Delirium

All too often on my Emergency Medicine rotation, we would hear on the EMS about a patient in route for altered mental status/confusion/delirium. Sometimes, these cases where fairly straightforward (a relatively healthy 88 yo female with sudden confusion and urosepsis) but more often we would have patients who had multiple problems, were on multiple medications, had baseline dementia or had no history at all! These cases could prove very challenging!

Delirium – The DSM IV lists four key features that characterize delirium

• Disturbance of consciousness with reduced ability to focus, sustain, or shift attention. Distractibility is the key work here!
• A change in cognition or the development of a perceptual disturbance that is not better accounted for by a preexisting, established, or evolving dementia.
• The disturbance develops over a short period of time (usually hours to days) and tends to fluctuate during the course of the day. Fluctuate is another key word!
• There is evidence from the history, physical examination, or laboratory findings that the disturbance is caused by a medical condition, substance intoxication, or medication side effect.

Unfortunately, the pathogenesis of delirium is poorly understood. The biologic basis is difficult to assess in part because it is not practical to run conventional tests on acutely ill patients and it is often difficult to separate delirium from other illnesses or medication side effects. However, uptodate reports some data on the pathogenesis and risk factors for developing delirium.

 Pathogenesis

• Cortical dysfunction – On EEG, there is a correlation with the slowing of the dominant posterior alpha waves and the appearance of abnormal slow-wave activity with a decreased level in consciousness (excluding causes of delirium such as drug and alcohol withdrawl).
• Subcortical dysfunction – Evoked potential studies as well as neuroimaging studies have shown that there is a connection with delirium and subcortical function. This research correlates with the finding that patients who have a dysfunction to the subcortical area (Parkinson’s and stroke patients) are more susceptible to delirium
• Neurotransmitter imbalance – Acetylcholine imbalance has been long known to have a part in delirium. When healthy patients are given anticholinergics, delirium can ensue. The role of acetylcholine is further supported by the fact that events precipitating delirium (hypoxia, hypoglycemia and thiamine deficiency) can all decrease the amount of acetylcholine synthesis in the body. It is modern practice to avoid anticholinergic medication in the elderly population which can be difficult (especially if the patient is post-op as the patient will received anticholinergics to prevent the muscarinic side effects when the patient is given an anticholinesterase inhibitor.) Other neurotransmitters thought to be involved include interleukins and tumor necrosis factor which would account for the high risk of delirium in patients with inflammatory conditions and sepsis.

Risk factors

• Factors that increase vulnerability – stroke, parkinson’s disease and dementia
• Factors that precipitate delirium – polypharmacy, dehydration, malnutrition, immobility and infection

Differential Diagnosis – I learned a helpful acronym when thinking of causes of delirium…MOVE STUPID

Metabolic – B12 or thiamine deficiency, serotonin syndrome
Oxygen – hypoxemia (cardiac, pulmonary or anemia) or hypercarbnia
Vascular – Hypertensive emergency, CVA, vasculitis and MI
Electrolytes  and Endocrine
Seizures
Toxins – lead, mercury and CO, trauma, tumor and temperature
Uremia from renal or hepatic dysfunction
Psychiatric or Porphyria
Infection
Drugs – anticholinergics, antipsychotics and withdrawl from drugs

Labs to order - should include serum electrolytes, creatinine, glucose, calcium, complete blood count, and urinalysis and urine culture. Drug levels, toxicology screen, liver function testing, and arterial blood gas should follow if the cause remains obscure. Neuroimaging or EEG should be further down the list of test when a cause continues to remain obscure.

Treatment - involves correcting the underlying factor and maintaining an environment that will not further precipitate the delirium. Recommendations from uptodate are below. When I rotated at a hospital in MN, this was part of an order set which I though was awesome!! I think that every hospital should have delirium prevention protocol order sets.

• Orientation protocol and cognitive stimulation for patients with cognitive impairment
• Environmental modification and nonpharmacologic sleep aids for patients with insomnia
• Early mobilization and minimizing use of physical restraints for patients with limited mobility
• Visual and hearing aids for patients with these impairments
• Early volume repletion for patients with dehydration