In traumatic brain injury, damage to the axons the projections that transmit messages between brain cells is usually a prominent feature and the brain can often create alternative connections to compensate for this.
In anoxic brain injury, the actual nerve cell bodies themselves are very vulnerable to damage and this damage is irreparable. As with other forms of acquired brain injury, people over the age of 50 years tend to do less well overall than younger ones, both in terms of how likely they are to survive in the first place and in the degree of long-term recovery.
However, there is evidence that older people are able to benefit from rehabilitation programmes after cerebral anoxia and so deserve equally vigorous efforts to achieve the best possible outcome. The outcome will be determined by how extensive the damage to the brain has been. This will depend on the length of time the brain was deprived of oxygen, which can often be estimated from information about what has happened.
For example, it may be known that it took 15 minutes to restore a normal heart beat after a cardiac arrest, or that someone was immersed in a swimming pool for six minutes in a near drowning incident. The duration of unconsciousness after an anoxic episode reflects the severity of the injury to the brain and helps predict the outcome. It should be noted that some comas are medically induced in order to protect the brain from further damage.
The duration of a medically induced coma does not give an indication of the outcome. Normally, the pupils will constrict when a bright light is shone into the eyes. However, following brain injury, this reflex may be lost, causing the pupils to become dilated and fixed, no longer reacting to light. This is an unfavourable sign following an anoxic brain injury and indicates a disturbance in the function of the brainstem. The EEG displays the electrical activity of the brain, recorded from a set of small metal disc electrodes placed on the scalp.
There has been a good deal of research on the EEG following cardiac arrest and the degree of EEG abnormality does have some value in helping to predict the outcome. This works best at the extremes. People with a normal EEG in the early stages after cardiac arrest have a very good chance of making a full recovery and those with profoundly abnormal EEGs often either do not survive at all, or will have severe disabilities. However, there is a large group who have intermediate degrees of EEG abnormality, where the outcome is less predictable.
Computed Tomography CT and Magnetic Resonance Imaging MRI can show if there is brain swelling and give an indication of the degree of damage to the brain and the areas affected. This can help in predicting the outcome and trying to anticipate what level of neurological disability is likely in the event of survival. However, brain scans may show very little in some patients and what they show depends on the nature of the brain injury and the interval between the anoxic episode and the scan.
They are mainly used for research purposes. SSEPs are the electrical responses of the brain to stimulation of the senses. They can normally be recorded from the scalp, following electrical stimulation of nerves at the wrist. These nerves transmit sensation from the arm to the brain.
The absence of SSEPs recorded from the scalp is associated with a poor outcome. The principles of rehabilitation after cerebral anoxia are the same as for other types of acquired brain injury.
The goal is to provide support from an integrated team with a range of specialist skills, able to help with the different problems which may occur and to support each individual to achieve the best possible outcome.
The outlook for anoxic brain injury can be uncertain and different specialists have expressed quite varied views on the timescale of recovery, based on their own individual experiences. Good improvement within the first month after an anoxic episode suggests that the outcome may be more favourable. The most rapid recovery is usually in the first six months, and by about one year the likely long-term outcome will have become clearer.
However, improvement may continue for much longer after brain injury, certainly for several years, although the steps may become more modest and gradual after the first few months. Adequate rehabilitation from the earliest possible stage is vital in order to achieve the best outcome. The effects of hypoxic or anoxic brain injury, where the brain is starved of oxygen, can range from mild, short-term symptoms such as dizziness or concentration problems, through to severe, long-term issues including vision, speech and memory.
The body will respond to cerebral anoxia by increasing blood flow to the brain in an attempt to restore an adequate supply of oxygen. However, it is only possible to increase brain blood flow to about twice the normal level. If this is not enough to compensate for the anoxia, brain function will be disturbed and symptoms will become apparent. If the cerebral anoxia is mild, there will be problems with concentration, attention, co-ordination and short-term memory, which may be relatively subtle to begin with.
There may be headache, light-headedness, dizziness, an increase in breathing rate and sweating. There can be a restriction in the field of vision, a sensation of numbness or tingling and feelings of euphoria. As the degree of anoxia becomes more pronounced, confusion, agitation or drowsiness appear, along with cyanosis - a bluish tinge to the skin, reflecting the lowered oxygen content of the blood, often most apparent around the lips, mouth and fingertips.
There may be brief jerks of the limbs myoclonus and seizures, both resulting from the damaging effects of lack of oxygen on the brain. If the anoxia is severe, it will result in loss of consciousness and coma. Editorial team. CPR - adult and child after onset of puberty. CPR involves: Rescue breathing, which provides oxygen to a person's lungs. Chest compressions, which keep the person's blood circulating. In adults, major reasons that heartbeat and breathing stop include: Drug overdose Excessive bleeding Heart problem heart attack or abnormal heart rhythm, fluid in the lungs or compressing the heart Infection in the bloodstream sepsis Injuries and accidents Drowning Stroke There are many things that cause an older child or teen's heartbeat and breathing to stop, including: Choking Drowning Electrical shock Excessive bleeding Head trauma or other serious injury Lung disease Poisoning Suffocation.
CPR should be done if a person has any of the following symptoms: No breathing or difficulty breathing gasping No pulse Unconsciousness.
Perform chest compressions : Place the heel of one hand on the breastbone -- right between the nipples. Place the heel of your other hand on top of the first hand.
Position your body directly over your hands. Give 30 chest compressions. These compressions should be fast and hard. Press down about 2 inches 5 centimeters into the chest. Each time, let the chest rise completely.
Count the 30 compressions quickly: "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30, off". If the person is not breathing or has trouble breathing : Cover their mouth tightly with your mouth. Pinch the nose closed. Keep the chin lifted and head tilted. Give 2 rescue breaths. Each breath should take about a second and make the chest rise. Doing so may cause the heart to stop beating. There are many other causes listed below that could lead the situation of oxygen deprivation:.
As noted above — hypoxic refers to the partial lack of oxygen to the brain, while anoxic means a total lack of oxygen to the brain. When there is lack of oxygen to the brain, there is not one place that lacks oxygen, but everywhere that blood normally flows. One thing is for sure — if the brain is lacking oxygen, every second counts. These statistics might not be the same for everyone. Nevertheless, it is imperative to find out whether your brain is affected.
Mild symptoms of oxygen deprivation to the brain can include memory loss and problems with motor function, such as movement. Severe cases of oxygen deprivation can result in seizures and brain death. Other symptoms of brain hypoxia or low oxygen levels in the brain can include:. The lack of oxygen to the brain is a medical emergency that requires immediate medical intervention and treatment, however projecting the recovery and care for anoxic or hypoxic brain injuries is difficult because each case is unique.
It is imperative that oxygen supply to the brain resumes without delay in order to prevent serious complications or brain death. The most important thing without a doubt is to get more oxygen into your body.
This means the person may have basic life functions, such as breathing, blood pressure, sleep-wake cycle, and eye opening, but the person is not alert and does not respond to their surroundings.
Such people usually die within a year, although some may survive longer. Length of survival depends partly on how much care is taken to prevent other problems. Major complications may include:. Cerebral hypoxia is a medical emergency. Call or the local emergency number immediately if someone is losing consciousness or has other symptoms of cerebral hypoxia. Prevention depends on the specific cause of hypoxia.
Unfortunately, hypoxia is usually unexpected. This makes the condition somewhat difficult to prevent. Anoxic-ischemic encephalopathy. Bradley's Neurology in Clinical Practice. Philadelphia, PA: Elsevier; chap Coma, vegetative state, and brain death.
Goldman-Cecil Medicine.
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