Cerebral oxygenation during intermittent hypoxemia and bradycardia in preterm infants

Extended CPAP or low-flow nasal cannula for intermittent hypoxaemia in preterm infants: a 24-hour randomised clinical trial

OBJECTIVE

Optimal timing of continuous positive airway pressure (CPAP) cessation in preterm infants remains undetermined. We hypothesised that CPAP extension compared with weaning to low-flow nasal cannula (NC) reduces intermittent hypoxaemia (IH) and respiratory instability in preterm infants meeting criteria to discontinue CPAP.

DESIGN

Single-centre randomised clinical trial.

SETTING

Level 4 neonatal intensive care unit.

PATIENTS

36 infants <34 weeks' gestation receiving CPAP≤5 cmH2O and fraction of inspired oxygen (FiO2) ≤0.30 and meeting respiratory stability criteria.

INTERVENTIONS

Extended CPAP was compared with weaning to low-flow NC (0.5 L/kg/min with a limit of 1.0 L/min) for 24 hours.

OUTCOMES

The primary outcome was IH (number of episodes with SpO2<85% lasting ≥10 s). Secondary outcomes included: coefficient of variability of SpO2, proportion of time in various SpO2 ranges, episodes (≥10 s) with SpO2<80%, median cerebral and renal oxygenation, median effective FiO2, median transcutaneous carbon dioxide and bradycardia (<100/min for≥10 s).

RESULTS

The median (IQR) episodes of IH per 24-hour period was 20 (6-48) in the CPAP group and 76 (18-101) in the NC group (p=0.03). Infants continued on CPAP had less bradycardia, time with SpO2 <91% and <85%, and lower FiO2 (all p<0.05). There were no statistically significant differences in IH<80%, median transcutaneous carbon dioxide or median cerebral or renal oxygenation.

CONCLUSION

In preterm infants meeting respiratory stability criteria for CPAP cessation, extended CPAP decreased IH, bradycardia and other hypoxaemia measures compared with weaning to low-flow NC during the 24-hour intervention.

TRIAL REGISTRATION NUMBER

NCT04792099.

Effects of vanilla odor on hypoxia-related periodic breathing in premature newborns: A pilot study

BACKGROUND

Periodic breathing (PB)-related intermittent hypoxia can have long-lasting deleterious consequences in preterm infants. Olfactory stimulation using vanilla odor is beneficial for apnea of prematurity in the first postnatal days/weeks. We aimed to determine for the first time whether vanilla odor can also decrease PB-related intermittent hypoxia.

METHOD

This pilot study was a balanced crossover clinical trial including 27 premature infants born between 30 and 33+6 weeks of gestation. We performed 12-h recordings on two nights separated by a 24-h period. All infants were randomly exposed to vanilla odor on the first or second study night. The primary outcome was the desaturation index, defined as the number per hour of pulse oximetry (SpO2) values <90 % for at least 5 s, together with a drop of ≥5 % from the preceding value. Univariate mixed linear models were used for the statistical analysis.

RESULTS

Overall, exposure to vanilla odor did not significantly decrease the desaturation index (52 ± 22 events/h [mean ± SD] on the intervention night vs. 57 ± 26, p = 0.2); furthermore, it did not significantly alter any secondary outcome. In a preliminary post hoc subgroup analysis, however, the effect of vanilla odor was statistically significant in infants with a desaturation index of ≥70/h (from 86 ± 12 to 65 ± 23, p = 0.04).

CONCLUSION

In this pilot study, vanilla odor overall did not decrease PB-related intermittent hypoxia in infants born at 30-33+6 weeks of gestation, which is when they are close to term. Preliminary results suggesting a beneficial effect in infants with the highest desaturation index, however, justify further studies in the presence of PB-related intermittent hypoxia as well as in infants born more prematurely.

Machine learning model with output correction: Towards reliable bradycardia detection in neonates

Bradycardia is a commonly occurring condition in premature infants, often causing serious consequences and cardiovascular complications. Reliable and accurate detection of bradycardia events is pivotal for timely intervention and effective treatment. Excessive false alarms pose a critical problem in bradycardia event detection, eroding trust in machine learning (ML)-based clinical decision support tools designed for such detection. This could result in disregarding the algorithm's accurate recommendations and disrupting workflows, potentially compromising the quality of patient care. This article introduces an ML-based approach incorporating an output correction element, designed to minimise false alarms. The approach has been applied to bradycardia detection in preterm infants. We applied five ML-based autoencoder techniques, using recurrent neural network (RNN), long-short-term memory (LSTM), gated recurrent unit (GRU), 1D convolutional neural network (1D CNN), and a combination of 1D CNN and LSTM. The analysis is performed on ∼440 hours of real-time preterm infant data. The proposed approach achieved 0.978, 0.73, 0.992, 0.671 and 0.007 in AUC-ROC, AUC-PRC, recall, F1 score, and false positive rate (FPR) respectively and a false alarms reduction of 36% when compared with methods without the correction approach. This study underscores the imperative of cultivating solutions that alleviate alarm fatigue and encourage active engagement among healthcare professionals.

Early versus late caffeine and/or non-steroidal anti-inflammatory drugs (NSAIDS) for prevention of intermittent hypoxia-induced neuroinflammation in the neonatal rat

Preterm infants often experience frequent intermittent hypoxia (IH) episodes which are associated with neuroinflammation. We tested the hypotheses that early caffeine and/or non-steroidal inflammatory drugs (NSAIDs) confer superior therapeutic benefits for protection against IH-induced neuroinflammation than late treatment. Newborn rats were exposed to IH or hyperoxia (50% O2) from birth (P0) to P14. For early treatment, the pups were administered: 1) daily caffeine (Caff) citrate (Cafcit, 20 mg/kg IP loading on P0, followed by 5 mg/kg from P1-P14); 2) ketorolac (Keto) topical ocular solution in both eyes from P0 to P14; 3) ibuprofen (Ibu, Neoprofen, 10 mg/kg loading dose on P0 followed by 5 mg/kg/day on P1 and P2); 4) Caff+Keto co-treatment; 5) Caff+Ibu co-treatment; or 6) equivalent volume saline (Sal). On P14, animals were placed in room air (RA) with no further treatment until P21. For late treatment, pups were exposed from P0 to P14, then placed in RA during which they received similar treatments from P15-P21 (Sal, Caff, and/or Keto), or P15-P17 (Ibu). RA controls were similarly treated. At P21, whole brains were assessed for histopathology, apoptosis, myelination, and biomarkers of inflammation. IH caused significant brain injury and hemorrhage, inflammation, reduced myelination, and apoptosis. Early treatment with Caff alone or in combination with NSAIDs conferred better neuroprotection against IH-induced damage than late treatment. Early postnatal treatment during a critical time of brain development, may be preferable for the prevention of IH-induced brain injury in preterm infants.

Does Perinatal Intermittent Hypoxia Affect Cerebrovascular Network Development?

Perinatal hypoxia is an inadequate delivery of oxygen to the fetus in the period immediately before, during, or after the birth process. The most frequent form of hypoxia occurring in human development is chronic intermittent hypoxia (CIH) due to sleep-disordered breathing (apnea) or bradycardia events. CIH incidence is particularly high with premature infants. During CIH, repetitive cycles of hypoxia and reoxygenation initiate oxidative stress and inflammatory cascades in the brain. A dense microvascular network of arterioles, capillaries, and venules is required to support the constant metabolic demands of the adult brain. The development and refinement of this microvasculature is orchestrated throughout gestation and in the initial weeks after birth, at a critical juncture when CIH can occur. There is little knowledge on how CIH affects the development of the cerebrovasculature. However, since CIH (and its treatments) can cause profound abnormalities in tissue oxygen content and neural activity, there is reason to believe that it can induce lasting abnormalities in vascular structure and function at the microvascular level contributing to neurodevelopmental disorders. This mini-review discusses the hypothesis that CIH induces a positive feedback loop to perpetuate metabolic insufficiency through derailment of normal cerebrovascular development, leading to long-term deficiencies in cerebrovascular function.

Periodic breathing in clinically stable very preterm infants

OBJECTIVE

We aimed to investigate the frequency and severity of periodic breathing (PB) in clinically stable very preterm infants and identify infant and maternal factors associated with increased time spent and severity of PB in these infants.

METHOD

Thirty-eight infants (28-32 weeks gestational age) who were ≥3 days off noninvasive respiratory support, were studied for 2-3 h with a daytime sleep study at 31-36 weeks postmenstrual age. Percent total sleep time spent in PB (%TSTPB) and time spent with SpO₂ <90%, <80%, and cerebral oxygenation <55% during PB were calculated. Infant and maternal characteristics were correlated with %TSTPB and hypoxia during PB.

RESULTS

The majority of infants (92%) had at least one episode of PB and infants spent a median 9.1 [interquartile range: 1.2, 15.5] %TSTPB. 80%, 37%, and 37% of infants experienced SpO₂ <90%, <80% and cerebral oxygenation <55%, respectively, during PB. Shorter duration of respiratory support, multigravida, multiparity, and maternal vitamin D deficiency were associated with higher %TSTPB. Multigravida, shorter duration on respiratory support, apnea of prematurity, and resuscitation at birth were associated with hypoxia during PB.

CONCLUSIONS

The majority of very preterm infants exhibited PB when they were off respiratory support and considered clinically stable. The time spent in PB was very variable between infants and was associated with significant hypoxia in some infants. Fewer days spent on respiratory support was associated with both increased frequency and severity of PB. However, the potential contribution of PB to neurocognitive outcomes remains uncertain and warrants further investigations.

Effect of one-lung ventilation on the correlation between left and right cerebral saturation

BACKGROUND

To investigate if the correlation between left and right cerebral tissue oxygen saturation (SctO₂) was affected by one-lung ventilation (OLV) in patients undergoing lung cancer surgery.

METHODS

Patients who underwent surgery for lung cancer were enrolled. Left and right SctO₂ were collected during anesthesia. The primary outcome was the correlation between left and right SctO₂ at 30 min after OLV which was analysed by Pearson correlation and linear regression model. Secondary outcomes included the trend of left-right SctO₂ change over the first 30 min after OLV, correlation of left-right SctO₂ during OLV for each patient; maximal difference between left-right SctO₂ and its relationship with postoperative delirium.

RESULTS

Left-right SctO₂ was moderately correlated at baseline (r = 0.690, P < 0.001) and poorly correlated at 30 min after OLV (r = 0.383, P < 0.001) in the Pearson correlation analysis. Linear regression analysis showed a poor correlation between left and right SctO₂ at 30 min after OLV (r = 0.323, P < 0.001) after adjusting for confounders. The linear mixed model showed a change in left-right SctO₂ over the first 30 min after OLV that was statistically significant (coefficient, -0.042; 95% CI, -0.070--0.014; P = 0.004). For the left-right SctO₂ correlation during OLV in each patient, 62.9% (78/124) patients showed a strong correlation, 19.4% (24/124) a medium correlation, and the rest a poor correlation. The maximal difference between the left and right SctO₂ was 13.5 (9.0, 20.0). Multivariate analysis showed that it was not associated with delirium (odds ratio [OR], 1.023; 95% CI, 0.963-1.087; P = 0.463).

CONCLUSIONS

The correlation between left and right SctO₂ was affected by one-lung ventilation in patients undergoing lung cancer surgery. This result indicates the requirement of bilateral SctO₂ monitoring to reflect brain oxygenation.

TRIAL REGISTRATION

This study was a secondary analysis of a cohort study approved by the Clinical Research Review Board of Peking University First Hospital (#2017-1378) and was registered in the Chinese Clinical Trial Registry on 10/09/2017 ( http://www.chictr.org.cn , ChiCTR-ROC-17012627).

Cumulative hypoxia, socioeconomic deprivation and neurodevelopmental outcomes in preterm infants

BACKGROUND

Hypoxia can adversely affect cognition, while socioeconomic deprivation has also been associated with impaired neurodevelopment in the newborn. We aimed to assess the impact of hypoxia and socioeconomic deprivation on the neurodevelopmental outcomes of preterm infants.

METHODS

Retrospective cohort study at a tertiary neonatal unit between 2015 and 2018. The motor, cognitive and language domain scores of the Bayley-III assessment were recorded at 24 months of corrected gestational age. The percentage of time with pulse oximetry (SpO₂) < 75% was measured from the nursing records, from admission to 36 weeks postmenstrual age in infants born < 30 weeks gestational age. The multiple deprivation index (MDI) and the main care giver's education domain of the MDI were also recorded.

RESULTS

A total of 93,767 data points from 80 infants (34 male) with a median (IQR) gestational age of 27.9(25.9-29.0) weeks and a birth weight of 0.94(0.74-1.23) kg were analysed. The median (IQR) motor score [103(91-110)] was significantly related to the median (IQR) time with SpO₂ < 75% [1.5(0.9-3.4)%, adjusted p = 0.020]. The median (IQR) cognitive score [100(90-105)] was negatively significantly related to the time with SpO₂ < 75% (adjusted p = 0.012) and the median (IQR) education decile of the MDI [7(6-9), adjusted p = 0.011]. The median (IQR) language score [91(77-100)] was significantly positively related to the education domain of the MDI (adjusted p = 0.025).

CONCLUSIONS

Hypoxia in preterm infants exerted a negative impact on motor function and cognition and conversely, higher educational attainment had a positive impact on cognition and language.

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

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

Neurally adjusted ventilatory assist in ventilated very preterm infants: A crossover study

OBJECTIVE

To assess the effects of neurally adjusted ventilatory assist (NAVA) ventilation on oxygenation and respiratory parameters in preterm infants.

STUDY DESIGN

An observational crossover study with a convenience sample of 19 infants born before 30 gestational weeks. Study parameters were recorded during 3-h periods of both NAVA and conventional ventilation. The proportion of time peripheral oxygen saturation (SpO₂ ) and cerebral regional oxygen saturation (cRSO₂ ) were within their target ranges, plus the number and severity of desaturation episodes were analyzed. In addition, electrical activity of the diaphragm (Edi), neural respiratory rates, and peak inspiratory pressures (PIPs) were recorded.

RESULTS

Infants were born at a median age of 26^4/7 gestational weeks (range: 23^0/7 -29^3/7 ); the study was performed at a median age of 20 days (range: 1-82). The proportion of time SpO₂ was within the target range, the number of peripheral desaturations or cRSO₂ did not differ between the modes. However, the desaturation severity index was lower (131 vs. 152; p = .03) and fewer manual supplemental oxygen adjustments (1.3 vs. 2.2/h; p = .006) were needed during the period of NAVA ventilation following conventional ventilation. The mean Edi (8.1 vs. 11.4 µV; p < .006) and PIP values (14.9 vs. 19.1; p < .001) were lower during the NAVA mode.

CONCLUSIONS

Although NAVA ventilation did not increase the proportion of time with optimal saturation, it was associated with decreased diaphragmatic activity, lower PIPs, less severe hypoxemic events, and fewer manual oxygen adjustments in very preterm infants.

Caffeine for the Pharmacological Treatment of Apnea of Prematurity in the NICU: Dose Selection Conundrum, Therapeutic Drug Monitoring and Genetic Factors

Caffeine citrate is the drug of choice for the pharmacological treatment of apnea of prematurity. Factors such as maturity and genetic variation contribute to the interindividual variability in the clinical response to caffeine therapy in preterm infants, making the optimal dose administered controversial. Moreover, the necessity for therapeutic drug monitoring (TDM) of caffeine is still worth discussing due to the need to achieve the desired target concentrations as well as concerns about the safety of higher doses. Therefore, we reviewed the pharmacokinetic profile of caffeine in preterm infants, evidence of the safety and efficacy of different doses of caffeine, therapeutic concentration ranges of caffeine and impact of genetic variability on caffeine therapy. Whereas the safety and efficacy of standard-dose caffeine have been demonstrated, evidence for the safety of higher administered doses is insufficient. Thus, preterm infants who lack clinical response to standard-dose caffeine therapy are of interest for TDM when dose optimization is performed. Polymorphisms in pharmacodynamics-related genes, but not in pharmacokinetics-related genes, have a significant impact on the interindividual variability in clinical response to caffeine therapy. For preterm infants lacking clinical response, how to develop individualized medication regimens for caffeine remains to be explored.

Early bradycardia detection and therapeutic interventions in preterm infant monitoring

In very preterm infants, cardio-respiratory events and associated hypoxemia occurring during early postnatal life have been associated with risks of retinopathy, growth alteration and neurodevelopment impairment. These events are commonly detected by continuous cardio-respiratory monitoring in neonatal intensive care units (NICU), through the associated bradycardia. NICU nurse interventions are mainly triggered by these alarms. In this work, we acquired data from 52 preterm infants during NICU monitoring, in order to propose an early bradycardia detector which is based on a decentralized fusion of three detectors. The main objective is to improve automatic detection under real-life conditions without altering performance with respect to that of a monitor commonly used in NICU. We used heart rate lower than 80 bpm during at least 10 sec to define bradycardia. With this definition we observed a high rate of false alarms (64%) in real-life and that 29% of the relevant alarms were not followed by manual interventions. Concerning the proposed detection method, when compared to current monitors, it provided a significant decrease of the detection delay of 2.9 seconds, without alteration of the sensitivity (97.6% vs 95.2%) and false alarm rate (63.7% vs 64.1%). We expect that such an early detection will improve the response of the newborn to the intervention and allow for the development of new automatic therapeutic strategies which could complement manual intervention and decrease the sepsis risk.

A Review of Cerebral Hemodynamics During Sleep Using Near-Infrared Spectroscopy

Investigating cerebral hemodynamic changes during regular sleep cycles and sleep disorders is fundamental to understanding the nature of physiological and pathological mechanisms in the regulation of cerebral oxygenation during sleep. Although sleep neuroimaging methods have been studied and have been well-reviewed, they have limitations in terms of technique and experimental design. Neurologists are convinced that Near-infrared spectroscopy (NIRS) provides essential information and can be used to assist the assessment of cerebral hemodynamics, and numerous studies regarding sleep have been carried out based on NIRS. Thus, a brief historical overview of the sleep studies using NIRS will be helpful for the biomedical students, academicians, and engineers to better understand NIRS from various perspectives. In this study, the existing literature on sleep studies is reviewed, and an overview of the NIRS applications is synthesized and provided. The paper first reviews the application scenarios, as well as the patterns of fluctuation of NIRS, which includes the investigation in regular sleep and sleep-disordered breathing. Various factors such as different sleep stages, populations, and degrees of severity were considered. Furthermore, the experimental design and signal processing, as well as the regulation mechanisms involved in regular and pathological sleep, are investigated and discussed. The strengths and weaknesses of the existing NIRS applications are addressed and presented, which can direct further NIRS analysis and utilization.

Cardiovascular and cerebrovascular responses to cardio-respiratory events in preterm infants during the transitional period

KEY POINTS

Non-invasive simultaneous multiparametric monitoring allows the in vivo evaluation of cerebral and cardiovascular haemodynamic responses to different types of recurrent episodes of intermittent hypoxia and/or bradycardia, also defined as cardio-respiratory events (CRE), in preterm neonates during postnatal transition. By decreasing left cardiac output, bradycardia further contributes to cerebral hypoxia during CRE. The presence of a haemodynamically significant patent ductus arteriosus results in a deeper impairment of cerebral oxygen status in response to CRE, whereas the brain-sparing remodelling of the fetal circulation resulting from placental insufficiency is associated with more favourable haemodynamic responses to intermittent hypoxia. During transition, the haemodynamic impact of CRE is influenced not only by the event type, but also by specific clinical features; this highlights the importance of developing individualized approaches to reduce the hypoxic burden in this delicate phase.

ABSTRACT

The present observational prospective study aimed to investigate cerebral and cardiovascular haemodynamic responses to different types of cardio-respiratory events (CRE) in preterm infants during postnatal transition, as well as evaluate the impact of relevant clinical characteristics. Infants with gestational age (GA) <32 weeks and/or birth weight <1500 g were enrolled after birth. Cerebral oxygenation index (cTOI), fractional oxygen extraction (cFTOE), cardiac output (CO), cardiac contractility (iCON) and systemic vascular resistances (sVR) were simultaneously monitored over the first 72 h by near-infrared spectroscopy and electrical velocimetry. CRE were clustered into isolated bradycardia (IB), isolated desaturation (ID) and combined desaturation/bradycardia (DB). For each parameter, percentage changes from baseline (%Δ) were calculated. The impact of different CRE types and clinical variables on %Δ was evaluated with generalized estimating equations. In total, 1426 events were analysed. %ΔcTOI significantly differed among ID, IB and DB (P < 0.001), with the latter showing the greatest drop. %ΔcFTOE decreased significantly during DB (P < 0.001) and ID (P < 0.001) compared to IB. DB and IB were associated with more negative %ΔCO (P < 0.001) and more positive %ΔsVR (P < 0.001) compared to ID. A slight iCON reduction was observed during DB compared to ID (P = 0.043). Antenatal umbilical Doppler impairment, GA and the presence of a haemodynamically significant patent ductus arteriosus had a significant independent impact on %ΔcTOI, %ΔcFTOE and %ΔCO. During the transitional period, the haemodynamic responses to CRE are influenced by the event type and by specific neonatal characteristics, suggesting the importance of targeted individualized approaches for minimizing the risk of cerebral injury in the preterm population.

Cardiorespiratory Events in Infants Born Preterm during the Transitional Period

OBJECTIVE

To investigate the features of cardiorespiratory events in infants born preterm during the transitional period, and to evaluate whether different neonatal characteristics may correlate with event type, duration, and severity.

STUDY DESIGN

Infants with gestational age (GA) <32 weeks and/or birth weight <1500 g were enrolled in this observational prospective study. Heart rate (HR) and peripheral oxygen saturation (SpO₂) were recorded continuously over the first 72 hours. Cardiorespiratory events of ≥10 seconds were clustered into isolated desaturation (SpO₂ <85%), isolated bradycardia (HR <100 bpm or <70% of baseline), or combined desaturation/bradycardia and classified as mild, moderate, or severe. The daily incidences of isolated desaturation, isolated bradycardia, and combined desaturation and bradycardia were analyzed. The effects of relevant clinical variables on cardiorespiratory event type and severity were assessed using generalized estimating equations.

RESULTS

Among the 1050 events analyzed, isolated desaturations were the most frequent (n = 625) and isolated bradycardias the least common (n = 171). The number of cardiorespiratory events increased significantly from day 1 to day 2 (P = .028). One in 5 events had severe characteristics; event severity was highest for combined desaturation and bradycardia (P < .001). Compared with other event types, the incidence of combined desaturation and bradycardia was inversely correlated with GA (P = .029) and was higher with the use of continuous positive airway pressure (P = .002). The presence of a hemodynamically significant patent ductus arteriosus was associated with the occurrence of isolated desaturations (P = .001) and with a longer duration of cardiorespiratory events (P = .003).

CONCLUSIONS

Cardiorespiratory events during transition exhibit distinct types, duration, and severity. Neonatal characteristics are associated with the clinical features of these events, indicating that a tailored clinical approach may reduce the hypoxic burden in preterm infants aged 0-72 hours.

NAVA-synchronized compared to nonsynchronized noninvasive ventilation for apnea, bradycardia, and desaturation events in VLBW infants

Neurally adjusted ventilatory assistance (NAVA) can overcome technical difficulties with synchronizing noninvasive ventilation breaths with the patient, a modality often used in very low birthweight infants (VLBW) with apnea of prematurity (AOP). This study is a retrospective single-center investigation into whether NAVA-synchronized noninvasive (niNAVA) ventilation is better than nonsynchronized (nasal intermittent positive pressure ventilation [nIPPV]) for symptomatic apnea in VLBW infants. Nursing records of apnea, bradycardia, and/or desaturations were abstracted from the electronic medical records of 108 VLBW infants admitted to the neonatal intensive care unit (NICU) from 2015 to 2017 who received either of the two modalities, 61 epochs of niNAVA totaling 488 days and 103 epochs of nIPPV totaling 886.5 days. niNAVA was associated with a significant reduction in the number of isolated bradycardic events/day (0.48 ± 0.14 vs 1.35 ± 0.27; P = .019) and overall bradycardias/day (2.42 ± 0.47 vs 4.02 ± 0.53; P = .042) and there were more epochs with no events with niNAVA compared with nIPPV (23.0% vs 6.8%; P = .004). These results justify a prospective trial of NAVA-synchronized noninvasive ventilation for VLBW infants with caffeine-resistant AOP.

Intermittent Hypoxemia in Preterm Infants

Intermittent hypoxemia (IH) events are common during early postnatal life, particularly in preterm infants. These events have been associated with multiple morbidities, including retinopathy of prematurity, sleep disordered breathing, neurodevelopmental impairment, and mortality. The relationship between IH and poor outcomes may depend on the patterns (frequency, duration, and timing) of the IH events. Current treatment modalities used in the clinical setting have been only partially successful in reducing the incidence of apnea and accompanying IH, but the risks and benefits of more aggressive interventions should include knowledge of the relationship between IH and morbidity.

Oxygen desaturations in the early neonatal period predict development of bronchopulmonary dysplasia

BACKGROUND

Bradycardia and oxygen desaturation episodes are common among preterm very low birth weight (VLBW) infants in the Neonatal Intensive Care Unit (NICU), and their association with adverse outcomes such as bronchopulmonary dysplasia (BPD) is unclear.

METHODS

For 502 VLBW infants we quantified bradycardias (HR < 100 for ≥ 4 s) and desaturations (SpO₂ < 80% for ≥ 10 s), combined bradycardia and desaturation (BD) events, and percent time in events in the first 4 weeks after birth (32 infant-years of data). We tested logistic regression models of clinical risks (including a respiratory acuity score incorporating FiO₂ and level of respiratory support) to estimate the risks of BPD or death and secondary outcomes. We then tested the additive value of the bradycardia and desaturation metrics for outcomes prediction.

RESULTS

BPD occurred in 187 infants (37%). The clinical risk model had ROC area for BPD of 0.874. Measures of desaturation, but not bradycardia, significantly added to the predictive model. Desaturation metrics also added to clinical risks for prediction of severe intraventricular hemorrhage, retinopathy of prematurity and prolonged length of stay in the NICU.

CONCLUSIONS

Oxygen desaturations in the first month of the NICU course are associated with risk of BPD and other morbidities in VLBW infants.

High-mobility group box-1 translocation and release after hypoxic ischemic brain injury in neonatal rats

Inflammation contributes to neonatal brain injury. Pro-inflammatory cytokines represent key inflammatory meditators in neonatal hypoxic-ischemic (HI) brain injury. The high mobility group box-1 (HMGB1) protein is a nuclear protein with pro-inflammatory cytokine properties when it is translocated from the nucleus and released extracellularly after stroke in adult rodents. We have previously shown that HMGB1 is translocated from the nucleus to cytosolic compartment after ischemic brain injury in fetal sheep. In the current study, we utilized the Rice-Vannucci model to investigate the time course of HMGB1 translocation and release after HI injury in neonatal rats. HMGB1 was located in cellular nuclei of brains from sham control rats. Nuclear to cytoplasmic translocation of HMGB1 was detected in the ipsilateral-HI hemisphere as early as zero h after HI, and released extracellularly as early as 6 h after HI. Immunohistochemical double staining detected HMGB1 translocation mainly in neurons along with release from apoptotic cells after HI. Serum HMGB1 increased at 3 h and decreased by 24 h after HI. In addition, rat brains exposed to hypoxic injury alone also exhibited time dependent HMGB1 translocation at 3, 12 and 48 h after hypoxia. Consequently, HMGB1 responds similarly after HI injury in the brains of neonatal and adult subjects. We conclude that HMGB1 is sensitive early indicator of neonatal HI and hypoxic brain injury.

Bradycardias are associated with more severe effects on cerebral oxygenation in very preterm infants than in late preterm infants

BACKGROUND

Commonly the magnitude and frequency of bradycardia is underestimated in the neonatal unit due to the long averaging time used in bedside oximeters. We aimed to assess the frequency and severity of bradycardia in preterm infants using the lowest averaging time (2 s) available on a clinical oximeter, compared with bradycardia detected using electrocardiogram (ECG), and whether bradycardia severity and postmenstrual age affected cerebral oxygenation.

METHODS

Preterm infants (10 M/9F) were studied longitudinally at 26-31 (very preterm) and 32-38 weeks (late preterm) postmenstrual age. Heart rate falls calculated from ECG were used to determine mild or moderate/severe (MS) bradycardias. Cerebral tissue oxygenation index (TOI, %) was recorded and fractional tissue oxygen extraction (FTOE) calculated.

RESULTS

Of the 615 bradycardias scored using ECG criteria, 10% were not detected by oximetry. TOI falls associated with bradycardias were greater for MS bradycardias compared with Mild for both groups (p < 0.001 for both). The FTOE associated with MS bradycardias was higher for the very preterm compared with the late preterm group (p < 0.001). In very preterm infants 61% of MS and 35% Mild bradycardias were associated with TOI nadirs below 55%.

CONCLUSION

Even the most sensitive oximeter setting underestimates bradycardias. The cerebral effect from bradycardias in very preterm infants is more severe than in late preterm infants. Even the mild bradycardias are associated with falls in cerebral oxygenation. Routine NIRS monitoring of cerebral oxygenation in NICUs may increase staff awareness for interventions to reduce the repetitive falls in cerebral oxygenation in preterm infants.

Interpretation of Cerebral Oxygenation Changes in the Preterm Infant

Near-infrared spectroscopy (NIRS) allows for continuous, non-invasive monitoring of end-organ tissue oxygenation. The use of NIRS, cerebral NIRS (cNIRS) in particular, in neonatal care has increased significantly over the last few years. This dynamic monitoring technique provides real-time information on the cerebral and haemodynamic status of the neonate and has the potential to serve as an important adjunct to patient care with some centres routinely utilising cNIRS to aid decision-making at the bedside. cNIRS values may be influenced by many variables, including cardiac, respiratory and metabolic parameters, and therefore it is essential to understand the pathophysiology behind alterations in cNIRS values. Correct interpretation is required to direct appropriate patient-specific interventions. This article aims to assist clinicians in deciphering cNIRS values by providing an overview of potential causes of fluctuations in cNIRS values, illustrated by common clinical scenarios, with particular emphasis on the preterm infant.

Feed-related Splanchnic Oxygenation in Preterm Infants With Abnormal Antenatal Doppler Developing Gut Complications

Preterm infants with antenatal absent or reversed end diastolic flow (AREDF) in umbilical arteries are at major risk for gastrointestinal (GI) complications, such as necrotizing enterocolitis, intestinal perforation and feeding intolerance. Near-infrared spectroscopy provides continuous monitoring of splanchnic oxygenation (SrSO2) and may represent a useful tool to predict GI outcomes in this high-risk population. This observational, pilot study assessed feed-related SrSO2 patterns at enteral feeding introduction and full enteral feeding (FEF) achievement in twenty AREDF infants with gestational age ≤34 weeks. Enrolled infants were divided into 2 groups according to the development versus lack of GI complications. Infants developing GI complications showed significantly lower SrSO2 and increased splanchnic oxygen extraction in response to enteral feeds at both enteral feeding introduction and FEF. The potential role of these findings in predicting GI complications in AREDF preterm infants seems promising and deserves further evaluation.

Cerebellar Growth Impairment Characterizes School-Aged Children Born Preterm without Perinatal Brain Lesions

BACKGROUND AND PURPOSE

Infants born preterm are commonly diagnosed with structural brain lesions known to affect long-term neurodevelopment negatively. Yet, the effects of preterm birth on brain development in the absence of intracranial lesions remain to be studied in detail. In this study, we aim to quantify long term consequences of preterm birth on brain development in this specific group.

MATERIALS AND METHODS

Neonatal cranial sonography and follow-up T1-weighted MR imaging and DTI were performed to evaluate whether the anatomic characteristics of the cerebrum and cerebellum in a cohort of school-aged children (6-12 years of age) were related to gestational age at birth in children free of brain lesions in the perinatal period.

RESULTS

In the cohort consisting of 36 preterm (28-37 weeks' gestational age) and 66 term-born infants, T1-weighted MR imaging and DTI at 6-12 years revealed a reduction of cerebellar white matter volume (β = 0.387, P < .001), altered fractional anisotropy of cerebellar white matter (β = -0.236, P = .02), and a reduction of cerebellar gray and white matter surface area (β = 0.337, P < .001; β = 0.375, P < .001, respectively) in relation to birth age. Such relations were not observed for the cerebral cortex or white matter volume, surface area, or diffusion quantities.

CONCLUSIONS

The results of our study show that perinatal influences that are not primarily neurologic are still able to disturb long-term neurodevelopment, particularly of the developing cerebellum. Including the cerebellum in future neuroprotective strategies seems therefore essential.

Cerebral oxygenation during skin-to-skin care in preterm infants not receiving respiratory support

OBJECTIVE

Skin-to-skin care (SSC) has proven benefits in preterm infants, but increased hypoxic and bradycardic events have been reported. This may make clinicians hesitant to recommend SSC as standard care. We hypothesised that regional cerebral oxygenation (rStO₂) measured with near infrared spectroscopy is not worse during SSC compared with standard incubator care.

DESIGN

Prospective, observational, non-inferiority study.

SETTING

Single tertiary perinatal centre in Australia.

PATIENTS

Forty preterm infants (median (IQR) 30.6 (29.1-31.7) weeks' gestation) not receiving respiratory support were studied on day 14 (8-38).

INTERVENTIONS

Recordings during 90 min of incubator care, followed by 90 min of SSC. Each infant acted as their own control and caregivers were blinded to the rStO₂ measurements.

MAIN OUTCOME MEASURES

The primary outcome was the mean difference in rStO₂ between SSC and incubator care. The prespecified margin of non-inferiority was -1.5%. Secondary outcomes included heart rate (HR), peripheral oxygen saturation (SpO₂), time in quiet sleep, temperature and hypoxic (SpO₂ <80% for >5 s) or bradycardic events (HR <80 bpm for >5 s) and time spent in cerebral hypoxia (rStO₂<55%) and hyperoxia (rStO₂>85%).

RESULTS

Mean (SD) rStO₂ was lower during SSC compared with incubator care: 73.6 (6.0)% vs 74.8 (4.6)%, mean difference (95% CI) 1.3 (2.2 to 0.4)%. HR was 5 bpm higher, SpO₂ 1% lower and time in quiet sleep 24% longer during SSC. Little evidence of a difference was observed in temperature. The number of hypoxic or bradycardic events as well as the proportion of time spent in cerebral hypoxia and hyperoxia was very low in both periods.

CONCLUSIONS

Mean rStO₂ was marginally lower during SSC without observed differences in hypoxic or bardycardic events but an increase in time spent in quiet sleep.

TRIAL REGISTRATION NUMBER

This trial is linked to Australian New Zealand Clinical Trials Registry: identifier 12616000240448. It was registered pre-results.

The role of near-infrared spectroscopy monitoring in preterm infants

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

Oxygen saturation targeting by pulse oximetry in the extremely low gestational age neonate: a quixotic quest

PURPOSE OF REVIEW

A collaboration of comparative effectiveness research trials of pulse oximeter saturation (SpO2) targeting in extremely low-gestational-age neonates have begun to report their aggregate results. We examine the results of those trials, collectively referred to as the Neonatal Oxygenation Prospective Meta-analysis or NeOProM. We also discuss the uncertainties that remain and the clinical challenges that lie ahead.

RECENT FINDINGS

The primary outcome from NeOProM was a composite of death or disability at 18-24 months corrected age. In 2016 the last of these reports was published. Although there were no differences in the primary outcome overall, analyses of secondary outcomes and data subsets following a pulse oximeter revision show significant treatment differences between targeting a lower compared with a higher SpO2.

SUMMARY

NeOProM represents the largest collaborative clinical research study of SpO2 targets in extremely low-gestational-age neonates. Although aggregate results give us some insight into the feasibility and efficacy of SpO2 targeting in this population, many questions remain. A patient-level analysis, tracking individual outcomes based on actual SpO2 experienced, may shed some light on these questions. However, finding a single optimal SpO2 range seems unlikely.

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.

Cerebral oxygenation and desaturations in preterm infants - a longitudinal data analysis

OBJECTIVE

Hypoxemic episodes commonly occur in very preterm infants and may be associated with several adverse effects. Cerebral tissue oxygen saturation (StO2) as measured by near infrared spectroscopy (NIRS) may be a useful measure to assess brain oxygenation. However, knowledge on variability of StO2 is limited in preterm infants at this time, so StO2 dependency on arterial oxygenation (SpO2) and heart rate (HR) was assessed in preterm infants using statistical methods of time series analysis.

STUDY DESIGN

StO2, SpO2, and HR were recorded from 15 preterm infants every 2 seconds for six hours. Statistical methods of time series and longitudinal data analysis were applied to the data.

RESULT

The mean StO2 level was found as 72% (95% confidence interval (CI) 55.5% -85.5%) based on a moving average process with a 5 minute order. Accordingly, longitudinal SpO2 measurements showed a mean level of 91% (95% CI 69% -98%). Generally, compensation strategies to cope with both StO2 and SpO2 desaturations were observed in the studied patients. SpO2 had a significant effect on cerebral oxygenation (p < 0.001), but HR did not, which led to inconclusive results considering different time intervals.

CONCLUSION

In infants with intermittent hypoxemia and bradycardia, we found a mean StO2 level of 72% and a strong correlation with SpO2. We observed large differences between individuals in the ability to maintain StO2 at a stable level.

Predicting Bradycardia in Preterm Infants Using Point Process Analysis of Heart Rate

OBJECTIVE

Episodes of bradycardia are common and recur sporadically in preterm infants, posing a threat to the developing brain and other vital organs. We hypothesize that bradycardias are a result of transient temporal destabilization of the cardiac autonomic control system and that fluctuations in the heart rate signal might contain information that precedes bradycardia. We investigate infant heart rate fluctuations with a novel application of point process theory.

METHODS

In ten preterm infants, we estimate instantaneous linear measures of the heart rate signal, use these measures to extract statistical features of bradycardia, and propose a simplistic framework for prediction of bradycardia.

RESULTS

We present the performance of a prediction algorithm using instantaneous linear measures (mean area under the curve = 0.79 ± 0.018) for over 440 bradycardia events. The algorithm achieves an average forecast time of 116 s prior to bradycardia onset (FPR = 0.15). Our analysis reveals that increased variance in the heart rate signal is a precursor of severe bradycardia. This increase in variance is associated with an increase in power from low content dynamics in the LF band (0.04-0.2 Hz) and lower multiscale entropy values prior to bradycardia.

CONCLUSION

Point process analysis of the heartbeat time series reveals instantaneous measures that can be used to predict infant bradycardia prior to onset.

SIGNIFICANCE

Our findings are relevant to risk stratification, predictive monitoring, and implementation of preventative strategies for reducing morbidity and mortality associated with bradycardia in neonatal intensive care units.

Myocardial function during bradycardia events in preterm infants

BACKGROUND

Transient bradycardia episodes are common in preterm infants and often secondary to apnea. Decreased ventilation with resultant hypoxemia is believed to be the predominant mechanism. Sudden bradycardias without apnea are also reported, possibly due to vagal stimulation. Point of care ultrasound is used to diagnose and follow cardiovascular complications in preterm infants. Inadvertently, the operator would sometimes capture bradycardia events. This study reports on left ventricular function during such events.

METHODS

We retrospectively reviewed our cardiac ultrasound database for bradycardia events. Apical four or three chamber images before, during and after a bradycardia event were analysed with speckle tracking software which provides systolic and diastolic parameters of myocardial motion, deformation and volume.

RESULTS

Over a 2year period, 15 bradycardia events were noted in 14 patients with a median gestational age of 26weeks (range 23 to 29). Heart rate decreased by an average of 43% (171/min to 98/min). Myocardial velocity and longitudinal strain rate during the atrial component of diastole were reduced during bradycardia. Longitudinal strain during systole was increased and radial deformation was unchanged. Ventricular volumes and ejection fraction did not change. Most parameters returned to baseline values after the event. Longitudinal systolic strain rate remained lower and stroke volume was 12% higher compared to baseline.

CONCLUSION

Parameters of systolic contractility and stroke volume were maintained and parameters of atrial contractility were reduced during mild to moderate bradycardia in preterm infants. Bradycardia reduces total cardiac output with a compensatory increase detected following the event.