Altered mental status (AMS) is a common presentation to the emergency department that comprises a group of clinical symptoms rather than a specific diagnosis. Patients with AMS present with cognitive, attention, arousal, or consciousness disruption. To understand emergency medicine, you should gain essential information about altered mental status.
Are you more of a visual learner? Check out our online video lectures and start your Emergency Medicine course now for free!


 Image : “Inauguración del Hospital Municipal de Chiconcuac” by Presidencia de la República Mexicana.  License: CC BY-SA 2.0 


Altered mental status refers to a clinical entity of altered brain function ranging from mild confusion, lethargy, delirium, amnesia, dementia, encephalopathy, and organic brain syndrome.

Epidemiology of AMS

The symptomatic diagnosis of AMS is quite common in the emergency department. Up to 1 % of those presenting to the emergency department complaining of AMS. The male to female ratio is 1:1. Most patients with AMS are older than 60 years. 36 % of those with AMS are younger than 40 years of age and 22.5 % are aged between 40 and 60 years.

Altered mental status age distribution shows to distinct peaks in incidence. One peak is observed at 33 years and another at 72 years. The etiologies of AMS differ according to the age of the patient.

AMS in the elderly is considered as an alarming presentation. Because of this, up to 43 % of those with AMS arrive at the emergency department by ambulance. Only 20 % of those with AMS arrive at the emergency department by walking. Those that come to the emergency department by walking are younger and usually have a non-life-threatening etiology of AMS.

Classification of AMS

Patients with an altered mental status do not necessarily have a decreased level of consciousness.

AMS can be classified into three main categories:

Central nervous system inhibition  Patients with central nervous system inhibition can present with confusion, drowsiness, decreased the level of consciousness, or coma.
Central nervous system stimulation  Patients might present with irritability or aggressiveness.
Abnormal behavior   Patients might present with hallucinations.

Up to 53 % of patients with central nervous system inhibition are found to have a Glasgow Coma Scale < 15 and are found to be difficult to get aroused. They might be disoriented to time, space and person. They can have diminished responsiveness to verbal or physical stimulation. 27 % of them can present with confusion and 21 % are found to be unable to remain awake.

Patients with central nervous system stimulation or abnormal behavior might present with inappropriate bizarre behavior (9 %) or hallucinations (7 %).

Emergency Assessment of AMS

When a patient presents to the emergency department with altered mental status, it is imperative to try to determine the cause of such a presentation. Therefore, the main goal of the emergency assessment of AMS is to formulate a causative diagnosis.

Clinical history taking is an essential skill in the assessment of a patient with AMS. The cause of AMS can be determined by history alone in up to 40 % of the cases. Medication history and previous medical history should be explored in all patients presenting with AMS. Physical examination should be complete and thorough as it can reveal the cause of AMS in up to 21 % of the cases. A trial of treatment can be also useful in determining the cause of AMS, especially when drug toxicity is suspected. Unfortunately, a complete assessment of AMS can reveal a clear cause only in 60 % of the cases.

Intracerebral hemorrage

 Image  “An intracranial hemorrhage, one cause of altered level of consciousness”  by Glitzy queen00.  License: Public Domain> 

Imaging studies are also useful in determining the cause of AMS in the emergency department. A brain computed tomography, for instance, might reveal an acute hemorrhagic stroke as the cause of AMS. Electrocardiography should be also used in the assessment of AMS in the emergency department. Arterial blood gas and blood chemistry are two useful laboratory tests in the assessment of AMS. A urinalysis should be obtained when sepsis is suspected.

Coagulation studies should be obtained in patients suspected to have hemorrhagic stroke, however, coagulation studies were found to be non-contributory to the causative diagnosis approach in the assessment of AMS. Electroencephalogram alone can determine the cause of AMS in up to 1 % of the cases.

When imaging, electrophysiological, laboratory, and clinical assessment tools are combined, the cause of AMS can be determined in up to 94.7 % of the cases.

Etiologies of AMS

The cause of AMS can be identified in up to 94.7 % of the cases if a systematic approach is followed when assessing the patient. The cause of altered mental status can be physical, psychological or environmental. The most common causes of AMS:

  • Cerebrovascular disease
  • End-organ dysfunction
  • Sepsis (10 % of the cases of AMS in the elderly)
  • Drug toxicity (most common cause in the middle-aged and young patient)

Neurological causes of AMS include:

  • Cerebrovascular disease
  • Traumatic brain injury
  • Encephalitis
  • Seizure-related disorders
  • Intracranial tumors
  • Hypo/hyper glycemia
  • Hypoxia
  • Dehydration
  • Thyroid abnormalities
  • Urinary tract infection

Limbic encephalitis and anti-NMDA receptor encephalitis are rare unclear causes of AMS.

Emergency treatment of AMS

Most patients with AMS are treated at the emergency department successfully and discharged home (28 %). Up to 5 % of AMS patients are admitted to the critical care unit for intensive care treatment after triage and before entering the emergency department. Of those who enter the emergency department, another 26 % end up in the critical care unit as well.

Patients who go to the critical care unit right after triage had an average length of hospital stay of 3.8, which can indicate a worse prognosis and higher mortality.

Tracheal intubation is indicated for patients with AMS who need intensive care unit treatment. The estimated mortality rate of AMS patients is around 8 %. Most deaths occur in the emergency department before being admitted to the hospital.

Suggested Algorithm for the Management of AMS

Step 1

The first step of the management of an AMS case is to secure airway, breathing, and consciousness. If the patient is unstable, he or she should be admitted to the critical care unit for circulatory monitoring and ventilation or circulation support should be considered. If the patient is found to be stable, it should be determined if he or she is a combative patient or a cooperative one.

Step 2

Combative patients should receive some form of physical restraint. Once the patient is found to be cooperative, oxygen administration should be started at the dose of 5 to 10 L/min. An intravenous line should be inserted at this stage and a complete blood count, serum glucose, electrolytes, hepatic, and renal function tests should be ordered. A bolus dose of intravenous glucose should be administered. If the patient is suspected to be an alcoholic, a bolus dose of thiamine is indicated. Naloxone should be administered at this stage if opioid toxicity is suspected.

If the patient improved after the second step, especially if after the administration of glucose, hypoglycemia should be excluded. Further emergency department observation is all that is needed at this stage. If the improvement occurred after the administration of naloxone, opioid toxicity is confirmed.

Step 3

If no improvement was observed after the second step, a re-evaluation step should be started. Arterial blood gas measurement should be ordered to exclude metabolic derangements and respiratory failure. If respiratory failure or shock is confirmed with arterial blood gas measurement, the patient should be admitted to the critical care unit. If metabolic derangements are excluded, we can proceed to step 4.

Step 4

A brief history should be obtained, and a complete physical examination should be performed. If the history of head trauma is suspected, emergency brain computed tomography scan should be performed. Otherwise, the stroke should be suspected, and acute stroke evaluation should be started. If the patient does not have any focal neurological deficits and the diagnosis of stroke is unlikely, one should look for symptoms and signs of meningitis. Meningitis can be excluded by a lumbar puncture.

Step 5

At this stage, neurological causes of AMS should be either confirmed or reliably excluded. A thorough history should be obtained, and toxicology screening should be started. Systemic organ dysfunction should be excluded. An epilepsy-related disorder should be excluded by an electroencephalogram. A psychiatric consultation might be needed if the cause of AMS cannot be determined.

Do you want to learn even more?
Start now with 1,000+ free video lectures
given by award-winning educators!
Yes, let's get started!
No, thanks!

Leave a Reply

Register to leave a comment and get access to everything Lecturio offers!

Free accounts include:

  • 1,000+ free medical videos
  • 2,000+ free recall questions
  • iOS/Android App
  • Much more

Already registered? Login.

Leave a Reply

Your email address will not be published. Required fields are marked *