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Delirium and Its Effects on Treating Pain
Cognitive failure (delirium), common in patients with advanced illness,158 is an etiologically nonspecific, global, cerebral dysfunction, characterized by concurrent disturbances of level of consciousness, attention, thinking, perception, memory, psychomotor behavior, emotion, and the sleep-wake cycle. Disorientation, fluctuation, waxing and waning of the above symptoms, and acute or abrupt onset of such disturbances are other critical features of delirium. Delirium is reversible, even in advanced illness. Still, it may not be reversible in the last 24 to 48 hours of life, most likely because of irreversible processes such as multiple organ failure.298
At times, it is difficult to differentiate delirium from dementia because they frequently share clinical features such as disorientation and impaired memory, thinking, and judgment. One difference is that the temporal onset of symptoms is more subacute or chronically progressive in dementia than in delirium. Occasionally, delirium is superimposed on an underlying dementia, such as in the case of an elderly patient, an AIDS patient, or a patient with a paraneoplastic syndrome.
Delirium can be due to the direct effects of cancer on the CNS, to indirect CNS effects of the disease or treatments (medications, electrolyte imbalance, failure of a vital organ or system, infection, vascular complications) and to preexisting cognitive impairment or dementia.
Medical and nursing staff sometimes conclude that a new symptom is psychologically based without first ruling out all possible organic causes. Given the many drugs that cancer patients require and the fragile state of their physiologic functioning, even routinely ordered hypnotics can be enough to precipitate delirium. Opioid analgesics, including levorphanol, morphine sulfate, methadone, and meperidine,72 can cause confusional states, particularly in the elderly and terminally ill. Clinicians should correct those underlying causes of delirium.7; 155; 280; 287;140
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