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Prisma Health Children's Hospital–Midlands

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Columbia, SC 29203

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Anoxic Brain Injury

Cerebral hypoxia

Cerebral hypoxia occurs when there is not enough oxygen getting to the brain. The brain needs a constant supply of oxygen and nutrients to function. Cerebral hypoxia affects the largest parts of the brain, called the cerebral hemispheres. However, the term is often used to refer to a lack of oxygen supply to the entire brain.

Causes

In cerebral hypoxia, sometimes only the oxygen supply is interrupted. This can be caused by:

  • Breathing in smoke (smoke inhalation), such as during a fire
  • Carbon monoxide poisoning
  • Choking
  • Diseases that prevent movement (paralysis) of the breathing muscles, such as amyotrophic lateral sclerosis (ALS)
  • High altitudes
  • Pressure on (compression) the windpipe (trachea)
  • Strangulation

In other cases, both oxygen and nutrient supply are stopped, caused by:

  • Cardiac arrest (when the heart stops pumping)
  • Cardiac arrhythmia (heart rhythm problems)
  • Complications of general anesthesia
  • Drowning
  • Drug overdose
  • Injuries to a newborn that occurred before, during, or soon after birth such as cerebral palsy
  • Stroke
  • Very low blood pressure

Brain cells are very sensitive to a lack of oxygen. Some brain cells start dying less than 5 minutes after their oxygen supply disappears. As a result, brain hypoxia can rapidly cause severe brain damage or death.

Symptoms

Symptoms of mild cerebral hypoxia include:

  • Change in attention (inattentiveness)
  • Poor judgment
  • Uncoordinated movement

Symptoms of severe cerebral hypoxia include:

  • Complete unawareness and unresponsiveness (coma)
  • No breathing
  • No response of the pupils of the eye to light

Exams and Tests

Cerebral hypoxia can usually be diagnosed based on the person's medical history and a physical exam. Tests are done to determine the cause of the hypoxia, and may include:

  • Angiogram of the brain
  • Blood tests, including arterial blood gases and blood chemical levels
  • CT scan of the head
  • Echocardiogram which uses ultrasound to view the heart
  • Electrocardiogram (ECG), a measurement of the heart's electrical activity
  • Electroencephalogram (EEG), a test of brain waves that can identify seizures and show how well brain cells work
  • Evoked potentials, a test that determines whether certain sensations, such as vision and touch, reach the brain
  • Magnetic resonance imaging (MRI) of the head

If only blood pressure and heart function remain, the brain may be completely dead.

Treatment

Cerebral hypoxia is an emergency condition that needs to be treated right away. The sooner the oxygen supply is restored to the brain, the lower the risk for severe brain damage and death.

Treatment depends on the cause of the hypoxia. Basic life support is most important. Treatment involves:

  • Breathing assistance (mechanical ventilation) and oxygen
  • Controlling the heart rate and rhythm
  • Fluids, blood products, or medicines to raise blood pressure if it is low
  • Medicines or general anesthetics to calm seizures

Sometimes a person with cerebral hypoxia is cooled to slow down the activity of the brain cells and decrease their need for oxygen. However, the benefit of this treatment has not been firmly established.

NIH: National Institute of Neurological Disorders and Stroke

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