ICU Delirium
Definition(DSM-5)
ICU delirium is an acute, fluctuating disturbance of consciousness and cognition, characterized by:
- Impaired attention
- Altered level of awareness
- Disorganized thinking ± perceptual disturbances
It develops over hours to days and is a manifestation of acute brain dysfunction.ICU psychosis’ is an outdated misnomer.
- DSM-5 criteria explicitly state that these new changes in mentation must be in the absence of a neurocognitive disorder that could explain the confusion and does not occur in the setting of a reduced level of arousal (e.g., coma,sedative administration).
- Delirium is a diagnosis of exclusion
Why ICU Delirium Matters
- Incidence: 30–80% of ICU patients (highest in ventilated, septic, elderly)
- Associated with:
- ↑ Mortality (short- and long-term)
- ↑ Duration of mechanical ventilation
- ↑ ICU & hospital LOS
- ↑ Long-term cognitive impairment (ICU-acquired dementia–like syndrome)
# Delirium is NOT benign and NOT just agitation.
Pathophysiology
Neurotransmitter Imbalance
- ↓ Acetylcholine
- ↑ Dopamine
- Altered GABA, serotonin, glutamate
Neuroinflammation
- Sepsis → cytokines (IL-1, IL-6, TNF-α)
- Blood–brain barrier dysfunction
Cerebral Hypoperfusion & Hypoxia
- Shock, anemia, respiratory failure
Stress Response
- ↑ Cortisol, catecholamines
Iatrogenic Factors
- Benzodiazepines
- Anticholinergics
- Opioids (especially meperidine)
Subtypes of ICU Delirium
|
Subtype |
Features |
Prognosis |
|
Hyperactive |
Agitation, restlessness, hallucinations |
Easily recognized |
|
Hypoactive |
Lethargy, withdrawal, ↓ responsiveness,confusion, |
Most missed, worse prognosis(increased 6-month mortality) |
|
Mixed |
Alternating features |
Most Common(50%) |
# Hypoactive delirium ≠ depression or fatigue
Risk Factors
Predisposing
- Advanced age
- Dementia, prior cognitive impairment
- Alcohol use disorder
- Sensory impairment
Precipitating(almost everything in the ICU)
- Sepsis
- Mechanical ventilation
- Benzodiazepines(There is insufficient evidence to make a recommendation on the use of benzodiazepines to treat anxiety in adult patients admitted to the ICU.PADIS-2025)
- Deep sedation
- Sleep deprivation
- Metabolic derangements
- Organ failure (hepatic, renal)
|
Mnemonic: THINK DELIRIUM |
|
T – Toxins, medications, withdrawal |
|
H – Hypoxia / Hypercapnia |
|
I – Infection |
|
N – Nutritional deficiency (thiamine, B₁₂) |
|
K – K⁺ and other electrolyte disturbances |
|
D – Dehydration / Drug adverse effects |
|
E – Endocrine disorders |
|
L – Liver or kidney failure |
|
I – Intracranial pathology (stroke, seizure, hemorrhage) |
|
R – Retention of urine / feces |
|
I – Ischemia (MI, mesenteric, limb) |
|
U – Uncontrolled pain |
|
M – Metabolic disturbances (glucose, acid-base, ammonia, lactate) |
A mnemonic bundle (DELIRIUM) was proposed (Saint Louis University Geriatrics Division and St. Louis Veterans Affairs)
- D=Drugs E=Eyes, ears, and other sensory deficits L=Low O2 states such as heart attack, stroke, and pulmonary embolism I=Infection R=Retention (of urine or stool)I=Ictal state U=Underhydraton/undernutrition M=Metabolic causes (e.g., diabetes, sodium abnormalities)
Diagnosis:
- Routine Screening is Mandatory
- Classic assessment of orientation to person, place, situation, and time may not be enough for the evaluation of delirium, as patients can be alert and oriented to all of these but still meet the criteria.
- The course of delirium can last days to months.
Diagnostic Evaluation of ICU Delirium (Targeted Investigations Based on Clinical Suspicion)
Principle: There is no routine diagnostic panel for delirium. Investigations should be guided by history, physical examination, medications, and suspected etiology rather than performed indiscriminately.
|
Suspected Cause |
Recommended Investigations |
|
Routine assessment |
CBC, renal function, LFTs, blood glucose, electrolytes, ABG/VBG (if indicated), ECG |
|
Infection / Sepsis |
CBC, CRP/Procalcitonin (if appropriate), blood cultures, urine analysis & culture, sputum culture, chest X-ray, source-specific imaging |
|
Metabolic abnormalities |
Serum glucose, Na⁺, K⁺, Ca²⁺, Mg²⁺, PO₄³⁻, bicarbonate, renal & liver function, serum ammonia, serum osmolality, lactate |
|
Drug toxicity / Withdrawal |
Medication review, serum drug levels (if available), urine toxicology screen, blood alcohol level |
|
Neurological disorders |
CT head (first-line), MRI brain (selected cases), EEG, lumbar puncture (if indicated) |
|
Vitamin deficiency |
Vitamin B₁ (thiamine), B₁₂, folate (selected patients) |
|
Endocrine disorders |
TSH, free T4, morning cortisol (if adrenal insufficiency suspected), HbA1c (if relevant) |
|
Cardiovascular causes |
ECG, troponin, echocardiography (if indicated) |
|
Urinary retention / Constipation |
Bladder scan, abdominal examination ± abdominal X-ray/CT if indicated |
|
Other targeted investigations |
Autoimmune, toxicology, heavy metal screen, HIV, syphilis, CSF studies |
Confusion Assessment Method(CAM-ICU)-Gold Standard
Diagnosis requires Feature 1 + Feature 2 + (Feature 3 or 4)
- Acute onset or fluctuating course
- Inattention
- Disorganized thinking
- Altered level of consciousness
✔ Validated in intubated & non-verbal patients
✔ Takes <2 minutes
✔ Recommended by SCCM / PADIS guidelines
Other Tools
- ICDSC (score ≥4 = delirium)
- DSM-5 (diagnostic standard, impractical in ICU)
Differential Diagnosis
|
Condition |
Key Difference |
|
Dementia |
Chronic, non-fluctuating |
|
Depression |
Attention usually intact |
|
Psychosis |
Consciousness preserved |
|
Sedation |
Improves on stopping sedatives |
|
Non-convulsive status epilepticus |
EEG required |
Management:
PREVENTION > TREATMENT(Treat reversible cause first)
Non-Pharmacological
ABCDEF Bundle
- A: Assess & manage pain
- B: Both SAT & SBT
- C: Choice of analgesia/sedation
- D: Delirium assessment & prevention
- E: Early mobilization
- F: Family engagement
Other Measures:
- Reorientation (clocks, calendars)
- Sleep promotion (lights off, noise reduction)
- Correct vision/hearing
- Hydration & nutrition
Sedation Strategy
|
Preferred |
Avoid |
|
Dexmedetomidine |
Benzodiazepines |
|
Light sedation (RASS −1 to 0) |
Deep continuous sedation |
|
Daily sedation interruption |
Unnecessary restraints |
# Benzodiazepines are an independent risk factor for delirium
#Soft restraints should be used judiciously and only after trying behavioral and pharmacological interventions
Pharmacological Treatment
Do NOT treat delirium simply because CAM-ICU is positive.Treat medications only when
- Dangerous agitation
- Self-extubation risk
- Pulling lines
- Harm to staff
- Preventing essential treatment
Antipsychotics(mixed evidence)
Haloperidol: for severe agitation threatening safety
- dopamine (D2) receptor antagonist.
- Dose- 2-10 mg (IV every six h)
# Do NOT prevent delirium
# Do NOT reduce mortality
# Monitor QTc, extrapyramidal effects
- Olanzapine (IM 5-10 mg; max: 30 mg/d,Minimal QT prolongation.)
- Risperidone (0.5-8 mg)
- Quetiapine (orally 50 mg(25 mg PO BID); max 400 mg/d)
- Ziprasidone.
Dexmedetomidine
- All over best(PADIS-SCCM 2025)
- Useful when agitation prevents extubation,Ventilator intolerance,Night-time delirium
- Preferred sedative in delirious ventilated patients
- Side effects-bradycardia and hypotension or hypertension.If a patient requires deep sedation or has a high risk of bradycardia, alternative sedative agents should be considered.
- Dose—0.2–1.5 µg/kg/hr
Melatonin
- We suggest administering melatonin over no melatonin in adult patients admitted to the ICU (conditional recommendation; for intervention; low certainty of evidence).
- Melatonin is not U.S. Food and Drug Administration (FDA)-regulated so quality may vary.
- Ramelteon, an FDA-approved melatonin receptor agonist, could be considered a melatonin alternative in countries where it is available.
Delirium in Special ICU Situations
Sepsis
- Often first sign of sepsis-associated encephalopathy
Post-operative ICU
- Elderly, major surgery → high risk
Alcohol Withdrawal
- Delirium tremens ≠ ICU delirium
- Benzodiazepines indicated only here
Prognosis & Long-Term Outcomes
- Delirium duration correlates with:
- Long-term cognitive decline
- Reduced quality of life
- Each additional delirium day → ↑ mortality risk
REFERENCE:
- Lewis K, Balas MC, Stollings JL, et al. A focused update to the clinical practice guidelines for the prevention and management of pain, anxiety, agitation/sedation, delirium, immobility, and sleep disruption in adult patients in the ICU. Crit Care Med. 2025 Mar;53(3):e711-e727.
- Isccm Icu protocols 3rd edition
- Isccm textbook of critical care 2026