Hyperthermia in the delivery: potential impact on neonatal mortality and morbidity

Thermoregulation for very preterm infants in the delivery room: a narrative review

Abnormal temperature in preterm infants is associated with increased morbidity and mortality. Infants born prematurely are at risk of abnormal temperature immediately after birth in the delivery room (DR). The World Health Organization (WHO) recommends that the temperature of newly born infants is maintained between 36.5-37.5oC after birth. When caring for very preterm infants, the International Liaison Committee on Resuscitation (ILCOR) recommends using a combination of interventions to prevent heat loss. While hypothermia remains prevalent, efforts to prevent it have increased the incidence of hyperthermia, which may also be harmful. Delayed cord clamping (DCC) for preterm infants has been recommended by ILCOR since 2015. Little is known about the effect of timing of DCC on temperature, nor have there been specific recommendations for thermal care before DCC. This review article focuses on the current evidence and recommendations for thermal care in the DR, and considers thermoregulation in the context of emerging interventions and future research directions. IMPACT: Abnormal temperature is common amongst very preterm infants after birth, and is an independent risk factor for mortality. The current guidelines recommend a combination of interventions to prevent heat loss after birth. Despite this, abnormal temperature is still a problem, across all climates and economies. New and emerging delivery room practice (i.e., delayed cord clamping, mobile resuscitation trolleys, early skin to skin care) may have an effect on infant temperature. This article reviews the current evidence and recommendations, and considers future research directions.

Severity of intrapartum fever and neonatal outcomes

BACKGROUND

The few studies that have addressed the relationship between severity of intrapartum fever and neonatal and maternal morbidity have had mixed results. The impact of the duration between reaching maximum intrapartum temperature and delivery on neonatal outcomes remains unknown.

OBJECTIVE

To test the association of severity of intrapartum fever and duration from reaching maximum temperature to delivery with neonatal and maternal morbidity.

STUDY DESIGN

This was a secondary analysis of a prospective cohort of term, singleton patients admitted for induction of labor or spontaneous labor who had intrapartum fever (≥38°C). Patients were divided into 3 groups according to maximum temperature during labor: afebrile (<38°C), mild fever (38°C-39°C), and severe fever (>39°C). The primary outcome was composite neonatal morbidity (umbilical artery pH <7.1, mechanical ventilation, respiratory distress, meconium aspiration with pulmonary hypertension, hypoglycemia, neonatal intensive care unit admission, and Apgar <7 at 5 minutes). Secondary outcomes were composite neonatal neurologic morbidity (hypoxic-ischemic encephalopathy, hypothermia treatment, and seizures) and composite maternal morbidity (postpartum hemorrhage, endometritis, and maternal packed red blood cell transfusion). Outcomes were compared between the maximum temperature groups using multivariable logistic regression. Cox proportional-hazards regression modeling accounted for the duration between reaching maximum intrapartum temperature and delivery.

RESULTS

Of the 8132 patients included, 278 (3.4%) had a mild fever and 74 (0.9%) had a severe fever. The incidence of composite neonatal morbidity increased with intrapartum fever severity (afebrile 5.4% vs mild 18.0% vs severe 29.7%; P<.01). After adjusting for confounders, there were increased odds of composite neonatal morbidity with severe fever compared with mild fever (adjusted odds ratio, 1.93 [95% confidence interval, 1.07-3.48]). Severe fevers remained associated with composite neonatal morbidity compared with mild fevers after accounting for the duration between reaching maximum intrapartum temperature and delivery (adjusted hazard ratio, 2.05 [95% confidence interval, 1.23-3.43]). Composite neonatal neurologic morbidity and composite maternal morbidity were not different between patients with mild and patients with severe fevers.

CONCLUSION

Composite neonatal morbidity correlated with intrapartum fever severity in a potentially dose-dependent fashion. This correlation was independent of the duration from reaching maximum intrapartum temperature to delivery, suggesting that clinical management of intrapartum fever, in terms of timing or mode of delivery, should not be affected by this duration.

Suspected clinical chorioamnionitis with peak intrapartum temperature <380C: the prevalence of confirmed chorioamnionitis and short term neonatal outcome

Background

Chorioamnionitis (CA) affects up to 3.9% of all deliveries worldwide and is one of the leading causes of early-onset neonatal sepsis. Fever≥38⁰C is an essential criterion for the diagnosis of clinical CA. Obstetricians frequently take the maternal risk factors into consideration, and many mothers are treated as CA even with peak intrapartum temperature (PIT) between 37.6⁰C to 37.9⁰C if they have other clinical signs and risk factors.

Aim

To estimate the prevalence of confirmed chorioamnionitis and adverse neonatal outcomes among those mothers with PIT below 38⁰C.

Materials and methods

Retrospective chart review among mothers delivered at Al-Wakra Hospital, Qatar, between1^stJanuary2016 to 31^stDecember 2019 with a clinical suspicion of CA.

Results

Among 21,471 mothers, 442 were suspected of having CA (2.06%, 95% CI 1.88 to 2.26%). After exclusions, 415 were included in the study, 203(48.9%) mothers had PIT between 37.6-37.9⁰C. There was no significant difference in the rate of confirmed CA between the low (<38⁰C) and higher (≥38⁰C) temperature groups (25.4%Vs.31.3%, OR0.75, 95%CI0.46-1.25 , p.262). More patients in the low-temperature group received paracetamol for PIT between 37.6 to 37.9 ⁰C, while it was less frequently used for such milder elevation in higher temperature group (88.2%Vs.38.9%, OR11.69, 95% CI 6.46-2.15, p <.001).

Conclusion

The incidence of suspected clinical CA in our institution was within the international rates. Although nearly half of the mothers with suspected clinical CA had peak temperature below the recommended diagnostic criteria, the rate of confirmed CA and neonatal outcome was not significantly different from those with PIT≥38⁰C. Early antipyretic use might have affected further elevation of temperature.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03239-9.

Interleukin-1 receptor antagonist, mode of analgesia and risk of Caesarean delivery after onset of labour: a Mendelian randomisation analysis

BACKGROUND

Lower circulating levels of the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1ra) are associated with intrapartum inflammation and epidural analgesia-related maternal fever, both of which increase the rate of obstetric interventions. We hypothesised that genetic variants determining IL-1ra levels would be associated with Caesarean delivery rates after the onset of labour.

METHODS

We performed Mendelian randomisation analyses in parous women ≥16 yr old who received either non-neuraxial or neuraxial analgesia for their first two labours (UK Biobank). We used an established genetic score (calculated as 0-4, determined by the presence/absence of rs6743376 and rs1542176 alleles), in which the complete absence of both alleles causes the lowest IL-1ra levels. The primary outcome was Caesarean delivery after the onset of labour (odds ratio [OR]: 95% confidence intervals).

RESULTS

There were 7731 women (mean [standard deviation] age at first birth: 25 [5] yr) who had complete genetic scores and delivery data. For women who received non-neuraxial analgesia, Caesarean delivery rates were different across allele scores (χ²=12.4; P=0.015): 104/596 (17.4%) women with zero allele score underwent Caesarean delivery, compared with 654/5015 (13.0%) with allele score ≥1 (OR 1.41; 1.12-1.77). For women who had neuraxial analgesia, Caesarean delivery was not different across allele scores, ranging from 18.1% to 20.8% (χ²=0.29; P=0.99). Caesarean delivery was independent of type of analgesia for 818/7731 (10.6%) women with zero allele scores (OR 0.93; 0.63-1.39), but was higher in women receiving neuraxial analgesia with allele scores ≥1 (OR 1.55; 1.35-1.79; P<0.001).

CONCLUSIONS

Mendelian randomisation analysis suggests that higher IL-1ra levels are associated with reduced Caesarean delivery rate. Neuraxial analgesia appears to disrupt this link.

CLINICAL TRIAL REGISTRATION

UK Biobank study 62745.

Management of clinical chorioamnionitis: an evidence-based approach

This review aimed to examine the existing evidence about interventions proposed for the treatment of clinical chorioamnionitis, with the goal of developing an evidence-based contemporary approach for the management of this condition. Most trials that assessed the use of antibiotics in clinical chorioamnionitis included patients with a gestational age of ≥34 weeks and in labor. The first-line antimicrobial regimen for the treatment of clinical chorioamnionitis is ampicillin combined with gentamicin, which should be initiated during the intrapartum period. In the event of a cesarean delivery, patients should receive clindamycin at the time of umbilical cord clamping. The administration of additional antibiotic therapy does not appear to be necessary after vaginal or cesarean delivery. However, if postdelivery antibiotics are prescribed, there is support for the administration of an additional dose. Patients can receive antipyretic agents, mainly acetaminophen, even though there is no clear evidence of their benefits. Current evidence suggests that the administration of antenatal corticosteroids for fetal lung maturation and of magnesium sulfate for fetal neuroprotection to patients with clinical chorioamnionitis between 24 0/7 and 33 6/7 weeks of gestation, and possibly between 23 0/7 and 23 6/7 weeks of gestation, has an overall beneficial effect on the infant. However, delivery should not be delayed to complete the full course of corticosteroids and magnesium sulfate. Once the diagnosis of clinical chorioamnionitis has been established, delivery should be considered, regardless of the gestational age. Vaginal delivery is the safer option and cesarean delivery should be reserved for standard obstetrical indications. The time interval between the diagnosis of clinical chorioamnionitis and delivery is not related to most adverse maternal and neonatal outcomes. Patients may require a higher dose of oxytocin to achieve adequate uterine activity or greater uterine activity to effect a given change in cervical dilation. The benefit of using continuous electronic fetal heart rate monitoring in these patients is unclear. We identified the following promising interventions for the management of clinical chorioamnionitis: (1) an antibiotic regimen including ceftriaxone, clarithromycin, and metronidazole that provides coverage against the most commonly identified microorganisms in patients with clinical chorioamnionitis; (2) vaginal cleansing with antiseptic solutions before cesarean delivery with the aim of decreasing the risk of endometritis and, possibly, postoperative wound infection; and (3) antenatal administration of N-acetylcysteine, an antioxidant and antiinflammatory agent, to reduce neonatal morbidity and mortality. Well-powered randomized controlled trials are needed to assess these interventions in patients with clinical chorioamnionitis.

Comparison of cord blood lactate measurement by gas analyzer and portable electrochemical devices

Objective To compare the accuracy of cord blood lactate measurement using gas analyzer and portable devices in order to assess possibility of implementation of these devices in clinical practice. Methods We performed a prospective observational study using 30 umbilical cord samples which were obtained immediately after birth. Portable electrochemical devices Lactate Scout (SensLab GmbH, Leipzig, Germany) and StatStrip Lactate (NOVA Biomedical, Waltham, MA, USA) were used to determine lactate level. A gas analyzer ABL800 FLEX (Radiometer Medical ApS, Brønshøj-Husum, Denmark) was used as a reference. Base excess (BE), pH, partial oxygen (pO2) and carbon dioxide (pCO2) pressure, hemoglobin (ctHb) and bilirubin (ctBl) levels were measured. Results The mean umbilical cord blood lactate level determined by the gas analyzer was 5.85 ± 2.66 mmol/L (ranging from 1.4 mmol/L to 13.4 mmol/L). Lactate level estimated by Lactate Scout was 5.66 ± 2.65 mmol/L and did not significantly differ from the reference method level (P = 0.2547). The mean lactate level determined by StatStrip Lactate was significantly lower than by the gas analyzer - 4.81 ± 2.38 mmol/L (P < 0.0001). Umbilical cord blood pH, BE, pO2 and pCO2, ctHb and ctBl levels did not affect the accuracy of the lactate measurement in absolute units (mmol/L). Conclusion Umbilical cord blood lactate level measured by StatStrip Lactate was lower than estimated by the ABL800 FLEX gas analyzer. This shows the necessity to develop decision-making reference points separately for each device. Umbilical cord blood pH, BE, pO2 and pCO2, ctHb and ctBl levels did not affect the accuracy of measurements by electrochemical portable devices.

Thermal conditions during neonatal anoxia affect the endogenous level of brain-derived neurotrophic factor

Anoxia during delivery is a complication that can disturb infant brain development leading to various types of neurological disorders. Our studies have shown that increased body temperature of newborn rats of both sexes intensifies the postanoxic oxidative stress and prevents triggering the endogenous adaptive response such as HIF-1α activation. Currently, brain-derived neurotrophic factor-BDNF is considered to be a modulator of neuronal plasticity. In the developing brain, mature BDNF and its precursor exhibit prosurvival action through the TrkB receptor and proapoptotic functions binding to p75^NTR , respectively. The aim of our experiments was to check the effects of body temperature on the postanoxic level of BDNF and on the expression of its receptors as well as on the marker of apoptosis-caspase-3 in the rat brain. Two-day-old Wistar Han rats (male/female ratio, 1:1) were exposed to anoxia in 100% nitrogen atmosphere for 10 min in different thermal conditions, which allowed them to regulate their rectal temperature at the following levels: normothermic-33°C; hyperthermic-37°C; and extremely hyperthermic-39°C. Thermal conditions during neonatal anoxia affected the level of proBDNF, BDNF as well as their receptors and caspase-3 in the forebrain. The increased BDNF protein level followed by decreased caspase-3 protein level was probably dependent on body temperature under anoxic conditions and was observed only in rats maintaining decreased body temperature. The positive effect of BDNF was not observed under hyperthermic conditions. Moreover, BDNF level changes correlated with body temperature probably affected the learning and spatial memory in juvenile rats.

Clinical impact of admission hypothermia in very low birth weight infants: results from Korean Neonatal Network

BACKGROUND

Preterm infants have difficulty maintaining body temperature after birth. However, clinical guidelines advocate that neonatal body temperature should be maintained at 36.5°C-37.5°C.

PURPOSE

We aimed to investigate the incidence of admission hypothermia in very low birth weight (VLBW) infants and to determine the association of admission temperature with in-hospital mortality and morbidities.

METHODS

A cohort study using prospectively collected data involving 70 neonatal intensive care units (NICUs) that participate in the Korean Neonatal Network. From registered infants born between January 2013 and December 2015, 5,343 VLBW infants born at less than 33 weeks of gestation were reviewed.

RESULTS

The mean admission temperature was 36.1°C±0.6°C, with a range of 31.9°C to 38.4°C. Approximately 74.1% of infants had an admission hypothermia of <36.5°C. Lower birth weight, intubation in the delivery room and Apgar score <7 at 5 minutes were significantly related to admission hypothermia. The mortality was the lowest at 36.5°C-37.5°C and adjusted odd ratios for all deaths increased to 1.38 (95% confidence interval [CI], 1.04-1.83), 1.44 (95% CI, 1.05-1.97) and 1.86 (95% CI, 1.22-2.82) for infants with admission temperatures of 36.0°C-36.4°C, 35.0°C-35.9°C, and <35.0°C, respectively. Admission hypothermia was also associated with high likelihoods of bronchopulmonary dysplasia, pulmonary hypertension, proven sepsis, pulmonary hemorrhage, air-leak, seizure, grade 3 or higher intraventricular hemorrhage and advanced retinopathy of prematurity requiring laser therapy.

CONCLUSION

A large portion of preterm infants in Korea had hypothermia at NICU admission, which was associated with high mortality and several important morbidities. More aggressive interventions aimed at reducing hypothermia are required in this high-risk population.

Temperature Probe Placement during Preterm Infant Resuscitation: A Randomised Trial

BACKGROUND

Hypothermia on admission to intensive care is associated with poor outcomes in preterm infants. The neonatal resuscitation program recommends the use of servo-control thermoregulation during resuscitation. Very little evidence exists to guide optimal temperature probe placement in the delivery room.

OBJECTIVE

The aim of this work was to determine, in moderately preterm infants, if temperature probe placement in the dorsal, thoracic, or axillary area during delivery room resuscitation would result in differing temperatures on admission to the neonatal intensive care unit (NICU).

METHODS

A randomised trial with 3 arms was conducted. In total, 122 inborn preterm infants born between 280/7 and 356/7 weeks of gestational age were recruited. The infants were randomly assigned to thermal probe placement in the left lower back, left upper thorax, or left axilla immediately after birth. Temperature was servo-controlled using an infant resuscitation table set to 36.5°C. The primary outcome was axillary temperature at admission to the NICU before transfer to a closed isolette, recorded with a digital thermometer. The secondary outcomes assessed were temperature within the target range (36.5-37.5°C), hypothermia (<36.5°C), and hyperthermia (>37.5°C).

RESULTS

All 122 infants were available for outcome analysis. The groups were comparable for birthweight, gestational age, and sex. The mean admission temperature was comparable between the 3 probe positions (mean, 95% CI): dorsum (36.7°C, 36.6-36.8), thorax (36.8°C, 36.7-36.9), and axilla (36.7°C, 36.6-36.9), p = 0.43. The proportion of infants with admission temperatures in the target range was comparable (87.2, 81.4, and 72.5% respectively), p = 0.44.

CONCLUSION

Dorsal, thoracic, or axillary temperature probe positioning during resuscitation yield similar admission temperatures in moderately preterm infants. Further studies are required in infants below 28 weeks of gestation to determine the best practice.

Admission Hypothermia in Very Preterm Infants and Neonatal Mortality and Morbidity

OBJECTIVE

To investigate the association between body temperature at admission to neonatal intensive care and in-hospital mortality in very preterm infants, stratified by postnatal age of death. Moreover, we assessed the association between admission temperature and neonatal morbidity.

STUDY DESIGN

In this cohort study from 19 regions in 11 European countries, we measured body temperature at admission for infants admitted for neonatal care after very preterm birth (<32 weeks of gestation; n = 5697) who were followed to discharge or death. Associations between body temperature at admission and in-hospital mortality and neonatal morbidity were analyzed by the use of mixed effects generalized linear models. The final model adjusted for pregnancy complications, singleton or multiple pregnancy, antenatal corticosteroids, mode of delivery, gestational age, infant size and sex, and Apgar score <7 at 5 minutes.

RESULTS

A total of 53.4% of the cohort had a body temperature at admission less than 36.5°C, and 12.9% below 35.5°C. In the adjusted model, an admission temperature <35.5°C was associated with increased mortality at postnatal ages 1-6 days, (risk ratio 2.41; 95% CI 1.45-4.00), and 7-28 days (risk ratio 1.79; 1.15-2.78) but not after 28 days of age. We found no associations between admission temperature and neonatal morbidity.

CONCLUSION

Admission hypothermia after very preterm birth is a significant problem in Europe, associated with an increased risk of early and late neonatal death.

Reducing hypothermia in preterm infants following delivery

BACKGROUND

Moderate hypothermia (temperature <36°C) at birth is common in premature infants and is associated with increased mortality and morbidity.

METHODS

A multidisciplinary practice plan was implemented to determine in premature infants <35 weeks old whether a multifaceted approach would reduce the number of inborn infants with an admitting axillary temperature <36°C by 20% without increasing exposure to a temperature >37.5°C. The plan included use of occlusive wrap a transwarmer mattress and cap for all infants and maintaining an operating room temperature between 21°C and 23°C. Data were obtained at baseline (n = 66), during phasing in (n = 102), and at full implementation (n = 193).

RESULTS

Infant axillary temperature in the delivery room (DR) increased from 36.1°C ± 0.6°C to 36.2°C ± 0.6°C to 36.6°C ± 0.6°C (P < .001), and admitting temperature increased from 36.0°C ± 0.8°C to 36.3°C ± 0.6°C to 36.7°C ± 0.5°C at baseline, phasing in, and full implementation, respectively (P < .001). The number of infants with temperature <36°C decreased from 55% to 6.2% at baseline versus full implementation (P < .001), and intubation at 24 hours decreased from 39% to 17.6% (P = .005). There was no increase in the number of infants with a temperature >37.5°C over time. The use of occlusive wrap, mattress, and cap increased from 33% to 88% at baseline versus full implementation. Control charts showed significant improvement in DR ambient temperature at baseline versus full implementation.

CONCLUSIONS

The practice plan was associated with a significant increase in DR and admitting axillary infant temperatures and a corresponding decrease in the number of infants with moderate hypothermia. There was an associated reduction in intubation at 24 hours. These positive findings reflect increased compliance with the practice plan.

Hypothermia and early neonatal mortality in preterm infants

OBJECTIVE

To evaluate intervention practices associated with hypothermia at both 5 minutes after birth and at neonatal intensive care unit (NICU) admission and to determine whether hypothermia at NICU admission is associated with early neonatal death in preterm infants.

STUDY DESIGN

This prospective cohort included 1764 inborn neonates of 22-33 weeks without malformations admitted to 9 university NICUs from August 2010 through April 2012. All centers followed neonatal International Liaison Committee on Resuscitation recommendations for the stabilization and resuscitation in the delivery room (DR). Variables associated with hypothermia (axillary temperature <36.0 °C) 5 minutes after birth and at NICU admission, as well as those associated with early death, were analyzed by logistic regression.

RESULTS

Hypothermia 5 minutes after birth and at NICU admission was noted in 44% and 51%, respectively, with 6% of early neonatal deaths. Adjusted for confounding variables, practices associated with hypothermia at 5 minutes after birth were DR temperature <25 °C (OR 2.13, 95% CI 1.67-2.28), maternal temperature at delivery <36.0 °C (OR 1.93, 95% CI 1.49-2.51), and use of plastic bag/wrap (OR 0.53, 95% CI 0.40-0.70). The variables associated with hypothermia at NICU admission were DR temperature <25 °C (OR 1.44, 95% CI 1.10-1.88), respiratory support with cold air in the DR (OR 1.40, 95% CI 1.03-1.88) and during transport to NICU (OR 1.51, 95% CI 1.08-2.13), and cap use (OR 0.55, 95% CI 0.39-0.78). Hypothermia at NICU admission increased the chance of early neonatal death by 1.64-fold (95% CI 1.03-2.61).

CONCLUSION

Simple interventions, such as maintaining DR temperature >25 °C, reducing maternal hypothermia prior to delivery, providing plastic bags/wraps and caps for the newly born infants, and using warm resuscitation gases, may decrease hypothermia at NICU admission and improve early neonatal survival.

Initial resuscitation and stabilization of the periviable neonate: the Golden-Hour approach

There is a paucity of data to support recommendations for stabilization and resuscitation of the periviable neonate in the delivery room. The importance of delivery at a tertiary center with adequate experience, resuscitation team composition, and training for a periviable birth is reviewed. Evidence for delayed cord clamping, delivery room temperature stabilization, strategies to establish functional residual capacity, and adequate ventilation as well as oxygen use in the delivery room is generally based on expert consensus, physiologic plausibility, as well as data from slightly more mature extremely low gestational-age neonates. Little is known about optimal care in the delivery room of these most fragile infants, and thus the need for research remains critical.

Decreasing hypothermia during delivery room stabilization of preterm neonates

BACKGROUND AND OBJECTIVE

Hypothermia during delivery room stabilization of very low birth weight (VLBW) newborns is independently associated with mortality, yet it occurred frequently both in collaborative networks and at our institution. We aimed to attain admission temperatures in the target range of 36 °C to 38 °C in ≥ 90% of inborn VLBW neonates through implementation of a thermoregulation bundle.

METHODS

This quality improvement project extended over 60 consecutive months, using sequential plan-do-check-act cycles. During the 14 baseline months, we standardized temperature measurements and developed the Operation Toasty Tot thermoregulation bundle (including consistent head and torso wrapping with plastic, warmed blankets, and a closed stabilization room). We introduced this bundle in month 15 and added servo-controlled, battery-powered radiant warmers for stabilization and transfer in month 21. We provided results and feedback to staff throughout, using simple graphics and control charts.

RESULTS

There were 164 inborn VLBW babies before and 477 after bundle implementation. Introduction and optimization of the bundle decreased the incidence of hypothermia, with rates remaining in the target range for the last 13 study months. The incidence of temperatures >38 °C was ~ 2% both before and after bundle implementation.

CONCLUSIONS

This thermoregulation bundle resulted in sustained improvement in normothermia rates during delivery room stabilization of VLBW newborns. Our benchmark goal of ≥ 90% admission temperatures above 36 °C was met without increasing hyperthermia rates. Because these results compare favorably with those of recently published research or improvement collaboratives, we aim to maintain our performance through routine surveillance of admission temperatures.

Strategies to prevent reperfusion injury to the brain following intrapartum hypoxia-ischemia

Hypoxia-ischemia is an infrequent event which may occur prior to or during delivery, following a period of decreased placental and/or fetal blood flow. Following recovery, a reperfusion phase and secondary energy failure may occur 6-48 h subsequent to the initial insult. Therapeutic hypothermia may be offered to infants at risk for evolving encephalopathy if identified within the 6 h therapeutic window, and should be instituted as early as possible for eligible infants. Additionally, the clinician must pay close attention to supportive measures such as avoidance of hyperthermia, as well as comprehensive management of clinical or electrographic seizures, blood pressure, blood glucoses, and carbon dioxide levels.

Hyperthermia, inflammation, and perinatal brain injury

Hyperthermia at the time of or following a hypoxic-ischemic insult has been associated with adverse neurodevelopmental outcome. Moreover, an elevation in temperature during labor has been associated with a variety of other adverse neurologic sequelae such as neonatal seizures, encephalopathy, stroke, and cerebral palsy. These outcomes may be secondary to a number of deleterious effects of hyperthermia including an increase in cellular metabolic rate and cerebral blood flow alteration, release of excitotoxic products such as free radicals and glutamate, and hemostatic changes. There is also an association between chorioamnionitis at the time of delivery and cerebral palsy, which is thought to be secondary to cytokine-mediated injury. We review experimental and human studies demonstrating a link between hyperthermia and perinatal brain injury.

Maternal hypertension and intrapartum fever are associated with increased risk of ischemic stroke during infancy

AIM

To examine maternal hypertension, diabetes, and intrapartum fever as potential risk factors for ischemic stroke in infants.

METHOD

We conducted a retrospective cohort study of 226,117 children born from January 2000 to December 2007 who were enrolled in the South Carolina Medicaid program. We linked maternal and child Medicaid billing records and birth certificate data. Children with ischemic stroke were identified based on the International Classification of Diseases, Ninth Revision (ICD-9), code 434 in the child's billing data. Independent variables and covariates were identified using ICD-9 codes and birth certificate data. We modeled the odds of ischemic stroke diagnosis in infants, either before 30 days of life or before 365 days.

RESULTS

Forty-three children were diagnosed with ischemic stroke before 30 days and 161 before 365 days. Maternal hypertension (odds ratio 2.31 before 30 d) and intrapartum fever (odds ratio 3.36 <30 d) were significantly associated with odds of ischemic stroke before 30 days and before 365 days; maternal diabetes was not.

INTERPRETATION

Maternal hypertension and intrapartum fever appear to be risk factors for ischemic stroke in infants. Additional research is needed to determine the mechanism(s) underlying these associations and to develop effective preventive methods for high-risk infants.

Use of chemical warming packs during delivery room resuscitation is associated with decreased rates of hypothermia in very low-birth-weight neonates

BACKGROUND

: Hypothermia is an independent contributor to neonatal mortality. All very low-birth-weight (VLBW) newborns have the potential to undergo cold stress or frank hypothermia during delivery room stabilization. Thus, clinicians aiming to maintain normothermia in VLBW neonates are compelled to use multiple adjuncts of unknown efficacy or safety.

OBJECTIVE

: To evaluate the effectiveness of thermoregulation procedures in maintaining normothermia during delivery room resuscitation and to assess the impact of an unanticipated change in equipment at our institution on the admission temperatures of VLBW newborns.

DESIGN/METHODS

: Institutional review board-approved, retrospective analysis of quality assurance data submitted to the Vermont-Oxford Network (VON) for 24 consecutive months starting January 2006. We compared the rate of hypothermia (admission temperature < 36.5°C) in our NICU during 2006 with the aggregate rates reported by VON. We then compared the rates of hypothermia and mean admission temperatures in our NICU during period 1 (when chemical warming packs were used routinely, in addition to plastic wrapping and warm blankets) and period 2 (after packs were discontinued owing to an incident of focal skin injury).

RESULTS

: In 2006, 42% of VLBW babies in our NICU had an admission temperature of less than 36.5°C compared with the VON rate of 61% (interquartile range 48%, 76%). During period 1, 39% of 183 VLBW neonates were hypothermic compared with 68% of 103 during period 2 (P < .001). Mean admission temperatures during periods 1 and 2 were 36.5°C and 36.1°C, respectively (P < .001). A control chart showed the shift in temperatures occurring as period 2 began. No change in practice other than discontinuation of the warming packs was instituted during period 2. The incidence of temperatures greater than 38°C (hyperthermia) was 1.6% during period 1 and 1.0% during period 2.

CONCLUSIONS

: The results associated with this isolated change in practice at our institution suggest that chemical warming packs were a useful adjunct in achieving above-average rates of normothermia during delivery room resuscitation of VLBW newborns. Their potential adverse effects should be weighed against the increased risk of mortality associated with hypothermia in this population.

Treatment of hypoxic-ischemic encephalopathy in newborns

Hypoxic-ischemic (HI) brain injury is the most common cause of encephalopathy and seizures in term newborn infants. There is no single, valid test for birth asphyxia leading to HI brain injury, and thus this disorder is often poorly characterized, and the timing and etiology of the injury can be difficult to ascertain. Optimal management of HI brain injury involves prompt resuscitation, careful supportive care including prevention of hyperthermia and hypoglycemia, and treatment of clinical and frequent or prolonged subclinical seizures. Recent evidence suggests that therapeutic hypothermia by selective head or whole-body cooling administered within 6 hours of birth reduces the incidence of death or moderate/severe disability at 12 to 22 months. Hypothermia is a promising new therapy that physicians should consider within the context of a registry or study. Optimal seizure treatment remains controversial because the most widely used drug, phenobarbital, has limited efficacy, and the value of monitoring and treating subclinical seizures is uncertain. There is compelling need for well-designed clinical trials to address treatment of ongoing brain injury in the setting of hypoxia-ischemia and seizures. Emerging evidence from preclinical studies suggests that future therapy for HI brain injury and neonatal encephalopathy will combine novel neuroprotective and anti-seizure agents. Pilot clinical trials of newer anticonvulsants are ongoing and will provide critical information for care of neonatal seizures.

Mild hypothermia reduces ischemic neuron death via altering the expression of p53 and bcl-2

OBJECTIVE

Studies exploring roles of p53 and bcl-2 in neuroprotection by hypothermia in focal cerebral ischemia have not provided consistent results. In the present study, we determined whether p53 and bcl-2 are involved in the hypothermia-induced neuroprotection.

METHODS

Male Sprague-Dawley rats were divided into four groups: normothermic (37-38 degrees C) ischemia, hypothermic (31-32 degrees C) ischemia, hyperthermic (41-42 degrees C) ischemia and sham-operated group. Global cerebral ischemia was established for 20 minutes using the Pulsinelli four-vessel occlusion model and the brain temperature was maintained at defined levels for 60 minutes following the 20 min ischemia. The mortality in rats was evaluated at 72 hour and 168 hour reperfusion. The expression of p53 and bcl-2 proteins was detected at 24, 48 and 72 hours after reperfusion. At the same intervals, neuron necrosis and apoptosis in brain regions was also detected using hematoxylin and eosin (HE) staining and terminal deoxynucleotldyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL).

RESULTS

The mortalities of rats in normothemia, hypothermia and hyperthermia groups was 33.3, 16.7 and 50% at 72 hour reperfusion. At 168 hours of reperfusion, the mortality in the three groups was 58.3, 25 and 100%, respectively. In light microscopy studies, necrotic neurons and apoptotic neurons were found in the hippocampus after global cerebral ischemia. Surviving neurons in hippocampus was increased in mild hypothermic ischemia group (p<0.05) and decreased in hyperthermia ischemia group (p<0.01) at 24, 48 and 72 hour reperfusion. TUNEL-positive neurons in hippocampus decreased in hypothermic ischemia group (p<0.05 or p<0.01) and increased in hyperthermic ischemia group (p<0.01) at 24, 48 and 72 hour reperfusion. The expression of p53 and bcl-2 proteins was found in the neurons of cerebral cortex after global cerebral ischemia. P53 decreased and bcl-2 increased in hypothermia group.

CONCLUSION

Hypothermia reduces ischemic neuronal necrosis and apoptosis by reducing p53 and increasing bcl-2 expression. Hyperthermia accelerated ischemic neuronal injury by increasing p53 and reducing bcl-2 expression.

Selective head cooling with mild systemic hypothermia after neonatal hypoxic-ischemic encephalopathy: a multicenter randomized controlled trial in China

OBJECTIVE

To investigate the efficacy and safety of selective head cooling with mild systemic hypothermia in hypoxic-ischemic encephalopathy (HIE) in newborn infants.

STUDY DESIGN

Infants with HIE were randomly assigned to the selective head cooling or control group. Selective head cooling was initiated within 6 hours after birth to a nasopharyngeal temperature of 34 degrees+/-0.2 degrees C and rectal temperature of 34.5 degrees to 35.0 degrees C for 72 hours. Rectal temperature was maintained at 36.0 degrees to 37.5 degrees C in the control group. Neurodevelopmental outcome was assessed at 18 months of age. The primary outcome was a combined end point of death and severe disability.

RESULTS

One hundred ninety-four infants were available for analysis (100 and 94 infants in the selective head cooling and control group, respectively). For the selective head cooling and control groups, respectively, the combined outcome of death and severe disability was 31% and 49% (OR: 0.47; 95% CI: 0.26-0.84; P=.01), the mortality rate was 20% and 29% (OR:0.62; 95% CI: 0.32-1.20; P=.16), and the severe disability rate was 14% (11/80) and 28% (19/67) (OR: 0.40; 95% CI: 0.17-0.92; P=.01).

CONCLUSIONS

Selective head cooling combined with mild systemic hypothermia for 72 hours may significantly decrease the combined outcome of severe disability and death, as well as severe disability.

Effect of hypothermia on amplitude-integrated electroencephalogram in infants with asphyxia

OBJECTIVES

Amplitude-integrated electroencephalogram (aEEG) at <6 hours is the best single outcome predictor in term infants with perinatal asphyxia at normothermia. Hypothermia has been used to treat those infants and proved to improve their outcome. The objectives of this study were to compare the predictive value of aEEG at <6 hours on outcomes in normothermia- and hypothermia-treated infants and to investigate the best outcome predictor (time to normal trace or sleep-wake cycling [SWC]) in normothermia- and hypothermia-treated infants.

METHODS

Seventy-four infants were recruited by using the CoolCap entry criteria, and their outcomes were assessed by using the Bayley Scales of Infant Development II at 18 months. The aEEG was recorded for 72 hours. Patterns and voltages of aEEG backgrounds were assessed.

RESULTS

The positive predictive value of an abnormal aEEG pattern at the age of 3 to 6 hours was 84% for normothermia and 59% for hypothermia. Moderate abnormal voltage background at 3 to 6 hours of age did not predict outcome. The recovery time to normal background pattern was the best predictor of poor outcome (96.2% in hypothermia, 90.9% in normothermia). Never developing SWC always predicted poor outcome. Time to SWC was a better outcome predictor for infants who were treated with hypothermia (88.5%) than with normothermia (63.6%).

CONCLUSIONS

Early aEEG patterns can be used to predict outcome for infants treated with normothermia but not hypothermia. Infants with good outcome had normalized background pattern by 24 hours when treated with normothermia and by 48 hours when treated with hypothermia.

Implementation of a 'Hypothermia for HIE' program: 2-year experience in a single NICU

Hypothermia has been shown to be neuroprotective in some newborns with moderate-to-severe perinatal hypoxic-ischemic encephalopathy (HIE). In 2006, the American Academy of Pediatrics recommended that institutions that choose to use therapeutic hypothermia do so in the context of a rigorous protocol, with systematic collection of patient data including neurodevelopmental follow-up. In this report, we describe our experience with implementation of a 'Hypothermia for HIE' program in a single tertiary care Neonatal Intensive Care Unit (NICU). Important components of the program include detailed protocols, staff and outreach education, early initiation of cooling in both inborn and outborn patients, maintaining stable hypothermia during neonatal transport, and comprehensive neurologic evaluation including serial EEGs, brain MRI and neurodevelopmental follow-up. In the first 2 years of the program, we have used hypothermia therapy in 21 patients, 18 with perinatal and 3 with early postnatal events leading to HIE. Eleven of fifteen outborn patients were cooled prior to and during transport, resulting in initiation of therapy 3 h sooner than if therapy had been delayed until arrival at our center. While lowering the body temperature of encephalopathic newborns is not difficult, addressing the complex medical problems of this vulnerable group of patients requires an experienced multidisciplinary team in regional referral centers.

Central and peripheral neuroimmune responses: hyporesponsiveness during pregnancy

There are periods in the life of a healthy animal (including humans) when the febrile response to an immune challenge is suppressed. One such period is during late pregnancy, particularly around the time of parturition. In the 30 or so years since this 'febrile hyporesponsiveness' was first noted, much work has been done to investigate the mechanisms and adaptive significance of this phenomenon. In this review we present some insight into how and why the body deliberately re-programmes itself to develop smaller fevers in response to an immune challenge and therefore to be potentially less successful at fighting infection.