3.1 Delirium

Delirium is an acute and fluctuating disturbance in cognition characterized by inattention.

In the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) [6], delirium is defined by the following criteria:

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  A A disturbance in attention (ie, reduced ability to direct, focus, sustain, and shift attention) and awareness (ie, reduced orientation to the environment)

  
  
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  B The disturbance develops over a short period of time (usually hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day

  
  
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  C An additional disturbance in a second cognitive domain (eg, memory deficit, disorientation, language, visuo spatial ability, or perception)

The disturbances in criteria A and C are not better explained by another preexisting, established, or evolving neurocognitive disorder. There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct physiological consequence of another environmental or medical condition, substance intoxication or withdrawal (ie, due to drug abuse or to medication).

Delirium can be clinically subclassified as hyperactive (ie, marked by agitation), hypoactive (ie, marked by lethargy and sedation), or mixed [7].

3.2 Dementia

Unlike delirium, dementia represents a progressive and irreversible loss in cognitive function. Current DSM criteria include memory impairment, but also emphasize deterioration in other cognitive domains like speech or language ability. Dementia, also called major neurocognitive disorder, is defined by the following [6]:

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  Evidence of substantial decline in one or more cognitive domains (ie, attention, awareness, memory, language, visuospatial ability, and perception), and a decline in neurocognitive performance (ie, two or more standard deviations below appropriate norms on formal testing or equivalent clinical evaluation)

  
  
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  The cognitive deficits are sufficient to interfere with independence

  
  
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  The cognitive deficits do not occur exclusively in the context of delirium

  
  
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  The cognitive deficits are not primarily attributable to another mental disorder (eg, major depressive disorder, and schizophrenia)

According to the DSM-V criteria, individuals with major neurocognitive disorder exhibit cognitive deficits that interfere with independence. Persons with mild neurocognitive disorder may retain the ability to be independent.

Typical assessment tools for dementia are of limited use in the acutely hospitalized fragility fracture patient (FFP), as these assessments are only valid when patients are at their baseline cognitive function. Abnormalities in dementia testing like the Mini-Mental Status Exam, Montreal Cognitive Assessment, or clock drawing tests can also be found in delirious patients. Information gained from patient history, such as the progressive inability to manage home medications or finances, may be of more use in identifying patients with previously undiagnosed dementia [8].

4.1 Pathogenesis

Delirium is typically due to multiple causal mechanisms. Several interacting biological factors result in disruption of the neuronal networks of the brain, leading to acute cognitive dysfunction. Current evidence suggests that neuroinflammatory processes, changes in balances of neurotransmitters, physiological stressors, metabolic derangements as well as electrolyte disorders and genetic factors contribute to the development of delirium [9].

Many neurotransmitters are implicated, but cholinergic deficiency and/or dopaminergic excess are of special importance. These systems are often influenced by drugs known to interfere with synaptic transmission and cause delirium. Cytokines, such as interleukin-1 (IL-1), IL-2, IL-6, tumor necrosis factor-α (TNF-α) and interferon, influence the permeability of the blood-brain barrier and disturb the process of neurotransmission. In addition, systemic inflammatory processes including trauma, hypoxia and surgery result in an increase of cytokine levels, causing activation of the microglia and increasing the risk for delirium [9].

4.2 Risk factors

Delirium typically results from acute stressors in a vulnerable patient. Identifying high-risk patients and common triggers are an essential workflow for optimal care of orthogeriatric patients. A standardized workup for the diagnosis and management of delirium should be integrated in an orthogeriatric comanagement model.

Patients with dementia are at particularly high risk for the development of delirium. This group should be identified as soon as possible and receive all available nonpharmacological prevention measures for delirium.

Common patient-related risk factors for delirium:

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  Preexisting dementia

  
  
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  Previous delirium

  
  
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  Older age

  
  
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  Severe comorbidities and polypharmacy

  
  
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  Visual and/or hearing impairment

  
  
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  Major fractures, eg, hip fracture

Because of the high prevalence of risk factors and the high incidence of delirium [4], all older patients should be managed as high-risk patients. One proposed risk assessment tool is described in Table 1.14-1 .