Body Temperature, Heart Rate, and Short-Term Outcome of Cooled Infants

Time to Reaching Target Cooling Temperature and 2-year Outcomes in Infants with Hypoxic-Ischemic Encephalopathy

OBJECTIVE

To determine if time to reaching target temperature (TT) is associated with death or neurodevelopmental impairment (NDI) at 2 years of age in infants with hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

Newborn infants ≥36 weeks of gestation diagnosed with moderate or severe HIE and treated with therapeutic hypothermia were stratified based on time at which TT was reached, defined as early (ie, ≤4 hours of age) or late (>4 hours of age). Primary outcomes were death or NDI. Secondary outcomes included neurodevelopmental assessment with Bayley Scales of Infant and Toddler Development, third edition (BSID-III) at age 2.

RESULTS

Among 500 infants, the median time to reaching TT was 4.3 hours (IWR, 3.2-5.7 hours). Infants in early TT group (n = 211 [42%]) compared with the late TT group (n = 289 [58%]) were more likely to be inborn (23% vs 13%; P < .001) and have severe HIE (28% vs 19%; P = .03). The early and late TT groups did not differ in the primary outcome of death or any NDI (adjusted RR, 1.05; 95% CI, 0.85-0.30; P = .62). Among survivors, neurodevelopmental outcomes did not differ significantly in the 2 groups (adjusted mean difference in Bayley Scales of Infant Development-III scores: cognitive, -2.8 [95% CI, -6.1 to 0.5], language -3.3 [95% CI, -7.4 to 0.8], and motor -3.5 [95% CI, -7.3 to 0.3]).

CONCLUSIONS

In infants with HIE, time to reach TT is not independently associated with risk of death or NDI at age 2 years. Among survivors, developmental outcomes are similar between those who reached TT at <4 and ≥4 hours of age.

TRIAL REGISTRATION

High-dose Erythropoietin for Asphyxia and Encephalopathy (HEAL); NCT02811263; https://beta.

CLINICALTRIALS

gov/study/NCT02811263.

Rectal temperature after hypoxia-ischemia predicts white matter and cortical pathology in the near-term ferret

BACKGROUND

Neonatal encephalopathy (NE) remains a common cause of infant morbidity and mortality. Neuropathological corollaries of NE associated with acute hypoxia-ischemia include a central injury pattern involving the basal ganglia and thalamus, which may interfere with thermoregulatory circuits. Spontaneous hypothermia (SH) occurs in both preclinical models and clinical hypoxic-ischemic NE and may provide an early biomarker of injury severity. To determine whether SH predicts the degree of injury in a ferret model of hypoxic-ischemic NE, we investigated whether rectal temperature (RT) 1 h after insult correlated with long-term outcomes.

METHODS

Postnatal day (P)17 ferrets were presensitized with Escherichia coli lipopolysaccharide before undergoing hypoxia-ischemia/hyperoxia (HIH): bilateral carotid artery ligation, hypoxia-hyperoxia-hypoxia, and right ligation reversal. One hour later, nesting RTs were measured.

RESULTS

Animals exposed to HIH were separated into normothermic (NT; ≥34.4 °C) or spontaneously hypothermic (SH; <34.4 °C) groups. At P42, cortical development, ex vivo MRI, and neuropathology were quantitated. Whole-brain volume and fractional anisotropy in SH brains were significantly decreased compared to control and NT animals. SH brains also had significantly altered gyrification, greater cortical pathology, and increased corpus callosum GFAP staining relative to NT and control brains.

CONCLUSION

In near-term-equivalent ferrets, nesting RT 1 h after HIH may predict long-term neuropathological outcomes.

IMPACT

High-throughput methods to determine injury severity prior to treatment in animal studies of neonatal brain injury are lacking. In a gyrified animal model of neonatal inflammation-sensitized hypoxic-ischemic brain injury in the ferret, rectal temperature 1 h after hypoxia predicts animals who will have increased cortical pathology and white matter changes on MRI. These changes parallel similar responses in rodents and humans but have not previously been correlated with long-term neuropathological outcomes in gyrified animal models. Endogenous thermoregulatory responses to injury may provide a translational marker of injury severity to help stratify animals to treatment groups or predict outcome in preclinical studies.

Time series analysis of non-invasive hemodynamic monitoring data in neonates with hypoxic-ischemic encephalopathy

Background and aims

Hemodynamic instability is common in neonates with hypoxic-ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH). Rewarming is a critical period and non-invasive circulatory monitoring may help guide cardiovascular supportive therapy. The aim of the study was to provide a comprehensive analysis of cardiac function parameters during TH and its relation to neurodevelopmental outcome.

Methods

In a prospective, observational study, 26 neonates with moderate-severe HIE were enrolled, born between 2016 and 2019. A hemodynamic monitor based on electrical velocimetry (ICON, Osypka Medical GmbH, Berlin, Germany) was used. Heart rate (HR), stroke volume (SV), cardiac output (CO) data were recorded continuously throughout TH and rewarming. Neurological outcome was assessed at 2 years of age using the Bayley Scales of Infant Development II. edition. Favorable outcome was defined as >70 points on both the psychomotor and mental scales. Time-series analysis was used and features of cardiac function were described to perform logistic regression modeling for outcome prediction.

Results

Fourteen (54%) patients had favorable and 12 (46%) had adverse outcome. Data collection started from median [IQR] of 11.8 [7.0; 24.3] hours (h) of life and lasted until 84.0. [81.8; 87.0] h. During TH, the mean HR of the favorable outcome group was significantly lower than that of the adverse outcome group (86 ± 13/min vs. 104 ± 18/min, p = 0.01). During rewarming HR increased similarly in both groups. SV was unaffected by rewarming, and showed a slowly increasing trend. SV of the favorable outcome group was significantly higher compared to the adverse outcome group (1.55 ± 0.23 ml/kg vs. 1.29 ± 0.30 ml/kg, p = 0.035). In line with this, CO was similar in both groups (136 ± 27 ml/kg/min vs. 134 ± 36 ml/kg/min), and a significant 25% increase in CO was observed during rewarming. Based on multiple regression modeling, HR during TH was independently associated with neurological outcome (p = 0.023).

Conclusion

Based on continuous hemodynamic monitoring, patients with adverse outcome have lower SV and higher HR to achieve similar CO to patients with favorable outcome during TH. HR during hypothermia is independently associated with the neurodevelopmental outcome.

Admission temperature of very low birth weight infants and outcomes at three years old

The lower body temperature of preterm newborns at admission to neonatal intensive care units (NICUs) is inversely associated with their morbidities and mortalities before discharge. This retrospective cohort study aimed to determine whether admission rectal temperature in very low birth weight infants (VLBWIs) is independently associated with a composite outcome of death or moderate-to-severe neurodevelopmental impairments as defined by a performance developmental quotient of < 70 at three years of age. VLBWIs admitted to the NICU between April 2010 and March 2016 were assesed. Developmental assessment was completed in 216 newborns. Nine and two infants died before and after discharge, respectively. A higher admission temperature was associated with a lower incidence of death or moderate-to-severe neurodevelopmental impairments with adjustment for gestational age, sex, antenatal steroid use, Apgar score, severe intraventricular hemorrhage, and severe bronchopulmonary dysplasia (odds ratio [OR] 0.424; 95% confidence interval [CI] 0.250-0.717; p = 0.001). The admission temperature remained as an independent variable of adverse outcome at three years of age even when the study cohort was limited to surviving infants (OR 0.448; 95% CI 0.259-0.774; p = 0.004). Further studies are needed to assess whether avoiding low body temperature at admission results in better long-term neurodevelopmental outcomes in VLBWIs.

Body temperature, heart rate and long-term outcome of cooled infants: an observational study

BACKGROUND

Therapeutic hypothermia is a standard of care for neonatal encephalopathy; however, approximately one in two newborn infants fails to respond to this treatment. Recent studies have suggested potential relationships between body temperature, heart rate and the outcome of cooled infants.

METHODS

The clinical data of 756 infants registered to the Baby Cooling Registry of Japan between January 2012 and December 2016 were analysed to assess the relationship between body temperature, heart rate and adverse outcomes (death or severe impairment at 18 months corrected age).

RESULTS

A lower body temperature at admission was associated with adverse outcomes in the univariate analysis (P < 0.001), the significance of which was lost when adjusted for the severity of encephalopathy and other covariates. A higher body temperature during cooling and higher heart rate before and during cooling were associated with adverse outcomes in both univariate (all P < 0.001) and multivariate (P = 0.012, P < 0.001 and P < 0.001, respectively) analyses.

CONCLUSIONS

Severe hypoxia-ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling, whereas causal relationships between slightly higher temperatures during cooling and adverse outcomes need to be elucidated in future studies.

IMPACT

In a large cohort of encephalopathic newborn infants, dual roles of body temperature to the outcome were shown; adverse outcomes were associated with a lower body temperature at admission and higher body temperature during cooling. A higher heart rate before and during cooling were associated with adverse outcomes. Severe hypoxia-ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling. The exact mechanism underlying the relationship between slightly higher body temperature during cooling and adverse outcomes remains unknown, which needs to be elucidated in future studies.

Blanket temperature during therapeutic hypothermia and outcomes in hypoxic ischemic encephalopathy

OBJECTIVE

Determine whether blanket temperatures during therapeutic hypothermia (TH) are associated with 18-22 month outcomes for infants with hypoxic ischemic encephalopathy (HIE).

STUDY DESIGN

Retrospective cohort study of 181 infants with HIE who received TH in two randomized trials within the Neonatal Research Network. We defined summative blanket temperature constructs and evaluated for association with a primary composite outcome of death or moderate/ severe disability at 18-22 months.

RESULTS

Each 0.5 °C above 33.5 °C in the mean of the highest quartile blanket temperature was associated with a 52% increase in the adjusted odds of death/ disability (aOR 1.52, 95% CI 1.09-2.11). Having >8 consecutive blanket temperatures above 33.5 °C rendered an aOR of death/disability of 5.04 in the first 24 h (95% CI 1.54-16.6) and 6.92 in the first 48 h (95% CI 2.20-21.8) of TH.

CONCLUSIONS

Higher blanket temperature during TH may be an early, clinically useful biomarker of HIE outcome.

A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows

The autonomic nervous system (ANS) is one of the main biological systems that regulates the body's physiology. Autonomic nervous system regulatory capacity begins before birth as the sympathetic and parasympathetic activity contributes significantly to the fetus' development. In particular, several studies have shown how vagus nerve is involved in many vital processes during fetal, perinatal, and postnatal life: from the regulation of inflammation through the anti-inflammatory cholinergic pathway, which may affect the functioning of each organ, to the production of hormones involved in bioenergetic metabolism. In addition, the vagus nerve has been recognized as the primary afferent pathway capable of transmitting information to the brain from every organ of the body. Therefore, this hypothesis paper aims to review the development of ANS during fetal and perinatal life, focusing particularly on the vagus nerve, to identify possible "critical windows" that could impact its maturation. These "critical windows" could help clinicians know when to monitor fetuses to effectively assess the developmental status of both ANS and specifically the vagus nerve. In addition, this paper will focus on which factors-i.e., fetal characteristics and behaviors, maternal lifestyle and pathologies, placental health and dysfunction, labor, incubator conditions, and drug exposure-may have an impact on the development of the vagus during the above-mentioned "critical window" and how. This analysis could help clinicians and stakeholders define precise guidelines for improving the management of fetuses and newborns, particularly to reduce the potential adverse environmental impacts on ANS development that may lead to persistent long-term consequences. Since the development of ANS and the vagus influence have been shown to be reflected in cardiac variability, this paper will rely in particular on studies using fetal heart rate variability (fHRV) to monitor the continued growth and health of both animal and human fetuses. In fact, fHRV is a non-invasive marker whose changes have been associated with ANS development, vagal modulation, systemic and neurological inflammatory reactions, and even fetal distress during labor.

Apgar score at 10 minutes and adverse outcomes among low-risk pregnancies

OBJECTIVE

Among low-risk pregnancies, we ascertained the association between 10-minute Apgar score and adverse outcomes of newborn infants.

METHOD

We conducted a retrospective cohort study using the U.S. vital statistics datasets (2011-2018), which included live births from low-risk women with non-anomalous singleton gestations who delivered at 37-41 weeks. When a newborn infant had an abnormal 5-minute Apgar score (0-5), a 10-minute Apgar score was documented in the birth certificate. Apgar score at 10 min was categorized as low (0-3), moderate (4-6), and normal (7-10). The primary outcome was composite neonatal adverse outcome. The secondary outcomes were individual neonatal adverse outcomes and infant mortality. Multivariable Poisson regression analyses were used to estimate the association between 10-minute Apgar score and adverse outcomes (using adjusted relative risk [aRR] and 95% confidence intervals [CI]).

RESULTS

Of 31.5 million live births delivered (2011-2018), 111,163 (0.4%) met inclusion criteria; of them, 74.2%, 20.7%, and 5.1% had normal, moderate, and low 10-minute Apgar scores, respectively. The overall composite neonatal adverse outcome was 100.6 per 1,000 live births and the risk was significantly higher among those with a moderate (aRR 3.19; 95% CI 3.06-3.31) or low 10-minute Apgar score (aRR 6.62; 95% CI 6.34-6.91) than with a normal 10-minute Apgar score. Infant mortality also showed a similar pattern. Newborn infants with improved Apgar scores from 5 to 10 min were associated with lower risks of the composite neonatal adverse outcome, as well as infant mortality, than those with scores that remained stable.

CONCLUSION

Among low-risk pregnancies, newborn infants with a lower 10-minute Apgar score were associated with a higher risk of adverse outcomes.

Outcomes related to 10-min Apgar scores of zero in Japan

OBJECTIVE

Apgar scores of zero at 10 min strongly predict mortality and morbidity in infants. However, recent data reported improved outcomes among infants with Apgar scores of zero at 10 min. We aimed to review the mortality rate and neurodevelopmental outcomes of infants with Apgar scores of zero at 10 min in Japan.

DESIGN

Observational study.

PATIENTS

Twenty-eight of 768 infants registered in the Baby Cooling Registry of Japan between 2012 and 2016, at >34 weeks' gestation, with Apgar scores of zero at 10 min who were treated with therapeutic hypothermia.

INTERVENTIONS

We investigated the time of first heartbeat detection in infants with favourable outcomes and who had neurodevelopmental impairments or died.

MAIN OUTCOME MEASURES

Clinical characteristics, mortality rate and neurodevelopmental outcomes at 18-22 months of age were evaluated.

RESULTS

Nine (32%) of the 28 infants died before 18 months of age; 16 (57%) survived, but with severe disabilities and 3 (11%) survived without moderate-to-severe disabilities. At 20 min after birth, 14 of 27 infants (52%) did not have a first heartbeat, 13 of them died or had severe disabilities and one infant, who had the first heartbeat at 20 min, survived without disability.

CONCLUSION

Our study adds to the recent evidence that neurodevelopmental outcomes among infants with Apgar scores of zero at 10 min may not be uniformly poor. However, in our study, all infants with their first heartbeat after 20 min of age died or had severe disabilities.