A delirium is a manifestation of an acute diffuse cerebral dysregulation, usually determined in a multifactorial manner. There is an imbalance in neurotransmitters, especially a shortage of acetylcholine and a (relative) excess of dopamine. It is for this reason that medication with an anticholinergic (side) effect may trigger a delirium and forms the basis for the use of dopamine antagonists in the drug-based treatment of a delirium.
There is always an underlying medical disorder or it is an effect of a drug or substance taken. Even in the palliative phase one or more of these underlying disorders may be treatable, and it is therefore appropriate to actively search for it.
In the aetiology, a distinction is made between predisposing factors and precipitating or triggering factors. If there are clear predisposing factors, a minor predisposing factor will already be sufficient to induce a delirium.
For example, a urinary tract infection can sometimes be enough to trigger a delirium with an old and fragile brain. On the other hand, very strong precipitating factors are needed to derail a young and healthy brain.
The following characteristics are predisposing factors for a delirium:
age ≥70 years
pre-existing cognitive disorders, such as dementia or CVA
visual and hearing disorders
disorders in the activities of daily living (ADL)
use of alcohol and opioids
The following characteristics are precipitating factors for the occurrence of a delirium:
brain tumours and metastases, carcinomatous meningitis
opioids: at the start of treatment or on increasing the dose, as well as with chronic use of the same dose during deterioration of the patient associated with weight loss, low serum albumin and/or dehydration
all medications with a sedative effect or side effect
benzodiazepines or withdrawal of these medications. A relative overdose of these medications may easily occur with liver and/or renal failure
corticosteroids may cause psychiatric disturbances, including a delirium. These disturbances especially occur with high doses and usually during the first two weeks of corticosteroid therapy. The latter is not a fixed rule, the disturbances may always occur, at any dose, at any moment and also when gradually reducing corticosteroids. It makes it difficult that corticosteroids are indicated for increased intracranial pressure, as is seen with cerebral metastases. If a delirium subsequently develops, it is sometimes unclear if the cause lies with the cerebral metastasis or the corticosteroid.
anticholinergics and drugs with an anticholinergic side effect (e.g. tricyclic antidepressants, some eye drops, phenothiazines, antihistamines, spasmolytics, anti-emetics and antiarrhythmics)
chemotherapeutic agents such as ifosfamide, asparaginase, chlorambucil, cytarabine, vincristine and vinblastine
some antibiotics, such as ciprofloxacin, isoniazid and voriconazole
other drugs: digoxin and ketamine
In most cases, there are multiple (on average three) precipitating factors. In a third of cases only one precipitating factor is involved.
The most common precipitating factors are (in decreasing order of prevalence):