Anoxic brain injury occurs when brain cells start to permanently die due to an of lack of oxygen for a period of five minutes or longer. Anoxic brain injury is also referred to as cerebral hypoxia or hypoxic-anoxic injury. Anoxic brain injury is a serious medical condition that can cause irreversible cognitive disabilities. Anoxic brain injuries are classified into 4 groups. Anemic anoxia which presents when the blood can not carry sufficient amounts of blood to the brain. Toxic anoxia presents when there are toxins in the blood that prevent the oxygen in blood from being efficiently used by the body. Stagnant anoxia presents when an internal condition prevents oxygenated blood from reaching the brain.