Hypoxic Ischemic Encephalopathy Overview
When an infant’s brain is deprived of oxygen for more than a few minutes, long-term damage and lifelong disabilities may develop. While 14 percent or less of cerebral palsy (CP) cases are caused from the form of birth asphyxia known as hypoxic-ischemic encephalopathy, the condition itself is responsible for nearly a quarter of all neonatal deaths.
A number of risk factors contribute to the likelihood of birth asphyxia, including pre-existing conditions related to the health of the mother and trauma, which may result from a long or complicated birth.
Once a newborn who has suffered from birth asphyxia has been stabilized, diagnostic procedures can be used to estimate the amount of damage that may have taken place. Although treatment options are limited, cooling of the infant can prevent further damage by providing brain cells time to recover and return to their normal metabolic state after the initial injury has occurred.
Prevention is always preferred over treatment; mothers who focus on nutrition and self-care during pregnancy can reduce the odds of their child experiencing perinatal asphyxia, as can those who ensure their medical providers are highly qualified to offer optimal care.
What Is Hypoxic Ischemic Encephalopathy?
The term hypoxic ischemic encephalopathy (HIE, intrapartum hypoxia-ischemia, or perinatal asphyxia) describes a lack of oxygen and damage to cells within the brain as a result of restricted blood flow and occurs in approximately four out of every 1,000 births. When blood oxygen levels become inadequate to support the normal metabolism of brain cells, the body attempts to increase blood flow to the region to compensate. Ischemia, or the lack of an adequate blood supply, prevents this increase in blood flow; the low oxygen environment then prompts brain cells to shift into an anaerobic form of metabolism that can only be sustained for a few minutes of time.
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Provided an adequate supply of oxygen returns in short order, cells will return to their normal aerobic mode of metabolism with no long-term effects; cells that continue to be deprived of oxygen will inevitably die. Even after the initial stage of oxygen deprivation has ended, the potential for secondary damage, or “reperfusion injury,” still exists while cells attempt to return to their normal state and simultaneously release toxins that have built up during anaerobic metabolism. Specific treatment options applied during this stage may minimize long-term brain damage.
When does Hypoxic Ischemic Encephalopathy Occur?
Brain damage that results from perinatal asphyxia can occur in the period before, during, or immediately following birth. The condition can impact both pre- and full-term infants and may lead to mild, moderate, or severe cases of HIE. The duration of time during which the infant’s brain has not received an adequate supply of oxygen determines the level of impact and damage. Although treatments, when applied in a timely manner, may improve the prognosis, the initial level of injury is the most significant factor determining the child’s long-term outcome.
Risk Factors and Causes of Hypoxic Ischemic Encephalopathy
Mothers who experience any of the following conditions during pregnancy have an increased chance of giving birth to a child affected by perinatal asphyxia:
- Preeclampsia (extremely high blood pressure) or very low blood pressure;
- Restricted placental blood flow
- A maternal infection such as pelvic inflammatory disease
- Cardiac disease
- Drug or alcohol abuse, or addiction
- Numerous issues occurring immediately prior to, during or after birth also increase the chance of perinatal asphyxia, including:
- Placental abruption or rupture of the placenta or uterus;
- Excessive and prolonged pinching of the umbilical cord, such as during cord prolapse or with a true umbilical knot
- An extended labor and delivery period, which may involve complications such as an abnormally positioned fetus, cephalopelvic disproportion (CPD), and/or excessive pressure on the infant’s cranium
- Medical malpractice and the failure to notice signs of fetal distress
- Poorly functioning neonatal lungs that are incapable of delivering the proper amount of oxygen to the brain immediately after birth
Symptoms and Signs of Hypoxic Ischemic Encephalopathy
Babies that have been impacted by perinatal asphyxia will show symptoms such as:
- Apgar scores of 3 or lower that last longer than five minutes
- Pale or blue skin coloration
- Weak or absent breathing patterns
- Low heart rate
- Acidosis of the blood
- Poor muscle tone and weak or absent reflexes
The baby may have passed their first stool in utero, staining the amniotic fluid with meconium before birth (a condition indicative of fetal distress). Seizures may begin within the first 48 hours, depending on the level of brain injury sustained.
The timing of the initial onset of seizures often serves as an indication of the level of damage that has occurred. Infants with mild HIE do not display this symptom, while those moderately impacted generally experience seizures that begin within their first few hours of life outside the womb and subside before 24 hours has passed. Severely affected babies will experience a delay in the onset of seizures, reflecting the ongoing damage that occurs during the reperfusion phase of injury. Seizures may be intense and may not respond to conventional treatment methods.
Diagnosing Hypoxic Ischemic Encephalopathy
The process of officially diagnosing hypoxic ischemic encephalopathy requires the use of imaging equipment such as echocardiography, cranial ultrasonography, and magnetic resonance imaging (MRI), as well as electroencephalography (EEG), an ophthalmic examination, and a hearing examination, as deafness is a common side effect of perinatal asphyxia if the child also required assisted ventilation. Laboratory testing to gather information regarding the infant’s arterial blood components, cardiac, liver, and renal functioning, as well as electrolyte levels and the functioning of their coagulation system will also be performed.
In addition to the procedures mentioned above, the American Academy of Pediatrics (AAP) and the American College of Obstetrics and Gynecology (ACOG) state that specific conditions must have occurred to meet criteria for the diagnosis of perinatal asphyxia. Such conditions include an Apgar score of 3 or lower for five minutes or longer, an umbilical cord artery blood sample with a pH of less than 7, effects in multiple organ systems (heart, kidney, lungs, etc.), and the presence of seizures, coma, or hypotonia shortly after birth.
Treatment Options for Hypoxic Ischemic Encephalopathy
After any initial stabilization and/or resuscitation techniques are complete, a neonate impacted with perinatal asphyxia is provided with supportive treatments including:
- Fluid, blood pressure, and perfusion management;
- Maintenance of appropriate blood glucose levels;
- Medications to control seizures, such as general anesthesia.
In addition, carefully applied hypothermia treatments may be initiated within six hours after birth if symptoms of perinatal asphyxia are present within that time frame. By reducing the temperature of the baby’s head and/or entire body to about 91 degrees F (33.5 degrees C) for up to 72 hours, the infant’s brain cells are given time to heal during the reperfusion phase, minimizing potential long-term damage such as the development of CP, other neurological disorders, and even death.
Prevention of Hypoxic Ischemic Encephalopathy
While not all cases of perinatal asphyxia can be prevented, awareness of maternal risk factors coupled with adequate nutrition and self-care go a long way in the direction of risk reduction. Working with highly qualified medical professionals who understand the importance of diet and lifestyle alterations during pregnancy will improve the health of the mother and reduce the chances of perinatal asphyxia before the onset of the birthing process. Ensuring the hospital delivery staff is aware of any special needs is an important factor in the prevention of medical negligence and/or errors.
The Cerebral Palsy Group provides a host of resources for families impacted by cerebral palsy. Treatment may be available to help your child and reaching out to others for support can be invaluable during the initial adjustment phase of life with a special needs child.