Body position-dependent changes in cerebral hemodynamics during apnea in preterm infants

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.

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.

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.

When does prone sleeping improve cardiorespiratory status in preterm infants in the NICU?

Study Objectives

Preterm infants undergoing intensive care are often placed prone to improve respiratory function. Current clinical guidelines recommend preterm infants are slept supine from 32 weeks’ postmenstrual age, regardless of gestational age at birth. However, respiratory function is also related to gestational and chronological ages and is affected by sleep state. We aimed to identify the optimal timing for adopting the supine sleeping position in preterm infants, using a longitudinal design assessing the effects of sleep position and state on cardiorespiratory stability.

Methods

Twenty-three extremely (24–28 weeks’ gestation) and 33 very preterm (29–34 weeks’ gestation) infants were studied weekly from birth until discharge, in both prone and supine positions, in quiet and active sleep determined by behavioral scoring. Bradycardia (heart rate ≤100 bpm), desaturation (oxygen saturation ≤80%), and apnea (pause in respiratory rate ≥10 s) episodes were analyzed.

Results

Prone positioning in extremely preterm infants reduced the frequency of bradycardias and desaturations and duration of desaturations. In very preterm infants, prone positioning only reduced the frequency of desaturations. The position-related effects were not related to postmenstrual age. Quiet sleep in both preterm groups was associated with fewer bradycardias and desaturations, and also reduced durations of bradycardia and desaturations in the very preterm group.

Conclusions

Cardiorespiratory stability is improved by the prone sleep position, predominantly in extremely preterm infants, and the improvements are not dependent on postmenstrual age. In very preterm infants, quiet sleep has a more marked effect than the prone position. This evidence should be considered in individualizing management of preterm infant positioning.

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 Longitudinal Effects of Persistent Apnea on Cerebral Oxygenation in Infants Born Preterm

OBJECTIVE

To assess the incidence and impact of persistent apnea on heart rate (HR), oxygen saturation (SpO₂), and brain tissue oxygenation index (TOI) over the first 6 months after term equivalent age in ex-preterm infants.

STUDY DESIGN

Twenty-four preterm infants born between 27 and 36 weeks of gestational age were studied with daytime polysomnography at 2-4 weeks, 2-3 months, and 5-6 months post-term corrected age. Apneas lasting ≥3 seconds were included and maximal percentage changes (nadir) in HR, SpO_2, and tissue oxygenation index (TOI, NIRO-200 Hamamatsu) from baseline were analyzed.

RESULTS

A total of 253 apneas were recorded at 2-4 weeks, 203 at 2-3 months, and 148 at 5-6 months. There was no effect of gestational age at birth, sleep state, or sleep position on apnea duration, nadir HR, SpO₂, or TOI. At 2-4 weeks, the nadirs in HR (-11.1 ± 1.2 bpm) and TOI (-4.4 ± 1.0%) were significantly less than at 2-3 months (HR: -13.5 ± 1.2 bpm, P < .05; TOI: -7.5 ± 1.1 %, P < .05) and at 5-6 months (HR: -13.2 ± 1.3 bpm, P < .01; TOI: -9.3 ± 1.2%, P < .01).

CONCLUSIONS

In ex-preterm infants, apneas were frequent and associated with decreases in heart rate and cerebral oxygenation, which were more marked at 2-3 months and 5-6 months than at 2-4 weeks. Although events were short, they may contribute to the adverse neurocognitive outcomes that are common in ex-preterm children.

Body positioning for spontaneously breathing preterm infants with apnoea

BACKGROUND

It has been proposed that body positioning in preterm infants, as compared with other, more invasive measures, may be an effective method of reducing clinically significant apnoea.

OBJECTIVES

To determine effects of body positioning on cardiorespiratory parameters in spontaneously breathing preterm infants with clinically significant apnoea.Subgroup analyses examined effects of body positioning of spontaneously breathing preterm infants with apnoea from the following subgroups.• Gestational age < 28 weeks or birth weight less than 1000 grams.• Apnoea managed with methylxanthines.• Frequent apnoea (> 10 events/d).• Type of apnoea measured (central vs mixed vs obstructive)

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group (CNRG) to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 10), MEDLINE via PubMed (1966 to 14 November 2016), Embase (1980 to 14 November 2016) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 2016 November 14). We also searched clinical trials databases and conference proceedings for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised and quasi-randomised controlled clinical trials with parallel, factorial or cross-over design comparing the impact of different body positions on apnoea in spontaneously breathing preterm infants were eligible for our review.

DATA COLLECTION AND ANALYSIS

We assessed trial quality, data extraction and synthesis of data using standard methods of the CNRG. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

The search conducted in November 2016 identified no new studies. Five studies (N = 114) were eligible for inclusion. None of the individual studies nor meta-analyses showed a reduction in apnoea, bradycardia, oxygen desaturation or oxygen saturation with body positioning (supine vs prone; prone vs right lateral; prone vs left lateral; right lateral vs left lateral; prone horizontal vs prone head elevated; right lateral horizontal vs right lateral head elevated, left lateral horizontal vs left lateral head elevated).

AUTHORS' CONCLUSIONS

We found insufficient evidence to determine effects of body positioning on apnoea, bradycardia and oxygen saturation in preterm infants. No new studies have been conducted since the original review was published. Large, multi-centre studies are warranted to provide conclusive evidence, but it may be plausible to conclude that positioning of spontaneously breathing preterm infants has no effect on their cardiorespiratory parameters.

The longitudinal effects of persistent periodic breathing on cerebral oxygenation in preterm infants

OBJECTIVES

Periodic breathing is common in preterm infants, but is thought to be benign. The aim of our study was to assess the incidence and impact of periodic breathing on heart rate (HR), oxygen saturation (SpO2), and brain tissue oxygenation index (TOI) over the first six months after term-equivalent age.

STUDY DESIGN

Twenty-four preterm infants (27-36 weeks gestational age) were studied with daytime polysomnography in quiet sleep (QS) and active sleep (AS) and in both the prone and supine positions at 2-4 weeks, 2-3 months, and 5-6 months post-term corrected age. HR, SpO2, and TOI (NIRO-200 spectrophotometer) were recorded. Periodic breathing episodes were defined as greater than or equal to three sequential apneas each lasting ≥3 s.

RESULTS

A total 164 individual episodes of periodic breathing were recorded in 19 infants at 2-4 weeks, 62 in 12 infants at 2-3 months, and 35 in 10 infants at 5-6 months. There was no effect of gestational age on periodic breathing frequency or duration. Falls in HR (-21.9 ± 2.7%) and TOI (-13.1 ± 1.5%) were significantly greater at 2-3 months of age compared to 2-4 weeks of age.

CONCLUSIONS

The majority of preterm infants discharged home without clinical respiratory problems had persistent periodic breathing. Although in most infants periodic breathing was not associated with significant falls in SpO2 or TOI, several infants had significant desaturations and reduced cerebral oxygenation especially during AS. The clinical significance of this on neurodevelopmental outcome is unknown and warrants further investigations.

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.

Body positioning for spontaneously breathing preterm infants with apnoea

BACKGROUND

It has been proposed that the use of body positioning may be a more effective way to reduce clinically significant apnoea than the use of more invasive measures.

OBJECTIVES

To determine the effect of body positioning on cardiorespiratory functioning in spontaneously breathing preterm infants with clinically significant apnoea.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2011), MEDLINE (1966 to March 2011), EMBASE (1988 to March 2011) and CINAHL (1988 to March 2011), abstracts of conference proceedings and citations of published articles.

SELECTION CRITERIA

All studies in which infants or their sequence of body positioning was randomised or quasi-randomised. We included cross-over studies.

DATA COLLECTION AND ANALYSIS

We performed assessment of trial quality, data extraction and synthesis of data using standard methods of the Cochrane Neonatal Review Group.

MAIN RESULTS

Five studies (N = 114) were eligible for inclusion. None of the individual studies or the meta-analyses showed a reduction in apnoea, bradycardia, oxygen desaturation or oxygen saturation with body positioning (supine versus prone; prone versus right lateral; prone versus left lateral; right lateral versus left lateral; prone horizontal versus prone head elevated; right lateral horizontal versus right lateral head elevated and left lateral horizontal versus left lateral head elevated).

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the role of body positioning on apnoea, bradycardia, oxygen desaturation and oxygen saturation. Large randomised controlled trials are needed to determine the effect of body positioning on cardiorespiratory function in spontaneously breathing preterm infants.

Effects of prone and supine position on cerebral blood flow in preterm infants

We evaluated the effect of prone and supine position on cerebral blood flow (CBF) in stable preterm infants. CBF, PO(2), and PCO(2) were measured in the two positions. Peripheral oxygenation increased and CBF decreased in prone position. We speculate that CBF autoregulation may compensate for increased peripheral oxygenation, by decreasing CBF.

Positioning of Preterm Infants for Optimal Physiological Development: a systematic review

EXECUTIVE SUMMARY

Positioning of preterm infants is a basic task of neonatal nursing care. A variety of outcomes are affected by different body positioning of preterm infants. This review evaluates the clinical evidence of the effects of positioning of preterm infants with regard to physiological outcomes and sleep states.

OBJECTIVES

To conduct a systematic review to determine the best available evidence related to the positioning of preterm infants. The specific review questions addressed were: the physiological outcomes affected by different positioning, and the best position for promoting sleep.

CRITERIA FOR CONSIDERING STUDIES FOR THIS REVIEW

This review considered all studies that included infants born before 37 weeks of gestational age in any hospital setting. Outcomes included measures for physiologic effects and sleep state. The review primarily considered any randomized clinical trails (RCTs) that explored different positions in preterm infant but also included quasi-experimental designs.

SEARCH STRATEGY FOR IDENTIFICATION OF STUDIES

The search sought to find published and unpublished studies. The database search included: Pubmed, CINAHL, ProQuest, EMBASE, Science Direct, and Dissertation Abstracts International. Studies were additionally identified from reference lists of all studies retrieved.

ASSESSMENT AND DATA EXTRACTION

All studies were checked for methodological quality by two reviewers and data was extracted using tools developed by the Joanna Briggs Institute.

DATA ANALYSIS

The study results were pooled in statistical meta-analysis using Review Manager Software and summarized in narrative form where statistical pooling was not appropriate or possible.

RESULTS

Thirty two studies were included in the review. The results of this review support the prone position in preterm infants for improvement of arterial oxygen saturation, improved lung and chest wall synchrony of respiratory improvements, decreased incidence of apnea in infants with a clinical history of apnea, promoted sleep, and decreased gastroesophageal reflux. However, the prone position increased postural abnormalities, orthopaedic abnormalities of the feet, and delayed developmental musculature. The combined use of a postural support roll and a postural nappy while very preterm infants are nursed, improved hip and shoulder posture up to term postmenstrual age. The change in body position from horizontal to head-up tilt in very immature and unstable infants may affect the cerebral homodynamic. The management of position per se may not be sufficient for assisting preterm neonates to cope with the painful procedure. Furthermore, preterm infants are susceptible to oxygen desaturation in car seats and carrying slings.

CONCLUSION

Prone positioning was shown to have many advantages for prematurely born infants. But the longer, deep sleep period and fewer awakenings associated with a prone position would support higher vulnerability for preterm infants to sudden infant death syndrome (SIDS). Therefore, all preterm infants placed in the prone position should have continuous cardio-respiratory and oxygen saturation monitoring. Preterm infants should be placed in a properly supported position to ensure functional support of all parts of the body as well as ensuring physical safety. In addition, preterm infants should not be left unattended in car safety seats and carrying slings.

Cerebral hemodynamics during arousals in preterm infants

The aim of the study was to evaluate potential changes of cerebral blood volume (CBV) related to arousals in preterm infants. As arousals are known to change different physiological parameters, it was postulated that this could also hold true for CBV. Polygraphic recordings were performed in 38 preterm infants (18 female, 20 male). The infants' gestational age at birth was 32.0+/-2.3 weeks, postconceptional age was 35.1+/-1.2 weeks and postnatal age at study entry was 24.3+/-2.9 days, birth weight was 1793+/-527 g and actual weight at study entry was 2011+/-324 g [mean (+/- standard deviation)]. CBV was measured using near infrared spectroscopy. Arousals were scored due to the guidelines of the "International Paediatric Work Group on Arousals" and categorized as either cortical (CA) or subcortical arousals (SCA). Altogether, 122 arousals (66 CA, 56 SCA) were scored. According to sleep stage, 77 arousals were analyzed in active sleep, 23 in quiet sleep and 22 in intermediate sleep. Mean duration of arousals was 8.8+/-0.3 s. CBV, cerebral vascular oxygenation and the balance between oxygen delivery and oxygen consumption remained constant during arousals in preterm infants. This was demonstrated for both CA and SCA and was independent of sleep stage, suggesting that the impact of arousals in stable preterm infants is too small to alter cerebral vascular autoregulation.

Impact of bradycardia on cerebral oxygenation and cerebral blood volume during apnoea in preterm infants

Apnoea in prematurity is a common problem in neonatology; and it is the impaired oxygen delivery during apnoea, which can harm the brain. The aim of this study was to evaluate the effect of bradycardia (below 80 beats min(-1)) on 'cerebral haemoglobin oxygenation index' (cHbD) and cerebral blood volume (CBV) during apnoea in stable preterm infants measured by means of near infrared spectroscopy. Twenty-six episodes of mixed and central apnoea with bradycardia (bradycardia group) in 20 preterm infants were compared to 26 episodes of mixed and central apnoea without bradycardia (non-bradycardia group) in 19 preterm infants. cHbD decreased significantly more in the bradycardia group (-11.33 micromol 1(-1) after 30 s) than in the non-bradycardia group (-6.36 micromol 1(-1) after 30 s) (p < 0.05). CBV decreased significantly in the bradycardia group (p < 0.05), whereas CBV did not change significantly in the non-bradycardia group. Peripheral oxygen saturation (SaO2) decreased similarly in both groups. The aggravation of decrease of cHbD and the decrease of CBV during bradycardia in association with apnoea could be explained by decrease in cerebral blood flow, which caused decrease in cerebral oxygen delivery. This decrease of oxygen delivery during bradycardia might worsen long-term neurodevelopmental outcome in preterm infants with apnoea.

Apnea associated with hypoxia in preterm infants: impact on cerebral blood volume

The present study analyzed changes in cerebral blood volume (CBV) during apnea associated with hypoxia compared to apnea without hypoxia. Hypoxia was defined as pulsoxymetric oxygen saturation <80%>10 s. The employed technique was near infrared spectroscopy combined with electrocardiogram, electroocologram, pulsoxymetry, sidestream capnography and two respiratory effort sensors. In 24 preterm infants 44 incidences of apnea were analyzed. Two main patterns were observed: a significant decrease or a significant increase of CBV. In the 'CBV decrease' group deltaCBV was -55 microl/100 g brain in hypoxic apnea, and -62 microl/100 g brain in non-hypoxic apnea. In the 'CBV increase' group the rise of CBV above preapneic values was +50 microl/100 g brain in hypoxic apnea, and +47 microl/100 g brain in non-hypoxic apnea. Heart rate showed a significant decrease only in the 'CBV decrease' group. Endexpiratory CO(2) increased significantly 1 min after apnea. In conclusion, this study observed significant changes of CBV during apnea in preterm infants, but no difference in CBV behavior regarding whether incidents of apnea were associated with hypoxia or not. It remains unclear which regulatory mechanisms are responsible for the two observed patterns of deltaCBV during apnea.