were admitted to the Department of Neonatology of Beijing Luhe Hospital Affiliated to Capital Medical University (Beijing, China) between September 2019 and October 2021 and required respiratory support were included. The variations of SrO2 level before and after the change of mechanical ventilation mode, including changing from Synchronized intermittent mandatory ventilation (SIMV) to noninvasive ventilation (NIV, group 1), and from NIV to oxygen inhalation (group 2), were monitored by Enginmed EGOS-600 A. The changes of SrO2 level at 30 min before and 1 h after the change of ventilation mode were compared between the two groups.

RESULTS

The SrO2 level in the group 1 30 min before, as well as 10 min, 30 min, and 1 h after the change of ventilation mode was 62.54 ± 3.36%, 65.43 ± 3.98%, 64.38 ± 4.23%, and 64.63 ± 3.71%, respectively. The SrO2 level at all the points after the change of ventilation mode increased compared with 30 min before the change (P < 0.05). The SrO2 level in the group 2 at each time point was 62.67 ± 4.69%, 64.61 ± 5.00%, 64.04 ± 4.48%, and 64.55 ± 4.32%, respectively. Compared with 30 min before ventilator weaning, the SrO2 level at all the points after ventilator weaning increased (P < 0.05). Peak inspiratory pressure (PIP) excluding Nasal Continuous Positive Airway Pressure (NCPAP)) in group 1 was lower than that before extubation, and the difference was statistically significant (P = 0) (Table 7).

CONCLUSIONS

SrO2 level showed an increasing trend after the change of ventilation mode, and the increase of SrO2 level at 10 min after the change of ventilation mode was the most prominent. From SIMV to NIV, increased SrO2 levels may be associated with decreased PIP.

The effect of head positioning on brain tissue oxygenation in preterm infants: a randomized clinical trial study

BACKGROUND

CNS injury in preterm infants is still one of the leading causes of mortality and morbidity. Routine care events might affect the perfusion and cerebral oxygenation of preterm infants. Although positioning the infant's head in a particular condition to improve brain oxygenation is included in many institutions, there is no robust clinical evidence to support this intervention's effectiveness.

OBJECTIVE

The present study aimed to determine the effect of head positioning on brain tissue oxygenation in preterm infants.

METHODS

This study is a randomized clinical trial. In the first 48 h after birth, 39 infants who met the study inclusion criteria underwent head positioning intervention. In this case, the infants were placed in the supine position, and every 2 h, the head position was changed continuously to one of six randomized modes [using random modes generated by SPSS]. During each head positioning, brain tissue oxygenation was recorded by NIRS.

RESULTS

The findings showed a significant difference in brain tissue oxygen saturation among these positions (P < 0.001). Dunn's test showed that the brain tissue oxygen saturation in the third position (head rotates 45-60 degrees from the midline to the right and the head of the bed is zero degrees) was significantly lower than the baseline (P = 0.029; Mean difference = 2.3). Also, in the third position, compared to the first position (P = 0.002; Mean difference = 1.9) and compared to the fourth position (P = 0.003; Mean difference = -2.1), and in the second position compared to the first position (P = 0.046; Mean difference = 1.3), the brain tissue oxygen saturation of the infants was lower.

CONCLUSION

Based on the results of the present study, head positioning was effective on brain tissue oxygenation in preterm infants in the first 48 h after birth; Therefore, it is recommended when possible, not to rotate the infant's head during the first 48 h after birth while the head of the bed is at 0°.

Brain and renal oxygenation measured by NIRS related to patent ductus arteriosus in preterm infants: a prospective observational study

Background

Patent ductus arteriosus (PDA) is common among preterm neonates. Haemodynamically significant ductus arteriosus (hsPDA) can cause ductal steal and contribute to poor outcomes. Our aim was to evaluate ductus arteriosus patency and significance using two-site near-infrared spectroscopy (NIRS) measurements in preterm infants older than 72 h as a supplemental tool to echocardiography.

Methods

In this prospective observational study, 123 preterm infants (gestational age (GA) < 32 weeks, birth weight < 1500 g) were enrolled. Sixty-four newborns had closed ductus arteriosus (noPDA), and 41 and 18 patients were assigned to the PDA and hsPDA groups, respectively, per predefined echocardiographic criteria. Cerebral and renal oxygenation were assessed during NIRS monitoring.

Results

A higher renal mean (±SD) regional tissue oxygen saturation (rSpO₂) (76.7 (±7.64)) was detected in the noPDA group than in the PDA (71.7 (±9.02)) and hsPDA (67.4 (±13.48)) groups (p < 0.001). Renal fractional tissue oxygen extraction (FTOE) (0.18 (±0.079)) was lower in the noPDA group than in the PDA (0.23 (±0.092)) and hsPDA (0.24 (±0.117))0.117 groups (p = 0.002). Cerebral oxygenation was significantly lower in the hsPDA group (77.0 (±5.16)) than in the noPDA (79.3 (±2.45)) and PDA (79.7 (±2.27)) groups (p = 0.004). There was no significant difference in cerebral fractional tissue oxygen extraction (FTOE) between any of the groups.

Conclusions

Our results suggest that renal oxygenation is affected by ductus patency in preterm infants older than 72 h. Significant differences in cerebral oxygenation were observed between the hsPDA group and the PDA and noPDA groups.

Trial registration

ClinicalTrials.gov Identifier: NCT04295395. Registration date: 4 March 2020. This study was retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04295395.

Assessment of neonatal perfusion

Disorders of perfusion in newborn infants are frequently observed in neonatal intensive care units. The current assessment practices are primarily based on clinical signs. Significant technologic advances have opened new avenues for continuous assessment at the bedside. Combining these devices with functional echocardiography provides an in-depth understanding of perfusion and allows targeting therapy to the pathophysiology rather than monitoring and targeting blood pressure. This change in approach is guided by the fact that perfusion disorders can result from a number of causes and a single management approach might do more harm than good. This approach has the potential to improve long term outcomes but needs to be tested in well-designed trials.

Cerebral oxygenation reflects fetal development in preterm monochorionic and dichorionic twins

BACKGROUND

Cerebral oxygenation (crSO₂) monitoring is increasingly used in high-risk infants. Monochorionic twins suffer from specific fetal pathologies that can affect cerebral hemodynamics. Limited data are available on crSO₂ and blood flow patterns in this population after birth.

OBJECTIVE

To evaluate crSO₂ changes in preterm monochorionic and dichorionic twins during the first 72 h of life.

METHODS

Near-infrared spectroscopy was used to measure crSO₂ in 62 infants from 31 twin pregnancies <32 weeks of gestation. The study group was divided into 4 subgroups: donor (1) and recipient (2) monochorionic twins (with twin-twin transfusion syndrome), fetal growth restriction (FGR) infants (3) and twins without fetal compromise (4).

RESULTS

There was significant difference in birth weight (p < 0.001) among 4 subgroups. We observed significant variation in crSO₂ among the subgroups using mixed model analysis (p < 0.001). The recipient twins exhibited the lowest crSO₂ (mean ± SE) throughout the study period (76 ± 0.3%), whereas the FGR and donor twins presented with the highest values (86 ± 0.3% and 83 ± 0.4% respectively). We found no statistically significant differences in neonatal mortality and morbidity among subgroups.

CONCLUSION

Our study revealed significant correlation between crSO₂ values postnatally and underlying fetal pathology in monochorionic and dichorionic preterm twins.

Comparing the response of pulse oximetry and regional cerebral oxygen saturation to hypoxia in preschool children

Pulse oximetry and measurement of regional cerebral oxygen saturation (rcSO₂) are used to monitor peripheral and cerebral oxygenation, respectively. However, the response of rcSO₂ and pulse oxygen saturation (SpO₂) to hypoxia in preschool children has not been previously assessed. A total of 36 preschool patients who had undergone a tonsillectomy [age, 4-6 years, American Society of Anesthesiologists grade I or II] were screened and prospectively enrolled in the present study. Hemodynamics, including rcSO₂, SpO₂, non-invasive blood pressure, heart rate, electrocardiogram and capnography, were continuously monitored throughout the study. Following pre-oxygenation, pressure-controlled ventilation with 100% oxygen was administered through a mask with a flow rate of 6 l/min, under total intravenous anesthesia, and the end-tidal carbon dioxide partial pressure was maintained between 30 and 40 mmHg. Tracheal intubation was then performed and ventilation was paused until SpO₂ decreased to 90% or rcSO₂ decreased by >10% of the baseline level. The duration from pausing of mechanical ventilation to the start of the rcSO₂ decline was shorter than that of SpO₂ (80.2±23.6 sec vs. 124.4±20.5 sec; P<0.001). Subsequent to the recovery of ventilation, the duration from the starting point to the increasing point of the baseline of rcSO₂ was longer than that of SpO₂ (84.8±24.3 sec vs. 15.2±6.8 sec; P<0.001). From the point where mechanical ventilation was paused to when rcSO₂/SpO₂ began to decrease, the rcSO₂ and SpO₂ values decreased and a significant correlation of them was observed (Pearson's correlation coefficient=0.317; P=0.027). From the time-point where mechanical ventilation was recovered to the time-point where rcSO₂ or SpO₂ began to increase, rcSO₂ and SpO₂ values decreased and a significant correlation of them was observed (Spearman's correlation coefficient=0.489; P=0.006). From the baseline to the minimum value, compared with the SpO₂, the rcSO₂ declined at a decreased rate (9.7±0.5% vs. 5.3±2.7%; P<0.001). The present clinical trial was registered at http://www.chictr.org.cn on 14th March 2016 (registration no. ChiCTR-OOC-16008095).

The impact of preterm adversity on cardiorespiratory function

NEW FINDINGS

What is the topic of this review? We review the influence of prematurity on the cardiorespiratory system and examine the common sequel of alterations in oxygen tension, and immune activation in preterm infants. What advances does it highlight? The review highlights neonatal animal models of intermittent hypoxia, hyperoxia and infection that contribute to our understanding of the effect of stress on neurodevelopment and cardiorespiratory homeostasis. We also focus on some of the important physiological pathways that have a modulatory role on the cardiorespiratory system in early life.

ABSTRACT

Preterm birth is one of the leading causes of neonatal mortality. Babies that survive early-life stress associated with immaturity have significant prevailing short- and long-term morbidities. Oxygen dysregulation in the first few days and weeks after birth is a primary concern as the cardiorespiratory system slowly adjusts to extrauterine life. Infants exposed to rapid alterations in oxygen tension, including exposures to hypoxia and hyperoxia, have altered redox balance and active immune signalling, leading to altered stress responses that impinge on neurodevelopment and cardiorespiratory homeostasis. In this review, we explore the clinical challenges posed by preterm birth, followed by an examination of the literature on animal models of oxygen dysregulation and immune activation in the context of early-life stress.

Simulation and in vivo investigation of light-emitting diode, near infrared Gaussian beam profiles

Near infrared spectroscopy is an optical imaging technique which offers a non-invasive, portable, and low-cost method for continuously measuring the oxygenation of tissues. In particular, it can provide the brain activation through measuring the blood oxygenation and blood volume in the cortex. Understanding and then improving the spatial and depth sensitivity of near infrared spectroscopy measurements to brain tissue are essential for designing experiments as well as interpreting research findings. In this study, we investigate the effect of applying two common light beam profiles including Uniform and Gaussian on the penetration depth of an LED-based near infrared spectroscopy. In this regard, two Gaussian profiles were produced by adjusting plano-convex and bi-convex lenses and the Uniform profile was provided by applying a flat lens. Two experiments were conducted in this study. First, a simulation experiment was carried out based on scanning the intra space of a liquid phantom by using static and pulsating absorbers to compare the penetration depth of the configurations applied on the LED-based near infrared spectroscopy with that of a laser-based near infrared spectroscopy. Second, to show the feasibility of the best proposed configuration applied, an in vivo experiment of stress assessment has been performed and its results have been compared with that results obtained by laser one. The results showed that the LED-based near infrared spectroscopy equipped with bi-convex lens provides a penetration depth and hence quality measurements of near infrared spectroscopy and its extracted heart rate variability signals as well as laser-based near infrared spectroscopy especially in the application of stress assessment.

Evaluation of hyperspectral NIRS for quantitative measurements of tissue oxygen saturation by comparison to time-resolved NIRS

Near-infrared spectroscopy (NIRS) is considered ideal for brain monitoring during preterm infancy because it is non-invasive and provides a continuous measure of tissue oxygen saturation (StO2). Hyperspectral NIRS (HS NIRS) is an inexpensive, quantitative modality that can measure tissue optical properties and oxygen saturation (StO2) by differential spectroscopy. In this study, experiments were conducted using newborn piglets to measure StO2 across a range of oxygenation levels from hyperoxia to hypoxia by HS and time-resolved (TR) NIRS for validation. A strong correlation between StO2 measurements from the two techniques was observed (R2 = 0.98, average slope of 1.02 ± 0.28); however, the HS-NIRS estimates were significantly higher than the corresponding TR-NIRS values. These regression results indicate that HS NIRS could become a clinically feasible method for monitoring StO2 in preterm infants.

Regional tissue oxygenation monitoring in the neonatal intensive care unit: evidence for clinical strategies and future directions

Near-infrared spectroscopy (NIRS)-based monitoring of regional tissue oxygenation (rSO₂) is becoming more commonplace in the neonatal intensive care unit (NICU). While increasing evidence supports rSO₂ monitoring, actual standards for applying this noninvasive bedside technique continue to evolve. This review highlights the current strengths and pitfalls surrounding practical NIRS-based monitoring in the neonatal population. The physiologic background of rSO₂ monitoring is discussed, with attention to understanding oxygen delivery/consumption mismatch and its effects on tissue oxygen extraction. The bedside utility of both cerebral and peripheral rSO₂ monitoring in the NICU is then explored from two perspectives: (1) disease/event-specific "responsive" monitoring and (2) "routine," continuous monitoring. Recent evidence incorporating both monitoring approaches is summarized with emphasis on practical applicability in the NICU. Finally, a future paradigm for a broad-based NIRS monitoring strategy is presented, with attention towards improving personalization of neonatal care and ultimately enhancing long-term outcomes.

Patterns of use of near-infrared spectroscopy in neonatal intensive care units: international usage survey

AIM

To assess uptake and applications of near-infrared spectroscopy (NIRS) by neonatal intensive care units (NICUs).

METHODS

A pre-piloted online questionnaire was distributed in May 2015 to 12 perinatal societies in Asia, Europe, Australasia, North America and Middle East for dissemination to NICUs. Questions surveyed demographics, NIRS research/clinical applications, usage frequency, training approaches and target infant populations.

RESULTS

In total, 255 responses from 235 NICUs were obtained. Of these, 85 (36%) owned a NIRS device. Australian and New Zealand NICUs were more likely to own NIRS technology than Asian (OR 1.12, 95% CI: 0.38-3.37) and North American (OR 2.63, 95% CI: 1.07-6.45) NICUs. A total of 69 (71%) used NIRS within clinical or mixed clinical-research settings, however routine reliance for management and prognostication was low (9% and 3%, respectively). Of those without NIRS technology, 96 (64%) had no acquisition intentions. The main limiting factors were controversial evidence on efficacy (59%) and financial considerations (50%). About 51% of respondents received in-house NIRS training and 32% had access to written guidelines.

CONCLUSION

There is considerable geographical variation in NIRS usage in NICUs that is, on the whole, limited by consumer perception of lack of evidence for its clinical utility. This knowledge gap should be addressed by future research.

Wavelet pressure reactivity index: a validation study

KEY POINTS

The brain is vulnerable to damage from too little or too much blood flow. A physiological mechanism termed cerebral autoregulation (CA) exists to maintain stable blood flow even if cerebral perfusion pressure (CPP) is changing. A robust method for assessing CA is not yet available. There are still some problems with the traditional measure, the pressure reactivity index (PRx). We introduce a new method, the wavelet transform method (wPRx), to assess CA using data from two sets of controlled hypotension experiments in piglets: one set had artificially manipulated arterial blood pressure (ABP) oscillations; the other group were spontaneous ABP waves. A significant linear relationship was found between wPRx and PRx in both groups, with wPRx providing a more stable result for the spontaneous waves. Although both methods showed similar accuracy in distinguishing intact and impaired CA, it seems that wPRx tends to perform better than PRx, although not significantly so.

ABSTRACT

We present a novel method to monitor cerebral autoregulation (CA) using the wavelet transform (WT). The new method is validated against the pressure reactivity index (PRx) in two piglet experiments with controlled hypotension. The first experiment (n = 12) had controlled haemorrhage with artificial stationary arterial blood pressure (ABP) and intracranial pressure (ICP) oscillations induced by sinusoidal slow changes in positive end-expiratory pressure ('PEEP group'). The second experiment (n = 17) had venous balloon inflation during spontaneous, non-stationary ABP and ICP oscillations ('non-PEEP group'). The wavelet transform phase shift (WTP) between ABP and ICP was calculated in the frequency range 0.0067-0.05 Hz. Wavelet semblance, the cosine of WTP, was used to make the values comparable to PRx, and the new index was termed wavelet pressure reactivity index (wPRx). The traditional PRx, the running correlation coefficient between ABP and ICP, was calculated. The result showed a significant linear relationship between wPRx and PRx in the PEEP group (R = 0.88) and non-PEEP group (R = 0.56). In the non-PEEP group, wPRx showed better performance than PRx in distinguishing cerebral perfusion pressure (CPP) above and below the lower limit of autoregulation (LLA). When CPP was decreased below LLA, wPRx increased from 0.43 ± 0.28 to 0.69 ± 0.12 (P = 0.003) while PRx increased from 0.07 ± 0.21 to 0.27 ± 0.37 (P = 0.04). Moreover, wPRx provided a more stable result than PRx (SD of PRx was 0.40 ± 0.07, and SD of wPRx was 0.28 ± 0.11, P = 0.001). Assessment of CA using wavelet-derived phase shift between ABP and ICP is feasible.

Applications of near infrared spectroscopy in the neonate

PURPOSE OF REVIEW

There has been a significant increase in the utilization of NIRS in neonatal care over the last few years, with some centers now routinely utilizing this monitoring technique for direct intervention at the bedside. In this review, we provide a summary of the most up-to-date evidence on near infrared spectroscopy utilization, with particular emphasis on measurement of cerebral oxygenation in preterm infants.

RECENT FINDINGS

There have been significant advances in the technology, leading to an increase in the number of available devices and in the use of this monitoring tool to reduce cerebral injury in preterm infants. The role of NIRS in assessing cerebral autoregulation in preterm and term infants, in evaluating somatic oxygenation, and in the management of newborns with hypoxic ischaemic encephalopathy is discussed.

SUMMARY

Two recent pilot randomized controlled trials highlight the potential of cerebral oxygenation monitoring to direct management in the delivery room and the neonatal intensive care unit. However, we urge caution against routine use and await the results of further studies in this area before considering this type of monitoring as standard of care.

Monitoring cerebral oxygenation of preterm infants using a neonatal specific sensor

INTRODUCTION

Cerebral oxygenation (rcSO₂) monitoring in preterm infants may identify periods of cerebral hypoxia or hyperoxia. We hypothesised that there was a relationship between rcSO₂ values and short term outcome in infants of GA < 32weeks.

METHODS

RcSO₂ values were recorded for the first 48 h of life using an INVOS monitor with a neonatal sensor. The association between cranial ultrasound scan measured brain injury and rcSO₂ was assessed.

RESULTS

120 infants were included. Sixty-nine percent (83) of infants had a normal outcome (no IVH, no PVL, and survival at 1 month); less than one-quarter, 22% (26), had low grade IVH 1 or 2 (moderate outcome); and 9% (11) of infants had a severe outcome (IVH ≥ 3, PVL or died before 1 month age). rcSO₂ values were lower for infants GA < 28weeks when compared with those GA 28-32, p < 0.001. There was no difference in absolute rcSO₂ values between the three outcome groups but a greater degree of cerebral hypoxia was associated with preterm infants who had low grade 1 or 2 IVH.

CONCLUSION

Infants of GA < 28 weeks have lower cerebral oxygenation in the first 2 days of life. A greater degree of hypoxia was seen in infants with grade 1 or 2 haemorrhage. Normative ranges need to be gestation specific.

Neonatal Hemodynamics: From Developmental Physiology to Comprehensive Monitoring

Maintenance of neonatal circulatory homeostasis is a real challenge, due to the complex physiology during postnatal transition and the inherent immaturity of the cardiovascular system and other relevant organs. It is known that abnormal cardiovascular function during the neonatal period is associated with increased risk of severe morbidity and mortality. Understanding the functional and structural characteristics of the neonatal circulation is, therefore, essential, as therapeutic hemodynamic interventions should be based on the assumed underlying (patho)physiology. The clinical assessment of systemic blood flow (SBF) by indirect parameters, such as blood pressure, capillary refill time, heart rate, urine output, and central-peripheral temperature difference is inaccurate. As blood pressure is no surrogate for SBF, information on cardiac output and systemic vascular resistance should be obtained in combination with an evaluation of end organ perfusion. Accurate and reliable hemodynamic monitoring systems are required to detect inadequate tissue perfusion and oxygenation at an early stage before this result in irreversible damage. Also, the hemodynamic response to the initiated treatment should be re-evaluated regularly as changes in cardiovascular function can occur quickly. New insights in the understanding of neonatal cardiovascular physiology are reviewed and several methods for current and future neonatal hemodynamic monitoring are discussed.

Objective cardiovascular assessment in the neonatal intensive care unit

Traditionally, cardiovascular well-being was essentially based on whether the mean blood pressure was above or below a certain value. However, this singular crude method of assessment provides limited insight into overall cardiovascular well-being. Echocardiography has become increasingly used and incorporated into clinical care. New objective modality assessments of cardiovascular status continue to evolve and are being evaluated and incorporated into clinical care. In this review article, we will discuss some of the recent advances in objective assessment of cardiovascular well-being, including the concept of multimodal monitoring. Sophisticated haemodynamic monitoring systems are being developed, including mechanisms of data acquisition and analysis. Their incorporation into clinical care represents an exciting next stage in the management of the infant with cardiovascular compromise.

The role of near-infrared spectroscopy monitoring in preterm infants

Neurological morbidities such as peri/intraventricular hemorrhage and periventricular leukomalacia largely determine the neurodevelopmental outcome of vulnerable preterm infants and our aim should be to minimize their occurrence or severity. Bed-side neuromonitoring could provide valuable pieces of information about possible hemodynamic disturbances that are significantly associated with neurological morbidities and increased mortality. Near-infrared spectroscopy offers evaluation of regional cerebral oxygenation, which in conjunction with other non-invasive methods may give us a more complete picture about end-organ perfusion. This monitoring tool could help us fully understand the pathophysiology of severe neurological morbidities and guide our management in order to reduce their incidence.

How to assess hemodynamic status in very preterm newborns in the first week of life?

BACKGROUND

Assessing hemodynamic status in preterm newborns is an essential task, as many studies have shown increased morbidity when hemodynamic parameters are abnormal. Although oscillometric monitoring of arterial blood pressure (BP) is widely used due to its simplicity and lack of side effects, these values are not always correlated with microcirculation and oxygen delivery.

OBJECTIVES

This review focuses on different tools for the assessment of hemodynamic status in preterm newborns. These include the measurement of clinical (BP, capillary refill time and urinary output (UO)) or biological parameters (lactate analysis), functional echocardiography, and near-infrared spectroscopy (NIRS). We describe the concepts and techniques involved in these tools in detail, and examine the interest and limitations of each type of assessment.

CONCLUSIONS

This review highlights the complementarities between the different parameters used to assess hemodynamic status in preterm newborns during the first week of life. The analysis of arterial BP measured by oscillometric monitoring must take into account other clinical data, in particular capillary refill time and UO, and biological data such as lactate levels. Echocardiography improves noninvasive hemodynamic management in newborns but requires specific training. In contrast, NIRS may be useful in monitoring the clinical course of infants at risk of, or presenting with, hypotension. It holds the potential for early and noninvasive identification of silent hypoperfusion in critically ill preterm infants. However, more data are needed to confirm the usefulness of this promising tool in significantly changing the outcome of these infants.

Recent advances in cerebral oximetry. Assessment of cerebral autoregulation with near-infrared spectroscopy: myth or reality?

In recent years, the feasibility of near-infrared spectroscopy to continuously assess cerebral autoregulation has gained increasing interest. By plotting cerebral oxygen saturation over blood pressure, clinicians can generate an index of autoregulation: the cerebral oximetry index (COx). Successful integration of this monitoring ability in daily critical care may allow clinicians to tailor blood pressure management to the individual patient's need and might prove to be a major step forward in terms of patient outcome.

Investigating the Role of Near-Infrared Spectroscopy in Neonatal Medicine

Near-infrared spectroscopy (NIRS) is a clinical tool that provides a bedside method of noninvasively measuring continuous, "real-time" oxygen consumption and monitoring for potential ischemia of somatic tissues, particularly the brain, kidneys, and intestine in neonates. Although the concept of NIRS seems promising, its implementation into clinical practice has been inconsistent for various reasons, including difficulty in interpreting regional oxygen saturation (rSO2), the wide variation in types of NIRS monitors and probes, the cost of new equipment, different monitoring modalities, large discrepancies in both intra- and interindividual use, a lack of defined universal normative values, and little to no data on outcomes or potentially harmful interventions made based on rSO2 readings. We combine findings from previously published informational articles and studies on the use of NIRS in neonatal medicine to provide a comprehensive overview of this tool and identify potential indications for clinical use.

Monitoring Cerebral Oxygenation in Neonates: An Update

Cerebral oxygenation is not always reflected by systemic arterial oxygenation. Therefore, regional cerebral oxygen saturation (rScO₂) monitoring with near-infrared spectroscopy (NIRS) is of added value in neonatal intensive care. rScO₂ represents oxygen supply to the brain, while cerebral fractional tissue oxygen extraction, which is the ratio between rScO₂ and systemic arterial oxygen saturation, reflects cerebral oxygen utilization. The balance between oxygen supply and utilization provides insight in neonatal cerebral (patho-)physiology. This review highlights the potential and limitations of cerebral oxygenation monitoring with NIRS in the neonatal intensive care unit.

Advanced neuroimaging and its role in predicting neurodevelopmental outcomes in very preterm infants

Up to 35% of very preterm infants survive with neurodevelopmental impairments (NDI) such as cognitive deficits, cerebral palsy, and attention deficit disorder. Advanced MRI quantitative tools such as brain morphometry, diffusion MRI, magnetic resonance spectroscopy, and functional MRI at term-equivalent age are ideally suited to improve current efforts to predict later development of disabilities. This would facilitate application of targeted early intervention therapies during the first few years of life when neuroplasticity is optimal. A systematic search and review identified 47 published studies of advanced MRI to predict NDI. Diffusion MRI and morphometry studies were the most commonly studied modalities. Despite several limitations, studies clearly showed that brain structural and metabolite biomarkers are promising independent predictors of NDI. Large representative multicenter studies are needed to validate these studies.

Identifying stable phase coupling associated with cerebral autoregulation using the synchrosqueezed cross-wavelet transform and low oscillation morlet wavelets

A novel method of identifying stable phase coupling behavior of two signals within the wavelet transform time-frequency plane is presented. The technique employs the cross-wavelet transform to provide a map of phase coupling followed by synchrosqueezing to collect the stable phase regime information. The resulting synchrosqueezed cross-wavelet transform method (Synchro-CrWT) is illustrated using a synthetic signal and then applied to the analysis of the relationship between biosignals used in the analysis of cerebral autoregulation function.

Perioperative use of cerebral and renal near-infrared spectroscopy in neonates: a 24-h observational study

BACKGROUND

Neonates undergoing surgery and intensive care still carry a significant morbidity and mortality often related to hypoxic/ischemic events; some of which may go undetected by conventional monitoring. Near-infrared spectroscopy (NIRS) is a noninvasive, continuous method of measuring regional tissue oxygen saturation, and may be used to supplement conventional monitoring to improve neonatal perioperative care. However, high costs and lack of evidence regarding improved outcomes have minimized wider perinatal use of NIRS. The aim of this study was to investigate the applicability of NIRS in neonates and premature infants undergoing noncardiac surgeries.

METHOD

Neonates were monitored with both cerebral and renal NIRS for 24 h after induction of anesthesia and compared with systemic blood pressure (BP), peripheral oxygen saturation (SpO2 ), and heart rate (HR).

RESULTS

A total of 23 368 min of data were collected from 21 neonates. NIRS reported cerebral/renal hypoxia 2.8 (±8.3)%/19.3 (±25.4)% of the time intraoperatively and 9.6 (±17.0)%/9.9 (±18.9)% of the time postoperatively. A moderate positive correlation was found between SpO2 and NIRS (φcerebral = 0.371, φrenal = 0.542). BP showed a weaker positive correlation (φcerebral = 0.231, φrenal = 0.246), and HR no correlation (φcerebral = -0.083, φrenal = -0.029). NIRS reported hypoxia two to three times more frequently than SpO2 , and SpO2 readings were 10-15 s delayed compared to NIRS. Furthermore, NIRS appeared effective at detecting postoperative apnea.

CONCLUSION

Near-infrared spectroscopy is an easily applicable technique that appears effective at detecting hypoxic events and postoperative apneas in neonates. The high incidences of regional hypoxia reported by NIRS in this study imply that there is a need for a more specific regional cerebral and renal monitoring. Despite some practical and economical limitations, NIRS may be considered a useful supplement to perinatal perioperative intensive care.

Enhanced Monitoring of the Preterm Infant during Stabilization in the Delivery Room

Monitoring of preterm infants in the delivery room (DR) remains limited. Current guidelines suggest that pulse oximetry should be available for all preterm infant deliveries, and that if intubated a colorimetric carbon dioxide detector should provide verification of correct endotracheal tube placement. These two methods of assessment represent the extent of objective monitoring of the newborn commonly performed in the DR. Monitoring non-invasive ventilation effectiveness (either by capnography or respiratory function monitoring) and cerebral oxygenation (near-infrared spectroscopy) is becoming more common within research settings. In this article, we will review the different modalities available for cardiorespiratory and neuromonitoring in the DR and assess the current evidence base on their feasibility, strengths, and limitations during preterm stabilization.

A Review of Wavelet Transform Time-Frequency Methods for NIRS-Based Analysis of Cerebral Autoregulation

Near-infrared spectroscopy (NIRS) has been proposed as a suitable technique for the analysis of cerebral autoregulation as it provides a simpler acquisition methodology and more artifact-free signal. A number of sophisticated wavelet transform methods have recently emerged to quantify the cerebral autoregulation mechanism using NIRS and blood pressure signals. These provide an enhanced partitioning of signal information via the time-frequency plane, which facilitates improved extraction of the components of interest. This area is reviewed, and enhancements to this form of analysis are suggested.