Acid-base study results deine a second HIE criterion. Low pH and base deficit levels raise the likelihood that neonatal encephalopathy was caused by HIE. Decreasing levels form a continuum of increasing risk, but most acidemic neonates will be neurologically normal (Wayock, 2013). A cord artery pH ?7.2 is very unlikely to be associated with HIE.
Magnetic resonance (MR) imaging or MR spectroscopy (MRS) is the best modality with which to visualize findings consistent with HIE. The 2014 Task Force concludes that cranial sonography and computed tomography (CT) lack sensitivity in the term newborn. Normal imaging indings after the first 24 hours of life, however, efectively exclude a hypoxic-ischemic cause of encephalopathy. MR imaging between 24 and 96 hours may be more sensitive for the timing of peripartum cerebral injury, and MR imaging at 7 to 21 days following birth is the best technique to delineate the full extent of cerebral injury.
Last, multisystem involvement of injury is consistent with HIE. hese include renal, gastrointestinal, hepatic, or cardiac injury; hematological abnormalities; or combinations of these. The severity of neurological injury does not necessarily correlate with injuries to these other systems.
The 20 14 Task Force also found that certain contributing factors may be consistent with an acute peripartum event. Of these, sentinel events are considered adverse obstetrical events that may lead to catastrophic clinical outcomes. Examples include ruptured uterus, severe placental abruption, cord prolapse, and amnionic fluid embolism. Ivfartinez-Biarge and associates (2012) studied almost 58,000 deliveries and identified 192 cases with one of these sentinel events. Of these 192 fetus/ newborns, 6 percent died intrapartum or in the early neonatal period, and 10 percent developed neonatal encephalopathy. Other risk factors for neonatal acidosis include prior or emergent cesarean delivery, maternal age ?35 years, thick meconium, chorioamnionitis, and general anesthesia (Ahlin, 2016; Johnson, 2014; Nelson, 2014).
Diferentiating an abnormal etal heart rate (FHR) tracing on presentation versus one that develops subsequently was also emphasized by the 20 14 Task Force. A category 1 or 2 FHR tracing associated with Apgar scores ?7 at 5 minutes, normal cord gases (± 1 SD), or both are not consistent with an acute HIE event (Graham, 2014). An FHR pattern at the time of presentation with persistently minimal or absent variability and lacking accelerations, with duration ?60 minutes, and even without decelerations is suggestive of an already compromised fetus (Chap. 24, p. 462). The 2014 Task Force further recommended that if fetal well-being cannot be established with these findings present, the woman should be evaluated for the method and timing of delivery.