Anesthesia intoxication occurs when the chemical components of anesthesia are not metabolized readily by the body. This occurs with great frequency in the elderly. Symptoms range from dementia and hallucinations to confusion and disorientation. This condition is often compounded by two other factors that affect the elderly post-operatively. One factor is the presence of toxins in the bloodstream as a by-product of being on a heart-lung machine for several hours during surgery. The heart-lung machine oxygenates and "scrubs" the blood for the patient, but is not as efficient as the body's own organs. Subsequently, these toxins are released into the brain, causing compounding symptoms. Another factor is what is referred to as "ICU psychosis," where mental state is affected not only by the physiological trauma of surgery, but also by the dislocating effect of being confined in an area where the normal landmarks of one's consciousness, such as time, are virtually non-existent.