A comparison of criteria for defining metabolic acidemia in live-born neonates and its effect on predicting serious adverse neonatal outcomes

BACKGROUND

Metabolic acidemia is a known risk factor for serious adverse neonatal outcomes in both preterm and term infants.

OBJECTIVE

This study aimed to evaluate the clinical significance of delivery umbilical cord gas measurements with regard to serious adverse neonatal outcomes, and to determine if distinct thresholds for defining metabolic acidemia differ in their ability to predict such adverse neonatal complications.

STUDY DESIGN

This is a retrospective cohort study of singleton live-born deliveries between January 2011 and December 2019. Stratification according to gestational age at birth (≥35 and <35 weeks of gestation) was performed, and comparisons of maternal characteristics, obstetrical complications, intrapartum events, and adverse neonatal outcomes were made between neonates with metabolic acidemia and those without. Metabolic acidemia (based on delivery umbilical cord gas analyses) was defined using both American College of Obstetricians and Gynecologists and Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria. The primary outcome of interest was hypoxic-ischemic encephalopathy requiring whole-body hypothermia.

RESULTS

A total of 91,694 neonates born at ≥35 weeks of gestation met the inclusion criteria. By American College of Obstetricians and Gynecologists criteria, 2659 (2.9%) infants had metabolic acidemia. Neonates with metabolic acidemia were at markedly increased risk for neonatal intensive care unit admission, seizures, need for respiratory support, sepsis, and neonatal death. Metabolic acidemia by American College of Obstetricians and Gynecologists criteria was associated with an almost 100-fold increased risk of hypoxic-ischemic encephalopathy requiring whole-body hypothermia (relative risk, 92.69; 95% confidence interval, 64.42-133.35) in neonates born at ≥35 weeks of gestation. Diabetes mellitus, hypertensive disorders of pregnancy, postterm deliveries, prolonged second stages, chorioamnionitis, operative vaginal deliveries, placental abruption and cesarean deliveries were associated with metabolic acidemia in neonates born ≥ 35 weeks of gestation. The highest relative risk was in those diagnosed with placental abruption (relative risk, 9.07; 95% confidence interval, 7.25-11.36). The neonatal cohort born <35 weeks of gestation had similar findings. When comparing those infants born ≥ 35 weeks of gestation with metabolic acidemia by American College of Obstetricians and Gynecologists criteria vs Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria, the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria identified more neonates at risk for serious adverse neonatal outcomes. In particular, 4.9% more neonates were diagnosed with metabolic acidemia, and 16 more term neonates were identified as requiring whole-body hypothermia. Mean 1-minute and 5-minute Apgar scores were similar and reassuring among neonates born at ≥35 weeks of gestation with and without metabolic acidemia as defined by both American College of Obstetricians and Gynecologists and Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria (8 vs 8 and 9 vs 9, respectively; P<.001). Sensitivity and specificity were 86.7% and 92.2%, respectively, with the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria, and 74.2% and 97.2% with the American College of Obstetricians and Gynecologists criteria.

CONCLUSION

Infants with metabolic acidemia identified on cord gas collection at delivery are at considerably greater risk of serious adverse neonatal outcomes, including an almost 100-fold increased risk of hypoxic-ischemic encephalopathy requiring whole-body hypothermia. Use of the more sensitive Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria for defining metabolic acidemia identifies more neonates born at ≥35 weeks of gestation at risk for adverse neonatal outcomes, including hypoxic-ischemic encephalopathy requiring whole-body hypothermia.

Blood biomarkers for neonatal hypoxic-ischemic encephalopathy in the presence and absence of sentinel events

OBJECTIVE

To determine if neonatal serum biomarkers representing different pathways of injury differ for cases of HIE of unknown cause to gain insight into timing and mechanism of injury.

STUDY DESIGN

In this cohort of all neonates with HIE admitted to our NICU, newborns with sentinel events were compared to those without during the 1st 3 days of life. Discard neonatal blood during the 1st 3 days of life was used for analysis.

RESULTS

Of 277 babies with HIE treated with whole-body hypothermia, 190 (68.6%) had blood available for biomarker analysis. In total, 71 (37.4%) were born within our system, and 119 (62.6%) were transferred in from outside hospitals. Of these babies, 77 (40.5%) had a sentinel event and 113 (59.6%) had no sentinel event. Although the degree of metabolic acidosis was similar, repeated measures analysis showed that during the initial 3 days of life neonates born with HIE in the absence of sentinel events had 41.4% decreased VEGF (p = 0.027) and 62.5% increased IL-10 serum concentrations (p = 0.005).

CONCLUSION

These changes indicate that neonatal HIE in the absence of sentinel events is not related to an unrecognized acute intrapartum event and is possibly related to chronic hypoxia of lower severity or recovery from a remote event.

Subcutaneous fat necrosis, a rare but serious side effect of hypoxic-ischemic encephalopathy and whole-body hypothermia

Objective To describe the clinical characteristics and risk factors in infants with subcutaneous fat necrosis (SFN) following therapeutic hypothermia for hypoxic-ischemic encephalopathy (HIE). Methods A case-control study was performed by a retrospective chart review of infants with moderate or severe HIE admitted to a level IV regional perinatal center and who underwent whole-body cooling. Results A total of 14 (8.1%) of 171 infants with moderate or severe HIE who underwent whole-body cooling developed SFN during hospitalization. There were more females [71% (10/14)] and large-for-gestational age (LGA) infants [28% (4/14)] in the SFN group vs. 36% females (57/157) and 8% LGA infants (13/157) in the group without SFN (P-values of 0.009 and 0.015, respectively). The mean lowest platelet count was lower 108 ± 55 109/L vs. 146 ± 62 109/L and the mean highest calcium level was higher 11.3 ± 2.5 vs. 10.6 ± 0.8 mg/dL in infants with SFN vs. infants without SFN, respectively (P-values of 0.0078 and 0.006, respectively). Distribution of skin lesions followed distinctive patterns representing the areas with direct contact with the cooling blanket. One infant developed severe, life-threatening hypercalcemia that required aggressive management, including diuretics, corticosteroids and bisphosphonates. Conclusion Although SFN is a rare complication of therapeutic hypothermia, it can be a life-threatening condition if complicated by severe hypercalcemia. Infants who undergo therapeutic hypothermia for HIE need regular skin examinations to evaluate for SFN. If SFN is identified, monitoring of serum calcium levels to prevent life-threatening hypercalcemia is recommended.

Perinatal risk factors for severe injury in neonates treated with whole-body hypothermia for encephalopathy

OBJECTIVE

Our objective was to identify perinatal risk factors that are available within 1 hour of birth that are associated with severe brain injury after hypothermia treatment for suspected hypoxic-ischemic encephalopathy.

STUDY DESIGN

One hundred nine neonates at ≥35 weeks' gestation who were admitted from January 2007 to September 2012 with suspected hypoxic-ischemic encephalopathy were treated with whole-body hypothermia; 98 of them (90%) underwent brain magnetic resonance imaging (MRI) at 7-10 days of life. Eight neonates died before brain imaging. Neonates who had severe brain injury, which was defined as death or abnormal MRI results (cases), were compared with surviving neonates with normal MRI (control subjects). Logistic regression models were used to identify risk factors that were predictive of severe injury.

RESULTS

Cases and control subjects did not differ with regard to gestational age, birthweight, mode of delivery, or diagnosis of nonreassuring fetal heart rate before delivery. Cases were significantly (P < .05) more likely to have had an abruption, a cord and neonatal arterial gas level that showed metabolic acidosis, lower platelet counts, lower glucose level, longer time to spontaneous respirations, intubation, chest compressions in the delivery room, and seizures. In multivariable logistic regression, lower initial neonatal arterial pH (P = .004), spontaneous respiration at >30 minutes of life (P = .002), and absence of exposure to oxytocin (P = .033) were associated independently with severe injury with 74.3% sensitivity and 74.4% specificity.

CONCLUSION

Worsening metabolic acidosis at birth, longer time to spontaneous respirations, and lack of exposure to oxytocin correlated with severe brain injury in neonates who were treated with whole-body hypothermia. These risk factors may help quickly identify neonatal candidates for time-sensitive investigational therapies for brain neuroprotection.

Clinical seizures in neonatal hypoxic-ischemic encephalopathy have no independent impact on neurodevelopmental outcome: secondary analyses of data from the neonatal research network hypothermia trial

It remains controversial as to whether neonatal seizures have additional direct effects on the developing brain separate from the severity of the underlying encephalopathy. Using data collected from infants diagnosed with hypoxic-ischemic encephalopathy, and who were enrolled in an National Institute of Child Health and Human Development trial of hypothermia, we analyzed associations between neonatal clinical seizures and outcomes at 18 months of age. Of the 208 infants enrolled, 102 received whole body hypothermia and 106 were controls. Clinical seizures were generally noted during the first 4 days of life and rarely afterward. When adjustment was made for study treatment and severity of encephalopathy, seizures were not associated with death, or moderate or severe disability, or lower Bayley Mental Development Index scores at 18 months of life. Among infants diagnosed with hypoxic-ischemic encephalopathy, the mortality and morbidity often attributed to neonatal seizures can be better explained by the underlying severity of encephalopathy.

Outcomes of safety and effectiveness in a multicenter randomized, controlled trial of whole-body hypothermia for neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Whole-body hypothermia reduced the frequency of death or moderate/severe disabilities in neonates with hypoxic-ischemic encephalopathy in a randomized, controlled multicenter trial.

OBJECTIVE

Our goal was to evaluate outcomes of safety and effectiveness of hypothermia in infants up to 18 to 22 months of age.

DESIGN/METHODS

A priori outcomes were evaluated between hypothermia (n = 102) and control (n = 106) groups.

RESULTS

Encephalopathy attributable to causes other than hypoxia-ischemia at birth was not noted. Inotropic support (hypothermia, 59% of infants; control, 56% of infants) was similar during the 72-hour study intervention period in both groups. Need for blood transfusions (hypothermia, 24%; control, 24%), platelet transfusions (hypothermia, 20%; control, 12%), and volume expanders (hypothermia, 54%; control, 49%) was similar in the 2 groups. Among infants with persistent pulmonary hypertension (hypothermia, 25%; control, 22%), nitric-oxide use (hypothermia, 68%; control, 57%) and placement on extracorporeal membrane oxygenation (hypothermia, 4%; control, 9%) was similar between the 2 groups. Non-central nervous system organ dysfunctions occurred with similar frequency in the hypothermia (74%) and control (73%) groups. Rehospitalization occurred among 27% of the infants in the hypothermia group and 42% of infants in the control group. At 18 months, the hypothermia group had 24 deaths, 19 severe disabilities, and 2 moderate disabilities, whereas the control group had 38 deaths, 25 severe disabilities, and 1 moderate disability. Growth parameters were similar between survivors. No adverse outcomes were noted among infants receiving hypothermia with transient reduction of temperature below a target of 33.5 degrees C at initiation of cooling. There was a trend in reduction of frequency of all outcomes in the hypothermia group compared with the control group in both moderate and severe encephalopathy categories.

CONCLUSIONS

Although not powered to test these secondary outcomes, whole-body hypothermia in infants with encephalopathy was safe and was associated with a consistent trend for decreasing frequency of each of the components of disability.