23:38:36 – Confusion | Anesthesia Key

Key Concepts

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Confusion and delirium are symptoms, not a diagnosis.
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Focal cortical dysfunction, such as from tumor or stroke, typically does not cause confusion.
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Any underlying clinical process that disrupts optimal central nervous system (CNS) functioning can result in confusion.
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Emergent causes of confusion that need immediate detection and treatment include hypoglycemia, hypoxemia, hypotension, sepsis, and toxic ingestions.
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Assessment of attention is fundamental for the assessment of patients with confusion as disturbances in attention are consistent with delirium versus psychiatric illness or dementia.
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Recommended tools for identifying patients with delirium in the emergency department are the Delirium Triage Screen (DTS) and brief Confusion Assessment Method (bCAM), if indicated.
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Delirium often goes unrecognized unless a structured assessment tool is used.
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Sedatives, including antipsychotics, are useful for managing undifferentiated agitation while the diagnostic evaluation is in progress.

Foundations

The term confusion indicates an acute impairment in higher cerebral functions, such as memory, attention, or awareness. The disorder has multiple synonyms, some of which imply causative mechanisms, and always represents a symptom of another underlying disease process. Confusion ranges in severity from mild disturbances of short-term memory to a global inability to relate to the environment and process sensory input. Along this spectrum, the disorder overlaps with the term delirium (see Chapter 90 ), and the two terms are often used interchangeably. The degree of confusion may fluctuate over time, as may the patient’s level of consciousness.

Delirium implicitly develops over a short period of time, typically hours or days, although it may persist for weeks. Although patients with preexisting dementia are at higher risk for developing delirium, the acute changes of delirium are distinct from and cannot be better explained diagnostically by a newly diagnosed or evolving dementia. The same pathophysiologic processes causing confusion and delirium may manifest with altered mentation and diminished alertness along the coma spectrum.

Confusion has many causes, and an orderly approach is helpful to discover the causative diagnosis. The assessment of mental status and cognitive impairment, with a focus on changes from baseline function, is an important part of the evaluation in older emergency department (ED) patients. Altered mental status may be a frequent finding even without a chief complaint of confusion. Collateral history from family or caregivers, a structured physical examination, and the use of a specific assessment tool may be needed to detect the presence of confusion.

Epidemiology

Emergency clinicians underestimate the incidence of confusion in patients. Because confusion is often accepted as an incidental or secondary component of another condition, it may be overshadowed by the primary condition being treated. When confusion exists as an isolated or unexplained finding, it is more likely to receive full and immediate consideration by the emergency clinician. Confusion occurs in a high percentage of hospitalized patients, with highest risk in frail, elderly, and critically ill populations. An estimate of ED prevalence of delirium in elderly patients is 8% to 17%, and delirium in the ED often persists into the hospitalization. Presence of delirium carries important negative prognostic implications for patients. In hospitalized patients, delirium is associated with higher mortality, worse functional and cognitive outcomes, and decreased rates of home discharge.

Pathophysiology

Conceptually, consciousness is divided into elements of alertness, or arousal, and elements constituting the content of consciousness. Although arousal may be abnormal, the characteristic disturbance in confusion is to the content portion of consciousness, resulting in abnormalities of attention and awareness. Any underlying clinical process that disrupts optimal central nervous system (CNS) functioning can result in confusion. Global CNS dysfunction usually results from substrate deficiencies (e.g., hypoglycemia, hypoxemia), neurotransmitter dysfunction, intoxication with or withdrawal from neuroactive drugs, or circulatory dysfunction. Individuals with a preexisting impairment are more sensitive to these factors and may become confused after even minor changes in their normal physiologic state.

Diagnostic Approach

Differential Considerations

Four major groups of disorders encompass most causes of confusion: (1) systemic diseases secondarily affecting the CNS; (2) primary intracranial disease; (3) exogenous toxins; and (4) drug withdrawal states ( Box 13.1 ). Within these groups, certain causes, such as hypoxia and hypoglycemia, require immediate evaluation and treatment. A more general mnemonic for causes of altered mental status, many of which can present with acute confusion, is presented in ( Table 13.1 ).

BOX 13.1

Critical and Emergent Causes of Confusion

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Critical
- Hypoxia
- Hypoventilation
- Hypoglycemia
- Delirium tremens
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Emergent
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  Primary intracranial disease
  - Seizure/nonconvulsive status epilepticus
  - Traumatic brain injury
  - Hypertensive encephalopathy
- •
  Systemic diseases secondarily affecting the central nervous system
  - Sepsis
  - Hepatic encephalopathy
  - Uremia/renal failure
  - Hyperthermia/hypothermia
  - Endocrinopathy
  - Nutritional deficiency
- •
  Exogenous toxins
  - Sedatives/hallucinogens
  - Ethanol/toxic alcohols
  - Narcotics
  - Antihistamines
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  Drug withdrawal
  - Alcohol
  - Drugs of abuse

TABLE 13.1

Mnemonic for Altered Mental Status

A	Alcohol or Drug Intoxication; Atypical migraine (confusional migraine)
E	Electrolytes, Environment (hyper/hypothermia), Endocrinopathy, Encephalopathy (Wernicke), Epilepsy
I	Infection (meningitis, encephalitis, sepsis)
O	Overdose, Oxygen (hypoxia, pulmonary embolism)
U	Uremia
T	Trauma, Tumor
I	Insulin (hypoglycemia, DKA, HHS)
P	Poisons, Psychosis
S	Stroke, Status epilepticus (petit mal)

DKA, Diabetic ketoacidosis; HHS, hyperosmolar hyperglycemic state.

Schizophrenia and mood disorders, such as bipolar and major depressive disorder, do not generally cause acute confusion, but similarities in presentation can lead to diagnostic difficulty. Many inpatients evaluated for new depression are eventually diagnosed with acute delirium. Likewise, the diagnosis of a psychiatric disorder requires exclusion of organic causes. Attention in patients with primary psychiatric disorders is typically normal unless psychosis or agitation is severe. A careful evaluation is required to differentiate between psychiatric and medical origins of thought disturbances ( Table 13.2 ).

TABLE 13.2

Findings to Help Differentiate Between Delirium and Primary Psychiatric Disturbance

Delirium	Psychiatric	Dementia
History
Acute onset	Onset usually over weeks to months	Onset over months to years
Any age	Onset usually age, 12–40 years	Usually >65, unless early-onset
Mental Status Examination
Fluctuating level of consciousness	Alert	Usually alert
Disoriented	Oriented	Often disoriented
Attention disturbances	Agitated, anxious	Memory impairment
Hallucinations—visual, tactile	Hallucinations- auditory	Usually absent, except in dementia with Lewy bodies
Cognitive changes	Delusions, illusions	Word-finding difficulties
Physical Examination
Abnormal vital signs	Normal vital signs	Normal vital signs
Nystagmus	No nystagmus	Neurologic deficits present in vascular dementia
Focal neurologic signs	Purposeful movement	Can show parkinsonism
Signs of trauma	No signs of trauma	No signs of trauma