INTRODUCTION
Delirium [Latin - "off the track"] is a transient global disorder of cognition. Delirium is a condition of severe confusion and rapid changes in brain function that develops quickly (over hours or days) and involves changes in consciousness, attention, cognition (thinking and reasoning), perception, psychomotor behavior, emotion, and the sleep-wake cycle. Delirium represents a sudden and significant decline from the previous level of functioning. Delirium is usually temporary and reversible and does not reflect a persistent psychiatric disorder. The condition is a medical emergency associated with increased morbidity and mortality rates. The clinical key identifying features are decreased attention span and a waxing and waning type of confusion.

It may occur at any age but is most common after the age of 60 years. The delirious state is transient and of fluctuating intensity; most cases recover within 4 weeks or less. However, delirium may last up to 6 months with fluctuations especially when arising in the course of chronic liver disease, carcinoma, or subacute bacterial endocarditis. A delirious state may progress into dementia. Full recovery is common.

SIGNS AND SYMPTOMS

• Recent memory is usually affected more than long-term memory.
• Disorientation usually occurs in regard to time or to place and sometimes also to people.
• Language disturbances are slurred speech, difficulty naming objects, difficulty writing, and the inability to speak or write or to understand speech or writing.
• Changes in perception are include visual as well as any of the senses (sight, hearing, touch, taste, and smell).
• Perceptual disturbances may include misinterpretations, illusions, and hallucinations.
• An illusion is perceiving one thing but thinking it is something else.
• A hallucination consists of seeing (or hearing, feeling, tasting, or smelling) things that do not exist.
• Other symptoms include sleep disturbances, changes in activity level, and trouble in focusing.
• Emotional disturbances may take the form of anxiety, fear, depression, irritability, anger, euphoria (an unrealistic or exaggerated feeling of happiness or well-being), or apathy.

DIAGNOSIS

• Impairment of consciousness and attention (on a continuum from clouding to coma; reduced ability to direct, focus, sustain, and shift attention)
• Global disturbance of cognition (perceptual distortions, illusions and hallucinations - most often visual; impairment of abstract thinking and comprehension, with or without transient delusions, but typically with some degree of incoherence; impairment of immediate recall and of recent memory but with relatively intact remote memory; disorientation for time as well as, in more severe cases, for place and person);
• Psychomotor disturbances (hypo- or hyperactivity and unpredictable shifts from one to the other; increased reaction time; increased or decreased flow of speech; enhanced startle reaction);

Diagnosis includes:

• acute brain syndrome acute confusional state (nonalcoholic)
• acute infective psychosis
• acute organic reaction
• acute psycho-organic syndrome

TYPES
On the basis of Pathophysiology:-

1. Hyperactive delirium(agitated) is observed in patients in a state of alcohol withdrawal or intoxication with to phencyclidine (PCP), amphetamine, and lysergic acid diethylamide (LSD). Affected patients are more prone to hallucinations, delusions, agitation, and disorientation.
2. Hypoactive delirium(lethargic) is observed in patients in states of hepatic encephalopathy and hypercapnia. They may be confused and tired but not have hallucinations, delusions, or illusions.
3. In mixed delirium, individuals display daytime sedation with nocturnal agitation and behavioral problems.

Another classification of Delirium:

1. Delirium due to general medical condition
2. Substance intoxication delirium
3. Substance withdrawal delirium
4. Delirium due to multiple etiologies
5. Delirium not otherwise specified

CAUSES of Delirium

• from use of drugs or similar substances; or from withdrawal from these substances
• from a general medical condition; physical or mental illness and are usually temporary and reversible
• include conditions that deprive the brain of oxygen or other substances
• by poisons
• by fluid/electrolyte or acid/base disturbances
• by other serious, acute conditions
• severe pre-existing brain injury (prior strokes, dementia) develop delirium from additional illness or infections like urinary tract infections or pneumonia

Some of the other common reversible causes include the following:

• Hypoxia
• Hypoglycemia
• Hyperthermia
• Anticholinergic delirium
• Alcohol or sedative withdrawal
• Infections
• Metabolic abnormalities
• Structural lesions of the brain
• Postoperative states

TREATMENT for Delirium

The goal of treatment is to control or reverse the cause of the symptoms, and will vary with the specific condition causing delirium. The person should be in a pleasant, comfortable, non-threatening, physically safe environment for diagnosis and initial care. Hospitalization may be required for a short time.
Stopping or changing medications that worsen confusion, or that are not essential, may improve cognitive functioning even before treatment of the underlying disorder. Medications that may worsen confusion include anticholinergics, analgesics, cimetidine, central nervous system depressants, lidocaine, and other medications (including alcohol and illegal drugs).
Disorders that contribute to confusion should be treated. These may include heart failure, decreased oxygen (hypoxia), excessive carbon dioxide levels (hypercapnia), thyroid disorders, anaemia, nutritional disorders, infections, kidney failure, liver failure, and psychiatric conditions (such as depression). Correction of co-existing medical and psychiatric disorders often greatly improves mental functioning. Medications may be required to control aggressive or agitated behaviors or behaviors that are dangerous to the person or to others. These are usually given in very low doses, with adjustment as required.

Medications that may be considered for use include:
-thiamine
-sedating medications such as clonazepam or diazepam
-serotonin-affecting drugs (trazodone, buspirone)
-dopamine blockers (such as haloperidol, olanzapine, Risperdal, clozapine)
-fluoxetine, imipramine, Celexa (may help stabilize mood)