Anoxia and 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.

Anoxia and hypoxia may be caused by a number of events, such as smoke or carbon monoxide inhalation, high altitude exposure, strangulation, anesthetic accidents, or poisoning. 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 occur.


Treatment of anoxia and hypoxia consists of establishing an adequate airway as soon as possible, using enough oxygen to saturate the blood, supporting the cardiovascular system as needed, and preventing or treating pneumonia. Respiratory assistance may be necessary.


If the patient's respiratory and cardiovascular systems can be supported properly, recovery may occur, but depends upon the severity of injury. As recovery proceeds, a variety of psychological and neurological abnormalities may appear, persist for a time, and then disappear. Mental changes such as dementia or a psychosis may occur. Mental confusion, personality regression, parietal lobe syndromes, amnesia, hallucinations, and memory loss may also occur.


The NINDS supports and conducts studies aimed at understanding neurological conditions that can damage the brain such as anoxia and hypoxia. The goals of these studies are to find ways to prevent and treat these conditions.

These articles, available from a medical library, are sources of in-depth information on anoxia and hypoxia:

Bradley, W, et al (eds). Neurology in Clinical Practice: Principles of Diagnosis and Management, vol. II, Butterworth-Heinemann, Boston, pp. 1343-1349 (1991).

Joynt, R (ed). Clinical Neurology, vol. 2, Chapter 17, J.B. Lippincott Co., Philadelphia, pp. 1-18 (1990).

Nyakas, C, Buwalda, B, and Luiten, P. "Hypoxia and Brain Development." Progress in Neurobiology, 49:1; 1-51 (May 1996).

National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892