The brain accounts for 2% of a person’s total body weight, but it consumes 20%-25% of the total oxygen inspired
While other organs can withstand deprivations of oxygen for extended periods of time, the brain can be effected by even subtle deprivations
If anoxia continues for more than a few minutes, an anoxic/ischemic encephalopathy will likely result, frequently involving both neuropsychological impairments, neuroradiological abnormalities, and neurobehavioral effects
Oxygen is breathed in through the lungs and diffused into the pulmonary arterial blood. It gets metabolized with glucose in the cells to form carbon dioxide, which is removed from the cells by the venous circulation.
The heart delivers oxygenated blood to the organs (specifically, it gets delivered to the brain via the internal carotids and the vertebral arteries)
Cognition begins to be affected at 75% arterial oxygen
Unconsciousness occurs at about 50% arterial oxygen
Death occurs at 30-40% arterial oxygen
Watershed areas are most affected (hippocampus, basal ganglia, cerebellum, occipital cortex, and some frontal regions)
Neuropsychological deficits following anoxia/hypoxia include impaired memory, executive dysfunction, apperceptive agnosia (problem with visual synthesis of objects), visual-spatial deficits, and overall cognitive decline
Affective changes may arise following hypoxia due to injury to the structures of the medial temporal and frontal lobes