Altered Sensorium in the ICU: A Bedside Clinical Approach

A State-of-the-Art Clinical Review for Intensivists

Dr Neeraj Manikath , claude.ai

Abstract

Altered sensorium represents one of the most challenging clinical scenarios in the intensive care unit, affecting up to 80% of mechanically ventilated patients and significantly impacting morbidity, mortality, and healthcare costs. This review provides a systematic, bedside-oriented approach to evaluating altered consciousness in critically ill patients, emphasizing practical clinical assessment techniques, diagnostic pearls, and evidence-based management strategies. We highlight the importance of differentiating delirium from other causes of altered mentation and provide actionable clinical hacks for real-world ICU practice.

Keywords: Delirium, Altered mental status, Critical care, Encephalopathy, ICU, Consciousness assessment

Introduction

Altered sensorium in the ICU is not a diagnosis but a clinical syndrome demanding systematic evaluation. The term encompasses a spectrum from subtle inattention to coma, with delirium being the most common manifestation. Despite its prevalence, altered consciousness remains underrecognized, with studies showing that non-delirium specialists miss the diagnosis in up to 75% of cases.(1) The implications are profound: each additional day of delirium increases mortality by 10% and is associated with long-term cognitive impairment comparable to mild Alzheimer's disease.(2,3)

The modern intensivist must approach altered sensorium with the rigor of a neurologist, the pragmatism of an emergency physician, and the holistic perspective of a geriatrician. This review provides a practical framework for bedside assessment and management.

Defining the Spectrum of Consciousness

The Consciousness Continuum

Normal consciousness requires both arousal (wakefulness) and awareness (content). Understanding this duality is fundamental:

Arousal is mediated by the reticular activating system in the brainstem
Awareness requires intact cortical function and connectivity

Clinical Pearl: A patient can be awake but unaware (vegetative state) or aware but not fully awake (minimally conscious state). This distinction guides both prognosis and family discussions.

Classification Framework

Quantitative disorders:

Confusion: Disoriented but arousable
Obtundation: Requires repeated stimulation
Stupor: Responds only to vigorous stimulation
Coma: Unresponsive to any stimulation

Qualitative disorders:

Delirium: Fluctuating consciousness with inattention
Encephalopathy: Global cerebral dysfunction

Bedside Hack: Use the mnemonic "COAT" - Confusion, Obtundation, Arousal deficit, Terminal (coma) to quickly categorize altered consciousness severity.

The Systematic Bedside Assessment

Step 1: Establish the Baseline

Critical First Question: "What was the patient's mental status before ICU admission?"

Obtaining collateral history from family, review of outpatient records, and nursing home documentation is mandatory. Pre-existing dementia is present in 40% of elderly ICU patients and profoundly affects assessment and prognosis.(4)

Oyster: Families often overestimate pre-ICU cognitive function. Probe specifically: "Could they manage their medications? Cook? Handle finances?" These instrumental activities of daily living reveal true baseline function.

Step 2: Rapid Consciousness Assessment

The Glasgow Coma Scale (GCS) remains the universal language but has limitations in ICU patients (intubation affects verbal score, sedation confounds assessment).

Better for ICU Use: The Richmond Agitation-Sedation Scale (RASS)

+4: Combative
+3: Very agitated
+2: Agitated
+1: Restless
0: Alert and calm
-1: Drowsy
-2: Light sedation
-3: Moderate sedation
-4: Deep sedation
-5: Unarousable

Clinical Pearl: Always assess RASS before evaluating for delirium. You cannot assess delirium in a deeply sedated patient. Target RASS should be -1 to 0 for most ICU patients.(5)

Step 3: Delirium Screening

The Confusion Assessment Method for ICU (CAM-ICU) has 95% sensitivity and 89% specificity.(6)

Four Features (mnemonic: ABCD):

Acute onset or fluctuating course
Inattention (cannot squeeze hand on letter "A" in SAVEAHAART)
Disorganized thinking (fails simple yes/no questions)
Altered level of consciousness (RASS other than 0)

Delirium = Features 1 AND 2 AND (3 OR 4)

Bedside Hack: The "picture recognition test" is more sensitive than letter tests in mechanically ventilated patients. Show 5 pictures, remove them, then show 10 pictures and ask the patient to indicate which they saw before.(7)

Step 4: Delirium Subtyping

Three Motor Subtypes:

Hyperactive (25%): Agitated, combative, easily recognized
Hypoactive (45%): Withdrawn, quiet, often missed
Mixed (30%): Alternating features

Critical Oyster: Hypoactive delirium has the worst prognosis but is missed 60-80% of the time because these patients are "easy" and don't disturb the ICU workflow.(8) Actively screen quiet patients.

The Etiological Detective Work

The "DELIRIUM WATCH" Framework

A comprehensive mnemonic for ICU-specific causes:

Drugs (sedatives, anticholinergics, steroids) Electrolytes (Na, Ca, Mg, PO4 abnormalities) Lack of drugs (withdrawal from alcohol, benzodiazepines) Infection/Inflammation (sepsis, encephalitis) Respiratory (hypoxia, hypercarbia) Intracranial (stroke, hemorrhage, seizure) Uremia/Metabolic (hepatic, renal failure) Myocardial (shock, hypoperfusion)

Withdrawal of essential medications Alcohol/Substance intoxication or withdrawal Trauma (traumatic brain injury) CNS infection (meningitis, encephalitis) Hypoglycemia/Hyperglycemia

The Physical Examination Renaissance

In our technology-dependent era, bedside examination remains irreplaceable.

The Focused Neurological Examination:

1. Pupillary Examination

Pinpoint pupils: Opiate toxicity, pontine lesion
Dilated, fixed pupils: Anticholinergic toxicity, severe hypoxia, herniation
Unilateral dilated pupil: Uncal herniation, third nerve palsy
Hippus (oscillating pupils): Suggests diencephalic dysfunction

Pearl: Use a bright smartphone light in a dark room if a formal pupil gauge is unavailable. Normal pupils constrict briskly; sluggish response suggests pathology.

2. Eye Movement Assessment

Spontaneous roving movements: Intact brainstem, cortical dysfunction
Dysconjugate gaze: Brainstem lesion, metabolic disorder
Oculocephalic reflex (doll's eyes): Tests brainstem integrity in comatose patients
Cold caloric testing: Definitive brainstem assessment (contraindicated if tympanic membrane perforation)

Hack: The "three-step test" for ophthalmoplegia can be done at bedside with a penlight and helps distinguish peripheral from central causes.

3. Motor Examination

Asterixis (flapping tremor): Metabolic encephalopathy (hepatic > renal > hypercapnia)
Myoclonus: Uremia, hypoxia, drug toxicity
Tremor: Alcohol withdrawal, lithium toxicity, hyperthyroidism
Focal weakness: Structural lesion until proven otherwise

Pearl: True asterixis requires the patient to be cooperative enough to hold arms extended. In obtunded patients, look for multifocal myoclonus instead.

4. Meningismus

Neck stiffness, Kernig's sign, Brudzinski's sign
Oyster: Absence of meningismus does NOT exclude meningitis in the elderly, immunosuppressed, or deeply comatose. Maintain high suspicion.

5. Respiratory Pattern

Cheyne-Stokes: Bihemispheric dysfunction, heart failure
Central neurogenic hyperventilation: Midbrain/pontine lesion
Apneustic breathing: Pontine damage
Ataxic breathing: Medullary dysfunction (pre-terminal)

Laboratory Investigation Strategy

Tier 1 (Everyone):

Complete blood count
Comprehensive metabolic panel (glucose, electrolytes, BUN, creatinine, liver enzymes)
Arterial blood gas
Urinalysis and culture
Chest X-ray
ECG

Tier 2 (High clinical suspicion):

Thyroid function tests
Cortisol level (especially if on chronic steroids or septic)
Ammonia level (if liver disease)
Toxicology screen and specific drug levels (digoxin, lithium, anticonvulsants)
Vitamin B12, thiamine levels (alcoholics, malnutrition)
Blood cultures

Tier 3 (Specific scenarios):

Lumbar puncture (unexplained fever, immunocompromised, seizure)
CT/MRI brain
EEG (if suspecting non-convulsive status epilepticus)
Autoimmune encephalitis panel (young patient, psychiatric features, refractory seizures)
HIV testing, syphilis serology (appropriate risk factors)

Clinical Hack: The "Rule of 120s" - If Na >120, glucose >120, and no obvious toxic-metabolic cause, get brain imaging. Don't wait.

Neuroimaging: When and What

Indications for Emergent CT Head

Absolute indications:

Focal neurological deficits
GCS <13 without clear reversible cause
Head trauma (even seemingly minor in anticoagulated patients)
Severe hypertension with headache
Suspected herniation (blown pupil, posturing)
New-onset seizure without known epilepsy

Relative indications:

Age >60 with undifferentiated altered sensorium
Persistent altered consciousness despite correction of metabolic abnormalities
Anticoagulated patients with any change in mental status
Immunocompromised patients (opportunistic CNS infections)

Pearl: Non-contrast CT is the first-line study in acute settings. It excellently identifies hemorrhage, hydrocephalus, mass effect, and large strokes. CT is fast, available, and doesn't require patient cooperation.

When to Upgrade to MRI

Suspected posterior fossa pathology (CT has artifacts)
Clinical picture suggests stroke but CT is negative (MRI with diffusion-weighted imaging)
Encephalitis (temporal lobe enhancement in HSV encephalitis)
Suspected venous sinus thrombosis (MR venography)
Demyelinating disease
Metabolic encephalopathies may show characteristic patterns (posterior reversible encephalopathy syndrome, osmotic demyelination)

Oyster: MRI requires 30-60 minutes of patient immobility. Agitated, hypoxic, or hemodynamically unstable patients are poor candidates. Don't delay treatment for imaging.

The EEG Decision

When to Consider EEG

Strong indications:

Suspected non-convulsive status epilepticus (subtle movements, eye deviation, persistent altered consciousness post-seizure)
Unexplained coma after cardiac arrest
Persistent encephalopathy without clear cause
Monitoring burst suppression during barbiturate coma

Supporting evidence: Non-convulsive seizures occur in 10-20% of ICU patients with unexplained altered consciousness.(9) The only way to diagnose is EEG.

Clinical Pearl: "Twitching" in ICU patients is seizure until proven otherwise. Even subtle rhythmic movements (finger twitching, eye deviation, chewing) warrant EEG.

Hack: Continuous EEG monitoring is ideal but resource-intensive. A 30-minute routine EEG captures seizures in 50% of cases, 24-hour monitoring increases yield to 80%.(10)

Special Scenarios and Diagnostic Pearls

The Post-Cardiac Arrest Patient

Avoid premature prognostication. The 2021 American Heart Association/European Resuscitation Council guidelines recommend multimodal assessment at ≥72 hours post-arrest in normothermic patients.(11)

Favorable prognostic signs:

Early motor response better than extensor posturing
Intact pupillary and corneal reflexes at 72 hours
Absence of myoclonic status epilepticus
EEG with continuous background activity

Unfavorable but not definitive:

Bilateral absence of N20 somatosensory evoked potential
Status myoclonus in first 72 hours
Highly malignant EEG patterns

Pearl: Sedation, hypothermia, and neuromuscular blockade can all confound neurological examination. Wait until these effects have cleared.

Alcohol Withdrawal Delirium (Delirium Tremens)

Timing is diagnostic:

Minor symptoms: 6-12 hours
Seizures: 12-48 hours
Delirium tremens: 48-96 hours

Clinical features:

Autonomic hyperactivity (tachycardia, hypertension, fever, diaphoresis)
Tremor
Hallucinations (classically visual)
Agitation

Oyster: Alcohol withdrawal can be superimposed on other causes of altered sensorium. Don't assume withdrawal explains everything in a chronic alcoholic.

Management Pearl: CIWA-Ar score guides benzodiazepine dosing, but in severe DT, phenobarbital loading may be superior.(12) Consider ICU-level monitoring and continuous benzodiazepine infusions.

Hepatic Encephalopathy

Grading (West Haven Criteria):

Grade 1: Trivial lack of awareness, short attention span
Grade 2: Lethargy, disorientation, inappropriate behavior
Grade 3: Somnolent but arousable, gross disorientation, bizarre behavior
Grade 4: Coma

Bedside Test: Number connection test (connect numbers 1-25 in order as fast as possible; >30 seconds abnormal)

Management Hack: Lactulose titrated to 2-3 soft bowel movements daily remains first-line. Rifaximin added for refractory cases. Zinc and L-ornithine-L-aspartate are adjuncts with some evidence.(13)

Pearl: Always search for precipitants: GI bleeding, infection, constipation, hypokalemia, excessive protein intake, medications (benzodiazepines, opioids).

Septic Encephalopathy

Most common cause of delirium in ICU. May precede other signs of sepsis.

Pathophysiology: Blood-brain barrier disruption, neuroinflammation, neurotransmitter dysregulation, microvascular dysfunction.

Diagnosis: Exclusion diagnosis. Requires systemic infection and absence of other explanations.

Pearl: Correction of sepsis resolves encephalopathy. Persistence despite sepsis control mandates reassessment for other causes.

Non-Convulsive Status Epilepticus (NCSE)

High index of suspicion required:

Subtle facial twitching
Eye deviation
Altered consciousness in known epileptic
Post-ictal confusion lasting >30 minutes

Diagnostic Gold Standard: EEG showing continuous or recurrent seizure activity

Management: Treat as status epilepticus with benzodiazepines, then antiepileptic drug loading. Neurology consultation essential.(14)

Medication-Related Altered Consciousness

The Prime Suspects

Anticholinergics:

Diphenhydramine, promethazine, scopolamine
Features: Dilated pupils, dry mucous membranes, urinary retention, absent bowel sounds, agitation
Mnemonic: "Blind as a bat, red as a beet, hot as a hare, dry as a bone, mad as a hatter"

Benzodiazepines/Propofol:

Dose-dependent sedation
Paradoxical agitation possible, especially in elderly
Propofol infusion syndrome: Metabolic acidosis, rhabdomyolysis, cardiac dysfunction

Opioids:

Pinpoint pupils, respiratory depression
Pearl: Pupil dilation occurs with severe hypoxia/anoxia; don't dismiss opioid toxicity if pupils are mid-sized

Steroids:

Can cause delirium, psychosis, or mania
More common with higher doses and longer duration

Oyster: Medication withdrawal is as dangerous as intoxication. Sudden cessation of benzodiazepines, baclofen, or beta-blockers can precipitate delirium.

The Anticholinergic Burden

Many ICU medications have anticholinergic properties. The cumulative effect is often underappreciated.

Common culprits:

H2 blockers (ranitidine > famotidine)
Antiemetics (promethazine, metoclopramide)
Antipsychotics (quetiapine, olanzapine)
Antidepressants (amitriptyline, paroxetine)
Antihistamines
Muscle relaxants (cyclobenzaprine)

Hack: Use the Anticholinergic Cognitive Burden Scale. Score ≥3 significantly increases delirium risk.(15)

Non-Pharmacological Prevention and Management

The ABCDEF Bundle (Evidence-Based Delirium Prevention)

Assess, prevent, and manage pain Both spontaneous awakening and breathing trials Choice of analgesia and sedation Delirium: assess, prevent, and manage Early mobility and exercise Family engagement and empowerment

Evidence: Implementation of the ABCDEF bundle reduces delirium incidence by 50%, decreases ICU length of stay, and improves survival.(16)

Practical Implementation Pearls:

1. Optimize the environment:

Windows for natural light (regulates circadian rhythm)
Minimize nighttime noise and interruptions
Remove unnecessary lines and catheters
Clocks and calendars for orientation

2. Sensory aids:

Ensure patients have glasses and hearing aids
Simple intervention, often overlooked, profoundly improves orientation

3. Early mobilization:

Even in mechanically ventilated patients
Reduces delirium duration and improves functional outcomes
Safety first: exclude contraindications (unstable fractures, active bleeding, hemodynamic instability)

4. Sleep promotion:

Consolidate nighttime care
Reduce alarm volumes at night
Consider melatonin or ramelteon (evidence for prevention, not treatment)
Avoid benzodiazepines for sleep

5. Family presence:

Liberalized visitation policies
Familiar voices and faces provide orientation
Family can identify subtle changes in baseline

Pharmacological Management of Delirium

The Uncomfortable Truth

No medication has been proven to reduce delirium duration, ICU length of stay, or mortality.(17)

Antipsychotics may reduce agitation and allow nursing care but do not treat underlying delirium.

When to Consider Pharmacotherapy

Indications:

Safety threat to self or staff
Severe agitation interfering with necessary care (mechanical ventilation, life-sustaining treatments)
Severe distress to patient

NOT indicated:

Quiet hypoactive delirium
Prophylaxis in non-delirious patients
Convenience of staff

Medication Options

Haloperidol:

0.5-2 mg IV/PO q4-6h PRN
Typical antipsychotic, fewer anticholinergic effects than atypicals
Risk: QTc prolongation, extrapyramidal symptoms, neuroleptic malignant syndrome
Pearl: Check baseline QTc; avoid if >500 ms

Quetiapine:

12.5-50 mg PO BID
Atypical antipsychotic
Advantage: May improve sleep
Disadvantage: Significant anticholinergic effects, cannot be given IV

Dexmedetomidine:

Alpha-2 agonist, provides sedation without respiratory depression
May reduce delirium duration compared to benzodiazepines(18)
Limitation: Expensive, requires continuous infusion, can cause bradycardia and hypotension
Sweet spot: Post-extubation agitation, difficult ventilator weaning

Avoid:

Benzodiazepines (except alcohol/benzodiazepine withdrawal): Worsen delirium, increase duration
Physical restraints unless absolutely necessary: Increase agitation and risk of injury

Hack: Start with lowest effective dose. Delirium medications are for agitation control, not delirium cure. Minimize duration of use.

Prognosis and Long-Term Outcomes

The Sobering Reality

Delirium is not a benign, reversible condition. It has profound long-term consequences:

Cognitive impairment: 40% of delirium survivors have cognitive deficits at 1 year, equivalent to moderate traumatic brain injury(19)
Functional decline: Decreased ability to perform activities of daily living
Increased mortality: Persists up to 1 year post-discharge
Post-ICU syndrome: Cognitive, psychiatric, and physical impairments

Family Counseling Pearl: Prepare families for the possibility of persistent cognitive changes. Early cognitive rehabilitation and structured follow-up may help.

Clinical Hacks and Practical Tips

The "Eyeball Test"

Before touching the chart, observe:

Is the patient tracking you with their eyes?
Are they reaching for lines/tubes?
What is the respiratory pattern?
Do they respond to their name?

This 10-second assessment provides more information than many realize.

The "MOVE" Protocol for Rapid Assessment

Motor: Any spontaneous movement? Purposeful? Ocular: Pupil size, light reflex, tracking Verbal: Any sounds, words, following commands? Emotional: Flat, agitated, fearful, appropriate?

Communication with Non-Verbal ICU Patients

The "Squeeze Technique":

"Squeeze my hand if you understand me"
"Squeeze once for yes, twice for no"
"Squeeze my right hand if you have pain"

Oyster: Inconsistent responses don't always mean delirium. Weakness, language barriers, and hearing impairment can interfere.

The "Sedation Vacation" Checklist

Before daily sedation interruption, ensure:

No active seizures
No escalating vasopressor requirements
No ongoing neuromuscular blockade
No active myocardial ischemia
Adequate oxygenation

Documentation Essentials

Record daily:

RASS score
CAM-ICU result
GCS (in non-sedated patients)
Delirium type (hyperactive/hypoactive/mixed)
Contributing factors identified
Interventions implemented

Summary: The 10 Commandments of ICU Altered Sensorium

Assume nothing: Always establish true baseline cognitive function
Screen systematically: Use validated tools (RASS, CAM-ICU) consistently
Don't miss the quiet ones: Hypoactive delirium is common and dangerous
Search for reversible causes: Use the DELIRIUM WATCH framework
Examine, don't just scan: Physical exam findings are irreplaceable
Image appropriately: CT for acute/focal findings; MRI for diagnostic dilemmas
Consider EEG liberally: Non-convulsive seizures are more common than appreciated
Prevent aggressively: ABCDEF bundle, non-pharm interventions first
Medicate judiciously: Antipsychotics control agitation but don't cure delirium
Think long-term: Counsel families about persistent cognitive effects

Conclusion

Altered sensorium in the ICU demands a systematic, evidence-based approach combined with clinical acumen honed through experience. While technology and imaging play important roles, the foundation remains a thorough history, meticulous examination, and critical thinking. The modern intensivist must be a diagnostic detective, recognizing that each case of altered consciousness is a puzzle requiring patience, persistence, and clinical wisdom.

As we continue to understand the devastating long-term consequences of ICU delirium, prevention through evidence-based bundles, early recognition through systematic screening, and aggressive treatment of underlying causes become imperative. The quality of our assessment today determines not just survival, but the cognitive future of our patients.

References

Ely EW, Stephens RK, Jackson JC, et al. Current opinions regarding the importance, diagnosis, and management of delirium in the intensive care unit. Crit Care Med. 2004;32(1):106-112.
Ely EW, Shintani A, Truman B, et al. Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit. JAMA. 2004;291(14):1753-1762.
Girard TD, Jackson JC, Pandharipande PP, et al. Delirium as a predictor of long-term cognitive impairment in survivors of critical illness. Crit Care Med. 2010;38(7):1513-1520.
Pisani MA, Redlich C, McNicoll L, et al. Underrecognition of preexisting cognitive impairment by physicians in older ICU patients. Chest. 2003;124(6):2267-2274.
Barr J, Fraser GL, Puntillo K, et al. Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit. Crit Care Med. 2013;41(1):263-306.
Ely EW, Margolin R, Francis J, et al. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Crit Care Med. 2001;29(7):1370-1379.
Patel MB, Bednarik J, Lee P, et al. Delirium monitoring in neurocritically ill patients: a systematic review. Crit Care Med. 2018;46(11):1832-1841.
Peterson JF, Pun BT, Dittus RS, et al. Delirium and its motoric subtypes: a study of 614 critically ill patients. J Am Geriatr Soc. 2006;54(3):479-484.
Claassen J, Mayer SA, Kowalski RG, et al. Detection of electrographic seizures with continuous EEG monitoring in critically ill patients. Neurology. 2004;62(10):1743-1748.
Struck AF, Ustun B, Ruiz AR, et al. Association of an electroencephalography-based risk score with seizure probability in hospitalized patients. JAMA Neurol. 2017;74(12):1419-1424.
Nolan JP, Sandroni C, Böttiger BW, et al. European Resuscitation Council and European Society of Intensive Care Medicine guidelines 2021: post-resuscitation care. Intensive Care Med. 2021;47(4):369-421.
Gold JA, Rimal B, Nolan A, Nelson LS. A strategy of escalating doses of benzodiazepines and phenobarbital administration reduces the need for mechanical ventilation in delirium tremens. Crit Care Med. 2007;35(3):724-730.
Vilstrup H, Amodio P, Bajaj J, et al. Hepatic encephalopathy in chronic liver disease: 2014 Practice Guideline by AASLD and EASL. Hepatology. 2014;60(2):715-735.
Brophy GM, Bell R, Claassen J, et al. Guidelines for the evaluation and management of status epilepticus. Neurocrit Care. 2012;17(1):3-23.
Salahudeen MS, Duffull SB, Nishtala PS. Anticholinergic burden quantified by anticholinergic risk scales and adverse outcomes in older people: a systematic review. BMC Geriatr. 2015;15:31.
Pun BT, Balas MC, Barnes-Daly MA, et al. Caring for critically ill patients with the ABCDEF bundle: results of the ICU Liberation Collaborative in over 15,000 adults. Crit Care Med. 2019;47(1):3-14.
Burry L, Mehta S, Perreault MM, et al. Antipsychotics for treatment of delirium in hospitalised non-ICU patients. Cochrane Database Syst Rev. 2018;6(6):CD005594.
Reade MC, Eastwood GM, Bellomo R, et al. Effect of dexmedetomidine added to standard care on ventilator-free time in patients with agitated delirium: a randomized clinical trial. JAMA. 2016;315(14):1460-1468.
Pandharipande PP, Girard TD, Jackson JC, et al. Long-term cognitive impairment after critical illness. N Engl J Med. 2013;369(14):1306-1316.

Conflict of Interest: None declared

Funding: None

Author Contributions: This review represents synthesis of clinical experience and current evidence-based practice in critical care medicine.

Sunday, January 18, 2026