Delirium can be defined as a condition characterized by a usually acute onset of several clinical features:

• alteration of or a fluctuation in consciousness
• disturbance in sleep wakefulness cycle
• impairment of basic cognition
• impairment of higher cognition

and is sometimes associated with other clinical features:

• alterations in emotional tone
• alterations in perception
• alterations in thought form or content
• disturbances in behaviour

It is important to recognise that although the onset is usually acute, the duration of symptoms depends on the cause(s) of the delirium, the delay in recognition and the institution of appropriate treatment.

In the general hospital setting, there is a low recognition rate of delirium. Delirium is also often wrongly diagnosed as an anxiety disorder, mood disorder, psychotic disorder, or as dementia. General hospital cases of delirium often have multifactorial aetiologies, even when toxicity due to poisoning is involved.

Prolonged delirium has adverse outcomes, including death, dementia, amnestic syndromes, and other regional organic brain syndromes. Delirium in the general hospital and delirium due to drug toxicity have a poorer prognosis than community and non hospital cases of delirium, where there are a greater proportion of brief, self limiting conditions as the causes of delirium.

Patients during episodes of delirium also have higher risk of self-harm due to accident or deliberate actions and are at greater risk of causing harm to staff members or others.

A duty of care is due to patients with delirium to ensure that they do not harm themselves or others. Patients exposed to the risk of death or serious physical harm due to drug toxicity are similarly entitled to the benefits of treatment that will reasonably be expected to decrease their chances of death or serious physical harm. This duty of care exists whether the patient is delirious or not and whether or not the patient consents. No such duty exists where the risk of harm is trivial or where there is no treatment reasonably known to be effective to reduce the risk of death or serious harm. In past events doctors have been found negligent in their duty of care by failing to administer appropriate treatment or restraining a patient in these circumstances.

In the clinical context of delirium due to drug toxicity in adult patients the commonest scenarios are:

• intentional self-harm drug overdose
• intentional recreational drug overdose
• iatrogenic drug toxicity
• withdrawal states

Accidental overdose is more common in children. Some work or recreational exposures also occur in adults.

In practical management strategies for the delirious (drug toxicity) patient there are several issues to consider.

All medical, nursing and ward staff should have basic clinical protocols to follow, educational programs, and ongoing clinical revision programs provided to allow them to perform as the central assessment and management unit. New staff should have an orientation and guided introduction to the clinical service issues.

Protocols for decontamination and emergency supportive management should include basic management strategies for the clinical issues of delirium.

Introduction, explanation and reorientation strategies for nursing staff, use of family members, appropriate lighting (and other cues) plus appropriate use of intravenous cannulae and IV fluids can be incorporated into basic protocols.

In certain clinical situations, specific drug treatment to “reverse” a drug-induced delirium may be useful for diagnostic assessment, management, or both.

Examples of these situations would include

• barbiturates for barbiturate withdrawal
• flumazenil for benzodiazepine intoxication
• physostigmine or tacrine for anticholinergic delirium

However, drug treatments are usually “nonspecific” and aimed at reducing distress, anxiety, cognitive disorganization, psychotic phenomena, or behavioural disturbance, or some combination of these features. This type of “non specific” pharmacological intervention should be reserved for situations in which the risks of harm to self or others is high, or the distress of the patient is unreasonable. These treatments should not be offered as a matter of course, but promptly instigated when the clinical indications are evident.

There are no clinical trials available to guide the choice for “non specific” pharmacological management and tradition tends to dominate the field. Our current practice leads to two basic choices, diazepam (or midazolam) or droperidol and occasionally a combination. The clinical indications for use dictate that an intravenous route of administration may be necessary to initiate treatment.

Initial dosage needs to be titrated to achieve the necessary clinical effect, that is, physical safety of the patient, and so a degree of sedation is usually the goal. Maintenance dosage should also be aimed at maintaining the patient's safety. Diazepam is the safest first line treatment, except where severe respiratory disease (CO2 retention) exists. Droperidol is usually our second line choice with haloperidol as an alternative.

Where distress of the patient is the focus of pharmacological treatment a regular dose approach (using diazepam or haloperidol) for several days may be more useful than single large doses or PRN dosage or some combination of those approaches. Where psychotic features predominate haloperidol may be the first line drug choice.