Cerebral hypoxia
Encyclopedia
Cerebral hypoxia refers to a reduced supply of oxygen
to the brain
. Cerebral anoxia refers to a complete lack of oxygen to the brain. There are four separate categories of cerebral hypoxia; in order of severity they are; diffuse cerebral hypoxia (DCH), focal cerebral ischemia, cerebral infarction, and global cerebral ischemia. Prolonged hypoxia induces neuron
al cell death via apoptosis
resulting in a hypoxic brain injury.
Cases of total oxygen deprivation are termed anoxia, which can be hypoxic in origin i.e. reduced oxygen availability, or ischemic in origin i.e., oxygen deprivation due to a disruption in blood flow. Brain injury as a result of oxygen deprivation either due to hypoxic or anoxic mechanisms are generally termed hypoxic/anoxic injuries (HAI). Hypoxic ischemic encephalopathy (HIE) is a condition that occurs when the entire brain is deprived of an adequate oxygen supply, but the deprivation isn't total. While HIE is associated in most cases with oxygen deprivation in the neonate due to birth asphyxia, it can occur in all age groups, and is often a complication of cardiac arrest
.
Cerebral hypoxia can also be classified by the cause of the reduced brain oxygen:
the brain's ability to receive or process oxygen. This event may be internal or external to the body.
Mild and moderate forms of cerebral hypoxia may be caused by various diseases that interfere with breathing and blood oxygenation. Severe asthma and various sorts of anemia can cause some degree of diffuse cerebral hypoxia. Other causes include work in nitrogen rich environments, ascent from a deep water dive
, flying at high altitudes in an un-pressurized cabin, and intense exercise at high altitudes prior to acclimatization
.
Severe cerebral hypoxia and anoxia is usually caused by traumatic events. Examples include choking
, drowning
, strangulation, smoke inhalation
, drug overdoses, crushing of the trachea
, status asthmaticus
, and shock. It is also recreationally self-induced in the fainting game and in erotic asphyxiation
.
However, if blood flow cannot be increased or if doubled blood flow does not correct the problem, symptoms of cerebral hypoxia will begin to appear. Mild symptoms include difficulties with complex learning tasks and reductions in short-term memory. If oxygen deprivation continues, cognitive disturbances and decreased motor control will result. The skin may also appear bluish (cyanosis
) and heart rate increases. Continued oxygen deprivation results in fainting, long term loss of consciousness, coma
, seizures, cessation of brain stem reflexes, and brain death.
Objective measurements of the severity of cerebral hypoxia depend on the cause. Blood oxygen saturation may be used for hypoxic hypoxia, but is generally meaningless in other forms of hypoxia. In hypoxic hypoxia 95-100% saturation is considered normal. 91-94% is considered mild. 86-90% is considered moderate. Anything below 86% is considered severe.
It should be noted that cerebral hypoxia refers to oxygen levels in brain tissue, not blood. Blood oxygenation will usually appear normal in cases of hypemic, ischemic and hystoxic cerebral hypoxia. Even in hypoxic hypoxia blood measures are only an approximate guide – the oxygen level in the brain tissue will depend on how the body deals with the reduced oxygen content of the blood.
applied within 6 hours of cerebral hypoxia effectively improves survival and neurological outcome. In adults however the evidence is less convincing and the first goal of treatment is to restore oxygen to the brain. The method of restoration depends on the cause of the hypoxia. For mild to moderate cases of hypoxia, removal of the cause of hypoxia may be sufficient. Inhaled oxygen may also be provided. In severe cases treatment may also involve life support and damage control measures.
A deep coma will interfere with body’s breathing reflexes even after the initial cause of hypoxia has been dealt with. Mechanical ventilation
may be required. Additionally severe cerebral hypoxia causes an elevated heart rate. In extreme cases the heart may tire and stop pumping. CPR, defibrilation, epinephrine
, and atropine
may all be tried in an effort to get the heart to resume pumping.
Severe cerebral hypoxia can also cause seizures. Seizures put the patient at risk of self injury. If convulsions are sufficiently severe medical professionals may not be able to provide medical treatment. Various anti-convulsant drugs may need to be administered before treatment can continue.
Brain damage can occur both during and after oxygen deprivation. During oxygen deprivation, cells die due to an increasing acidity in the brain tissue (acidosis
). Additionally, during the period of oxygen deprivation, materials that can easily create free radicals build up. When oxygen enters the tissue these materials interact with oxygen to create high levels of oxidants. Oxidants interfere with the normal brain chemistry and cause further damage. This is called reperfusion injury
.
Techniques for preventing damage to brain cells are an area of on-going research.Hypothermia therapy for neonatal encephalopathy
is the only evidence-supported therapy, but anti-oxidant drugs, control of blood glucose levels, and hemodilution (thinning of the blood) coupled with drug-induced hypertension are some treatment techniques currently under investigation.
In severe cases it is extremely important to act quickly. Brain cells are very sensitive to reduced oxygen levels. Once deprived of oxygen they will begin to die off within five minutes.
If cerebral hypoxia was localized to a specific part of the brain, brain damage will be localized to that region. The long term effects will depend on the purpose of that portion of the brain. Damage to the Broca's area
and the Wernicke's area
of the brain (left side) typically causes problems with speech and language. Damage to the right side of the brain may interfere with the ability to express emotions or interpret what one sees. Damage on either side can cause paralysis of the opposite side of the body.
The effects of certain kinds of severe generalized hypoxias may take time to develop. For example, the long term effects of serious carbon monoxide poisoning usually may take several weeks to appear. Recent research suggests this may be due to an autoimmune response caused by CO induced changes in the myelin sheath surrounding neurons.
If hypoxia results in coma, the length of unconsciousness is often used as an indication of long term damage. In some cases coma can give the brain an opportunity to heal and regenerate, but, in general, the longer a coma continues the greater the likelihood that the person will remain in a vegetative state until death. Even if the patient wakes up, brain damage is likely to be significant enough to prevent a return to normal functioning.
The effects of long term comas are not limited to the comatose person. Long term coma can have significant impact on their families. Families of coma victims often have idealized images of the outcome based on Hollywood movie depictions of coma. Adjusting to the realities of ventilators, feeding tubes, bedsores and muscle wasting may be difficult. Treatment decision often involve complex ethical choices and can strain family dynamics.
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
to the brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
. Cerebral anoxia refers to a complete lack of oxygen to the brain. There are four separate categories of cerebral hypoxia; in order of severity they are; diffuse cerebral hypoxia (DCH), focal cerebral ischemia, cerebral infarction, and global cerebral ischemia. Prolonged hypoxia induces neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
al cell death via apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
resulting in a hypoxic brain injury.
Cases of total oxygen deprivation are termed anoxia, which can be hypoxic in origin i.e. reduced oxygen availability, or ischemic in origin i.e., oxygen deprivation due to a disruption in blood flow. Brain injury as a result of oxygen deprivation either due to hypoxic or anoxic mechanisms are generally termed hypoxic/anoxic injuries (HAI). Hypoxic ischemic encephalopathy (HIE) is a condition that occurs when the entire brain is deprived of an adequate oxygen supply, but the deprivation isn't total. While HIE is associated in most cases with oxygen deprivation in the neonate due to birth asphyxia, it can occur in all age groups, and is often a complication of cardiac arrest
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
.
Classification
Cerebral hypoxia is typically grouped into four categories depending on the severity and location of the brain’s oxygen deprivation:- Diffuse cerebral hypoxia. A mild to moderate impairment of brain function due to low oxygen levels in the blood.
- Focal cerebral ischemia; is a stroke occurring in a localized area that can either be acute (sudden onset)and/ or transient (of short duration). This may be due to a variety of medical conditions such as an aneuryrsmAneurysmAn aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
which causes a hemorrhagic stroke, or an occlusion occurring in the affected blood vessel/s due to a thrombusThrombusA thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system...
(thrombotic stroke) or embolusEmbolusAn embolus is any detached, itinerant intravascular mass carried by circulation, which is capable of clogging arterial capillary beds at a site distant from its point of origin.By contrast there are non-traveling blockages that develop locally from vascular trauma or...
(embolic stroke). Focal cerebral ischemia constitutes a large majority of the clinical cases in stroke pathology with the infarct usually occurring in the middle cerebral arteryMiddle cerebral artery-External links:*...
(MCA). - Global cerebral ischemia. A complete stoppage of blood flow to the brain.
- Massive Cerebral infarctionCerebral infarctionA cerebral infarction is the ischemic kind of stroke due to a disturbance in the blood vessels supplying blood to the brain. It can be atherothrombotic or embolic. Stroke caused by cerebral infarction should be distinguished from two other kinds of stroke: cerebral hemorrhage and subarachnoid...
; is a "stroke", caused by complete oxygen deprivation due to an interference in cerebral blood flowCerebral blood flowCerebral blood flow, or CBF, is the blood supply to the brain in a given time. In an adult, CBF is typically 750 millitres per minute or 15% of the cardiac output. This equates to 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. CBF is tightly regulated to meet the brain's...
which affects multiple areas of the brain.
Cerebral hypoxia can also be classified by the cause of the reduced brain oxygen:
- Hypoxic hypoxiaHypoxic hypoxiaHypoxic hypoxia is a result of insufficient oxygen available to the lungs. A blocked airway, a drowning or a reduction in partial pressure are obvious examples of how lungs can be deprived of oxygen. Some medical examples are abnormal pulmonary function or respiratory obstruction, or a...
. Limited oxygen in the environment causes reduced brain function. Divers, aviators, mountain climbers and fire fighters are all at risk for this kind of cerebral hypoxia. The term also includes oxygen deprivation due to obstructions in the lungs. Choking, strangulation, the crushing of the windpipe all cause this sort of hypoxia. Severe asthmatics may also experience symptoms of hypoxic hypoxia. - Hypemic hypoxia. Reduced brain function is caused by inadequate oxygen in the blood despite adequate environmental oxygen. Anemia and carbon monoxide poisoningCarbon monoxide poisoningCarbon monoxide poisoning occurs after enough inhalation of carbon monoxide . Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect...
are common causes of hypemic hypoxia. - Ischemic hypoxia (a.k.a. stagnant hypoxia). Reduced brain oxygen is caused by inadequate blood flow to the brain. StrokeStrokeA stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, shock, and heart attacks are common causes of stagnant hypoxia. Ischemic hypoxia can also be created by pressure on the brain. Cerebral edemaCerebral edemaCerebral edema or cerebral œdema is an excess accumulation of water in the intracellular or extracellular spaces of the brain.-Vasogenic:Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier...
, brain hemorrhages and hydrocephalusHydrocephalusHydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...
exert pressure on brain tissue and impede their absorption of oxygen. - Histotoxic hypoxiaHistotoxic hypoxiaHistotoxic hypoxia is the inability of cells to take up or utilize oxygen from the bloodstream, despite physiologically normal delivery of oxygen to such cells and tissues...
. Oxygen is present in brain tissue but cannot be metabolized. Cyanide poisoning is a well known example.
Causes
Cerebral hypoxia can be caused by any event that severely interferes withthe brain's ability to receive or process oxygen. This event may be internal or external to the body.
Mild and moderate forms of cerebral hypoxia may be caused by various diseases that interfere with breathing and blood oxygenation. Severe asthma and various sorts of anemia can cause some degree of diffuse cerebral hypoxia. Other causes include work in nitrogen rich environments, ascent from a deep water dive
Deep water blackout
A deep water blackout is a loss of consciousness caused by cerebral hypoxia on ascending from a deep freedive or breath-hold dive, typically of ten metres or more when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have...
, flying at high altitudes in an un-pressurized cabin, and intense exercise at high altitudes prior to acclimatization
Effects of high altitude on humans
The effects of high altitude on humans are considerable. The percentage saturation of hemoglobin with oxygen determines the content of oxygen in our blood. After the human body reaches around 2,100 m above sea level, the saturation of oxyhemoglobin begins to plummet...
.
Severe cerebral hypoxia and anoxia is usually caused by traumatic events. Examples include choking
Choking
Choking is the mechanical obstruction of the flow of air from the environment into the lungs. Choking prevents breathing, and can be partial or complete, with partial choking allowing some, although inadequate, flow of air into the lungs. Prolonged or complete choking results in asphyxia which...
, drowning
Drowning
Drowning is death from asphyxia due to suffocation caused by water entering the lungs and preventing the absorption of oxygen leading to cerebral hypoxia....
, strangulation, smoke inhalation
Smoke inhalation
Smoke inhalation is the primary cause of death in victims of indoor fires.Smoke inhalation injury refers to injury due to inhalation or exposure to hot gaseous products of combustion. This can cause serious respiratory complications....
, drug overdoses, crushing of the trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
, status asthmaticus
Status asthmaticus
Status asthmaticus is an acute exacerbation of asthma that does not respond to standard treatments of bronchodilators and steroids. Symptoms include chest tightness, rapidly progressive dyspnea , dry cough, use of accessory muscles, labored breathing and extreme wheezing. It is a life-threatening...
, and shock. It is also recreationally self-induced in the fainting game and in erotic asphyxiation
Erotic asphyxiation
Erotic asphyxiation or breath control play is the intentional restriction of oxygen to the brain for sexual arousal. The sexual preference for that behavior is variously called asphyxiophilia, autoerotic asphyxia, hypoxyphilia. Colloquially, a person engaging in the activity is sometimes called a...
.
- Transient ischemic attackTransient ischemic attackA transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
(TIA), is often referred to as a "mini-stroke". The American Heart Association and American Stroke Association (AHA/ASA) refined the definition of transient ischemic attack. TIA is now defined as a transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction. The symptoms of a TIA can resolve within a few minutes unlike a stroke. TIAs share the same underlying etiologyEtiologyEtiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
as strokes; a disruption of cerebral blood flow. TIAs and strokes present with the same symptoms such as contralateral paralysis (opposite side of body from affected brain hemisphere), or sudden weakness or numbness. A TIA may cause sudden dimming or loss of vision, aphasiaAphasiaAphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
, slurred speech and mental confusion. The symptoms of a TIA typically resolve within 24 hours unlike a stroke. Brain injury may still occur in a TIA lasting only a few minutes. Having a TIA is a risk factor for eventually having a stroke.
- Silent strokeSilent strokeA silent stroke is a stroke that does not have any outward symptoms, and the patient is typically unaware they have suffered a stroke. Despite not causing identifiable symptoms a silent stroke still causes damage to the brain, and places the patient at increased risk for both transient ischemic...
is a strokeStrokeA stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
which does not have any outward symptoms, and the patient is typically unaware they have suffered a stroke. Despite not causing identifiable symptoms a silent stroke still causes damage to the brain, and places the patient at increased risk for a major stroke in the future. In a broad study in 1998, more than 11 million people were estimated to have experienced a stroke in the United States. Approximately 770,000 of theses strokes were symptomatic and 11 million were first-ever silent MRI infarcts or hemorrhages. Silent strokes typically cause lesionLesionA lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s which are detected via the use of neuroimaging such as fMRI. The risk of silent stroke increases with age but may also affect younger adults. Women appear to be at increased risk for silent stroke, with hypertensionHypertensionHypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
and current cigarette smoking being predisposing factors.
Signs and symptoms
The brain requires approximately 3.3 ml of oxygen per 100 g of brain tissue per minute. Initially the body responds to lowered blood oxygen by redirecting blood to the brain and increasing cerebral blood flow. Blood flow may increase up to twice the normal flow but no more. If the increased blood flow is sufficient to supply the brain’s oxygen needs then no symptoms will result.However, if blood flow cannot be increased or if doubled blood flow does not correct the problem, symptoms of cerebral hypoxia will begin to appear. Mild symptoms include difficulties with complex learning tasks and reductions in short-term memory. If oxygen deprivation continues, cognitive disturbances and decreased motor control will result. The skin may also appear bluish (cyanosis
Cyanosis
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
) and heart rate increases. Continued oxygen deprivation results in fainting, long term loss of consciousness, coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
, seizures, cessation of brain stem reflexes, and brain death.
Objective measurements of the severity of cerebral hypoxia depend on the cause. Blood oxygen saturation may be used for hypoxic hypoxia, but is generally meaningless in other forms of hypoxia. In hypoxic hypoxia 95-100% saturation is considered normal. 91-94% is considered mild. 86-90% is considered moderate. Anything below 86% is considered severe.
It should be noted that cerebral hypoxia refers to oxygen levels in brain tissue, not blood. Blood oxygenation will usually appear normal in cases of hypemic, ischemic and hystoxic cerebral hypoxia. Even in hypoxic hypoxia blood measures are only an approximate guide – the oxygen level in the brain tissue will depend on how the body deals with the reduced oxygen content of the blood.
Treatment
For newborn infants starved of oxygen during birth there is now evidence that hypothermia therapy for neonatal encephalopathyHypothermia therapy for neonatal encephalopathy
Brain hypothermia, induced by cooling a baby to around 33°C for three days after birth, is a treatment for birth asphyxia. It has recently been proven to be the only medical intervention which reduces brain damage, and improves an infant's chance of normal survival...
applied within 6 hours of cerebral hypoxia effectively improves survival and neurological outcome. In adults however the evidence is less convincing and the first goal of treatment is to restore oxygen to the brain. The method of restoration depends on the cause of the hypoxia. For mild to moderate cases of hypoxia, removal of the cause of hypoxia may be sufficient. Inhaled oxygen may also be provided. In severe cases treatment may also involve life support and damage control measures.
A deep coma will interfere with body’s breathing reflexes even after the initial cause of hypoxia has been dealt with. Mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
may be required. Additionally severe cerebral hypoxia causes an elevated heart rate. In extreme cases the heart may tire and stop pumping. CPR, defibrilation, epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
, and atropine
Atropine
Atropine is a naturally occurring tropane alkaloid extracted from deadly nightshade , Jimson weed , mandrake and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a drug with a wide variety of effects...
may all be tried in an effort to get the heart to resume pumping.
Severe cerebral hypoxia can also cause seizures. Seizures put the patient at risk of self injury. If convulsions are sufficiently severe medical professionals may not be able to provide medical treatment. Various anti-convulsant drugs may need to be administered before treatment can continue.
Brain damage can occur both during and after oxygen deprivation. During oxygen deprivation, cells die due to an increasing acidity in the brain tissue (acidosis
Acidosis
Acidosis is an increased acidity in the blood and other body tissue . If not further qualified, it usually refers to acidity of the blood plasma....
). Additionally, during the period of oxygen deprivation, materials that can easily create free radicals build up. When oxygen enters the tissue these materials interact with oxygen to create high levels of oxidants. Oxidants interfere with the normal brain chemistry and cause further damage. This is called reperfusion injury
Reperfusion injury
Reperfusion injury is the tissue damage caused when blood supply returns to the tissue after a period of ischemia or lack of oxygen. The absence of oxygen and nutrients from blood during the ischemic period creates a condition in which the restoration of circulation results in inflammation and...
.
Techniques for preventing damage to brain cells are an area of on-going research.Hypothermia therapy for neonatal encephalopathy
Hypothermia therapy for neonatal encephalopathy
Brain hypothermia, induced by cooling a baby to around 33°C for three days after birth, is a treatment for birth asphyxia. It has recently been proven to be the only medical intervention which reduces brain damage, and improves an infant's chance of normal survival...
is the only evidence-supported therapy, but anti-oxidant drugs, control of blood glucose levels, and hemodilution (thinning of the blood) coupled with drug-induced hypertension are some treatment techniques currently under investigation.
In severe cases it is extremely important to act quickly. Brain cells are very sensitive to reduced oxygen levels. Once deprived of oxygen they will begin to die off within five minutes.
Prognosis
Mild and moderate cerebral hypoxia generally has no impact beyond the episode of hypoxia. Severe cerebral hypoxia is another matter. Outcome will depend on the success of damage control measures, the amount of brain tissue deprived of oxygen, and the speed with which oxygen was restored to the brain.If cerebral hypoxia was localized to a specific part of the brain, brain damage will be localized to that region. The long term effects will depend on the purpose of that portion of the brain. Damage to the Broca's area
Broca's area
Broca's area is a region of the hominid brain with functions linked to speech production.The production of language has been linked to the Broca’s area since Pierre Paul Broca reported impairments in two patients. They had lost the ability to speak after injury to the posterior inferior frontal...
and the Wernicke's area
Wernicke's area
Wernicke's area is one of the two parts of the cerebral cortex linked since the late nineteenth century to speech . It is involved in the understanding of written and spoken language...
of the brain (left side) typically causes problems with speech and language. Damage to the right side of the brain may interfere with the ability to express emotions or interpret what one sees. Damage on either side can cause paralysis of the opposite side of the body.
The effects of certain kinds of severe generalized hypoxias may take time to develop. For example, the long term effects of serious carbon monoxide poisoning usually may take several weeks to appear. Recent research suggests this may be due to an autoimmune response caused by CO induced changes in the myelin sheath surrounding neurons.
If hypoxia results in coma, the length of unconsciousness is often used as an indication of long term damage. In some cases coma can give the brain an opportunity to heal and regenerate, but, in general, the longer a coma continues the greater the likelihood that the person will remain in a vegetative state until death. Even if the patient wakes up, brain damage is likely to be significant enough to prevent a return to normal functioning.
The effects of long term comas are not limited to the comatose person. Long term coma can have significant impact on their families. Families of coma victims often have idealized images of the outcome based on Hollywood movie depictions of coma. Adjusting to the realities of ventilators, feeding tubes, bedsores and muscle wasting may be difficult. Treatment decision often involve complex ethical choices and can strain family dynamics.
See also
- Altitude sicknessAltitude sicknessAltitude sickness—also known as acute mountain sickness , altitude illness, hypobaropathy, or soroche—is a pathological effect of high altitude on humans, caused by acute exposure to low partial pressure of oxygen at high altitude...
- Deep water blackoutDeep water blackoutA deep water blackout is a loss of consciousness caused by cerebral hypoxia on ascending from a deep freedive or breath-hold dive, typically of ten metres or more when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have...
- Physical traumaPhysical traumaTrauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
- Hypoxia (medical)Hypoxia (medical)Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
- Choking gameChoking gameThe fainting game , refers to intentionally cutting off oxygen to the brain with the goal of inducing temporary syncope and euphoria. There are two distinct methods used to achieve oxygen deprivation: strangulation and self-induced hypocapnia.-Differences from erotic asphyxiation:According to Dr...
- Space exposureSpace exposureSpace exposure is the subjection of a human to the conditions of outer space, without protective clothing and beyond the Earth’s atmosphere in a vacuum.-Explanation and history:...
- Olympic Cool-Cap SystemOlympic Cool-Cap SystemThe Olympic Cool-Cap System is a helmet designed to provide hypothermia therapy for neonatal encephalopathy caused by hypoxic-ischemic encephalopathy , preventing cerebral palsy in babies born with little or no oxygen....