The brain requires a constant flow of oxygen to function normally. A hypoxic-anoxic injury, also known as HAI, occurs when that flow is disrupted, essentially starving the brain and preventing it from performing vital biochemical processes. Hypoxic refers to a partial lack of oxygen; anoxic means a total lack. In general, the more complete the deprivation, the more severe the harm to the brain and the greater the consequences.
The diminished oxygen supply can cause serious impairments in cognitive skills, as well as in physical, psychological and other functions. Recovery can occur in many cases, but it depends largely on the parts of the brain affected, and its pace and extent are unpredictable.
As a result, HAI can have a catastrophic impact on the lives not only of those injured but their families, friends and caregivers as well. Treatment can be costly and complicated, especially because HAI patients frequently need substantial medical and rehabilitative help and may suffer from significant long-term disabilities. A shortage of easy-to-understand, accessible information about HAI can make the situation even more stressful for affected individuals and their families. This Fact Sheet will help answer your questions about this condition.
Why is oxygen important to us? Our bodies require oxygen in order to metabolize glucose. This process provides energy for the cells. The brain consumes about a fifth of the body’s total oxygen supply, and needs energy to transmit electrochemical impulses between cells and to maintain the ability of neurons to receive and respond to these signals.
Cells of the brain will start to die within a few minutes if they are deprived of oxygen. The result is a cascade of problems. In particular, the disruption of the transmission of electrochemical impulses impacts the production and activity of important substances called neurotransmitters, which regulate many cognitive, physiological and emotional processes.
There are many neurotransmitters, and they perform a wide variety of important functions, although the specific ways neurotransmitters work is not fully understood. Some, such as serotonin, dopamine and norepinephrine, play an important role in regulating moods. Endorphins are critical for controlling pain and enhancing pleasure, while acetylcholine is important for memory functions.
A variety of disease processes and injuries can cause HAI. The most common is called hypoxicischemic injury, also known as HII or stagnant anoxia. This occurs when some internal event prevents enough oxygen-rich blood from reaching the brain. While strokes and cardiac arrhythmia can both result in HII, the most frequent cause is cardiac arrest.
Anesthesia accidents and cardiovascular disease each account for just under a third of cardiac arrests, according to a 1989 study. Other possible causes are asphyxia, generally caused by suicide attempts or near-drownings (16 percent), chest trauma (10 percent), electrocution (6.5 percent), severe bronchial asthma (3 percent) and barbiturate poisoning (3 percent).
Occasionally, HAI is caused by anoxic anoxia, which is when the air itself does not contain enough oxygen to be absorbed and used by the body. This can occur at high altitudes, where the air is thinner than at sea level, but is extremely unusual otherwise. Another syndrome, toxic anoxia, involves the presence in the body of toxins or other substances that may interfere with the way an individual processes oxygen.
Another occasional cause of HAI is anemic anoxia, which can occur when someone does not have enough blood or hemoglobin, a chemical in the red blood cells, which carry oxygen throughout the body. Acute hemorrhage, chronic anemia, and carbon monoxide poisoning are conditions that can result in anemic anoxia.
Acute hemorrhage is essentially massive bleeding, caused, for example, by a gunshot or other wound. Chronic anemia is an ailment in which a person suffers from persistently low levels of red blood cells or hemoglobin. Carbon monoxide poisoning, which appears to damage parts of the brain controlling movement, occurs in suicide attempts using automobile exhaust, but can also happen due to malfunctioning furnaces and other accidents involving machinery and industrial equipment.
HAI is generally marked by an initial loss of consciousness or coma, a condition which looks like sleep but from which a person cannot be awakened. The period of unconsciousness, whether short or long, might be followed by a persistent vegetative state, in which a person is neither comatose nor responsive to external stimuli. This state is frequently referred to as “wakeful unresponsiveness.”
Even when a person has fully recovered consciousness, he or she might suffer from a long list of symptoms. In many ways, these symptoms are similar to those commonly seen after a blow to the head. The effects can vary widely depending upon the part of the brain that has been injured and the extent of the damage. Some of the major cognitive (thought) problems are:
Some common physical deficits are:
Other symptoms can include: hallucinations and delusions; increased agitation and confusion; depression and other mood disorders; personality changes, such as irritability and a reduced threshold for frustration; and an inability to focus or concentrate.
Because people with HAI have often suffered extensive damage, complete recovery is not assured. In fact, predicting the outcome of HAI is a bit like estimating how high a rocket will go. There are some general factors that are helpful in making initial forecasts, but the actual course of the rocket is also dependent upon real-world conditions and many unforeseeable variables.
Studies that have been done suggest that recovery may be more limited than in cases where a person has suffered a traumatic brain injury of comparable severity. Nonetheless, there are some clues that can clearly offer a bit of guidance in judging the likelihood of at least a partial recovery. These include:
Many patients come out of a coma but remain in what is called a persistent vegetative state, a sort of wakeful unresponsiveness in which some brain functions continue to operate but with no apparent consciousness. Some doctors believe that if the persistent vegetative state in a patient with HAI continues for more than three months, there is virtually no chance of further recovery.
Unfortunately, direct treatment of anoxia is limited. Some studies have suggested that the use of barbiturates, which slow down the brain’s activity, may be helpful in the first two or three days after the onset of the injury. Otherwise, the general medical approach is to maintain the body’s status.
Once a person’s condition has been stabilized, the next question is to what extent he or she can recover. Recovery can take many months and even years, and in many cases the person never regains his or her prior level of functioning. In general, the sooner rehabilitation starts, the better.
During rehabilitation, the individual and family members may interact with a variety of professionals as the need for constant medical attention from a doctor decreases. Such professionals may include a physical therapist, who aids in improving motor skills such as walking; an occupational therapist, who assists in retraining the person to perform skills of daily living, such as dressing and going to the bathroom; a speech therapist, who may help address cognitive problems as well as language disorders; and a neuropsychologist, who may assess the level and type of cognitive impairment, collaborate on retraining and assist both the individual and family members with behavior and emotional issues.
As recovery may take months and even years, it is important for both the patient and family members involved in rehabilitation efforts to establish a good working relationship with the various specialists. It’s important to understand that rehab often proceeds in an unpredictable way, with progress measured in small steps rather than giant leaps.
Patients and family caregivers, therefore, often experience intense bouts of frustration at what they perceive to be the slow pace of recovery. Expectations and hope may at times outstrip the person’s actual level of progress, and the potential for disappointment and misunderstanding—between patient and family, or caregivers and rehabilitation professionals—can be significant.
While the process will never be easy, the following tips may help to minimize possible tension and conflict: