Delirium and Altered Mental Status


Delirium describes an acute failure of brain functioning. In this way, delirium is analogous to other acute organ failures such as heart failure, liver failure, or kidney failure.

The term Delirium, from latin Delirare (“deviate from the furrow”), refers to acute alterations in attention, consciousness, and cognition. Altered Mental Status (AMS), Encephalopathy, or Altered level of consciousness (ALOC) are terms used interchangeably with delirium in medical settings.

How Common is Delirium?

Prevalence rates vary depending on age, setting, and study. While there is little consistency in reported prevalence rates across studies, many report rates as high as 70-87% in patients admitted to the Intensive Care Unit (ICU) and 15-53% in elderly patients after surgery. In patients admitted to medical-surgical hospitals, rates may be as high as 10-31%. These prevalence rates highlight how common this disorder is and how important it is to recognize and treat. In fact, the mortality rate of untreated delirium can be as high as 15%!

What are common Signs and Symptoms of Delirium?

The hallmark sign of delirium is an acute or abrupt change, within hours or days, in an individual’s mental status. Typically, consciousness, arousal, and attention fluctuate over time (“wax and wane”) such that individuals may go through periods of apparent lucidity followed by periods of confusion. In addition to changes in consciousness, arousal, and attention, other symptoms often include:
  • Cognitive problems 
  • Memory impairment (usually limited to recent memories and formation of new memories)
  • Disorientation to time and place (but rarely to self)
  • Speech and language problems
  • Perceptual disturbances such as illusions and hallucinations (visual hallucinations are probably more common in delirium than auditory hallucinations)
  • Delusions (fixed, false beliefs such as paranoia)

What is the Pathophysiology of Delirium?

The pathophysiology of delirium remains a mystery. However, delirium is probably a final common pathway with many different causes involving inflammatory mediators (cytokines), hormones, and dysregulation of aminergic, cholinergic, glutamatergic, and GABAergic neurotransmission. It is important to note that delirium is always attributable to a medical or organic cause even if the cause cannot be identified (which is often the case). 

Current theory postulates that delirium results from a combination of predisposing factors and precipitating factors. That is, various factors increase the risk for developing delirium but other factors precipitate the delirious state. Think of delirium as spilling water from a cup. The predisposing factor is a cup full of water and the precipitating factor is someone bumping into you.

Predisposing Factors include

  • History of delirium increases the risk for another episode
  • Advanced age
  • Neurocognitive disorders (Dementia)
  • Depression
  • Any neurological insult (Stroke, Traumatic Brain Injury)
  • Alcohol Abuse
  • History of Delirium Tremens
  • Sensory impairment (especially hearing/vision)
  • Recent surgery (especially neurosurgery, cardiac, and transplant)
  • Intensive Care Unit (ICU) stay
  • Sleep deprivation

 Precipitating Factors include

  • Infections: Urinary tract infections (UTI), Pneumonia, Sepsis, Encephalitis, Meningitis, HIV/AIDS
  • Hypoperfusion/Hypoxia: Significant blood loss/volume loss (bleeding), Heart failure, cardiac arrest, arrhythmia, Cerebrovascular Accident (CVA), Anemia (sickle cell, B12 def, Folate def, Iron def)
  • Metabolic Derangement: Hypoglycemia/Hyperglycemia, Hyponatremia/hypernatremia, Uremia, Hyperammonemia
  • Increased Intracranial Pressure: Cerebral edema, Tumors/Mass lesions, Intracranial Hemorrhage, Hypertensive crisis
  • Seizures
  • Poisons
  • Autoimmune diseases: NMDA Receptor Encephalitis, Lupus Cerebritis
  • Tacrolimus (Posterior Reversible Encephalopathy Syndrome)
  • Opioids/Opiates
  • Barbiturates
  • Antihistamines
  • Anticholinergics
  • Benzodiazepines
  • Lithium toxicity
  • Valproic Acid toxicity
  • Tricyclic Antidepressant (TCA) toxicity
  • Serotonin Syndrome
  • Neuroleptic Malignant Syndrome (NMS)
  • Illicit Drugs: Alcohol intoxication/withdrawal, Wernicke-Korsakoff Syndrome, Inhalant Intoxication, Opioid intoxication/withdrawal, Marijuana Intoxication, Synthetic cannabinoids (K2, Spice), Synthetic Cathinones (bath salts), PCP, LSD, Psilocybin

Who is at highest risk?

  • Elderly (>60 years old)
  • Cognitively Impaired Patients
  • Patients with history of CVA
  • Post-op patients
  • Sensory Impaired patients (blind, deaf)
  • Patients in the Intensive Care Unit (ICU)
  • Patients with multiple medical conditions
  • Patients with sepsis (i.e., blood infections)

How do we screen for delirium?

Screening Tools for high risk patients include the Confusion Assessment Method (CAM), Confusion Assessment Method for the ICU (CAM-ICU), Intensive Care Delirium Screening Checklist, Delirium Rating Scale, Memorial Delirium Assessment Scale, and the Nursing Delirium Screening Scale (NuDESC). 

Delirium can be prevented by using various strategies that reduce an individual’s risk. These prevention strategies include close observation (having someone sit with the patient), frequently reorienting the individual to their location/time/date, and enhancing social interaction by engaging and interacting with the patient as much as possible. It is important to keep visible the time (via a large clock), date, and location in case a patient forgets. Encouraging family to visit can be helpful as familiar faces or familiar items (pictures, blankets, etc) can prevent confusion. 

If sensory impairments are present, these need to be addressed (such as providing hearing aids and glasses). One of the most common mistakes hospitals make is closing the curtains and turning out the lights during the day. It is essential to maintain a consistent sleep/wake cycle by minimizing naps during the day and ensuring adequate sunlight so the patient can easily estimate the time of day. Because sleep deprivation is a common precipitating factor, every effort should be made to minimize the disruption of sleep during the night. Lastly, help the patient maintain adequate nutrition and strongly encourage ambulation and/or physical activity.

How is Delirium Treated?

Prevention is the best treatment

Delirium is reversible and should be considered a medical emergency. If the cause of the delirium is identifiable, treating the medical cause is considered the primary treatment. While addressing the medical cause, it is important to continue to use the prevention strategies above to minimize any contributing factors. A thorough review of medications may provide insight into the cause of confusion. For example, benzodiazepines, opioids, antihistamines, and anticholinergic medications can cause or exacerbate delirium in older adults.

Behavioral strategies

  • Correcting any sensory impairments, if present (e.g., providing hearing aids and glasses)
  • Keeping the lights on during the day and lights off at night
  • Maintaining a consistent sleep-wake cycle by minimizing naps during the day and ensuring adequate sunlight so the patient can easily estimate the time of day
  • Minimizing the disruption of sleep during the night (e.g., decrease frequency of vital sign checks)
  • Maintaining adequate nutrition
  • Encouraging ambulation and/or physical activity
  • Keeping the date and time visible in the room
  • Frequently asking the patient where he or she is, their name, the time of day, and the reason for being there

If behavioral strategies are not effective, then medications may be used to prevent harm to the patient and staff. Physical restraints should be considered a last resort for severe agitation and violence. 

Medication Options (for agitation and aggression)


  • Haloperidol (1mg-5mg PO/IM q6hr PRN)
  • Risperidone (0.5mg-2mg PO BID PRN)
  • Quetiapine (25mg-100mg PO q6hr PRN)
  • Olanzapine (2.5mg-10mg PO/IM q6hr PRN)
  • Ziprasidone (10mg-20mg PO/IM q6hr PRN)

Melatonin Modulators 

  • Ramelteon (8mg PO QHS)
  • Melatonin (3mg-10mg PO QHS)

Acetylcholinesterase Inhibitors

  • Physostigmine
  • Donepezil (5mg PO Daily)

Other Medication Options

  • Clonidine
  • Dexmedetomidine (commonly used in ICU)


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