Brain hypoxia may result from disorders of the respiratory, circulatory or nervous systems. These three systems are so closely related to each other in their functions that the cessation or even a short-term problem of one of them causes the other two to cease or disturb in a short time. Brain hypoxia is a life-threatening condition and therefore requires immediate attention. What could be the causes of cerebral hypoxia? How is the treatment going?
Brain hypoxiais the result of the brain not getting enough oxygen to function properly. The brain needs about 3.3 ml of oxygenated blood for 100 g of brain tissue. Initially, the body responds to the decreased level of oxygen in the blood (hypoxemia) by increasing cerebral flow. If the increased blood flow is enough to replenish the oxygen deficiency in the brain, there are no disturbing symptoms. However, if the blood flow cannot be increased or the increase in blood flow does not solve the hypoxia problem, there aresymptoms of oxygen deficiency in the brain(hypoxia).
A really short break in the supply of oxygen is enough for the brain to be severely damaged and even die. The cortex of the brain is particularly sensitive to lack of oxygen. Its deficiency under normal temperature conditions causesdeath of the cerebral cortexafter only 3-4 minutes. The destruction of the cerebral cortex, responsible for human consciousness, leads to its permanent, irreversible loss, even other parts of the brain resistant to hypoxia have been saved. The tolerance time of the whole brain to hypoxia is not long, e.g. breathing control centers die after 20-30 minutes.
Brain hypoxia is a life-threatening condition , because even a short-term stoppage of blood movement can damage its cells (neurons). This is why immediate help is so important in this case. Research indicates that restoring blood oxygen delivery within the first 3-4 minutes can prevent hypoxia and damage to the central nervous system. Therefore, the later the patient receives professional medical attention, the greater the consequences of hypoxia will be.
Brain hypoxia - symptoms
SymptomsBrain hypoxia can appear suddenly and worsen over time. Initially, these are:
- headache
- visual disturbance
- short-term memory problems
- nausea
- vomiting
Further brain hypoxia leads to:
- cognitive impairment
- disturbance of balance and coordination
- sensory disturbance
- cyanosis
- increase in heart rate (tachycardia)
If the patient is not given first aid, the following happens:
- fainting
- unconscious
- seizures
- comas
- followed by brain death
The sudden nature of the symptoms of cerebral hypoxia usually indicates cardiovascular failure - a sudden decrease in the amount of blood flowing to the brain, for example in paroxysmal atrial fibrillation or a blood clot that leads to an ischemic stroke.
Brain hypoxia can also be chronic and manifest as worsening problems with concentration, memory, associating facts, persistent sleepiness, and even mental disorders. Chronic cerebral hypoxia can occur, for example, in the course of undiagnosed or poorly treated diabetes, which leads to progressive destruction of the vessels.
Brain hypoxia - types
There are several types of brain hypoxia in medical terminology:
- ischemic (total) or cerebral infarction- occurs when blood flow stops in the entire brain or in an area supplied by one artery. It is ischemia that is the root cause of cerebral hypoxia. After approximately 2 minutes of cardiac arrest, the oxygen concentration in the brain tissues drops to zero. During this time, harmful metabolites, such as adenosine and lactic acid, accumulate, and a large amount of free radicals are produced, which causes the progressive destruction of cells
- oligemic (partial)- takes place in a generalized or regional reduction in blood flow
- anoxic- caused by reduction of oxygen tension in arterial blood
- hypoxic- caused by reduced oxygen partial pressure in arterial blood
- anemic- caused by a deficiency of the oxygen carrier - hemoglobin
- histotoxic- resulting in blockage of enzyme systems involved in energy transformations of nerve cells
Brain hypoxia - causes
The most common causes of brain hypoxia include:
- cardiovascular arrest, incl. in the course of a heart attackcardiac muscle, ventricular fibrillation, sudden hemorrhage
- cardiovascular failure: cardiomyopathy, severe myocarditis
- drop in blood pressure, e.g. caused by haemorrhagic shock, anaphylactic shock, septic shock, traumatic or painful shock (e.g. burns on a large body surface)
- obstruction of the carotid arteries as a result of atherosclerosis, thrombosis, embolism, dissecting aneurysm
- severe anemia
- respiratory diseases: severe pneumonia (e.g. in the course of COVID-19), severe asthma attack, emphysema, pleural hemorrhage, pneumothorax, COPD, sleep apnea syndrome
Brain hypoxia due to diabetes
Diabetes may lead to macroangiopathy, i.e. pathological changes in large blood vessels, which may result in ischemic heart disease, myocardial infarction, stroke or atherosclerosis of the lower limbs.
Perinatal Hypoxia
Perinatal hypoxia is a newborn's respiratory failure caused by insufficient oxygen before, during, or after delivery. The causes of perinatal hypoxia may include hypoxia of the baby before delivery, compression of the umbilical cord during delivery, premature or complex delivery, and administration of an anesthetic to the pregnant woman. In turn, the effects of cerebral palsy, epilepsy and intellectual disability.
Hypoxic Ischemic Encephalopathy (ENN)
Hypoxic-ischemic encephalopathy (ENN) is one of the diseases of the neonatal period, the consequences of which result from damage to the central nervous system. The occurrence of the disease is influenced by many factors, such as intrauterine infection, cerebral flow disorders, fetal immaturity. The long-term consequences of the disease in a child of developmental age may include cerebral palsy, neurodevelopmental disorders, learning difficulties, epilepsy, amblyopia and hearing disorders.
Brain hypoxia and carbon monoxide poisoning
Poisoning with carbon monoxide or inhaling smoke (e.g. during a fire) depresses the respiratory center in the brainstem - then breathing becomes ineffective.
Brain hypoxia and degeneration of the spine
The degeneration of the spine can lead to circulatory problems in the vertebral artery (which carries blood to the brain) and, consequently, to cerebral hypoxia.
Brain hypoxia and high altitude disease
Altitude sickness is a group of symptoms that result from a maladjustment of the bodyto stay at very high altitudes (above 2,500 m above sea level), where, due to the dilution of the atmosphere, the oxygen content in the air is low. One of the most dangerous complications of alpine disease is pulmonary edema, which leads to cerebral hypoxia.
Brain hypoxia and decompression sickness
Decompression sickness is a group of symptoms that affect a person exposed to external pressure that drops too quickly. If a large amount of nitrogen is found in a diver's blood as a result of a long or deep dive, ascent directly to the surface can cause nitrogen bubbles to form in the bloodstream, which can cause congestion and hypoxia to the brain.
Brain hypoxia and hypothermia
Hypothermia, i.e. lowering the body's internal temperature below normal, may be caused by staying in too cold water or in cold air for too long. The greatest danger is being in cold water, which conducts heat much better and cools the body 25 times faster than air. Prolongation of this state causes a drop in body temperature and oxygen deficiency in the brain.
Other causes of brain hypoxia may be:
- drowning
- asphyxiation
- foreign body stuck in the respiratory tract
- amyotrophic lateral sclerosis (ALS), which paralyzes the respiratory muscles
- degenerative nerve diseases
Hypoxia can also be a complication of general anesthesia or drug overdose.
Brain hypoxia - treatment
Treatment of brain hypoxia always takes place in a hospital setting and its goal is also to start the transport of oxygen to the brain. The detailed course of therapy depends on the cause of cerebral hypoxia.
About the author
Monika Majewska A journalist specializing in he alth issues, especially in the areas of medicine, he alth protection and he althy eating. Author of news, guides, interviews with experts and reports. Participant of the largest Polish National Medical Conference "Polish woman in Europe", organized by the "Journalists for He alth" Association, as well as specialist workshops and seminars for journalists organized by the Association.
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