Hypoxic Ischemic Brain Injury - An Overview

Introduction

The energy consumption of the brain is massive when compared with its physical parameters like size and weight. It shows tremendous metabolic activity and is sensitive to hypoxia and hypoperfusion. Anoxic or hypoxic brain injuries occur when oxygen delivered to the brain tissue is markedly compromised. The supply of oxygen to the brain is determined by blood flow and the amount of oxygen present in it. The cellular injury starts within a few minutes, and permanent tissue damage and brain injury would occur if immediate interventions are not implemented. Moreover, brain injury due to hypoxia could occur when blood flow to the brain is interrupted in clinical conditions like strangulation, cardiac arrest, and systemic derangements altering the oxygen content of the blood.

What Is Cerebral Hypoxia?

Cerebral hypoxia is caused due to inadequate supply of oxygen to the brain tissue. Anoxia is a similar condition where the oxygen supply to the brain is completely stopped. Both terminologies are interchangeably used by healthcare professionals when hypoxic or anoxic brain injuries occur. The brain cells die without the oxygen supply causing brain injury. This could happen even during enough blood supply is present with decreased oxygen content as in the case of individuals breathing in smoke or carbon monoxide. Only supportive treatment can be provided to individuals with injuries to the brain tissue due to cerebral hypoxia; the damage to the brain cells (cell death) is irreversible. This condition leads to lifelong damage or brain dysfunction. It becomes fatal if the damage continues over a prolonged period of time.

What Is the Histopathology of Hypoxic Brain Injury?

There are two pathways to ischemic cellular death, namely, apoptosis and necrosis. When the brain undergoes ischemic hypoxia, the acute energy shutdown causes an imbalance in ion homeostasis. This causes intracellular accumulation of calcium and sodium ions, leading to osmotic edema and swelling, eventually resulting in a breakdown of the membrane. The second phase of nerve cell death is initiated after a few hours.

How Is the Brain Affected by Lack of Oxygen?

It can be understood through a few points:

• The brain runs the nervous system, and it needs oxygen to function.

• Also, the brain uses about a fifth of the body’s total oxygen supply.

• Oxygen helps in sending nerve signals and messages throughout the body.

• Cellular death of brain cells occurs when the oxygen supply to these cells gets diminished beyond optimal levels.

• Cell death happens within five minutes of low oxygen.

What Causes Decreased Oxygen Flow To the Brain?

Diverse factors that contribute to the reduced flow of oxygen to the brain cells are as follows -

• Suffocation or strangulation.

• Choking.

• Electrocution.

• Drowning.

• Head injuries due to trauma.

• Traumatic brain injuries.

• Cardiovascular events like heart attack, stroke, and arrhythmia.

• Disorders due to substance use, such as drug overdose or misuse of inhalants.

• Carbon monoxide gas poisoning.

• Inhalation of smoke.

• Seizures.

• Severe bleeding or excessive hemorrhage.

• Complications due to anesthesia or surgical procedures.

What Are the Clinical Manifestations of Cerebral Hypoxia?

The common symptoms experienced by individuals under hypoxia are as follows -

• Disorientation and slurring of speech.

• Rapid or shallow breathing or cessation of breathing.

• Bluish and grayish discoloration of the skin, especially the lips.

• Dilatation of pupils.

• Convulsion or seizure episodes.

• Unresponsiveness when asking the affected person’s name or asking them to perform any activity like squeezing the hand.

What Are the Long lasting consequences of Cerebral Hypoxia?

Individuals recovering from cerebral or brain hypoxia have some persistent problems like -

• Cognitive dysfunction or impairment.

• Memory loss.

• Changes in personality.

• Reduced judgment skills.

• Inability or difficulty to focus.

• Problems in physical orientation such as coordination, balance, and walking.

• Muscle contractions and muscle spasms are experienced all over the body.

• Problems in articulation like speaking and swallowing.

• Visual disturbances.

How Serious Are the Complications of Cerebral Hypoxia?

Severe deprivation of oxygen led to life-threatening consequences such as coma and seizures.

Brain death occurs when there is no oxygen supply to the brain for 10 minutes, causing no activity in the brain. The affected person requires measures for life support, such as mechanical ventilators to assist with breathing and keeping them alive. Brain injury due to anoxia leads to prolonged coma, and the recovery pattern is significantly slower, with fewer chances of coming back to normal.

How Is Cerebral Hypoxia Detected?

Healthcare professionals prescribe investigations to assess the severity of brain injury, such as -

• Cerebral angiography for assessment of blood flow and circulation in the brain.

• Chromatography and magnetic resonance imaging detect clinical signs like stroke, intracerebral bleeding, brain edema or swelling, and any other trauma.

• An electroencephalogram is used to measure electrical activity in the brain.

• The evoked potential test is used to assess the brain’s response to sensations like touch.

How Can Cerebral Hypoxia Be Prevented?

If someone stops breathing, individuals can perform cardiopulmonary resuscitation and provide basic life support such as rescue breaths. These immediate efforts restore blood flow and oxygen supply to the brain until the arrival of the medical assistance team. These actions may prevent serious brain injury. It is essential to manage high-risk conditions such as high blood pressure and triggering conditions that lead to heart attack and stroke. People should take safety precautionary measures to reduce accident risks resulting in cerebral injury and hypoxia. A person and their family can:

• Always use seat belts while traveling.

• Installation of detectors to alarm for the presence of smoke or carbon monoxide in living spaces.

• Using life vests, swimming at safer places (presence of lifeguards), and supervising children near water bodies, including splash pools and bathtubs.

• Wearing helmets when involved in high-impact exercises like skating, skiing, and biking.

What Is the Prognosis of Hypoxic Brain Injury?

Some individuals with mild forms of cerebral hypoxia develop fewer symptoms and also recover gradually without noticeable long-term effects. Studies show that individuals who recover from a coma within four weeks have an increased chance of recovery with minimal long-term effects. Some people remain persistent, which means they appear to be awake, but they cannot consciously respond to commands or communicate. The prognosis of cerebral hypoxia in individuals primarily depends on the following:

• The duration of the hypoxic condition (time-lapse when the brain is deprived of oxygen).

• The severity of brain damage.

• The age factor matters a lot at the time of the incident.

Conclusion

As per studied above, if the brain goes too long without oxygen, then a person can suffer from hypoxic brain injury. But it can be managed by taking a few precautions, which can save a person from getting attacked. A healthcare provider also plays an important role in managing the disease, which includes certain tests that can be followed to prevent the injury.