Why is Delirium Important?

Despite a high prevalence, and substantial morbidity and mortality, delirium, or an acute confusional state, is frequently misdiagnosed by physicians. Delirium occurs in 10 to 15% of hospitalized medical and surgical adult patients. Prevalence rates vary greatly, depending on the patient population: surgical (15 to 40%), critical care (20 to 40%), psychiatric and neurological (20 to 30%), or general medicine (15 to 20%). Recent studies report mortality rates from 15 to 30%. Other complications include falls, aspirations, pressure ulcers, immobility and dehydration.

What are the Clinical features of Delirium?

Delirium is a clinical diagnosis for which there are three hallmark criteria: 1) disturbance of consciousness (i.e. reduced clarity of awareness of the environment) with reduced ability to focus, sustain, or shift attention, 2) a change in cognition (such as memory deficit, disorientation, language disturbance) or the development of a perceptual disturbance that is not better accounted for by a preexisting conditions such as dementia; and 3) acute onset. Additionally, many delirious patients are lethargic or stuporous. Thinking is disorganized resulting in incoherent or rambling speech, and memory is impaired. Disorientation to time and place follows, but disorientation to person is rarely seen.

Many patients describe persecutory delusions, suspiciousness, bizarre thoughts and images, and loose associations. Perceptual abnormalities may include distortions, illusions, or frank hallucinations. Visual illusions and hallucinations are most common, followed in frequency by auditory and tactile illusions. Hallucinations occur less frequently in the elderly than in middle-aged persons.

How Does Delirium Differ From Dementia and Sundowning?

Physicians frequently mistake delirium for dementia. Whereas, with rare exception, dementia presents insidiously, delirium presents as an acute loss of global cognitive function in the setting of an acute medical or surgical illness . However, dementia and delirium are not mutually exclusive; it is common to find a demented patient with a superimposed delirium. Distinguishing dementia from delirium superimposed on dementia requires knowledge of the patients prior cognitive function. The delirious patient with no history of dementia manifests new cognitive deficits, whereas delirious patients with a prior dementia demonstrates a manifests a worsening of baseline cognitive dysfunction. If present, lethargy or stupor always indicate delirium, as these physical signs are not manifestations of dementia. Because the symptoms of delirium are exacerbated by sensory deprivation, delirium is often equated with sundowning, a behavioral phenomenon of agitation caused by sensory deprivation. However, delirium is a psychiatric diagnosis with specific diagnostic features, and significant morbidity and mortality, not a description of behavior.

What are the Common Causes of Delirium?

Multiple acute illnesses can precipitate delirium: systemic disease outside the central nervous system (metabolic, infectious, endocrine, cardiorespiratory, and paraneoplastic syndromes); primary intracranial disease (infectious, degenerative dementia, collagen vascular, mass lesion, trauma, and stroke); exogenous toxic agents including some medications; withdrawal from drugs; depression; and epilepsy. In the elderly, the most common associated conditions are the use of psychotropic drugs, particularly those with anticholinergic properties, urinary tract infections, and the presence of an underlying dementing illness in combination with an acute illness. Rather than a single cause, most patients have two or more coexisting problems.

Medications, particularly psychotropic drugs, deserve special consideration as causes of delirium. In addition to primary anticholinergic drugs, many other medications, such as some of the antidepressants, have anticholinergic properties. Among the neuroleptics, the phenothiazines have prominent anticholinergic properties that may cause delirium. Long-acting sedatives, such as chlordiazepoxide and diazepam, and shorter-acting agents, such as triazolam, temazepam and lorazepam, may cause delirium. Among the antihypertensives, the central alpha-receptor blockers and the beta-receptor blockers are associated with the greatest risk of delirium. Digitalis may cause delirium in the absence of cardiotoxic effects.

What is the Value of Laboratory Testing, Lumbar Puncture, or Electroencephalogram?

Laboratory testing of delirious patients should include: complete blood count, electrolyte panel, metabolic panel, thyroid function tests, urinalysis, electrocardiogram and chest radiograph. CT or MRI Imaging studies are indicated in patients with a history of or signs of head trauma, those with focal neurologic symptoms or signs, and those without a reasonable explanation for delirium. The lumbar puncture is indicated in the delirious patient in the absence of an apparent precipitant. Although a lumbar puncture should always be performed when the cause of delirium is inapparent, many elderly patients with localized infections, such as a urinary tract infection, develop delirium without spread of the infection to the central nervous system. The electroencephalogram may be useful in diagnosing delirium. However, the electroencephalogram is not pathognomonic of delirium, nor can it distinguish delirium from dementia. Diffuse slowing can be seen with either condition. In patients in whom no organic basis for delirium is apparent, a completely normal EEG would suggest that the patients symptoms may be due to a functional psychiatric illness.

How Should Delirium be Treated?

Pharmacologic and nonpharmacologic modalities are equally important in managing delirium. Of most relevance are (1) the treatment of the specific underlying illness, (2) general support of fluid and electrolytes, (3) nonpharmacologic interventions, and (4) the use of psychotropic medications. First, the physician must determine whether the patient is critically ill, as reflected by cardiorespiratory status and level of consciousness. Irregular respiratory patterns, particularly apneic episodes, and stupor may necessitate intensive cardiac and respiratory monitoring. All unnecessary medications with potential adverse effects on the central nervous system must be discontinued. Infections, which frequently precipitate delirium will require antibiotics and patients with and fluid and electrolytes will require corrective measures.

The presence or absence of nonpharmacologic factors will influence the course of delirium. Continuity of care provided by staff familiar to the delirious patient greatly allays agitation. Patients should be given their eyeglasses and hearing aides, and staff should employ simple and repetitive instructions regarding tests and other procedures. Verbal reminders of the setting and time should be used regularly. Physical restraints, in particular, should be avoided as they may induce fear and anger, exacerbating motor restlessness. They should be used only when necessary to facilitate evaluation and treatment. There will almost never be an indication for all four extremities to be restrained in the elderly.

How should Psychotropics be Used to Treat Delirium?

The goals of pharmacologic therapy are to reverse psychotic signs and symptoms, to stop potentially dangerous behavior, and to calm the patient sufficiently to conduct the necessary evaluation and treatment. Unfortunately, there are no controlled clinical studies on which to base the choice of psychotropic medication for delirious elderly patients. Well designed clinical trials of psychotropic drugs, particularly neuroleptics, have been conducted in patients with functional psychoses and dementia, but not in delirious patients. Nevertheless, clinical experience and knowledge of the pharmacologic properties of alternative psychotropic agents provide a rationale for drug selection. First, no psychotropic medication should be given unless necessary to accomplish the aforementioned goals. For example, the lethargic delirious patient with due to a hyperglycemic hyperosmolar state requires fluid and electrolytes, not a psychotropic medication. Second, medications with anticholinergic effects should be avoided if possible because of the cholinergic deficits present in delirium. Thus, chlorpromazine and thioridazine may cause more harm than benefit in delirious patients.

In most instances, the drug of choice is haloperidol or a similarly potent antipsychotic. Unlike the sedative-hypnotics, haloperidol is unlikely to oversedate the patient, and its antipsychotic properties are useful in treating delusions, paranoia, and perceptual disturbances. The exception to haloperidol use are patients in withdrawal states, in whom sedative-hypnotics are the drugs of choice.

The dose and route of administration of haloperidol are important. Intramuscular haloperidol reaches peak absorption in 30 to 60 minutes, whereas the peak absorption after oral haloperidol may be 2 to 6 hours.31 The delayed onset of action may result in patients being given a second dose of haloperidol or, even more regretfully, another psychotropic drug before the first dose of haloperidol has had an opportunity to take effect. Therefore, when haloperidol is used, intramuscular or intravenous treatment is recommended initially in all but the mildest case. The dose of haloperidol required in elderly delirious patients is dictated by the severity of the patient's symptoms. Although typically doses ranging from 0.5 to 5 mg once or twice per day are sometimes necessary, the initial dose should be in the lower range from 0.5 to 2 mg. When oral doses of halperidol are used, administration of a single dose in the early evening is recommended to allow for the slow absorption.