Study guide
Delirium & Toxic-Metabolic Encephalopathy in the ICU
ABPN Neurocritical Care Study Guide Exam
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1 Chapter 1: Neurologic Examination & Coma Assessment in the ICU
Current Examination, Blueprint & Preparation Neurologic Examination in Critically Ill Patients Coma Evaluation & Consciousness Alterations Delirium & Toxic-Metabolic Encephalopathy in the ICU
2 Chapter 2: Cerebral Physiology & Intracranial Dynamics
Cerebral Blood Flow, Metabolism & Autoregulation Intracranial Pressure & Compliance Cerebral Edema & Herniation Syndromes
3 Chapter 3: Intracranial Hypertension & Cerebral Perfusion Management
Tiered ICP Management Protocols Hyperosmolar Therapy & Fluid Management Advanced & Refractory ICP Interventions
4 Chapter 4: Airway, Mechanical Ventilation & Pulmonary ICU Management
Emergency Airway Management & Neuro-Intubation Mechanical Ventilation Strategies in Acute Brain Injury Tracheostomy & Ventilator Weaning in Neurocritical Care Pulmonary Complications in the Neuro-ICU Obstructive Lung Disease, Pulmonary Hypertension & Bronchoscopy
5 Chapter 5: Hemodynamics, Shock & Cardiovascular Management
Hemodynamic Monitoring & Blood Pressure Targets Vasoactive Agents: Inotropes, Vasopressors & Antihypertensives Cardiac Complications of Brain Injury
6 Chapter 6: Neuropharmacology, Analgesia & Sedation
ICU Sedation & Analgesia Neuromuscular Blockade & Monitoring Propofol Infusion Syndrome & Drug Toxicities Antiseizure Drug Pharmacology in the ICU
7 Bleeding, Thrombosis & Hematologic Emergencies
Warfarin & Heparin Reversal Direct Oral Anticoagulant (DOAC) Reversal Antiplatelet Management & Platelet Dysfunction Venous Thromboembolism Prophylaxis & Management Transfusion, Coagulopathy, TMA & Cellular-Therapy Neurotoxicity
8 Chapter 8: Systemic ICU Care, Fluids, Electrolytes & Endocrine
Hyponatremia & Osmoregulation: SIADH vs Cerebral Salt Wasting Diabetes Insipidus, Hypernatremia & Endocrine Crises Critical Care Prophylaxis, Nutrition & Infection Prevention
9 Systemic Trauma & Environmental Injury
Polytrauma, Chest Injury & Abdominal Hemorrhage Burns, Electrical Injury & Hanging
10 Cardiac Emergencies & Mechanical Support
IABP, Ventricular Devices & ECMO Acute Coronary, Valvular, Rhythm & Aortic Emergencies
11 Kidney Injury, Acid–Base & Renal Replacement
Acute Kidney Injury & Renal Drug Clearance Acid–Base Disorders, Electrolytes & Renal Replacement
12 Systemic Infection & Endocrine Emergencies
Sepsis, Endocarditis & Antimicrobial Principles Thyroid, Adrenal & Dysglycemic Emergencies
13 Gastrointestinal & Hepatic Emergencies
Acute Abdomen, GI Bleeding & Abdominal Compartment Syndrome Acute Liver Failure, Cirrhosis & Hepatic Drug Effects
14 Chapter 9: Neuroimaging in the Neuro-ICU
Non-Contrast CT & CT Angiography CT Perfusion & Advanced Perfusion Imaging Magnetic Resonance Imaging in Critical Illness
15 Chapter 10: Electrophysiology & Neuromonitoring
Continuous EEG & ACNS Standardized Critical Care Terminology Invasive Neuromonitoring: ICP & External Ventricular Drains Multimodal Monitoring: PbtO2, Microdialysis & Transcranial Doppler
16 Angiography, Electrodiagnosis & CSF Analysis
Conventional Angiography & Cranial–Spinal Shunts EMG, Nerve Conduction & Acute Muscle Disease CSF Analysis: Infection, Inflammation & Hemorrhage
17 Chapter 11: Bedside Procedures, Ultrasound & Death by Neurologic Criteria
Critical Care Procedural Skills Critical Care Ultrasound & Echocardiography Determination of Death by Neurologic Criteria
18 Chapter 12: Acute Ischemic Stroke & Reperfusion Therapies
Acute Ischemic Stroke Management & Thrombolysis Endovascular Thrombectomy & Large Vessel Occlusion Malignant Hemispheric & Cerebellar Infarction
19 Chapter 13: Spontaneous Intracerebral Hemorrhage & Intraventricular Hemorrhage
Acute Intraparenchymal Hemorrhage Management Intraventricular Hemorrhage & Hydrocephalus Surgical Evacuation & Minimally Invasive Surgery in ICH
20 Chapter 14: Aneurysmal Subarachnoid Hemorrhage & Delayed Cerebral Ischemia
Aneurysmal Subarachnoid Hemorrhage: Acute Resuscitation & Securing Delayed Cerebral Ischemia & Cerebral Vasospasm Non-Aneurysmal Subarachnoid Hemorrhage & Vascular Malformations
21 Venous, Spinal & Traumatic Vascular Disease
Cerebral Venous Thrombosis & Spinal Cord Infarction Traumatic Dissection, Carotid–Cavernous Fistula & Penetrating Injury
22 Chapter 15: Traumatic Brain & Spinal Cord Injury
Severe Traumatic Brain Injury & Contusions Acute Traumatic Spinal Cord Injury & Neurogenic Shock Spine Trauma, Fractures & Cord Syndromes
23 Chapter 16: Status Epilepticus, Seizures & Neuromuscular Emergencies
Status Epilepticus: Convulsive & Non-Convulsive Refractory & Super-Refractory Status Epilepticus Acute Neuromuscular Respiratory Failure
24 Chapter 17: Post-Cardiac Arrest Care, CNS Infections & Encephalitis
Targeted Temperature Management & Post-Cardiac Arrest Care Post-Cardiac Arrest Neuroprognostication Acute CNS Infections, Encephalitis & Inflammatory Emergencies
25 Neuroinflammation & Neurooncology
Fulminant Demyelination & Autoimmune Encephalitis Brain, Spinal & Leptomeningeal Cancer Emergencies
26 Pregnancy, Transplantation & Pediatric Care
Pregnancy, Postpartum & Post-Transplant Neurologic Care Pediatric Neurocritical Care
27 Chapter 18: Neurosurgical & Perioperative Emergencies
Postoperative Neurosurgical Complications Device Complications: EVDs, Shunts & ICP Monitors Cerebral Hyperperfusion Syndrome & Post-Interventional Emergencies
28 Chapter 19: Ethics, Palliative Care & Organ Donation in the Neuro-ICU
Communication, Surrogate Decision-Making & Conflict Resolution Neuroprognostication Ethics, Withdrawal of Life Support & Palliative Care Organ Donation & Management of the Deceased Donor
Delirium & Toxic-Metabolic Encephalopathy in the ICU
Key Takeaways Explain This Topic AI
Delirium in the neuro-ICU is an independent predictor of prolonged mechanical ventilation, accelerated long-term cognitive decline, and increased 1-year mortality, with hypoactive presentations particularly easy to miss.
The Confusion Assessment Method for the ICU (CAM-ICU) requires an acute fluctuating course (Feature 1) and inattention (Feature 2), combined with either an altered level of consciousness (Feature 3) or disorganized thinking (Feature 4).
Cefepime neurotoxicity is a frequent and dangerous cause of encephalopathy, multifocal myoclonus, and non-convulsive status epilepticus in patients with renal impairment due to crossing an altered blood-brain barrier and antagonizing GABA-A receptors.
Routine administration of typical or atypical antipsychotics does not shorten delirium duration, reduce ventilator days, or improve survival; evidence-based management relies on the non-pharmacologic ABCDEF bundle and sleep-wake preservation.
Deliriogenic sedatives—particularly benzodiazepines—must be minimized in favor of targeted light sedation protocols using dexmedetomidine or propofol.
Last updated: October 2026
Delirium & Toxic-Metabolic Encephalopathy in the ICU
Delirium is an acute, fluctuating syndrome characterized by impaired attention, altered consciousness, and disorganized thinking. Occurring in up to 70–80% of ventilated ICU patients, it signifies acute cerebral organ failure. In the neuro-ICU, delirium independently predicts prolonged mechanical ventilation, increased ICU stay, long-term cognitive decline, and doubled 1-year mortality.
Pathophysiology of Delirium and Acute Brain Dysfunction
Delirium arises from intersecting neurochemical and neuroinflammatory cascades:
Cholinergic Deficiency: Depleted central acetylcholine from the nucleus basalis of Meynert degrades cortical attention, sensory gating, and cognitive processing.
Dopaminergic Excess: Elevated central dopamine drives psychomotor agitation, paranoia, delusions, and hallucinations.
GABA and Serotonergic Flux: Dysregulated inhibitory transmission and serotonin alterations disrupt sleep-wake architecture and circadian rhythms.
Neuroinflammation and Microvascular Dysfunction: Systemic cytokines (TNF-alpha, IL-1beta, IL-6) degrade blood-brain barrier ( B B B BBB BBB ) tight junctions. Microglial activation and endothelial injury induce cerebral microvascular thrombosis, astrocytic edema, and diffuse synaptic failure.
Validated Delirium Screening Tools
Clinical impression can miss delirium, especially hypoactive presentations. Use a validated tool at the institution’s specified intervals and assess competing neurologic causes.
Confusion Assessment Method for the ICU (CAM-ICU)
The CAM-ICU is the standard bedside diagnostic instrument. Patients must first be arousable: a Richmond Agitation-Sedation Scale (RASS) score of -4 or -5 indicates coma, rendering the patient unassessable.
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The CAM-ICU evaluates four sequential features:
Feature 1: Acute Onset or Fluctuating Course: Acute mental status change from baseline or fluctuating consciousness over the prior 24 hours.
Feature 2: Inattention: The clinician reads the 10-letter sequence S-A-V-E-A-H-A-A-R-T at 1-second intervals. The patient squeezes on "A". > 2 >2 > 2 errors indicates positive inattention .
Feature 3: Altered Level of Consciousness: Any current RASS score other than 0 (alert and calm) is positive (e.g., + 1 +1 + 1 to + 4 +4 + 4 , or − 1 -1 − 1 to − 3 -3 − 3 ).
Feature 4: Disorganized Thinking: Evaluated using four simple logic questions (e.g., "Will a stone float on water?") and a two-step command. > 1 >1 > 1 error indicates positive disorganized thinking .
Important
Delirium is confirmed when a patient demonstrates [Feature 1 AND Feature 2] AND [EITHER Feature 3 OR Feature 4] .
Intensive Care Delirium Screening Checklist (ICDSC)
The ICDSC is an 8-item observational checklist scored over an 8-to-24-hour nursing shift (assessing consciousness, inattention, disorientation, hallucinations, psychomotor activity, speech/mood, sleep disturbance, and symptom fluctuation). A score of ≥ 4 \ge 4 ≥ 4 confirms delirium; 1 to 3 indicates subsyndromal delirium.
Delirium Motor Subtypes and Prognosis
Motor Subtype Clinical Features Frequency Prognosis & Significance
Hypoactive Apathy, psychomotor slowing, lethargy, decreased responsiveness 60–70% (Most common) Frequently missed; is often missed and is associated with adverse outcomes
Hyperactive Agitation, combativeness, line pulling, emotional lability 5–10% (Least common) Immediately identified; lower mortality, but high accidental extubation risk
Mixed Fluctuations between hypoactive apathy and hyperactive agitation 25–35% Unpredictable course; requires frequent re-evaluation
Common Toxic-Metabolic Encephalopathies
Sepsis-Associated Encephalopathy (SAE): Acute cerebral dysfunction resulting from circulating inflammatory cytokines and microvascular hypoperfusion without CNS infection. Presents with delirium and EEG slowing (generalized theta/delta rhythms or triphasic waves).
Hepatic Encephalopathy (HE): Hyperammonemia impairs astrocytic metabolism. Astrocytic glutamine synthetase converts ammonia into glutamine, drawing fluid osmotically to cause cytotoxic edema. Presents with asterixis, fetor hepaticus, and triphasic waves on EEG. Treated with lactulose (acidifying the colon to trap N H 4 + NH_4^+ N H 4 + ) and rifaximin.
Uremic Encephalopathy: Accumulation of guanidino compounds and nitrogenous waste produces encephalopathy with prominent multifocal myoclonus, asterixis, and seizures. Rapidly improves with hemodialysis.
Electrolyte Derangements: Severe hyponatremia causes cerebral edema; rapid overcorrection ( > 8 mEq/L >8\text{ mEq/L} > 8 mEq/L in 24 hours) risks fatal Osmotic Demyelination Syndrome (ODS) (central pontine myelinolysis), causing delayed pseudobulbar palsy, quadriplegia, and locked-in state.
Critical Care Antimicrobial and Sedative Neurotoxicities
Warning
Cefepime Neurotoxicity: In renal failure without aggressive dose adjustment, cefepime accumulates and competitively antagonizes G A B A A GABA_A G A B A A receptors. Patients develop encephalopathy, multifocal myoclonus, asterixis, and non-convulsive status epilepticus within 2 to 5 days, accompanied by generalized periodic discharges (GPDs) or triphasic waves. Management requires immediate drug cessation, dose reduction, hemodialysis, and supportive antiseizure therapy.
Fluoroquinolones (Ciprofloxacin, Levofloxacin): Inhibit G A B A A GABA_A G A B A A receptors and stimulate NMDA receptors, triggering agitation, hallucinations, and lowering seizure thresholds.
Benzodiazepines: Potent independent deliriogens. Continuous infusions of midazolam or lorazepam significantly increase delirium incidence and must be minimized.
Evidence-Based Management: The ABCDEF Bundle
The multicomponent ABCDEF Bundle represents the evidence-based standard:
A — Assess, Prevent, and Manage Pain: Proactively treat pain with validated behavioral scales (CPOT/BPS) before sedating (analgesia-first approach).
B — Both SAT and SBT: Coordinate daily paired Spontaneous Awakening and Breathing Trials to reduce sedative accumulation and ventilator days.
C — Choice of Sedation: Target light sedation ( R A S S 0 to − 1 RASS\ 0\text{ to } -1 R A SS 0 to − 1 ). Avoid benzodiazepines; use dexmedetomidine (selective α 2 \alpha_2 α 2 -agonist providing non-REM-like cooperable sedation without respiratory depression) or propofol.
D — Delirium: Assess, Prevent, and Manage: Screen routinely using CAM-ICU or ICDSC; aggressively reverse systemic triggers.
E — Early Mobility and Exercise: Protocolized physical and occupational therapy supports recovery and may reduce delirium burden; effects vary by study and patient.
F — Family Engagement: Facilitate family presence, reorientation, and familiar sensory cues.
Environmental Optimization and Sleep Hygiene
Preserve circadian rhythm through daytime natural light exposure, nighttime noise reduction ( < 45 dB <45\text{ dB} < 45 dB ), clustering nocturnal care, and returning sensory aids (glasses, hearing aids) promptly.
Pharmacologic Management: The MIND-USA Trial
Note
The multicenter MIND-USA trial showed that neither haloperidol nor ziprasidone reduces delirium duration, mechanical ventilation time, ICU stay, or mortality compared to placebo. Routine antipsychotic prophylaxis is not recommended.
Antipsychotics (haloperidol, olanzapine, quetiapine) are reserved strictly for acute, dangerous agitation threatening patient safety after non-pharmacologic measures fail. Before administration, clinicians must verify baseline Q T c < 500 ms QTc < 500\text{ ms} QT c < 500 ms on 12-lead ECG, monitor for torsades de pointes, and watch for neuroleptic malignant syndrome.