Case 3 Anoxia (Monday evening)

Anoxia refers to a complete absence of available oxygen while hypoxia refers to an inadequate amount of oxygen. A high percentage of individuals who survive five or more minutes of oxygen deprivation (anoxia), or 15 or more minutes of oxygen insufficiency (hypoxia) sustain permanent brain damage.

Hypoxia and ischemia are not synonymous. In hypoxia the availability of oxygen is reduced, but the flow of the blood continues. Ischemia refers to reduced blood flow to a region of the body that negatively affects the delivery of glucose, oxygen, and other substances in the blood and prevents the removal of metabolic by-products from that region of the body.

Mild hypoxia usually presents with temporary cognitive dysfunction and impaired dexterity. If the condition is severe, prolonged, or frequently recurs, the abnormalities may become permanent.

Following prolonged anoxia, if the individual does not die outright, coma or persistent vegetative states are common occurrences. If the individual survives and is not comatose, the patient typically presents with impaired learning but relatively intact recall of information stored before the anoxic episode, a condition known as anterograde amnesia. The overall severity of the cognitive deficits can range from a relatively isolated memory dysfunction to global cognitive dysfunction, depending on the extent of the cortical damage. Memory disturbances, changes in personality and behavior, and visuospatial or visual recognition problems are not uncommon. Changes in social competency have also been reported. Such changes may include lack of motivation/reduced spontaneity, deficits in planning, impulsivity and loss of self-control, decline in social hygiene, and deterioration in social habits. Such changes in social competency may actually be more debilitating than the memory problems.

Cardiac and pulmonary failure are the conditions most frequently associated with acute oxygen deprivation. Near-drowning accidents, failed hanging attempts, and anesthesia are also potential causes of acute oxygen deprivation. Conditions that result in a combination of hypoxia and reduced blood flow, hypoxia and ischemia, are most likely to result in injury to the brain.