
Am Fam Physician. 2021;104(5):461-470
Author disclosure: No relevant financial affiliations.
Potential precipitating factors for the recent onset of altered mental status (AMS) include primary central nervous system insults, systemic infections, metabolic disturbances, toxin exposure, medications, chronic systemic diseases, and psychiatric conditions. Delirium is also an important manifestation of AMS, especially in older people who are hospitalized. Clinicians should identify and treat reversible causes of the AMS, some of which require urgent intervention to minimize morbidity and mortality. A history and physical examination guide diagnostic testing. Laboratory testing, chest radiography, and electrocardiography help diagnose infections, metabolic disturbances, toxins, and systemic conditions. Neuroimaging with computed tomography or magnetic resonance imaging should be performed when the initial evaluation does not identify a cause or raises concern for intracranial pathology. Lumbar puncture and electroencephalography are also important diagnostic tests in the evaluation of AMS. Patients at increased risk of AMS benefit from preventive measures. The underlying etiology determines the definitive treatment. When intervention is needed to control patient behaviors that threaten themselves or others, nonpharmacologic interventions are preferred to medications. Physical restraints should rarely be used and only for the shortest time possible. Medications should be used only when nonpharmacologic treatments are ineffective.
Altered mental status (AMS) can present as changes in consciousness, appearance, behavior, mood, affect, motor activity, or cognitive function.1–3 Recent changes are the focus of this article and are approached differently than chronic changes. Recent changes occur within seconds to days and usually pose a more immediate threat to a patient's well-being than chronic changes.2–4

Recommendation | Sponsoring organization |
---|---|
Do not assume a diagnosis of dementia in an older adult who presents with an altered mental status and/or symptoms of confusion without assessing for delirium or delirium superimposed on dementia using a brief, sensitive, validated assessment tool. | American Academy of Nursing |
Do not use antipsychotics as the first choice to treat behavioral and psychological symptoms of dementia. | American Geriatrics Society |
Do not use physical or chemical restraints, outside of emergency situations, when caring for long-term care residents with dementia who display behavioral and psychological symptoms of distress; instead, assess for unmet needs or environmental triggers and intervene using nonpharmacologic approaches initially whenever possible. | American Academy of Nursing |

Setting | Rate |
---|---|
Incidence during hospital admission | |
After hip fracture | 28% to 61% |
After surgery | 15% to 53% |
During hospitalization (medical inpatients) | 3% to 29% |
Prevalence | |
Intensive care unit | |
With mechanical ventilation | 60% to 80% |
Without mechanical ventilation | 20% to 50% |
Hospice | 29% |
Community (people 85 years or older) | 14% |
At hospital admission | 10% to 31% |
Long-term care facility and postacute care | 1% to 60% |
The differential diagnosis for AMS is broad. A history and physical examination are the cornerstones of diagnosis, and their findings guide diagnostic testing. Preventive measures can decrease incidence and are important to use in patients at high risk. The goal of treatment is to correct the precipitating cause of the AMS.2,3,9–11
Causes of Recent AMS
Causes of recent AMS include primary central nervous system insults, systemic infections, metabolic disturbances, toxin exposure, medications, chronic systemic diseases, and psychiatric conditions (Table 2).2–4,9,10 Although a single abnormality may cause the alteration in mental status (e.g., opiate overdose), often the cause is multifactorial (e.g., dehydration, constipation, high-risk medication use).2–4,9,10

Central nervous system insults | |
Demyelinating conditions Direct brain trauma (concussion) Epidural hematoma Intraparenchymal hemorrhage Ischemic stroke Meningoencephalitis Neoplasm (primary or metastatic) Seizure (status epilepticus, nonconvulsive status epilepticus, or postictal state) Subarachnoid hemorrhage Subdural hematoma | |
Commonly used medications | |
Antibiotics (fluoroquinolones, cephalosporins) Antidepressants (tertiary amine tricyclics, monoamine oxidase inhibitors) Antipsychotics Benzodiazepines Beta blockers Bladder antispasmodics Dopamine agonists General anesthetics Opioid analgesics Sedatives or hypnotics Skeletal muscle relaxants Sympathomimetics | |
Metabolic disturbances | |
Hepatic failure Hypercalcemia Hypermagnesemia Hypoadrenalism/hyperadrenalism Hypoglycemia/hyperglycemia Hyponatremia/hypernatremia Hypophosphatemia Hypothyroidism/hyperthyroidism Renal failure Thiamine deficiency | |
Systemic diseases or conditions | |
Arrhythmia Autoimmune conditions Constipation Dehydration Heart failure Hypercapnia Hypertensive emergency Hypothermia Hypoxia Myocardial infarction Pain Pancreatitis Primary psychiatric conditions Sleep deprivation Urinary retention | |
Systemic infections | |
Acute viral (influenza, COVID-19, and others) Intra-abdominal Pneumonia Sepsis Urinary tract | |
Toxins | |
Alcohol (withdrawal or intoxication) Illicit substances (withdrawal or intoxication) |
Among the most common and important presentations of AMS is delirium, especially in older adults who are hospitalized.6,9 The hallmarks of delirium are acute, fluctuating changes in attention, awareness, and cognition that are not attributable to a neurocognitive disorder. Evidence of a secondary cause of AMS is often also present.6,9 Other features include sleep disturbances, hallucinations, delusions, inappropriate behavior, and emotional instability.11 Delirium was reviewed in a previous American Family Physician article.6
Evaluation
Changes in consciousness, appearance, behavior, mood, affect, or motor activity are usually apparent by general observation and interaction with the patient.
URGENT INTERVENTION

Once the ABCs have been stabilized, clinicians should evaluate for other conditions for which rapid intervention is needed to decrease the risk of morbidity and mortality. Abnormal vital signs may identify an obvious cause such as hypothermia, hypoxemia, or a hypertensive emergency, and such abnormalities should be addressed urgently.2,3,10
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