Delirium is a cognitive impairment disorder, meaning that it affects how a person thinks, remembers, and reasons. The primary signs are a sudden change of a person's state of arousal (such as feeling drowsy or agitated) or consciousness. For example, a person with delirium may experience confusion, disorientation, an inability to focus, memory problems, or perceptual disturbances (such as hallucinations, or experiencing events that aren't really happening).
Delirium is the most common sign of medical complications of cancer or cancer treatment affecting the brain and mind. It is a common problem for people with cancer, especially those with advanced cancer or those at the end of life, occurring in 15% to 30% of patients who are hospitalized for cancer and in up to 85% of those in the final weeks of life. Because of its troubling symptoms and association with the end of life, delirium is often very stressful for the patient and family members. Furthermore, delirium complicates the ability of the health care staff to assess and manage a person's other symptoms such as pain, and interferes with a patient's ability to undergo treatments for the cancer.
It is important to clarify the difference between delirium and dementia because they have some of the same symptoms. A person with delirium develops the symptoms suddenly and has problems with both level of arousal (for example, being agitated or drowsy) and cognition (for example, memory or knowing where he or she is). In a person with delirium, these symptoms are typically reversible with treatment. The symptoms of dementia, on the other hand, develop more gradually, typically become worse, and are not reversible. Although a person with dementia may have memory or orientation symptoms, he or she won't show a change in arousal or consciousness.
Types and symptoms
Relieving side effects, also called symptom management, palliative care , or supportive care, is an important part of cancer care and treatment. Talk with your health care team about any symptoms of delirium you or the person you are caring for experience, including any new symptoms or a change in symptoms.
There are three types of delirium:
- Hypoactive, meaning that the person acts sleepy or withdrawn
- Hyperactive, meaning that a person is agitated
- Mixed, meaning that a person alternates between these two types
More than two thirds of all delirium are hypoactive or mixed, and a patient may experience hallucinations and delusions with any of the subtypes.
Symptoms of delirium include the following:
- An altered level of consciousness or awareness
- A shortened attention span
- Memory problems
- Disorganized thinking and speech
- A reversal of day and night
- Difficulty writing, drawing, or finding words
- Personality changes
- Depression 
- Delusions or hallucinations
- Restlessness, anxiety, sleep disturbance, or irritability
Delirium typically has multiple causes. In patients with cancer who are frail or severely ill, even a slight change in medication can result in delirium. Therefore, finding the cause of delirium is important because it may be treated or reversed. For example, delirium may be the result of a brain tumor or another cancer that has spread to the brain. In addition, people with advanced cancer  often take many medications, including chemotherapy and pain medications, and may have more than one medical condition related to age or cancer, which makes it more likely that they will experience delirium.
Other causes include the following:
- Withdrawal from medication
- Fluid and electrolyte (such as calcium or potassium) imbalance
- Organ failure
- Brain disorders
- Lack of oxygen in the blood
- Nutritional problems
To find out whether a patient is experiencing delirium, doctors may do a physical examination or blood tests. They will also do a mental status examination, using tests that check motor skills, memory, and attention level.
The main goals in managing delirium are to concurrently find and treat the causes of delirium. The doctor may use both drug and non-drug interventions to treat the symptoms of delirium while keeping the patient comfortable and safe. It is important to work with the health care team to mange the symptoms of delirium. These tips may help:
- Provide a reassuring environment for the patient, such as a quiet, well-lit room with familiar people and objects, and place a clock and wall calendar within the patient's field of vision.
- Talk with the doctor, nurse, or other member of the health care team about the patient's hallucinations or other irregular behaviors to learn how to manage these symptoms and what to expect.
- Ask about discontinuing or switching medications that may contribute to the patient's mental confusion and whether there are other, untreated medical conditions that may be the cause of delirium
- In some cases, giving antipsychotic medications helps control the symptoms of delirium. Although these drugs can have side effects, most can be managed successfully.
Delirium at the end of life
People have different opinions about treating delirium at the end of life . Some believe that the hallucinations at the end of life are part of the dying process and should not be treated. For example, patients who see dead family members welcoming them to an afterlife may find great comfort. However, delirium can switch with very little warning from a peaceful, pleasant experience into a frightening one; in these situations, treatment may be helpful.
One treatment option for delirium at the end of life is controlled sedation, which involves giving drugs that put a patient into a deep sleep. This makes the patient more comfortable, but it may leave family members with a premature sense of loss. Sedation is not intended to speed up death but to provide comfort to a patient at the end of life. Even with sedation, a patient may experience moments of clarity and have the ability to talk with family members.
Each decision about managing delirium depends on the individual. It is important for patients and their family members to talk with the doctors and other members of the health care team to understand all of the available treatment options.