Protection of the brain from hypoxia: a review.

A functional classification of hypoxia of the brain has been presented and some of its significant aspects have been discussed. Mechanisms of protection from hypoxia of the brain were reviewed under the headings of prevention, hyperventilation, hypothermia and protection by barbiturates. In prevention of hypoxia of the brain, avoidance of factors producing a fall in cerebral perfusing pressure was emphasized. Hyperventilation is not advised unless one can readily measure regional cerebral blood flow. In the operating room, normocarbia or slight hypocarbia is recommended. Animal studies indicate a protective role of barbiturates in ischaemic hypoxia of the brain. However, it should be emphasized that, at present, hypothermia is the only established means of protection against hypoxia of the brain in man, when it is induced prior to the hypoxic insult. The evidence for protection by barbiturates has been found only in experimental animals. If one can extrapolate the results of studies in animals to man, then potential benefits would be expected in clinical stroke, cardiac arrest, in operations on the carotid artery and in head injury.