DELIRIUM
DEFINITION
An acute reversible alteration in cognitive function and/or behaviour
that occurs as a direct toxic effect of a substance or secondary to
some underlying medical condition.
TOXIC CAUSES
Substances of abuse
Amphetamines
3,4-Methylenedioxymethamphetamine (MDMA, ecstasy)
Amphetamine
Methamphetamine
Cocaine
Lysergic acid diethylamide (LSD)
Phencyclidine (PCP)
Solvents e.g. toluene
Plants and Mushrooms
Psylocybin-containing (hallucinogenic) mushrooms
Datura species
Mescaline
Nutmeg
Industrial/Environmental chemicals
Carbon monoxide
Bromide
Mercury (inorganic)
Methylbromide
Solvents
Pharmaceuticals
Common causes
Anticholinergic drugs
Antihistamines
Atropine
Benztropine
Scopolamine
Phenothiazines
Tricyclic antidepressants
Corticosteroids
Ketamine
Methylphenidate
Serotonergic drugs
Sympathomimetics
Phenylpropanolamine
Pseudoephedrine
Unusual causes
Cimetidine
Ergotamine
Flecainide
Ketoconazole
Levodopa
Mefloquine
Non-steroidal antiinflammatories (NSAIDs)
Ofloxacin
Propanolol
Salicylates
NON-TOXIC CAUSES
Drug withdrawal syndromes
Ethanol
Opiates
Sedative-hypnotics
Cerebral disease
Seizure
Trauma
Tumour
Vascular
Environmental
Hypothermia
Hyperthermia
Infection
CNS infections
Sepsis
Metabolic
Acidosis
Electrolyte disturbances
Hypoglycaemia
Hypoxia
Hypercarbia
Liver failure
Thyrotoxicosis
Uraemia
Vitamin deficiency
Niacin
Pyridoxine
Thiamine
Note: Some of these non-toxic causes may occur as a complication of
an intoxication.
CLINICAL FEATURES
The clinical features of the altered cognition and behaviour
associated with delirium are extremely variable in type and severity,
and may fluctuate with time. They may include drowsiness, anxiety,
restlessness, inability to concentrate, impaired memory, poorly-formed
delusions, agitation, confusion, disorientation, disturbed speech
content, emotional lability, and visual and auditory hallucinations.
The disturbance in cognition and behaviour may result in the patient
causing physical harm to themselves or others.
Other clinical features of the underlying intoxication (e.g.
anticholinergic, beta adrenergic, serotonin syndrome) may also be
noted.
DIFFERENTIAL DIAGNOSIS
Acute psychotic illness
Central nervous system depression
Dementia
Malingering
RELEVANT INVESTIGATIONS
The major role of biomedical investigations is to exclude or diagnose
non-toxic causes of delirium. Investigations should be selected
according to clinical judgement and may include:
Arterial blood gases
Blood sugar level
Chest X-ray
CT of the head
ECG
Electroencephalogram
Pulse oximetry
Renal and hepatic function tests
Serum electrolytes
Thyroid function tests
TREATMENT
Treatment is essentially supportive and should be continued until
cognitive function and behaviour returns to normal.
General supportive measures are aimed at alleviating distressing
symptoms, preventing self-harm and maintaining adequate fluid and
electrolyte fluid balance. These measures may include:
Intravenous fluids (if the patient is not taking oral fluids)
Provision of a calm environment (no bright lights, no noise, away
from windows)
Reassurance
Protection of the patient from self-inflicted injury
Relief of urinary retention (anticholinergic agents)
Pharmacological sedation
The delirious patient should never be left unattended. Physical
restraint should be minimized to that required to gain initial control
of an uncooperative patient and to undertake procedures and prevent
self-harm prior to pharmacological sedation. When required, physical
restraint is best accomplished by holding the patient with the
assistance of several people. Extremely violent patients should be
subdued by a team of people who have allocated roles to stabilise each
limb and the head. The prolonged use of bindings, restraints or other
restrictive devices should be avoided as they do not necessarily
protect the patient from injury.
Pharmacological sedation is best accomplished with a benzodiazepine
and/or haloperidol. Suggested agents and doses are:
Diazepam. Give 5 to 10 mg of diazepam intravenously over 1 to 3
minutes. This dose may be repeated as necessary to a maximal total
dose of 30 mg. In children, give 0.25 to 0.4 mg/kg up to maximal
total dose of 5 mg if under 5 years of age and 10mg if over 5 years of
age. Diazepam should not be given intramuscularly.
Midazolam. Give 0.1 mg/kg intravenously and repeat every 5 to 10
minutes as required. If unable to obtain venous access, 0.25 mg/kg
can be given intramuscularly. The intramuscular dose should not be
repeated in less than 1 hour.
Haloperidol. Give 0.05 to 0.1 mg/kg intravenously and repeat after
20 minutes if required. Haloperidol may also be given intramuscularly.
Intramuscular doses should not be repeated in less than 1 hour.
The aim is to sedate the patient to the point of being physically and
mentally calm but still rouseable with stimulation. If the patient
cannot be controlled despite sedation with the doses described above,
further doses should not be used unless facilities for intubation and
ventilation are available.
Specific supportive or antidotal therapy may be necessary where the
delirium is a consequence of a specific toxin or specific complication
of intoxication (e.g. respiratory failure, hyperthermia, hypothermia,
hypoglycaemia, hyponatraemia, hypernatraemia, hypomagnesaemia).
Physostigmine may be considered in the management of delirium
associated with poisoning by anticholinergic agents. The delirium
associated with serotonin syndrome may be improved by the
administration of cyproheptadine or chlorpromazine.
CLINICAL COURSE AND MONITORING
The duration of delirium varies with the intoxication but rarely lasts
longer than 72 hours. The patient should be carefully and
continuously observed until mental status normalizes. Mental status
and respiratory function must be carefully monitored after sedation.
LONG-TERM COMPLICATIONS
Rare, provided patients do not injure themselves whilst delirious.
Disturbing recurrences of symptoms ("flash-backs") sometimes occur
following ingestion of LSD or other hallucinogens
AUTHOR(S)/REVIEWERS
Authors: Dr J. Pronczuk, International Programme for Chemical
Safety, Geneva, Switzerland.
Dr R. Dowsett, Departments of Clinical Pharmacology and
Emergency Medicine, Westmead Hospital, Westmead, NSW
2145, Australia.
Reviewers: Cardiff 3/95, Berlin 10/95: R. Dowsett, J. Pronczuk,
Cardiff 9/96 T. Meredith, L. Murray
Birmingham 3/99: T. Meredith, L. Murray, A. Nantel,
J. Szajewski.