Asphyxia, when severe enough, leads to HIE (hypoxic ischemic encephalopathy). HIE is the clinical syndrome caused by significantly prolonged asphyxia. HIE may be confirmed by the following:
A compressed umbilical cord. A compressed umbilical cord has a high correlation with HIE because it is associated with compression of the umbilical blood vessels which then leads to impedance of blood flow to the fetus. There is a high correlation between prolapsed cord and HIE. In a hospital setting, a prolapsed cord is a medical emergency necessitating immediate delivery (i.e., within minutes). A long delay between diagnosis of a prolapsed cord and eventual delivery lead to the strong presumption that for significant times the cord was compressed enough to cause significant hypoxia or anoxia.
Meconium aspiration. Meconium in the amniotic fluid is another indicator of fetal distress. A fetus will excrete meconium into the amniotic fluid as a result of distress, such as is caused by lack of sufficient blood flow. This is the early warning sign from the fetus that it is in some sort of trouble.
Bradycardia. A fetal heart rate of 60 is considered bradycardia (low heart rate for a fetus) and indicates fetal distress and that the fetus is not getting enough blood flow to the body and brain. This is a secondary phenomenon to the heart, itself, not getting sufficient oxygen.
Low Apgar scores. Apgar scores are a way of assessing the status of an infant at the time of delivery, both initially and after any resuscitation. An Apgar score of 3 or lower at 10 minutes has been well-established to be associated with high risk for HIE and subsequent cerebral palsy (CP).
Acidosis. Acidosis is caused by the build-up of excessive lactic acid, a byproduct of anaerobic (i.e., absence of oxygen) metabolism of sugar. Fetal acidosis may be caused by infection, poor gut flow due to bowel obstruction, inborn errors of metabolism, etc.
Neonatal hypoxic encephalopathy. Neonatal hypoxic encephalopathy is severe disturbance of brain function in a newborn. It is indicated by minimal movements, lethargy and significant hypotonia. Transient jitteriness (tremors) and seizures are also a frequent finding in neonatal hypoxic encephalopathy. Infection as well as low glucose, sodium, or calcium can also lead to jitteriness and seizures.
Abnormal brain MRI and/or EEG. HIE affects both hemispheres of the brain. If an abnormal brain MRI indicates bilateral insult and/or an EEG shows bilateral brain dysfunction, it would be consistent with HIE.
Hypoxic ischemic encephalopathy (HIE) in newborn medical expert witness specialties include neonatology, maternal-fetal medicine, pathology, pediatric neurology, neuropsychology, obstetrics, and maternal-fetal pathology.