Delirium may be caused by cancer, cancer treatment, or other medical conditions.

There is often more than one cause of delirium in a cancer patient, especially when the cancer is advanced and the patient has many medical conditions. Causes of delirium include the following:

• Organ failure, such as liver or kidney failure.
• Electrolyte imbalances: Electrolytes are important minerals (including salt, potassium, calcium, and phosphorous) in blood and body fluids. These electrolytes are needed to keep the heart, kidneys, nerves, and muscles working the way they should.
• Infections.
• Paraneoplastic syndromes: Symptoms that occur when cancer-fighting antibodies or white blood cells attack normal cells in the nervous system by mistake.
• Side effects of medicines and treatments: Patients with cancer may take medicines with side effects that include delirium and confusion. The effects usually go away after the medicine is stopped.
• Withdrawal from medicines that depress (slow down) the central nervous system (brain and spinal cord).

It is important to know the risk factors for delirium.

Patients with cancer are likely to have more than one risk factor for delirium. Identifying risk factors early may help prevent delirium or decrease the time it takes to treat it. Risk factors include the following:

• Serious illness.
• Having more than one disease.
• Older age.
• Dementia.
• Low level of albumin (protein) in the blood, which is often caused by liver problems.
• Infection.
• High level of nitrogen waste products in the blood, which is often caused by kidney problems.
• Taking medicines that affect the mind or behavior.
• Taking high doses of pain medicines, such as opioids.

The risk increases when the patient has more than one risk factor. Older patients with advanced cancer who are hospitalized often have more than one risk factor for delirium.