Birth Asphyxia & Hypoxic-Ischemic Encephalopathy

A lack of oxygen to a baby’s brain, or birth asphyxia, is the most common cause of birth injuries in newborns. Birth asphyxia and decreased blood flow to the baby’s brain can result in a serious condition called hypoxic-ischemic encephalopathy (HIE). HIE can be treated with hypothermia (brain cooling) therapy, but the cooling must begin within 6 hours of the time the birth asphyxia occurred. Treatment may help some babies avoid permanent brain damage. For many babies, however, HIE and other brain injuries cause long-term problems such as the following:

Causes of Birth Asphyxia

An unborn baby receives oxygen-rich blood through the following pathway: maternal circulation –> uteroplacental circulation –> umbilical vein –> fetal circulation. There are numerous causes of birth asphyxia, but the most common causes include problems with the uterus, placenta, and umbilical cord. A very low blood pressure in the mother is another common cause of birth asphyxia, since it usually results in decreased uteroplacental circulation.

The following is a list of conditions that can cause birth asphyxia if not properly managed. These conditions usually occur during or near the time of delivery:

placenta; fetal oxygenation; pregnancy; umbilical cord

Normal placenta and umbilical cord function

How Does Birth Asphyxia Cause Brain Injuries?

The degree of brain injury a baby experiences when birth asphyxia occurs depends on the severity of the birth asphyxia, how long the asphyxia lasts, the baby’s age and oxygen reserves, and medical management of the baby during and after birth. When a baby is experiencing birth asphyxia, the fetal heart rate monitor will exhibit nonreassuring heart tracings. When these tracings occur, the medical team should perform interventions – such as giving the mother IV fluids, changing the mother’s position, and giving oxygen – designed to increase blood flow and oxygenation in the baby. While these interventions are taking place, the team should also prepare for a prompt C-section delivery. A C-section delivery is usually the fastest and safest way to deliver a baby in distress. The sooner the baby is delivered, the sooner the medical team can directly help them.

When birth asphyxia occurs, the baby becomes hypoxic (has insufficient oxygen) and usually hypercarbic (has high carbon dioxide in the blood). Hypoxia causes anaerobic metabolism and lactic acid production. When a lot of acid builds up in the baby’s blood, it is called acidosis. Acidosis and hypoxia can decrease heart function, which can cause the baby to have very low blood pressure (hypotension) and insufficient blood flow in the brain (ischemia). Ischemia then further impairs oxygen delivery to the baby. Hypoxia and ischemia also result in a cascade of events that disrupt metabolic pathways. Prolonged birth asphyxia causes the baby to have a hypoxic-ischemic state, which causes the brain to be deprived of glucose and all other nutrients as well as oxygen. In addition, the process of waste-removal is disrupted, which causes more metabolic issues and other health problems. Typically, the longer a hypoxic-ischemic state continues, the more injury there will be to the brain.

If a hypoxic-ischemic event is severe enough to damage the brain, the baby will usually develop cerebral edema within 12 – 24 hours. A baby with HIE may exhibit the following signs:

  • Seizures, especially within the first 24 – 48 hours of life
  • Hypotonia (baby is floppy/limp)
  • Poor feeding
  • Depressed level of consciousness
  • Multiple organ problems
  • Breathing problems
  • An abnormal response to light

At birth, babies with HIE may also have had the following:

The type of brain damage a baby experiences depends on the type and extent of birth asphyxia:

  • Total/near total asphyxia: Usually the deep gray matter is injured. This may include structures like the basal ganglia, thalamus, and brain stem.
  • Partial, prolonged asphyxia: this mainly leads to cortical injury in the watershed and parasagittal regions, with relative sparing of damage to the deep gray matter.

Babies can also experience more than one type of asphyxia, which causes a mixed brain injury pattern.

Hypoxic-Ischemic Brain Injury Is an Ongoing Process

Hypoxic-ischemic encephalopathy (HIE) is an evolving process. In addition to the first set of injurious events that start to occur when there is a hypoxic-ischemic/asphyxic insult, there is also a delayed cascade of molecular events triggered by the initial insult. For example, MRI studies show that the size of abnormal tissue (lesion size) increases over the first few days after injury. Within the first few hours after a baby experiences near total asphyxia, findings on MRI are usually subtle and are often only seen on a specific type of MRI called diffusion weighted imaging. This type of imaging typically shows initial small lesions in the putamen and thalami that usually progress over the next 3 – 4 days to involve more extensive regions of the baby’s brain.

Research shows that during this period of days after the initial asphyxic insult, many neurons and other cells are programmed to die or survive. Research has also helped scientists understand the progression of energy failure in the cell, as well as the severe cell swelling and accumulation of intracellular calcium that cause cell death. A hypoxic-ischemic brain injury can progress over days and weeks, which is why it is important for the a medical team to perform regular brain imaging studies on a baby with encephalopathy.

Hypothermia Treatment for Hypoxic-Ischemic Encephalopathy

Hypothermia (brain cooling) treatment for HIE has been shown to halt almost every injurious process that starts to occur when the brain experiences a hypoxic-ischemic/asphyxic insult. Scientists think that one of key reasons this treatment protects the brain is that it stops the signaling events inside the cells that initiate a cell death cascade. Hypothermia treatment can minimize the extent of permanent brain injury in a baby who has HIE. This treatment can help prevent a baby with HIE from developing cerebral palsy, or the baby may have a less severe form of CP.

Hypothermia treatment must, however, be given within 6 hours of the time the baby experienced the birth asphyxia, which often means that babies must receive the treatment within 6 hours of birth. Most hospitals have methods in place to quickly assess a baby’s eligibility for hypothermia treatment.

Other Treatments for Hypoxic-Ischemic Encephalopathy

When a baby has HIE, the medical team must make sure that there is no further disruption in oxygen and blood flow to the brain. In addition, they must ensure that the baby has good blood pressure, perfusion, oxygenation, ventilation, and acid content.

Seizures in the neonatal period are caused by abnormal brain activity, which can be from HIE. Seizures can cause brain injury and worsen existing brain damage, so they must be promptly diagnosed and treated. Many neonatal intensive care units throughout the U.S. have the ability to perform continuous electroencephalography (EEG), which is the recording of electrical activity in the brain. When a baby is suspected of having hypoxic-ischemic encephalopathy, they should have continuous EEG monitoring, if possible, or frequent EEG testing. Often, EEG results are the only indication a baby is having seizures.

Other signs of seizure activity include the following:

  • Apnea (periods of breathing cessation)
  • Repetitive facial movements, such as sucking, chewing, or eye movements
  • Unusual bicycling or pedaling movements
  • Staring
  • Clonic seizure activity, which consists of rhythmic jerking movements that may involve the muscles of the face, tongue, arms, legs, or other body regions
  • Myoclonic seizure activity, which consists of quick, single jerks involving one arm or leg, or the entire body
  • Tonic seizure activity, which involves stiffening or tightening of muscle groups; the head or eyes may turn to one side, or the baby may bend or stretch one or more arms or legs

If there is a metabolic or other underlying medical problem that may be causing the baby to have seizures, the problem should be promptly treated. Phenobarbital is the medication physicians usually give first to babies experiencing seizures.

 


How Do You Pronounce Birth Asphyxia?


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Video: Hypoxic-Ischemic Encephalopathy Attorneys Discuss Birth Asphyxia

Video: Award Winning Birth Injury Attorney Jesse Reiter

Watch a video of hypoxic ischemic encephalopathy attorneys Jesse Reiter & Rebecca Walsh discussing the numerous causes of birth asphyxia and HIE.


The information presented above is intended only to be a general educational resource. It is not intended to be (and should not be interpreted as) medical advice.


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