Noninvasive continuous monitoring of the effects of head position on brain hemodynamics in ventilated infants

Predicting severe intraventricular hemorrhage or early death using machine learning algorithms in VLBWI of the Korean Neonatal Network Database

Severe intraventricular hemorrhage (IVH) in premature infants can lead to serious neurological complications. This retrospective cohort study used the Korean Neonatal Network (KNN) dataset to develop prediction models for severe IVH or early death in very-low-birth-weight infants (VLBWIs) using machine-learning algorithms. The study included VLBWIs registered in the KNN database. The outcome was the diagnosis of IVH Grades 3-4 or death within one week of birth. Predictors were categorized into three groups based on their observed stage during the perinatal period. The dataset was divided into derivation and validation sets at an 8:2 ratio. Models were built using Logistic Regression with Ridge Regulation (LR), Random Forest, and eXtreme Gradient Boosting (XGB). Stage 1 models, based on predictors observed before birth, exhibited similar performance. Stage 2 models, based on predictors observed up to one hour after birth, showed improved performance in all models compared to Stage 1 models. Stage 3 models, based on predictors observed up to one week after birth, showed the best performance, particularly in the XGB model. Its integration into treatment and management protocols can potentially reduce the incidence of permanent brain injury caused by IVH during the early stages of birth.

Precision and normal values of cerebral blood volume in preterm neonates using time-resolved near-infrared spectroscopy

AIM

To investigate cerebral blood volume (CBV) in preterm neonates using time-resolved near-infrared spectroscopy.

METHODS

In this prospective observational study, time-resolved near-infrared spectroscopy measurements of CBV using tNIRS-1 were performed in 70 preterm neonates. For measurements, a sensor was placed for a duration of 1 min, followed by four further reapplications of the sensor, overall five measurements.

RESULTS

In this study, 70 preterm neonates with a mean ± SD gestational age of 33.4 ± 1.7 weeks and a birthweight of 1931 ± 398 g were included with a postnatal age of 4.7 ± 2.0 days. Altogether, 2383 CBV values were obtained with an overall mean of 1.85 ± 0.30 mL/100 g brain. A total of 95% of the measured CBV values varied in a range from -0.31 to 0.33 from the overall individual mean. Taking the deviation of the mean of each single application for each patient, this range reduced from -0.07 to 0.07. The precision of the measurement defined as within-variation in CBV was 0.24 mL/100 g brain.

CONCLUSION

The overall mean CBV in stable preterm neonates was 1.85 ± 0.30 mL/100 g brain. The within-variation in CBV was 0.24 mL/100 g brain. Based on the precision obtained by our data, CBV of 1.85 ± 0.30 mL/100 g brain may be assumed as normal value for this cohort.

Cerebral oxygenation and body position in the preterm infant: A systematic review and meta-analysis

AIM

After preterm birth, supine head midline position is supported for stable cerebral blood flow (CBF) and prevention of intraventricular haemorrhage (IVH), while prone position supports respiratory function and enables skin-to-skin care. The prone compared to supine position could lead to a change in near-infrared derived cerebral tissue oxygen saturation (rScO2), which is a surrogate for cerebral blood flow (CBF). By monitoring rScO2 neonatologists aim to stabilise CBF during intensive care and prevent brain injury. In this systematic review and meta-analysis, we investigate the effect of the body position on rScO2.

METHODS

A comprehensive literature search was performed to identify all trials that included preterm infants in the first 2 weeks after birth and compared rScO2 in the prone versus supine head in midline position of the infant. A meta-analysis, including two subgroup analyses based on postnatal age (PNA) and gestational age (GA), was performed.

RESULTS

Six observational cohort studies were included. In the second, but not the first week after birth, a significant higher rScO2 in the prone position was found with a mean difference of 1.97% (95% CI 0.87-3.07). No rScO2 difference was observed between positions in the extremely preterm nor the preterm group.

CONCLUSION

No consistent evidence was found that body position influences rScO2 in the first 2 weeks after preterm birth. Subgroup analysis suggests that in the second week after birth, the prone position might result in higher cerebral rScO2 than the supine position with head in midline. Multiple factors determine the best body position in preterms.

Effectiveness of a care bundle for primary prevention of intraventricular hemorrhage in high-risk neonates: a Bayesian analysis

OBJECTIVE

To determine whether an intraventricular hemorrhage (IVH) prevention bundle featuring midline-elevated positioning reduced IVH among high-risk infants.

STUDY DESIGN

In a retrospective study design, we compared outcomes of infants <1250 grams birth weight or <30 weeks gestation before (N = 205) and after (N = 360) implementation of an IVH prevention bundle, using Bayesian and frequentist logistic regression to determine whether the intervention decreased any grade IVH.

RESULTS

In both the Bayesian and frequentist analyses, there was no difference in odds of any grade IVH before and after the implementation of the prevention bundle (OR 0.993; 95% Credible Interval 0.751-1.323 and OR 1.23; 95% Confidence Interval 0.818-1.864 respectively). Bias analyses suggested that these results were robust to bias from potential deaths attributable to IVH.

CONCLUSION

In this retrospective analysis, we found no evidence for a protective effect of an IVH prevention bundle on IVH incidence among high-risk neonates at a level IV NICU.

Neuroprotection care bundle implementation is associated with improved long-term neurodevelopmental outcomes in extremely premature infants

OBJECTIVE

To study the impact of an evidence-based neuroprotection care (NPC) bundle on long-term neurodevelopmental impairment (NDI) in infants born extremely premature.

STUDY DESIGN

An NPC bundle targeting predefined risk factors for acute brain injury in extremely preterm infants was implemented. We compared the incidence of composite outcome of death or severe neurodevelopmental impairment (sNDI) at 21 months adjusted age pre and post bundle implementation.

RESULTS

Adjusting for confounding factors, NPC bundle implementation associated with a significant reduction in death or sNDI (aOR, 0.34; 95% CI 0.17-0.68; P = 0.002), mortality (aOR, 0.31; 95% CI (0.12-0.79); P = 0.015), sNDI (aOR, 0.37; 95% CI: 0.12-0.94; P = 0.039), any motor, language, or cognitive composite score &lt;70 (aOR, 0.48; 95% CI: 0.26-0.90; P = 0.021).

CONCLUSION

Implementation of NPC bundle targeting predefined risk factors is associated with a reduction in mortality or sNDI in extremely preterm infants.

Prevention of severe brain injury in very preterm neonates: A quality improvement initiative

OBJECTIVE

To determine the impact of neuroprotection interventions bundle on the incidence of severe brain injury or early death (intraventricular hemorrhage grade 3/4 or death by 7 days or ventriculomegaly or cystic periventricular leukomalacia on 1-month head ultrasound, primary composite outcome) in very preterm (27^0/7 to ≤ 29^6/7 weeks gestational age) infants.

STUDY DESIGN

Prospective quality improvement initiative, from April 2017-September 2019, with neuroprotection interventions bundle including cerebral NIRS, TcCO₂, and HeRO monitoring-based management algorithm, indomethacin prophylaxis, protocolized bicarbonate and inotropes use, noise reduction, and neutral positioning.

RESULT

There was a decrease in the incidence of the primary composite outcome in the intervention period on unadjusted (N = 11/99, pre-intervention to N = 0/127, intervention period, p < 0.001) and adjusted analysis (adjusted for birthweight and Apgar score <5 at 5 min, aOR = 0.042, 95% CI = 0.003-0.670, p = 0.024).

CONCLUSIONS

Neuroprotection interventions bundle was associated with significant decrease in severe brain injury or early death in very preterm infants.

Impact of quality improvement outreach education on the incidence of acute brain injury in transported neonates born premature

OBJECTIVE

To evaluate impact of a quality improvement (QI) outreach education on incidence of acute brain injury in transported premature neonates.

STUDY DESIGN

Neonates born at &lt;33 weeks gestation outside the tertiary center were included. The QI intervention was a combination of neuroprotection care bundle, in-person visits, and communication system improvement. Descriptive and regression (adjusting for Gestational Age, Birth Weight, Gender, and antenatal steroids, Mode of delivery, Apgars at 5 minutes, Prophylactic indomethacin, PDA, and Inotropes use) analyses were performed. The primary outcome was a composite of death and/or severe brain injury on cranial ultrasound using a validated classification.

RESULTS

181 neonates studied (93 before and 88 after). The rate and adjusted odds of death and/or severe brain injury reduced significantly post intervention (30% vs 15%) and (AOR 0.36, 95%CI, 0.15-0.85, P = 0.02) respectively.

CONCLUSION

Implementation of outreach education targeting neuroprotection can reduce acute brain injury in transported premature neonates.

Association of Cerebrovascular Stability Index and Head Circumference Between Infants With and Without Congenital Heart Disease

Congenital heart disease (CHD) is a common birth defect in the United States. CHD infants are more likely to have smaller head circumference and neurodevelopmental delays; however, the cause is unknown. Altered cerebrovascular hemodynamics may contribute to neurologic abnormalities, such as smaller head circumference, thus we created a novel Cerebrovascular Stability Index (CSI), as a surrogate for cerebral autoregulation. We hypothesized that CHD infants would have an association between CSI and head circumference. We performed a prospective, longitudinal study in CHD infants and healthy controls. We measured CSI and head circumference at 4 time points (newborn, 3, 6, 9 months). We calculated CSI by subtracting the average 2-min sitting from supine cerebral oxygenation (rcSO₂) over three consecutive tilts (0-90°), then averaged the change score for each age. Linear regressions quantified the relationship between CSI and head circumference. We performed 177 assessments in total (80 healthy controls, 97 CHD infants). The average head circumference was smaller in CHD infants (39.2 cm) compared to healthy controls (41.6 cm) (p < 0.001) and head circumference increased by 0.27 cm as CSI improved in the sample (p = 0.04) overall when combining all time points. Similarly, head circumference increased by 0.32 cm as CSI improved among CHD infants (p = 0.04). We found CSI significantly associated with head circumference in our sample overall and CHD infants alone, which suggests that impaired CSI may affect brain size in CHD infants. Future studies are needed to better understand the mechanism of interaction between CSI and brain growth.

Regional oxygenation, perfusion and body and/or head position: Are preterm infants adversely impacted? A systematic review

This review addresses regional oxygenation and perfusion changes for preterm infants and changes with body position, with or without head rotation. Future directions for improving neurodevelopmental and clinical outcomes are suggested. The MEDLINE, Embase and Scopus databases were searched up to July 2021. Fifteen out of 470 studies met the inclusion criteria. All were prospective, observational studies with a moderate risk of bias. Significant variation was found for the baseline characteristics of the cohort, postnatal ages, and respiratory support status at the time of monitoring. When placed in a non-supine position, preterm infants showed a transient reduction in cardiac output and stroke volume without changes to heart rate or blood pressure. No studies reported on long-term neurodevelopmental outcomes. Overall, side lying or prone position does not appear to adversely affect regional, and specifically cerebral, oxygenation or cerebral perfusion. The effect of head rotation on regional oxygenation and perfusion remains unclear.

A Quality Improvement Bundle to Improve Outcomes in Extremely Preterm Infants in the First Week

OBJECTIVES

Our objective with this quality improvement initiative was to reduce rates of severe intracranial hemorrhage (ICH) or death in the first week after birth among extremely preterm infants.

METHODS

The quality improvement initiative was conducted from April 2014 to September 2020 at the University of Alabama at Birmingham's NICU. All actively treated inborn extremely preterm infants without congenital anomalies from 22 + 0/7 to 27 + 6/7 weeks' gestation with a birth weight ≥400 g were included. The primary outcome was severe ICH or death in the first 7 days after birth. Balancing measures included rates of acute kidney injury and spontaneous intestinal perforation. Outcome and process measure data were analyzed by using p-charts.

RESULTS

We studied 820 infants with a mean gestational age of 25 + 3/7 weeks and median birth weight of 744 g. The rate of severe ICH or death in the first week after birth decreased from the baseline rate of 27.4% to 15.0%. The rate of severe ICH decreased from a baseline rate of 16.4% to 10.0%. Special cause variation in the rate of severe ICH or death in the first week after birth was observed corresponding with improvement in carbon dioxide and pH targeting, compliance with delayed cord clamping, and expanded use of indomethacin prophylaxis.

CONCLUSIONS

Implementation of a bundle of evidence-based potentially better practices by using specific electronic order sets was associated with a lower rate of severe ICH or death in the first week among extremely preterm infants.

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.

Evaluation of the suitability and clinical applicability of different electrodes for aEEG/cEEG monitoring in the extremely premature infant

INTRODUCTION

Monitoring of brain function using continuous electroencephalography (aEEG/cEEG) is an essential tool in the standard care of the term infant, and its use is growing in the premature infant as a biomarker of lesion and brain maturity. However, the placing of the electrodes is a great challenge, particularly in the extremely premature infant, which often discourages neuromonitoring. The aim of this study is to assess the different electrodes available, to select the one that best suits the peculiarities of the extremely premature infant, and evaluate its applicability in clinical practice.

POPULATION AND METHODS

With the aim of designing a neuromonitoring study protocol using aEEG/cEEG in <28 weeks premature infants, an analysis was made of our experience with the type of electrodes available. The electrode that was considered most suitable for this population was chosen by assessing: the need of preparing the scalp, speed in positioning the electrodes, if the application was invasive or not, the possibility of repositioning, risk of skin injuries, sterility of the technique, and durability. The electrode chosen was used for continuous electroencephalographic monitoring started in the first 24 h of life, and maintained until at least 72 h of life.

RESULTS

The electrodes evaluated were: subdermal needles, silver cups, and 2 types of self-adhesive electrodes (solid hydrogel and wet gel). The wet gel electrodes were chosen. They were used on 41 neonates with a mean gestational age of 25.8 ± 1.1 weeks. Good stable impedance was rapidly obtained, without the need of excessive manipulations, and no skin injuries were observed. The satisfaction of the staff involved in positioning them was very high.

CONCLUSION

The self-adhesive disposable electrodes with wet gel and integrated cable enabled the electrodes to be positioned rapidly and provided continuous non-invasive and good quality aEEG/cEEG monitoring in the extremely premature infant.

Evaluating the Effect of a Neonatal Care Bundle for the Prevention of Intraventricular Hemorrhage in Preterm Infants

Germinal matrix intraventricular hemorrhage (IVH) remains a severe and common complication in preterm infants. A neonatal care bundle (NCB) was implemented as an in-house guideline at a tertiary neonatal intensive care unit to reduce the incidence of IVH in preterm infants. The NCB was applied either to preterm infants <1250 g birth weight or <30 weeks gestational age or both, and standardized patient positioning, nursing care, and medical procedures within the first week of life. A retrospective cohort study was performed to investigate the effect of the NCB and other known risk factors on the occurrence and severity of IVH. Data from 229 preterm infants were analyzed. The rate of IVH was 26.2% before and 27.1% after implementing the NCB. The NCB was associated neither with reducing the overall rate of IVH (odds ratio (OR) 1.02; 95% confidence interval (CI) 0.57–1.84; p = 0.94) nor with severe IVH (OR 1.0; 95% CI 0.67–1.55; p = 0.92). After adjustment for group differences and other influencing factors, amnion infection syndrome and early intubation were associated with an increased risk for IVH. An NCB focusing on patient positioning, nursing care, and medical interventions had no impact on IVH in preterm infants. Known risk factors for IVH were confirmed.

Germinal Matrix-Intraventricular Hemorrhage: A Tale of Preterm Infants

Germinal matrix-intraventricular hemorrhage (GM-IVH) is a common intracranial complication in preterm infants, especially those born before 32 weeks of gestation and very-low-birth-weight infants. Hemorrhage originates in the fragile capillary network of the subependymal germinal matrix of the developing brain and may disrupt the ependymal lining and progress into the lateral cerebral ventricle. GM-IVH is associated with increased mortality and abnormal neurodevelopmental outcomes such as posthemorrhagic hydrocephalus, cerebral palsy, epilepsy, severe cognitive impairment, and visual and hearing impairment. Most affected neonates are asymptomatic, and thus, diagnosis is usually made using real-time transfontanellar ultrasound. The present review provides a synopsis of the pathogenesis, grading, incidence, risk factors, and diagnosis of GM-IVH in preterm neonates. We explore brief literature related to outcomes, management interventions, and pharmacological and nonpharmacological prevention strategies for GM-IVH and posthemorrhagic hydrocephalus.

Elevated supine midline head position for prevention of intraventricular hemorrhage in VLBW and ELBW infants: a retrospective multicenter study

OBJECTIVE

To evaluate the impact of elevated supine midline head position on intraventricular hemorrhage (IVH) in very-low-birth-weight (VLBW) infants.

STUDY DESIGN

We reviewed data from four Level III/IV units. Two of these units (mid-line group) cared for infants in midline position and the other two (routine care group) provided routine care. We compared incidence of any and severe IVH in two groups using multivariate logistic regression analyses.

RESULTS

Of 2201 VLBW infants, 1041 were extremely-low-birth-weight (ELBW). Odds of any IVH were not different either for VLBW or ELBW infants. Odds of severe IVH were higher for VLBW infants in mid-line group (OR 1.43, 95% CI 1.007-2.02; p value 0.046) but not for ELBW infants (OR 0.9, 95% CI 0.6-1.4; p value 0.73).

CONCLUSIONS

The incidence of any IVH was similar in the two groups but the incidence of severe IVH was higher in VLBW infants in mid-line group.

The Use of Near-Infrared Spectroscopy (NIRS) to Measure Cerebral Oxygen Saturation During Body Position Changes on Infants Less than One Year Old

OBJECTIVE

To describe the state of the literature for near-infrared spectroscopy (NIRS) to measure cerebral oxygen saturation during body position changes on infants <1 year old.

INTRODUCTION

Although regional cerebral oxygen saturation is commonly used in critically ill populations, it is not usual practice to tailor care based on differences in the cerebral oxygen saturation during measurements in different body positions. We believe that alterations in cerebral oxygen saturation during position changes can also inform clinicians regarding brain health, such as the regulation of brain blood flow.

INCLUSION CRITERIA

We included studies in infants <1 year old; who had cerebral oxygen saturation measured in varying positions (e.g. supine versus side-lying).

METHODS

On March 30, 2019, we searched Medline, Embase, Cochrane CENTRAL, CINAHL, and Web of Science for studies written in English with no restriction on publication dates. We selected studies that involved infants <1 year old and measured cerebral oxygen saturation during varying body positions.

RESULTS

We found 24 primary studies on 694 infants. The authors investigated whether brain oxygen saturation was influenced by body position. A majority of the studies found a statistically significant difference between cerebral oxygen saturation in various body positions.

CONCLUSIONS

More research needs to be performed on variations in brain oxygen saturation during body position changes and the correlation with outcomes. Knowledge of brain oxygen saturation can provide clinicians an understanding of the infant's brain health. Healthcare providers may adapt care specifically to improve brain health with NIRS-based brain oxygen saturation monitoring.

[Evaluation of the suitability and clinical applicability of different electrodes for aEEG/cEEG monitoring in the extremely premature infant]

INTRODUCTION

Monitoring of brain function using continuous electroencephalography (aEEG/cEEG) is an essential tool in the standard care of the term infant, and its use is growing in the premature infant as a biomarker of lesion and brain maturity. However, the placing of the electrodes is a great challenge, particularly in the extremely premature infant, which often discourages neuromonitoring. The aim of this study is to assess the different electrodes available, to select the one that best suits the peculiarities of the extremely premature infant, and evaluate its applicability in clinical practice.

POPULATION AND METHODS

With the aim of designing a neuromonitoring study protocol using aEEG/cEEG in<28 weeks premature infants, an analysis was made of our experience with the type of electrodes available. The electrode that was considered most suitable for this population was chosen by assessing: the need of preparing the scalp, speed in positioning the electrodes, if the application was invasive or not, the possibility of repositioning, risk of skin injuries, sterility of the technique, and durability. The electrode chosen was used for continuous electroencephalographic monitoring started in the first 24h of life, and maintained until at least 72h of life.

RESULTS

The electrodes evaluated were: subdermal needles, silver cups, and 2 types of self-adhesive electrodes (solid hydrogel and wet gel). The wet gel electrodes were chosen. They were used on 41 neonates with a mean gestational age of 25.8±1.1 weeks. Good stable impedance was rapidly obtained, without the need of excessive manipulations, and no skin injuries were observed. The satisfaction of the staff involved in positioning them was very high.

CONCLUSION

The self-adhesive disposable electrodes with wet gel and integrated cable enabled the electrodes to be positioned rapidly and provided continuous non-invasive and good quality aEEG/cEEG monitoring in the extremely premature infant.

Head midline position for preventing the occurrence or extension of germinal matrix-intraventricular haemorrhage in preterm infants

BACKGROUND

Head position during care may affect cerebral haemodynamics and contribute to the development of germinal matrix-intraventricular haemorrhage (GM-IVH) in very preterm infants. Turning the head toward one side may occlude jugular venous drainage while increasing intracranial pressure and cerebral blood volume. It is suggested that cerebral venous pressure is reduced and hydrostatic brain drainage improved if the infant is cared for in the supine 'head midline' position.

OBJECTIVES

To assess whether head midline position is more effective than other head positions for preventing (or preventing extension) of GM-IVH in very preterm infants (< 32 weeks' gestation at birth).

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 9), MEDLINE via PubMed (1966 to 12 September 2019), Embase (1980 to 12 September 2019), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 12 September 2019). We searched clinical trials databases, conference proceedings, and reference lists of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing caring for very preterm infants in a supine head midline position versus a prone or lateral decubitus position, or undertaking a strategy of regular position change, or having no prespecified position. We included trials enrolling infants with existing GM-IVH and planned to assess extension of haemorrhage in a subgroup of infants. We planned to analyse horizontal (flat) versus head elevated positions separately for all body positions.

DATA COLLECTION AND ANALYSIS

We used standard methods of Cochrane Neonatal. For each of the included trials, two review authors independently extracted data and assessed risk of bias. The primary outcomes were GM-IVH, severe IVH, and neonatal death. We evaluated treatment effects using a fixed-effect model with risk ratio (RR) for categorical data; and mean, standard deviation (SD), and mean difference (MD) for continuous data. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

Three RCTs, with a total of 290 infants (either < 30 weeks' gestational age or < 1000 g body weight), met the inclusion criteria. Two trials compared supine midline head position versus head rotated 90° with the cot flat. One trial compared supine midline head position versus head rotated 90° with the bed tilted at 30°. We found no trials that compared supine versus prone midline head position. Meta-analysis of three trials (290 infants) did not show an effect on rates of GM-IVH (RR 1.11, 95% confidence interval (CI) 0.78 to 1.56; I² = 0%) and severe IVH (RR 0.71, 95% CI 0.37 to 1.33; I² = 0%). Neonatal mortality (RR 0.49, 95% CI 0.25 to 0.93; I² = 0%; RD -0.09, 95% CI -0.16 to -0.01) and mortality until hospital discharge (typical RR 0.50, 95% CI 0.28 to 0.90; I² = 0%; RD -0.10, 95% CI -0.18 to -0.02) were lower in the supine midline head position. The certainty of the evidence was very low for all outcomes because of limitations in study design and imprecision of estimates. We identified one ongoing study.

AUTHORS' CONCLUSIONS

We found few trial data on the effects of head midline position on GM-IVH in very preterm infants. Although meta-analyses suggest that mortality might be reduced, the certainty of the evidence is very low and it is unclear whether any effect is due to cot tilting (a co-intervention in one trial). Further high-quality RCTs would be needed to resolve this uncertainty.

Neonatal care bundles are associated with a reduction in the incidence of intraventricular haemorrhage in preterm infants: a multicentre cohort study

OBJECTIVE

To investigate the effect of a nursing intervention bundle, applied during the first 72 hours of life, on the incidence of germinal matrix-intraventricular haemorrhage (GMH-IVH) in very preterm infants.

DESIGN

Multicentre cohort study.

SETTING

Two Dutch tertiary neonatal intensive care units.

PATIENTS

The intervention group consisted of 281 neonates, whereas 280 infants served as historical controls (gestational age for both groups <30 weeks).

INTERVENTIONS

After a training period, the nursing intervention bundle was implemented and applied during the first 72 hours after birth. The bundle consisted of maintaining the head in the midline, tilting the head of the incubator and avoidance of flushing/rapid withdrawal of blood and sudden elevation of the legs.

MAIN OUTCOME MEASURES

The incidence of GMH-IVH occurring and/or increasing after the first ultrasound (but within 72 hours), cystic periventricular leukomalacia and/or in-hospital death was the primary composite outcome measure. Logistic regression analysis was used to explore differences between groups.

RESULTS

The nursing intervention bundle was associated with a lower risk of developing a GMH-IVH (any degree), cystic periventricular leukomalacia and/or mortality (adjusted OR 0.42, 95% CI 0.27 to 0.65). In the group receiving the bundle, also severe GMH-IVH, cystic periventricular leukomalacia and/or death were less often observed (adjusted OR 0.54, 95% CI 0.33 to 0.91).

CONCLUSIONS

The application of a bundle of nursing interventions is associated with reduced risk of developing a new/progressive (severe) GMH-IVH, cystic periventricular leukomalacia and/or mortality in very preterm infants when applied during the first 72 hours postnatally.

Effect of neck extension on ultrasonographic optic nerve sheath diameter as a surrogate for intracranial pressure in patients undergoing palatoplasty: A prospective observational study

Palatoplasty is performed with neck extension in patients with a cleft palate. The neck extension required for a better surgical view during palatoplasty can affect intracranial pressure. We evaluated the effect of neck extension on intracranial pressure by measuring the optic nerve sheath diameter using ultrasonography during palatoplasty. The optic nerve sheath diameter was measured in 30 patients at 10 min after anesthetic induction in the supine position (T1), at 10 min after neck extension before preparing for a sterile field (T2), at the end of surgery with neck extension (T3), and at 10 min after the supine position (T4). Hemodynamic and respiratory variables such as systolic blood pressure, heart rate, end-tidal carbon dioxide partial pressure, and peak airway pressure were also measured at the same time points. In comparison with the optic nerve sheath diameter measured at 10 min after anesthetic induction in the supine position (T1), the mean optic nerve sheath diameters were significantly increased at 10 min after neck extension before preparing for a sterile field (T2), at the end of surgery with neck extension (T3), and at 10 min after the supine position (T4; 4.19 ± 0.26, 5.20 ± 0.29, 4.38 ± 0.36, and 4.35 ± 0.30 mm, respectively). However, hemodynamic and respiratory variables were not significantly different at all time points. We found that the optic nerve sheath diameter, an indicator of intracranial pressure, was increased during palatoplasty with neck extension, which suggests that the position may affect the intracranial pressure of patients with a cleft palate.

Neuroprotection from acute brain injury in preterm infants

Infants born at ≤32+6 weeks gestation are at higher risk for intracranial ischemic and hemorrhagic injuries, which often occur in the first 72 hours postbirth. Antenatal strategies to reduce the incidence of acute brain injuries include administering maternal corticosteroids and prompt antibiotic treatment for chorioamnionitis. Perinatal strategies include delivery within a tertiary centre, delayed cord clamping, and preventing hypothermia. Postnatal strategies include empiric treatment with antibiotics when chorioamnionitis is suspected, the cautious use of inotropes, the avoidance of blood PCO2 fluctuation, and neutral head positioning. Clinicians should be aware of the policies and procedures that, especially when combined, can provide neuroprotection for preterm infants.

Elevated midline head positioning of extremely low birth weight infants: effects on cardiopulmonary function and the incidence of periventricular-intraventricular hemorrhage

OBJECTIVE

Changes in cerebrovascular hemodynamics associated with head position may be important in the pathogenesis of periventricular-intraventricular hemorrhage (PIVH) in premature infants. This study evaluated the effect of elevated midline head positioning on cardiopulmonary function and the incidence of PIVH.

STUDY DESIGN

ELBW infants were randomized to FLAT (flat, supine) or ELEV (supine, bed elevated 30 degrees) for 96 h. Cardiopulmonary function, complications of prematurity, and the occurrence of PIVH were documented.

RESULTS

Infants were randomized into FLAT (n = 90) and ELEV groups (n = 90). No significant differences were seen in the incidence of BPD or other respiratory complications. The ELEV group developed significantly fewer grade 4 hemorrhages (p = 0.036) and survival to discharge was significantly higher in the ELEV group (p = 0.037).

CONCLUSIONS

Managing ELBW infants in an elevated midline head position for the first 4 days of life appears safe and may decrease the likelihood of severe PIVH and improve survival.

Head midline position for preventing the occurrence or extension of germinal matrix-intraventricular hemorrhage in preterm infants

BACKGROUND

Preterm birth is known to constitute the major risk factor for development of germinal matrix-intraventricular hemorrhage (GM-IVH). Head position may affect cerebral hemodynamics and thus may be involved indirectly in development of GM-IVH. Turning the head toward one side may functionally occlude jugular venous drainage on the ipsilateral side while increasing intracranial pressure and cerebral blood volume. Thus, it has been suggested that cerebral venous pressure is reduced and hydrostatic brain drainage improved if the patient is in supine midline position with the bed tilted 30°. The midline position might be achieved in the supine position and, with the use of physical aids, in the lateral position as well. Midline position should be kept, at least when the incidence of GM-IVH is greatest, that is, during the first two to three days of life.

OBJECTIVES

Primary objective To assess whether head midline position is more effective than any other head position for preventing or extending germinal matrix-intraventricular hemorrhage in infants born at ≤ 32 weeks' gestational age. Secondary objectives To perform subgroup analyses regarding gestational age, birth weight, intubated versus not intubated, and with or without GM-IVH at trial entry.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 8), MEDLINE via PubMed (1966 to September 19, 2016), Embase (1980 to September 19,.2016), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to September 19, 2016). We searched clinical trials databases, conference proceedings, and reference lists of retrieved articles for randomized controlled trials and quasi-randomized trials.

SELECTION CRITERIA

Randomized clinical controlled trials, quasi-randomized trials, and cluster-randomized controlled trials comparing placing very preterm infants in a head midline position versus placing them in a prone or lateral decubitus position, or undertaking a strategy of regular position change, or having no prespecified position. We included trials enrolling infants with existing GM-IVH and planned to assess extension of hemorrhage in a subgroup of infants. We planned to analyze horizontal (flat) versus head elevated positions separately for all body positions.

DATA COLLECTION AND ANALYSIS

We used standard methods of the Cochrane Neonatal Review Group. For each of the included trials, two review authors independently extracted data (e.g., number of participants, birth weight, gestational age, initiation and duration of head midline position, co-intervention with horizontal vs head elevated position, use of physical aids to maintain head position) and assessed risk of bias (e.g., adequacy of randomization, blinding, completeness of follow-up). The primary outcomes considered in this review are GM-IVH , severe IVH, and neonatal death.

MAIN RESULTS

Our search strategy yielded 2696 references. Two review authors independently assessed all references for inclusion. Two randomized controlled trials, for a total of 110 infants, met the inclusion criteria of this review. Both trials compared supine midline head position with the bed at 0° versus supine head rotated 90° with the bed at 0°. We found no trials that compared supine versus prone midline head position, and no trials that compared effects of head tilting. We found no significant differences in rates of GM-IVH (typical risk ratio [RR] 1.14, 95% confidence interval [CI] 0.55 to 2.35; typical risk difference [RD] 0.03, 95% CI -0.13 to 0.18; two studies, 110 infants; I² = 0% for RR and I² = 0% for RD), severe IVH (typical RR 1.57, 95% CI 0.28 to 8.98; typical RD 0.02, 95% CI -0.06 to 0.10; two studies, 110 infants; I² = 0% for RR and I² = 0% for RD), and neonatal mortality (typical RR 0.52, 95% CI 0.16 to 1.65; typical RD -0.07, 95% CI -0.18 to 0.05; two studies, 110 infants; I² = 28% for RR and I² = 44% for RD). Among secondary outcomes, we found no significant differences in terms of cystic periventricular leukomalacia (one study; RR 3.25, 95% CI 0.14 to 76.01; RD 0.04, 95% CI -0.07 to 0.15), retinopathy of prematurity (one study; RR 2.27, 95% CI 0.85 to 6.11; RD 0.25, 95% CI -0.02 to 0.53), and severe retinopathy of prematurity (one study; RR 2.73, 95% CI 0.31 to 24.14; RD 0.09, 95% CI -0.09 to 0.26). None of the included trials reported on the other specified outcomes of this review (i.e., cerebellar hemorrhage, brain magnetic resonance imaging abnormalities, impairment in cerebral hemodynamics, long-term neurodevelopmental outcomes, and major neurodevelopmental disability). The quality of evidence supporting these findings is limited owing to the imprecision of the estimates. We identified no ongoing studies.

AUTHORS' CONCLUSIONS

Given the imprecision of the estimate, results of this systematic review are consistent with beneficial or detrimental effects of a supine head midline position versus a lateral position and do not provide a definitive answer to the review question.

The Effect of Head Positioning and Head Tilting on the Incidence of Intraventricular Hemorrhage in Very Preterm Infants: A Systematic Review

BACKGROUND

Despite advances in neonatal intensive care, germinal matrix-intraventricular hemorrhage (GMH-IVH) remains a frequent, serious complication of premature birth. Neutral head position and head tilting have been suggested to reduce the risk of GMH-IVH in preterm infants during the first 72 h of life.

OBJECTIVE

The aim of this study was to provide a systematic review of the effect of neutral head positioning and head tilting on the incidence of GMH-IVH in very preterm infants (gestational age ≤30 weeks). In addition, we reviewed their effect on cerebral hemodynamics and oxygenation.

METHODS

Literature was searched (June 2016) in the following electronic databases: CINAHL, Embase, Medline, SCOPUS, and several trial registers.

RESULTS

One underpowered trial studied the effect of head positioning on the incidence of GMH-IVH. This randomized controlled trial enrolled 48 preterm infants and found no effect on the occurrence of GMH-IVH. Three observational studies investigated the effect of head rotation and/or tilting on cerebral oxygenation in 68 preterm infants in total. Their results suggest that cerebral oxygenation is not significantly affected by changes in head positioning. The effect of head positioning and/or tilting on cerebral hemodynamics was described in 2 observational studies of 28 preterm infants and found no significant effect.

CONCLUSIONS

There is insufficient evidence regarding the effect of head positioning and tilting on the incidence of GMH-IVH and cerebral hemodynamics and oxygenation in preterm infants. We recommend further research in this field, especially in extremely preterm and clinically unstable infants during the first postnatal days.

Head Position Change Is Not Associated with Acute Changes in Bilateral Cerebral Oxygenation in Stable Preterm Infants during the First 3 Days of Life

OBJECTIVE

Several recent intraventricular hemorrhage prevention bundles include midline head positioning to prevent potential disturbances in cerebral hemodynamics. We aimed to study the impact of head position change on regional cerebral saturations (SctO2) in preterm infants (< 30 weeks gestational age) during the first 3 days of life.

STUDY DESIGN

Bilateral SctO2 was measured by near-infrared spectroscopy. The infant's head was turned sequentially to each side from midline (baseline) in 30-minute intervals while keeping the body supine. Bilateral SctO2 before and after each position change were compared using paired t-test.

RESULTS

In relatively stable preterm infants (gestational age 26.5 ± 1.7 weeks, birth weight 930 ± 220 g; n = 20), bilateral SctO2 remained within normal range (71.1-75.3%) when the head was turned from midline position to either side.

CONCLUSION

Stable preterm infants tolerated brief changes in head position from midline without significant alternation in bilateral SctO2; the impact on critically ill infants needs further evaluation.

Angiogenesis induced by prenatal ischemia predisposes to periventricular hemorrhage during postnatal mechanical ventilation

BACKGROUND

Three risk factors are associated with hemorrhagic forms of encephalopathy of prematurity (EP): (i) prematurity, (ii) in utero ischemia (IUI) or perinatal ischemia, and (iii) mechanical ventilation. We hypothesized that IUI would induce an angiogenic response marked by activation of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9), the latter degrading vascular basement membrane and increasing vulnerability to raised intravenous pressure during positive pressure mechanical ventilation.

METHODS

We studied a rat model of hemorrhagic-EP characterized by periventricular hemorrhages in which a 20-min episode of IUI is induced at E19, pups are born naturally at E21-22, and on P0, are subjected to a 20-min episode of positive pressure mechanical ventilation. Tissues were studied by H&E staining, immunolabeling, immunoblot, and zymography.

RESULTS

Mechanical ventilation of rat pups 2-3 d after 20-min IUI caused widespread hemorrhages in periventricular tissues. IUI resulted in upregulation of VEGF and MMP-9. Zymography confirmed significantly elevated gelatinase activity. MMP-9 activation was accompanied by severe loss of MMP-9 substrates, collagen IV and laminin, in microvessels in periventricular areas.

CONCLUSION

Our findings are consistent with the hypothesis that positive pressure mechanical ventilation of the newborn in the context of recent prenatal ischemia/hypoxia can predispose to periventricular hemorrhages.

The protective effect of glibenclamide in a model of hemorrhagic encephalopathy of prematurity

We studied a model of hemorrhagic encephalopathy of prematurity (EP) that closely recapitulates findings in humans with hemorrhagic EP. This model involves tandem insults of 20 min intrauterine ischemia (IUI) plus an episode of elevated venous pressure induced by intraperitoneal glycerol on post-natal day (P) 0. We examined Sur1 expression, which is upregulated after focal ischemia but has not been studied after brief global ischemia including IUI. We found that 20 min IUI resulted in robust upregulation of Sur1 in periventricular microvessels and tissues. We studied tandem insult pups from untreated or vehicle-treated dams (TI-CTR), and tandem insult pups from dams administered a low-dose, non-hypoglycemogenic infusion of the Sur1 blocker, glibenclamide, for 1 week after IUI (TI-GLIB). Compared to pups from the TI-CTR group, pups from the TI-GLIB group had significantly fewer and less severe hemorrhages on P1, performed significantly better on the beam walk and accelerating Rotarod on P35 and in tests of thigmotaxis and rapid learning on P35–49, and had significantly greater body and brain weights at P52. We conclude that low-dose glibenclamide administered to the mother at the end of pregnancy protects pups subjected to IUI from post-natal events of elevated venous pressure and its consequences.

Effects of antenatal magnesium sulfate treatment on cerebral blood flow velocities in preterm neonates

OBJECTIVE

The objective of this study is to investigate the effects of antenatal magnesium sulfate (MgSO4) on cerebral blood flow (CBF) velocities in preterm neonates.

STUDY DESIGN

In this prospective case-control study, we included 53 neonates born between 26 and 34 weeks of gestation. Twenty neonates were exposed to MgSO4 antenatally and 33 were not. Serial daily Doppler flow measurements of middle cerebral artery (MCA) were performed.

RESULT

Significantly increased MCA mean velocities were found in the MgSO4 group. A progressive increase in serial Doppler measurements of MCA mean velocity from day 1 to day 5 of life was detected in both groups.

CONCLUSION

There is significant increase in MCA mean velocities in preterm neonates receiving antenatal MgSO4. This increment in CBF velocities might explain the protective role of MgSO4 in ischemic events and hypoxic brain damage.

Volume expansion does not alter cerebral tissue oxygen extraction in preterm infants with clinical signs of poor perfusion

BACKGROUND

Preterm infants with signs of poor perfusion are often treated with volume expansion, although evidence regarding its effect on cerebral perfusion is lacking. Moreover, the effect is questionable in preterm infants with an adequate cerebrovascular autoregulation (CAR). A useful measure to assess perfusion is cerebral fractional tissue oxygen extraction (cFTOE).

OBJECTIVES

To assess the effect of volume expansion on cFTOE in preterm infants with signs of poor perfusion.

METHODS

In this observational study, we assessed cFTOE using near-infrared spectroscopy in preterm infants with signs of poor perfusion before, during and 1 h after volume expansion treatment. Simultaneously, we measured mean arterial blood pressure (MABP). We tested the effect of volume expansion on both cFTOE and MABP, using multi-level analyses. We intended to define a subgroup that responded to volume expansion with an increase in blood pressure and a decrease in cFTOE, suggesting absent CAR.

RESULTS

In 14 preterm infants, with a median gestational age of 26.7 weeks (25.0-28.7 weeks) and a median birth weight of 836 g (615-1,290 g), we found a small increase in MABP during (1.4 ± 1.4 mm Hg, p = 0.003) and after (1.8 ± 1.7 mm Hg, p = 0.001) volume expansion, but no change in cFTOE during (-0.19 ± 0.1% p = 0.44) or after (-0.53 ± 0.1% p = 0.34) volume expansion. We were unable to define a subgroup lacking CAR.

CONCLUSIONS

Cerebral perfusion, as assessed by cFTOE, does not improve in preterm infants with signs of poor perfusion following volume expansion. In these infants, either CAR is present or volume expansion is inadequate to affect cFTOE.

The SafeBoosC phase II randomised clinical trial: a treatment guideline for targeted near-infrared-derived cerebral tissue oxygenation versus standard treatment in extremely preterm infants

Near-infrared spectroscopy-derived regional tissue oxygen saturation of haemoglobin (rStO2) reflects venous oxygen saturation. If cerebral metabolism is stable, rStO2 can be used as an estimate of cerebral oxygen delivery. The SafeBoosC phase II randomised clinical trial hypothesises that the burden of hypo- and hyperoxia can be reduced by the combined use of close monitoring of the cerebral rStO2 and a treatment guideline to correct deviations in rStO2 outside a predefined target range.

AIMS

To describe the rationale for and content of this treatment guideline.

METHODS

Review of the literature and assessment of the quality of evidence and the grade of recommendation for each of the interventions.

RESULTS AND CONCLUSIONS

A clinical intervention algorithm based on the main determinants of cerebral perfusion-oxygenation changes during the first hours after birth was generated. The treatment guideline is presented to assist neonatologists in making decisions in relation to cerebral oximetry readings in preterm infants within the SafeBoosC phase II randomised clinical trial. The evidence grades were relatively low and the guideline cannot be recommended outside a research setting.

The effects of environmental noise and infant position on cerebral oxygenation

PURPOSE

To assess how different infant positions and peak sound levels affected cerebral oxygen saturation over time.

SUBJECTS

Twenty-four premature infants who were born less than 32 weeks' gestational age without congenital cardiac, neurologic, and gastrointestinal anomalies.

DESIGN

Repeated-measures design with the first observation between 2 and 48 hours of life; once again between 49 and 96 hours of life; on day of life 7; and every 7 days thereafter until discharge home, transfer to another hospital, or 40 weeks postmenstrual age, whichever came first.

METHODS

Continuous sound levels (decibels) were obtained and 2 infant positions were performed while measuring cerebral oxygen saturation during 40-minute observation periods.

MAIN OUTCOME MEASURES

Effect of peak sound and differences in infant position on cerebral oxygen saturation.

RESULTS

Peak sound levels 5 dB above the average ambient sound level did not significantly change cerebral oxygen saturation values. Differences in cerebral oxygenation were significantly less when infants were changed from a supine, head midline position to a right lateral, 15° head elevation compared with a left lateral, 0° elevation position.

CONCLUSIONS

Aspects of the current neonatal intensive care unit environment do not appear to affect cerebral oxygen saturation.

Effect of head rotation on cerebral blood velocity in the prone position

Background. The prone position is applied to facilitate surgery of the back and to improve oxygenation in the respirator-treated patient. In particular, with positive pressure ventilation the prone position reduces venous return to the heart and in turn cardiac output (CO) with consequences for cerebral blood flow. We tested in healthy subjects the hypothesis that rotating the head in the prone position reduces cerebral blood flow. Methods. Mean arterial blood pressure (MAP), stroke volume (SV), and CO were determined, together with the middle cerebral artery mean blood velocity (MCA V_mean) and jugular vein diameters bilaterally in 22 healthy subjects in the prone position with the head centered, respectively, rotated sideways, with and without positive pressure breathing (10 cmH₂O). Results. The prone position reduced SV (by 5.4 ± 1.5%; P < 0.05) and CO (by 2.3 ± 1.9 %), and slightly increased MAP (from 78 ± 3 to 80 ± 2 mmHg) as well as bilateral jugular vein diameters, leaving MCA V_mean unchanged. Positive pressure breathing in the prone position increased MAP (by 3.6 ± 0.8 mmHg) but further reduced SV and CO (by 9.3 ± 1.3 % and 7.2 ± 2.4 % below baseline) while MCA V_mean was maintained. The head-rotated prone position with positive pressure breathing augmented MAP further (87 ± 2 mmHg) but not CO, narrowed both jugular vein diameters, and reduced MCA V_mean (by 8.6 ± 3.2 %). Conclusion. During positive pressure breathing the prone position with sideways rotated head reduces MCA V_mean ~10% in spite of an elevated MAP. Prone positioning with rotated head affects both CBF and cerebrovenous drainage indicating that optimal brain perfusion requires head centering.

Neutral head positioning in premature infants for intraventricular hemorrhage prevention: an evidence-based review

With the advancement of neonatal medicine during the past several decades, premature and critically ill infants are living past the neonatal period and surviving. The survival of these infants at smaller birth weights and younger gestational ages puts them at an increased risk for intraventricular hemorrhages (IVHs). Although shifts in cerebral perfusion have been linked to the development of these brain bleeds, many seemingly benign care activities have been linked to changes in cerebral blood flow patterns, possibly contributing to IVHs. The purpose of this article is to evaluate the current evidence to determine if the practice of midline positioning for infants born less than 32 weeks gestation for possible IVH prevention is supported by the literature. Many of the researchers involved in these studies attributed the consequential venule leakage of blood to occlusion of the jugular venous drainage system following a turn in the position of the head. Additionally, the articles that examined the connection between the effects of head tilting on brain hemodynamics attributed changes on the infants' potential inability to autoregulate cerebral blood flow adequately. Both of these findings were linked to the development of IVHs. Based on physiologic data and expert opinion, the authors found support in the literature and recommend implementing a plan of care that includes midline head positioning for premature infants.

Cerebral and mesenteric tissue oxygenation by positional changes in very low birth weight premature infants

AIM

There has been no clear consensus of the appropriate positioning in preterm infants. We aimed to evaluate the changes of cerebral and mesenteric tissue oxygenation in three different positions, by near infrared spectroscopy (NIRS), in stable very low birth weight (VLBW) infants of postnatal >30 days.

METHODS

NIRS monitoring of cerebral and mesenteric tissue oxygenation in three different positions was performed in 29 stable preterm newborns in neonatal intensive care unit (NICU). The patients were observed in three different positions consecutively, each lasting for 4h. The demographic features, cerebral and mesenteric tissue oxygenation with positional changes and feeding periods were recorded.

RESULTS

Mean gestational age, mean birth weight and mean postnatal age of the patients were 27.6±1.7 weeks, 1046±308 g and 42.4±15.7 days, respectively. There were no statistically significant differences in cerebral and mesenteric tissue regional SO(2) values in each position (p=0.954 and p=0.151, respectively). The values of cerebral and mesenteric tissue regional SO(2) before and after feeding did not show any statistically significant difference in each position.

CONCLUSIONS

Clinically stable very low birth weight infants are able to maintain a stable cerebral and mesenteric tissue oxygenation in different positions, both before and after feeding. Positional changes seem to be safe in VLBW stable infants and this influence should be considered in care of these patients in the NICU. Clinical Trials Identification Number: NCT01255189.

Quantitative estimates of stimulation-induced perfusion response using two-photon fluorescence microscopy of cortical microvascular networks

Functional hyperemia, or the increase in focal perfusion elicited by neuronal activation, is one of the primary functions of the neurovascular unit and a hallmark of healthy brain functioning. While much is known about the hemodynamics on the millimeter to tenths of millimeter-scale accessible by MRI, there is a paucity of quantitative data on the micrometer-scale changes in perfusion in response to functional stimulation. We present a novel methodology for quantification of perfusion and intravascular flow across the 3D microvascular network in the rat somatosensory cortex using two-photon fluorescence microscopy (2PFM). For approximately 96% of responding microvessels in the forelimb representation of the primary somatosensory cortex, brief (~2s) forepaw stimulation resulted in an increase of perfusion 20±4% (mean±sem). The perfusion levels associated with the remaining 4% of the responding microvessels decreased 10±9% upon stimulation. Vessels irrigating regions of lower vascular density were found to exhibit higher flow (p<0.02), supporting the notion that local vascular morphology and hemodynamics reflect the metabolic needs of the surrounding parenchyma. High dispersion (~77%) in perfusion levels suggests high spatial variation in tissue susceptibility to hypoxia. The current methodology enables quantification of absolute perfusion associated with individual vessels of the cortical microvascular bed and its changes in response to functional stimulation and thereby provides an important tool for studying the cellular mechanisms of functional hyperemia, the spatial specificity of perfusion response to functional stimulation, and, broadly, the micrometer-scale relationship between vascular morphology and function in health and disease.

Quantitative tandem mass spectrometric imaging of endogenous acetyl-L-carnitine from piglet brain tissue using an internal standard

Matrix-assisted laser desorption/ionization (MALDI) based mass spectrometric imaging (MSI) is increasingly being used as an analytical tool to evaluate the molecular makeup of tissue samples. From the direct analysis of a tissue section, the physical integrity of sample is preserved; thus, spatial information of a compound's distribution may be determined. One limitation of the technique, however, has been the inability to determine the absolute concentration from a tissue sample. Here we report the development of a quantitative MSI technique in which the distribution of acetyl-L-carnitine (AC) in a piglet brain sample is quantified with MALDI MSI. An isotopically labeled internal standard was applied uniformly beneath the tissue section, and wide-isolation tandem mass spectrometry was performed. Normalizing the analyte ion signal by the internal standard ion signal resulted in significant improvements in MS images, signal reproducibility, and calibration curve linearity. From the improved MS images, the concentration of AC was determined and plotted producing a concentration-scaled image of the distribution of AC in the piglet brain section.

Near-infrared spectroscopy: a methodology-focused review

Near infrared spectroscopy (NIRS) is a light-based technology used to monitor tissue oxygen status. Refinements to the method since it was first described have extended its applicability to different research and clinical settings due to its non-invasiveness, instrument portability and ease of use. Classic NIRS recordings, based in the Beer-Lambert law, can be used for the trend monitoring of changes in tissue perfusion-oxygenation parting from an arbitrary zero point. However, in order to derive intermittently quantitative values in absolute terms, certain manoeuvres must be performed. More recently, the evolution of the technique has led to the development of instruments that provide an absolute value of regional hemoglobin saturation in a continuous manner. This review will focus on the physical principles of tissue spectroscopy including a brief description of the different operating principles that are currently in use or under development. The theoretical details, experimental procedures and data analysis involved in the measurements of physiological variables using NIRS will be described. The future beyond the scope of NIRS and potential lines of research will also be discussed.

The chemical nature of mercury in human brain following poisoning or environmental exposure

Methylmercury is among the most potentially toxic species to which human populations are exposed, both at high levels through poisonings and at lower levels through consumption of fish and other seafood. However, the molecular mechanisms of methylmercury toxicity in humans remain poorly understood. We used synchrotron X-ray absorption spectroscopy (XAS) to study mercury chemical forms in human brain tissue. Individuals poisoned with high levels of methylmercury species showed elevated cortical selenium with significant proportions of nanoparticulate mercuric selenide plus some inorganic mercury and methylmercury bound to organic sulfur. Individuals with a lifetime of high fish consumption showed much lower levels of mercuric selenide and methylmercury cysteineate. Mercury exposure did not perturb organic selenium levels. These results elucidate a key detoxification pathway in the central nervous system and provide new insights into the appropriate methods for biological monitoring.

Quantitative cerebral blood flow with optical coherence tomography

Absolute measurements of cerebral blood flow (CBF) are an important endpoint in studies of cerebral pathophysiology. Currently no accepted method exists for in vivo longitudinal monitoring of CBF with high resolution in rats and mice. Using three-dimensional Doppler Optical Coherence Tomography and cranial window preparations, we present methods and algorithms for regional CBF measurements in the rat cortex. Towards this end, we develop and validate a quantitative statistical model to describe the effect of static tissue on velocity sensitivity. This model is used to design scanning protocols and algorithms for sensitive 3D flow measurements and angiography of the cortex. We also introduce a method of absolute flow calculation that does not require explicit knowledge of vessel angles. We show that OCT estimates of absolute CBF values in rats agree with prior measures by autoradiography, suggesting that Doppler OCT can perform absolute flow measurements in animal models.

Influence of ventilation mode on neonatal cerebral blood flow and volume

BACKGROUND

Cerebral hemodynamics is supposed to be influenced by the different ventilation approach. Ventilation support can be classified as non-invasive (N-CPAP) or invasive (SIMV and HFV), the last known to induce endotrauma. Our aim was the non-invasive NIRS assessment of neonatal absolute cerebral blood flow (CBF) and relative cerebral blood volume changes (DeltaCBV) during synchronized intermittent ventilation (SIMV), or high frequency ventilation (HFV) and nasal continuous positive airways pressure (CPAP).

METHODS

An observational study in a tertiary referral NICU. CBF and DeltaCBV changes were assessed in 41 preterm newborn infants with respiratory distress syndrome treated using mechanical ventilation or the CPAP device.

RESULTS

Basal chromophore traces enabled DeltaCBV (mL/100 g) changes to be calculated. CBF was calculated in mL/100 g/min from the saturation rise integral and rate of rise [O(2)Hb-HHb]. Median DeltaCBV was 0.07 (range 0.01-0.13) in SIMV group, 0.07 (0.01-0.19) in HFV group and 0.13 (0.10-1.28) in CPAP group. Median CBF was 14.44 (2.70-32.10), 9.20 (2.94-19.58) and 31.69 (13.59-34.93) respectively. A multiple regression model showed a significant correlation between DeltaCBV or CBF and ventilation approach.

CONCLUSION

In the light of our results, we might speculate that, assuming that hemodynamic autoregulation is safe and arterial blood pressure is preserved, ventilation per se influences brain circulation.