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Q: long term effect of very low oxygen levels on adult brain ( Answered,   0 Comments )
Subject: long term effect of very low oxygen levels on adult brain
Category: Health > Conditions and Diseases
Asked by: emk1143-ga
List Price: $150.00
Posted: 02 Sep 2003 09:06 PDT
Expires: 02 Oct 2003 09:06 PDT
Question ID: 251426
delayed effect of hypoxic ischemic brain injury in adults

Request for Question Clarification by journalist-ga on 02 Sep 2003 10:47 PDT
Greetings Emk1143:

It may depend on what casued the hypoxia and you may require a
medically-trained Researcher to provide the final word.  For instance:

Delayed neurological effects of hypoxia due to carbon monoxide
poisoning -
"Unfortunately, some patients regress and develop delayed neurological
sequelae or delayed, subsequent effects. This delayed syndrome is
reported in 2 - 12% of CO poisoned patients. The onset may rapidly
occur (within two days of the apparent recovery) or may be delayed for
four to six weeks.  The most prevalent symptoms include mental
deterioration, fecal and/or urinary incontinence and gait (ability to
walk) disturbances. Common aspects of mental deterioration include
persistent headaches, personality changes, confusion, memory loss, and
irritability. Long-term follow up in one series of patients revealed a
75% recovery rate after two years, but another study reported that 11%
displayed gross neuropsychiatric damage, 33% had personality
deterioration, and 43% suffered memory loss when they were
re-evaluated three years after the poisoning incident.  It is not
possible to predict who will develop delayed effects."

Delayed memory following cerebral malaria

If you could share the circumstances of the hypoxia, it may assist a
Researcher.  All clarifications are appreciated.

Best regards,

hypoxia "delayed effects" adults
"long term" "neurological effects" delayed hypoxia

Clarification of Question by emk1143-ga on 02 Sep 2003 10:57 PDT
This situation would result from the presence of septic shock, flash
pulmonary edema and ventilator support and a period of several hours
with a blood oxygen level of 50% or less.
Subject: Re: long term effect of very low oxygen levels on adult brain
Answered By: umiat-ga on 03 Sep 2003 09:07 PDT
Hello, emk1143-ga! 

 Brain injuries are extremely complex and there is no definitive list
of symptoms and long-range outcomes that can be applied to all
individuals. The information supplied below is general in nature and
does not in any way constitute a medical opinion.

 I have preceded the section on possible associated brain injury with
some background information concerning septic shock and hypoxia in
hopes of providing an understandable and comprehensive answer.


 Septic shock is an infection of the blood, often stemming from an
internal organ infection that has spread into the circulatory system.
Septic shock is a serious condition which can become severe enough to
induce shock and subsequent drops in blood pressure. As blood pressure
drops, oxygen flow to the brain in minimized, and serious consequences
often result.

"The most damaging consequences of these bacteria and toxins include
poor functioning of the heart muscle; widening of the diameter of the
blood vessels; a drop in blood pressure; activation of the blood
clotting system, causing blood clots, followed by a risk of
uncontrollable bleeding; damage to the lungs, causing acute
respiratory distress syndrome; liver failure; kidney failure; and

From "Shock." :


"The primary risk of septic shock is death. Lung, heart, kidney,
brain, and other organ damage may also occur. This damage is often
reversible with treatment, though it can be permanent in severe

From "Septic shock," by Adam Brochert, MD. Discovery Health Channel.
(September 2003) 


 Acute respiratory distress syndrome, or non-cardiogenic pulmonary
edema, is commonly associated with septic shock. Even with respiratory
help, blood oxygen levels can remain dangerously low because the
stiffened lungs make expansion difficult.

For further information, read "ARDS (acute respiratory distress
syndrome)." Medline plus.


Brain Anoxia or Hypoxia:

"Specifically, anoxia is a condition in which there is an absence of
oxygen supply to an organ's tissues although there is adequate blood
flow to the tissue. Hypoxia is a condition in which there is a
decrease of oxygen to the tissue in spite of adequate blood flow to
the tissue. Anoxia and hypoxia, however, are often used
interchangeably -- without regard to their specific meanings -- to
describe a condition that occurs in an organ when there is a
diminished supply of oxygen to the organ's tissues."

"In severe cases of anoxia and hypoxia, from any cause, the patient is
often stuperous or comatose (in a state of unconsciousness) for
periods ranging from hours to days, weeks, or months. Seizures,
myoclonic jerks (muscle spasms or twitches), and neck stiffness may

From "Brain Anoxia or Hypoxia." Healthlink. Medical College of


"Stagnant (ischemic) anoxia (also called hypoxic-ischemic injury, or
HII)  --  not enough cerebral blood flow to carry blood to the brain.
Injury can be localized (such as ischemic strokes) or generalized
(circulatory collapse secondary to cardiac arrhythmias or cardiac
arrest). This type of injury causes general, diffuse damage to the
cerebral cortex and cerebellum. Areas of the brain that are very
sensitive to lack of oxygen include the hippocampus (a region critical
for memory), borderzone areas of the cerebral cortex (the
parieto-occipital and frontoparietal regions), cerebellum, basal
ganglia, and spinal cord (thoracic region)."

From "Fact Sheet:Hypoxic-Anoxic Brain Injury." Family Caregiver


"Oxygen saturation is a measurement of the blood's oxygen content. 
Saturation is a percentage:  the percentage of oxygen carrying sites
in the blood that are carrying oxygen.  Usually in the arteries oxygen
occupies more than 95% of carrying sites = "95% saturated".  Below a
level of 80% cells do not receive enough oxygen to continue to
function normally.  At 30% saturation there are cells dying.  How much
damage results from a low oxygen saturation depends on for how long
the "de-saturation" lasts.  Unfortunately some of the more serious
injury to cells due to low oxygen (hypoxia) or no oxygen (anoxia) are
irreversible - even neurons that are not quite dead after an episode
of a few minutes' anoxia, will die over the next few minutes to hours
even if normal oxygen supply (and saturation) are restored."

From "Oxygen." Glossary - Neurosurgical Terms in Plain English.


"Why is oxygen important? The brain consumes about 20% of the body's
total oxygen. 90% of the brain's total energy is used to send
electrochemical impulses and maintain the neurons' ability to send
these impulses. Much like the base of a pyramid on which everything
else rests, oxygen is necessary to metabolize glucose which is used to
provide the energy for all living cells."

"If oxygen is not available, a cascade-effect of problems occurs.
Oxygen and glucose are responsible, either directly or indirectly, for
a variety of chemical reactions which are involved in the production
of important chemical-like brain neurotransmitters (e.g., dopamine,
norepinephrine, and serotonin). Such neurotransmitters act to regulate
the brain's many complex functions. One particular neurotransmitter,
acetylcholine (Ach), seems to play a direct role in memory."

From "Fact Sheet:Hypoxic-Anoxic Brain Injury." Family Caregiver


 Acquired brain injuries result from conditions not associated with
direct physical trauma to the head. Brain injury due to hypoxia or
anoxia falls under this category.

"If the blood flow is depleted of oxygen, irreversible brain injury
from ANOXIA (no oxygen) or HYPOXIA (reduced oxygen) can result in just
a few minutes. Anoxia and hypoxia axe often caused by heart attacks,
respiratory failure, drops in blood pressure, and a low oxygen
environment. This type of brain injury can result in severe cognitive
and memory deficits."

From "Brain Injury:  Types of Brain Injury."


"Acquired brain injury takes place at the cellular level within the
brain. Therefore, injury from acquired brain injury can effect cells
throughout the entire brain, instead of just in specific areas as with
traumatic brain injury."

"Most symptoms of acquired brain injuries are very similar to that of
traumatic brain injuries; however, there are some difficulties that
are experienced more frequently or to a greater degree by persons with
acquired brain injuries."

These symptoms can include:

Cognitive impairment- Thinking skills, especially memory
Longer lengths of time spent in a vegetative state
Severe behavior problems- Psychosis, depression, restlessness,
combativeness, hostility
Muscle movement disorders

From "Types of Brain Injury." Brain Injury Association of America.




Hypoxic-ischemic injury:

"Why is the recovery of from HAI different from traumatic brain
injuries or strokes? Recovery is thought to occur for a variety of
reasons. One theory is that there exists a neuronal reserve which is
used to compensate for lost nerve cells. Because an anoxic injury is
diffuse and widespread, this may deplete the reserve capacity

"Predicting outcome is much like estimating how high a rocket will go
up. There are some general factors at the start of the launch which
will be helpful, but the actual course of the rocket will also point
out future progress. In other words, past and current changes will
predict future recovery. Below is a list of these factors."

"Coma duration--as might be expected, the longer a person is in a
coma, the less promising the outcome. One study suggested that if coma
is less than 12 hours, there is no or little transient damage. If coma
is greater than 12 hours, recovery may be slow and incomplete (lasting
deficits). If coma is 24 hours or more, the person is at a greater
chance of dying.
Another study showed that 21% of HAI patients who remained in coma
four weeks or less had a good recovery, and 79% had a poor recovery.
100% of those patients who remained in coma more than four weeks had a
poor recovery. Also, the patients whose coma durations were greater
than four weeks tended to show minimal recovery (functional gains)
after the first four months."

"If a person does not "wake up" from a coma, then significant damage
to the cerebral cortex, called laminar necrosis may have occurred.
Like wood-paneling, the cerebral cortex is made up of a number of
layers. If these cells die, the layers become separated from each
other. This results in neocortical death while lower brain functions
continue to operate (called a persistent vegetative state).

Short Term Effects:

"The symptoms of hypoxic-ischemic injury (HII) are related to the
areas of the brain and spinal cord that are damaged. A brief summary
of the types of symptoms and regions of the brain responsible are
described below. Symptoms will be divided into cognitive and physical

Cognitive deficits:
The cognitive symptoms observed from most to least common are: 

* Short-term memory loss. This is by far the most common, virtually
universal, symptom of HII. The reason is that one portion of the brain
believed to be critical for learning new information (called the
hippocampus) has neurons which are highly sensitive to changes in
chemistry or trauma.

* Executive functioning (reasoning/judgment, initiation,
perseveration, and impulsivity).
* Word-finding difficulties (also called anomia). 

* Visual disturbances. A person may have difficulty processing
incoming visual information. In rare instances, a disorder called
cortical blindness (Anton's Syndrome) may be observed in HII. In this
case, the area of the brain responsible for vision becomes
disconnected from the rest of the brain. Because the brain cannot tell
that this part of the brain is damaged or disconnected, a person may
act as though he/she can see, even though he/she shows no ability to
identify or discriminate objects, shapes, or colors.

Physical deficits:
Commons symptoms may include: 

* Ataxia (incoordination). These symptoms are similar to those seen in
alcohol-intoxicated individuals. Areas of the brain that may be
affected are the cerebellum, basal ganglia, and putamen.
* Apraxia (inability to follow a sequence of commands). 

* Spasticity, rigidity, myoclonus. Abnormal movements.
* Quadriparesis (weakness of all four extremities), paresis (weakness)
or paralysis (inability to move). This can also occur due to spinal
cord damage.

From "Fact Sheet:Hypoxic-Anoxic Brain Injury." Family Caregiver


Long-Term Effects:

 Severe deprivation of oxygen to the brain can cause permanent brain
injury. When the brain is deprived of oxygen, hypoxic ischemic
encephalopathy, or permanent brain injury, may be the result.


This condition can be caused by a number of medical situations,
including septic shock.


"Permanent disabilities that can occur from brain damage due to a lack
of oxygen include the following. Please note that these disabilities
often overlap in various combinations, although any one of them may be
the main disability experienced."

* Abnormal movements 

* Long-term coma
* Seizures: sudden, violent, involuntary muscle movements

* Inability in recognizing visual objects even though vision is

* Loss of muscle coordination due to damage to an area in the back of
the brain known as the cerebellum.

* Rapid, uncontrollable jerking muscle movements that occur at rest or
at movement.

* Choreoathetosis: abnormal body movements characterized by a choreic
(involuntary, irregular, dance-like, movements of the arms, legs, and
face) and athetoid (involuntary, slow, twisting movements of the
hands, fingers, toes, and feet) pattern.

* Dementia: a mental disorder that gets worse over time and is
characterized by confusion, impaired thinking abilities, poor memory,
poor judgment, personality changes, unawareness of the environment,
unresponsiveness, and doing things based on impulse.

* Disorientation (confusion), severely impaired memory of recent
events (also known as anterograde amnesia, and an inability to learn
new skills.


"There are some patients that will make a recovery and then get worse
after a period of 1 to 4 weeks. These patients usually feel confused,
irritable, and experience a lack of interest in things. Some patients
feel agitated and high-strung.


This worsening of symptoms is uncommon and not well understood. It is
known as delayed postanoxic encephalopathy.


Many patients survive it, but some are left with serious impairments
in thinking and movement. Some patients continue to worsen and die
within 1 to 2 weeks. After death, such patients are found to have
experienced widespread destruction of myelin in the brain. Myelin is a
substance that makes up the tube-shaped covering of various nerve
fibers in the body and helps them transmit messages fast."

"There are also some patients that slowly get worse over weeks and
months until they stop speaking, are stiff, and cannot help themselves
in any way. In such patients, the damage is mostly located in an area
known as the basal ganglia. The basal ganglia are paired groups of
nerve cells located deep within the brain that play an important part
in smooth, continuous muscle movements and in starting and stopping


 In very severe hypoxia when death is not the immediate result,
patients are often left with serious impairments:

"...some patients do not speak afterwards, will not respond to others,
and are unaware of their environment for weeks, months, or years. Some
improvement may occur over the long-term, but the patient appears not
to know anything about the present, has lost the ability to reason,
live independently, recall memories from the past, and interact with
others in a socially acceptable way."

From "Hypoxic ischemic encephalopathy."


"Almost all persons surviving five minutes or more of complete oxygen
depravation or 15 minutes of "substantial" hypoxia sustain permanent
brain damage (J.N. Walton, 1994)."

From "Coma: Some Facts." Brain (Updated:December 2002)


"The brain is more susceptible to injury through lack of oxygen
(hypoxia) than any other part of the body. Hypoxia can occur in
conjunction with other injuries (heart attack) or from any other
situation where breathing or oxygen intake is impaired. Damage from
hypoxia is often seen in the hippocampus, an area of the brain
necessary for laying down new memories."

From "How Can the Brain be Injured?" Brain
(Updated:December 2002)


"Hypoxic injuries result when there is a substantial or complete lack
of oxygen supplied to the brain, despite an adequate supply of blood
flow. In severe cases of hypoxia, the person is often in comatose (in
a state of unconsciousness) for periods ranging from hours to days,
weeks, or months. Following the emergence from coma, the person may
remain confused and disoriented for a period of time, having no
capacity to remember ongoing events. This may also last for hours,
days, weeks or months. In this state the person may be partially or
fully awake, but can be confused, agitated and disoriented, absorbing
little from the environment."

"The diminished oxygen supply to the brain may produce significant
cognitive, physical and emotional impairments. As a result, a hypoxic
injury can have a profound impact, in terms of functional deficits,
cost involved in treatment and the disruption it can have on people's
lives and that of their families."

"Hypoxia." The Brain Foundation of Victoria. 

 Further information is available in the Foundation's fact sheet:
"Hypoxia - Common Causes, Symptoms and Treatment." Brain Foundation of
Victoria. 2002


 I hope this information is helpful. If anything is unclear, please
let me know in a clarification and I will help to the best of my

 Thank you for a most interesting question!


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