When the Brain Goes Offline

From first look to disposition: an ED algorithm for AMS + coma scales + ICP screening

Altered mental status (AMS) is not a diagnosis. It’s a warning signal—sometimes the first and only outward sign of hypoxia, sepsis, intracranial hemorrhage, toxic ingestion, metabolic collapse, or impending respiratory failure. And in the Emergency Department, AMS is also a cognitive trap: it invites broad differentials, scattered testing, delays in definitive therapy, and false reassurance.

What saves patients isn’t doing everything. It’s doing the right things first, in a structured sequence, while continuously reassessing.

This post lays out a practical ED approach to AMS: stabilise physiology, rapidly screen reversible causes, identify structural catastrophe early, and disposition safely. Along the way, we’ll also cover:

• GCS vs FOUR score (and when each makes more clinical sense)

• ONSD eye POCUS as a bedside screen for raised ICP, with a quick “how I do it” ?

1) AMS in the ED: a syndrome of urgency

AMS accounts for a significant portion of ED presentations and carries high admission rates and meaningful mortality in cohort studies (Kanich, 2002; Xiao, 2012; Cherukuri, 2020). But beyond epidemiology, the operational truth is:

With AMS, you can’t afford a slow workup. You must run physiology and etiology in parallel.

Think of AMS management as two simultaneous tracks:

Track A: stabilise physiology

• Oxygenation

• Ventilation

• Perfusion

• Glucose

• Temperature

Track B: find the cause

• Structural CNS catastrophe?

• Toxic/metabolic?

• Infection/systemic organ failure?

• Seizure/non-convulsive status?

• Psychiatric mimic?

This two-track mindset is consistent across ED and prehospital evidence-based guidance (Sanello, 2018; Smith, 2019).

2) First 2 minutes: Stabilise before you intellectualise

Primary survey: ABCD + vitals

Start with airway, breathing, circulation, disability (GCS/alertness) and full vital signs. AMS patients deteriorate quickly and often silently (Han, 2013; Sanello, 2018; Smith, 2019).

Immediate ED actions

• Bedside glucose (treat hypoglycaemia immediately)

• IV access

• Cardiac monitor + ECG

• SpO₂ monitoring and oxygen as needed

• Temperature (hypo/hyperthermia can mimic neuro catastrophe)

This core bundle is repeatedly reinforced in ED evaluation frameworks (Sanello, 2018; Xiao, 2012).

3) The “coma cocktail” isn’t dead — it’s targeted now

Old teaching often suggests: dextrose + naloxone + thiamine.

Modern practice keeps the spirit but improves the precision:

• Dextrose → if hypoglycaemic

• Naloxone → if opioid toxicity suspected (respiratory depression, typical toxidrome)

• Thiamine → if malnourished, alcohol use disorder, or strong suspicion of deficiency

You’re not giving a ritual. You’re preventing irreversible brain injury while searching for cause (Han, 2013; Smith, 2019).

4) The patient can’t speak — but the story is still there

The AMS history usually comes from the surroundings, not the patient:

• EMS and scene narrative (pills, CO exposure, trauma mechanism)

• Family/bystanders

• Prior medical records

• Medication lists

• Phone photos of prescriptions

Collateral history is consistently emphasized because it often contains the diagnostic key (Smith, 2019; Sanello, 2018; Ali, 2024).

5) Exam: the highest-yield “test” you already have

One underappreciated finding from ED cohort work is that history and physical examination can outperform broad routine testing for diagnostic yield (Kanich, 2002).

Your exam should aim to:

• Identify toxidromes and systemic clues

• Find occult trauma

• Detect focal neurologic deficits

• Look for meningitis/encephalitis clues

• Confirm or refute an immediately life-threatening hypothesis

A full neurologic exam should include pupils, gaze, tone, symmetry, reflexes, plantar response, and respiratory pattern.

6) Delirium: the diagnosis we miss most (and pay for later)

In older adults, AMS frequently represents delirium, which is common, serious, reversible—and frequently missed, especially hypoactive delirium (Han, 2013; Wilber, 2016; Odiari, 2015).

A structured mental status exam focusing on attention, orientation, cognition and perception improves recognition (Koita, 2010).

7) The central fork: structural vs non-structural AMS

At the bedside, you must quickly decide whether AMS is likely:

Structural CNS - Focal signs present

• Hemorrhage / ischemic stroke with edema

• Space-occupying lesions

• Hydrocephalus

• Trauma

• Herniation physiology

Non-structural - B/l signs present

• Toxins / medication effects

• Metabolic/endocrine crisis

• Hypoxia/hypercapnia

• Sepsis/systemic failure

• Seizure/postictal state

This fork determines imaging urgency, ICU threshold, and neurosurgical involvement.

8) Imaging: CT head is powerful—but only when indicated

CT head should be decisive, not reflexive. Indications commonly include:

• Focal deficit

• Head trauma

• Anticoagulation

• New severe headache

• Persistent coma / low GCS without explanation

• Concern for hemorrhage/herniation

The ACR Appropriateness Criteria supports targeted imaging strategies in AMS/delirium/psychosis contexts (Soares, 2024; Ali, 2024).

9) Testing should be broad—but not blind

Workup should be guided by your structured differential:

• Core labs: glucose, electrolytes, renal/hepatic function, CBC, infection markers

• ABG/VBG if ventilation/metabolic derangement suspected

• Toxicology if relevant

• EEG if nonconvulsive status epilepticus suspected

• LP if CNS infection is plausible (after appropriate imaging)

Rare causes exist and matter—but are best pursued after stabilization and common killers are excluded (Hagerman, 2022).

GCS vs FOUR Score: Choosing the right “language of coma”

A structured approach to AMS is incomplete without a reliable method to quantify consciousness over time.

The Glasgow Coma Scale (GCS) remains the most used tool in emergency and trauma care because it is simple and universally recognised. But its verbal component becomes unusable in intubated patients, limiting granularity and trend value in many ED/ICU scenarios.

The Full Outline of UnResponsiveness (FOUR) score addresses this gap by removing the verbal element and replacing it with brainstem reflexes and respiratory pattern, making it fully usable in ventilated patients and better able to detect states such as locked-in syndrome, impending herniation, or evolving brain death physiology (Schey, 2024; Pandey, 2024; Ramazani, 2019).

Systematic reviews suggest both scales are valid and reliable; FOUR may have slightly better inter-rater reliability and may offer a modest prognostic edge for mortality in ICU cohorts, though ED studies in medical/non-trauma AMS show broadly comparable performance (Brun, 2024; Schey, 2024; Pandey, 2024). Practically: GCS remains the common language for trauma triage, while FOUR is especially useful when the patient is ventilated and neurological granularity matters.

ONSD Eye POCUS: a bedside screen for raised ICP—useful, not definitive

In ED patients with AMS—especially those with trauma, seizures, stroke symptoms, severe headache, or unexplained depressed consciousness—optic nerve sheath diameter (ONSD) measurement using ocular POCUS provides a rapid, non-invasive screen for elevated ICP while definitive imaging is arranged (Lau, 2023; Blaivas, 2003; Komut, 2016).

It is particularly useful when CT is delayed, unavailable, or when the patient is too unstable to leave the resuscitation bay, helping clinicians prioritise imaging and consider early ICP-mitigating measures (e.g., head elevation, hyperosmolar therapy) in the appropriate clinical context (Lau, 2023; Cannata, 2022).

Meta-analyses and ED data suggest ONSD has high diagnostic accuracy (often around ~90%+ sensitivity/specificity depending on cutoffs), and early ED series showed excellent performance against CT markers of raised ICP (Blaivas, 2003; Lau, 2023). However, ONSD is best viewed as a triage and trend tool, not an endpoint—cutoffs vary, measurements are operator dependent, and it cannot identify the cause of intracranial hypertension, meaning it should never delay CT/MRI, neurosurgical consultation, or invasive monitoring when indicated (Komut, 2016; Lau, 2023). Standardisation efforts, including international consensus quality criteria, reinforce that its value depends on disciplined technique and interpretation, not casual measurement (Hirzallah, 2024).

More About it, read here —> ONSD

Image taken from Rosen’s 10 edition.

Disposition: AMS is often an ICU conversation

Cohort data suggests AMS patients are frequently admitted, with nontrivial mortality (Kanich, 2002; Xiao, 2012; Cherukuri, 2020). A pragmatic ED disposition framework:

• ICU: coma, airway risk, unstable vitals, recurrent seizures/status epilepticus, severe derangements, suspected CNS catastrophe

• Ward: identified cause needing treatment/monitoring

• Observation: transient AMS fully resolved with reassuring evaluation

• Discharge (rare): baseline mental status restored, benign reversible cause corrected, reliable support + follow-up

Decision tools exist, but should support—not replace—clinical judgment (Simkins, 2021; Wood, 2022).

AMS isn’t a “workup.”
It’s emergency neuro-resuscitation plus diagnostic discipline—and the quality of your structure directly shapes outcomes.

References

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