Laura M.L. Dix

Comparing near-infrared spectroscopy devices and their sensors for monitoring regional cerebral oxygen saturation in the neonate

Background:Near-infrared spectroscopy (NIRS) is an upcoming clinical method for monitoring regional cerebral oxygen saturation (rScO2) in neonates. There is a growing market offering different devices and sensors. Even though this technique is increasingly clinically applied, little is known about the similarities and/or differences in rScO2 values between the different devices and sensors. The aim of this study was to compare the rScO2 values obtained in (preterm) neonates with all available sensors of three frequently used NIRS devices.Methods:Fifty-five neonates admitted to our neonatal intensive care unit (NICU) were included in this study. rScO2 was simultaneously monitored bilaterally with two different NIRS sensors (left and right frontoparietal) for at least 1 h. Then, the sensors were switched, and measurements were collected for at least another hour.Results:We detected a rather close correlation between all investigated sensors from the three different NIRS devices, but absolute rScO2 values showed substantial differences: Bland–Altman analysis showed average differences from 10 to 15%.Conclusion:Although the rScO2 values correlated well between different NIRS sensors, sometimes there were substantial differences between the absolute rScO2 values, which may complicate clinical application.

Reference values of regional cerebral oxygen saturation during the first 3 days of life in preterm neonates

Background:Currently, reliable reference values of regional cerebral oxygen saturation (rScO2) for different gestational age (GA) groups are lacking, which hampers the implementation of near-infrared spectroscopy (NIRS) alongside monitoring arterial oxygen saturation (SaO2) and blood pressure in neonatal intensive care. The aim of this study was to provide reference values for rScO2 and cerebral fractional tissue oxygen extraction (cFTOE; (SaO2 − rScO2)/SaO2) for small adult and neonatal NIRS sensors.Methods:In this study, 999 infants born preterm (GA <32 wk) were monitored with NIRS during the first 72 h of life. Mixed modeling was used to generate reference curves grouped per 2 wk of GA. In addition, the influence of a hemodynamically significant patent ductus arteriosus, gender, and birth weight were explored.Results:Average rScO2 was ~65% at admission, increased with GA (1% per week) and followed a parabolic curve in relation to postnatal age with a peak at ~36 h. The cFTOE showed similar but inverse effects. On average, the neonatal sensor measured 10% higher than the adult sensor.Conclusion:rScO2 and cFTOE reference curves are provided for the first 72 h of life in preterm infants, which might support the broader implementation of NIRS in neonatal intensive care.

Cerebral oxygenation and echocardiographic parameters in preterm neonates with a patent ductus arteriosus: an observational study

Background A haemodynamically significant patent ductus arteriosus (hsPDA) is clinically suspected and confirmed by echocardiographic examination. A hsPDA decreases cerebral blood flow and oxygen saturation by the ductal steal phenomenon. Aim To determine the relationship between echocardiographic parameters, cerebral oxygenation and a hsPDA in preterm infants. Methods 380 preterm infants (<32 weeks gestational age) born between 2008 and 2010 were included. Blinded echocardiographic examination was performed on the second, fourth and sixth day after birth. Examinations were deblinded when hsPDA was clinically suspected. Regional cerebral oxygen saturation (rScO2) was continuously monitored by near-infrared spectroscopy during 72 h after birth, and afterwards for at least 1 h before echocardiography. Echocardiographic parameters included ductal diameter, end-diastolic flow in the left pulmonary artery, left atrium/aorta ratio and ductal flow pattern. Results rScO2 was significantly related only to ductal diameter over time. Mixed modelling analysed the course of rScO2 over time, where infants were divided into four groups: a closed duct, an open haemodynamically insignificant duct (non-sPDA), a hsPDA, which was successfully closed during study period (SC hsPDA) or a hsPDA, which was unsuccessfully closed during study period (UC hsPDA). SC hsPDA infants showed the highest rScO2 on day 6, while UC hsPDA infants had the lowest rScO2 values. Conclusions Ductal diameter is the only echocardiographic parameter significantly related to cerebral oxygenation over time. Cerebral oxygenation takes a different course over time depending on the status of the duct. Low cerebral oxygenation may be suggestive of a hsPDA.

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.

Reduction in Cerebral Oxygenation due to Patent Ductus Arteriosus Is Pronounced in Small-for-Gestational-Age Neonates

Background: A haemodynamically significant patent ductus arteriosus (hsPDA) reduces cerebral oxygenation in appropriate-for-gestational-age (AGA) preterm neonates. Reduced cerebral oxygenation has been associated with brain injury. Preterm small-for-gestational-age (SGA) neonates show higher cerebral oxygenation than AGA peers throughout the first postnatal days. To date, no studies have investigated the effect of hsPDA on cerebral oxygenation in preterm SGA neonates. Objective: We aimed to assess the effect of hsPDA on cerebral oxygenation in preterm SGA neonates compared to AGA peers. We hypothesised that higher baseline cerebral oxygenation would reduce the impact of hsPDA on cerebral oxygenation in preterm SGA neonates. Methods: We monitored regional cerebral oxygen saturation (rScO2) with near-infrared spectroscopy and calculated the cerebral fractional tissue oxygen extraction (cFTOE) for 72 h after birth. Retrospective analysis compared 36 preterm SGA neonates (birth weight <10th percentile, 18 with hsPDA) to 36 preterm AGA neonates (birth weight 20th to 80th percentile, 18 with hsPDA). Results: In contrast to the other groups, SGA-hsPDA neonates demonstrated a significant fall in rScO2 [69% (SEM 2.5) at 4-8 h to 61% (2.7) at 68-72 h, p < 0.001] with a concurrent rise in cFTOE [0.26 (0.026) at 4-8 h to 0.34 (0.030) at 68-72 h, p < 0.001]. Conclusions: Contrary to our hypothesis, hsPDA had a significant negative effect on cerebral oxygenation in preterm SGA neonates. Future studies should explore the potential benefits of early screening and treatment for hsPDA on long-term neurodevelopmental outcome in preterm SGA neonates.

Carbon Dioxide Fluctuations Are Associated with Changes in Cerebral Oxygenation and Electrical Activity in Infants Born Preterm

OBJECTIVES To evaluate the effects of acute arterial carbon dioxide partial pressure changes on cerebral oxygenation and electrical activity in infants born preterm. STUDY DESIGN This retrospective observational study included ventilated infants born preterm with acute fluctuations of continuous end-tidal CO2 (etCO2) as a surrogate marker for arterial carbon dioxide partial pressure, during the first 72 hours of life. Regional cerebral oxygen saturation and fractional tissue oxygen extraction were monitored with near-infrared spectroscopy. Brain activity was monitored with 2-channel electroencephalography. Spontaneous activity transients (SATs) rate (SATs/minute) and interval between SATs (in seconds) were calculated. Ten-minute periods were selected for analysis: before, during, and after etCO2 fluctuations of ≥5  mm Hg. RESULTS Thirty-eight patients (mean ± SD gestational age of 29 ± 1.8 weeks) were included, with 60 episodes of etCO2 increase and 70 episodes of etCO2 decrease. During etCO2 increases, brain oxygenation increased (regional cerebral oxygen saturation increased, fractional tissue oxygen extraction decreased; P < .01) and electrical activity decreased (SATs/minute decreased, interval between SATs increased; P < .01). All measures recovered when etCO2 returned to baseline. During etCO2 decreases, brain oxygenation decreased (regional cerebral oxygen saturation decreased, fractional tissue oxygen extraction decreased; P < .01) and brain activity increased (SATs/minute increased, P < .05), also with recovery after return of etCO2 to baseline. CONCLUSION An acute increase in etCO2 is associated with increased cerebral oxygenation and decreased brain activity, whereas an acute decrease is associated with decreased cerebral oxygenation and slightly increased brain activity. Combining continuous CO2 monitoring with near-infrared spectroscopy may enable the detection of otherwise undetected fluctuations in arterial carbon dioxide partial pressure that may be harmful to the neonatal brain.

Severe hypercapnia causes reversible depression of aEEG background activity in neonates: an observational study.

Introduction Elevated carbon dioxide (CO2) blood levels have a depressant effect on the central nervous system and can lead to coma in adults. Less is known about the effect of CO2 on the neurological function of infants. Objective To describe the effect of acute severe hypercapnia (PaCO2 >70 mm Hg) on amplitude-integrated electroencephalography (aEEG) and cerebral oxygenation in newborn infants. Study design Observational study of full-term and preterm infants with acute severe hypercapnia (identified by arterial blood gas measurements), monitored with aEEG. Visual analysis of the aEEG was performed in all infants. In preterm infants <32 weeks postmenstrual age (PMA), analysis of two-channel EEG was performed. Mean spontaneous activity transients (SAT) rate (SATs/min), interval between SATs (ISI in seconds) and the ISI percentage (ISP) were calculated for 10-min periods before, during and after hypercapnia. Mean regional cerebral oxygen saturation (rScO2) and fractional tissue oxygen extraction (FTOE) measured with near-infrared spectroscopy were also calculated for these periods. Results Twenty-five infants (21 preterm, 4 full-term) comprising 32 episodes of acute severe hypercapnia were identified. Twenty-seven episodes were accompanied by a transient aEEG depression. Twenty-two episodes in 15 preterm infants <32 weeks PMA were quantitatively analysed. During hypercapnia, SAT rate decreased and ISI and ISP increased significantly. No significant change occurred in rScO2 or FTOE during hypercapnia. Conclusion Profound depression of brain activity due to severe hypercapnia is also seen in infants. It can be recognised by an acute depression of the aEEG, without clinically detectable changes in cerebral oxygenation.

Comparing Different NIRS Devices and their Sensors for Monitoring Regional Cerebral Oxygen Saturation in Neonates

Background and aim: Near-infrared spectroscopy (NIRS)-monitored regional cerebral oxygen saturation (rScO2) in neonates has been increasingly used to assess cerebral oxygen delivery and extraction. Consequently neonatal sensors were designed with their own algoritms to separate the signals of oxy- and deoxyhemoglobin. However,published reference values are mostly based on studies using adult (conventional) sensors with different algoritms.To compare rScO2 values between the conventional NIRS-sensors of 3 different brands and those especially designed for use on the neonatal head.Methods: 56 neonates admitted to our NICU were included. rScO2‘s were measured left and right fronto-parietally with a conventional and neonatal sensor on each side for at least one hour.Then the sensors were switched to the opposite side and measurements were continued for at least another hour.Results: We found a significant correlation between conventional and neonatal sensors (p< 0.01-p< 0.001). However, Bland-Altman analysis showed a consistent difference between sensors from 8-to-13%, showing higher values obtained with the neonatal sensors.Conclusions: Although a good correlation between conventional and neonatal NIRS sensors was detected, reference values should be re-established when using newly designed neonatal sensors.Moreover rScO2 values in the higher range measured with neonatal sensors appeared to be less reliable which may be a problem in case of hyperoxia, which is in particular a problem in the extremely preterm neonate whose brain is prone for hyperoxic-induced brain damage.

Effects of caffeine on the preterm brain: An observational study

BACKGROUND AND AIM Caffeine improves neurodevelopmental outcome of preterm infants. This study analyses the effects of caffeine on the neonatal brain. We hypothesized that caffeine has a neuroprotective effect through an increase in oxygen metabolism; reflected by increased cerebral oxygen extraction, electrical function, and perfusion. METHODS Preterm infants <32 weeks gestation (GA) receiving their primary dose caffeine-base (10 mg/kg) were included. Ten minutes of stable monitoring were selected before, during, and every hour up to 6 h after caffeine. Near-infrared spectroscopy monitored regional cerebral oxygenation (rScO2) and extraction (FTOE). Amplitude-integrated electroencephalogram (aEEG) monitored minimum, mean and maximum amplitudes. Spontaneous activity transients (SAT) rate and the interval between SATs (ISI) were calculated. Mean arterial blood pressure (MABP), heart rate (HR) and arterial oxygen saturation (SaO2) were monitored. Arterial pCO2s were collected before and 4 h after caffeine. Brain perfusion was assessed 1 h before and 3 h after caffeine by Doppler-measured resistance-index (RI), peak systolic velocity (PSV) and end-diastolic velocity (EDV), in the anterior cerebral artery (ACA) and internal carotid artery (ICA). Results were presented in mean ± SD. RESULTS 34 infants, mean GA 28.8 ± 2.1 wk, were included. rScO2 significantly decreased from 69 ± 11 to 63 ± 12 1 h after caffeine, and recovered at 6 h (66 ± 10). FTOE increased correspondingly. MABP and HR increased significantly. PSV in the ACA decreased slightly. Other Doppler variables, aEEG parameters, and SaO2 were unaffected. CONCLUSION Caffeine increases oxygen extraction, suggesting a (transient) stimulating effect on brain metabolism. However, no substantial changes were found in brain perfusion and in electrical brain activity.