Encephalopathy and Delirium — Clinical Documentation Guide (2026)

🔍 Definition

Encephalopathy is a broad term for any diffuse brain dysfunction characterized by altered mental status, cognitive impairment, or changes in consciousness — caused by an underlying systemic, metabolic, toxic, or structural disorder. The term encompasses a spectrum from mild confusion to deep coma, and its etiology determines both the correct ICD-10-CM code and the clinical management approach.

Delirium (ICD-10-CM F05) is a specific neuropsychiatric syndrome characterized by an acute onset of fluctuating disturbance in attention, awareness, and cognition — not attributable to a pre-existing or evolving neurocognitive disorder, and not explained by a severely reduced level of arousal. Delirium is acute, reversible in most cases, and multifactorial, but a single etiology (e.g., medications, infection, metabolic derangement) often predominates.

For clinical documentation and coding purposes, the distinction between encephalopathy subtypes is critical: CMS ICD-10-CM FY2026 assigns different codes — and different MS-DRG weight impacts — depending on whether the condition is metabolic, toxic, anoxic, hepatic, uremic, hypertensive, or substance-induced. A non-specific “altered mental status” (R41.0) carries no CC/MCC, while documented metabolic encephalopathy (G93.41) triggers MCC status in most DRGs.

🗂️ Alternative Terminology

The following table maps commonly used clinical terms to their formal ICD-10-CM equivalents. Coders and CDI specialists should recognize all variants in physician documentation and query accordingly.

🩺 Signs & Symptoms

Recognizing the clinical presentation is essential for CDI specialists to identify query opportunities before physician attestation is secured. The following manifestations, when documented without an underlying confirmed diagnosis, represent prime query triggers.

🧭 Differential Diagnosis

A rigorous differential is the foundation of accurate documentation. The CDI specialist’s role is to ensure the physician has documented to the appropriate level of specificity — not just “encephalopathy” but the etiological subtype, and not just “delirium” but whether it is due to a medical condition, substance use, or withdrawal.

📋 Clinical Indicators for Coders/CDI

The following clinical indicators, when present in the medical record, represent documentation gaps or query opportunities. CDI specialists should review these indicators during concurrent or retrospective review.

🦴 Anatomy & Pathophysiology

Understanding the underlying pathophysiology of encephalopathy and delirium enables CDI specialists to recognize when clinical findings are consistent with physician documentation — and when a query is warranted.

Normal Brain Function: The cerebral cortex and reticular activating system (RAS) maintain arousal, attention, and cognition through neurotransmitter balance (acetylcholine, dopamine, GABA, glutamate). The blood-brain barrier (BBB) protects neural tissue from systemic toxins.

Metabolic Encephalopathy Mechanism: Systemic metabolic derangements — elevated ammonia, uremic toxins, hyperglycemia/hypoglycemia, hypoxia, hypercapnia, electrolyte disturbances — penetrate or disrupt the BBB, impairing neuronal energy metabolism and neurotransmitter synthesis. Acetylcholine deficiency is a common final pathway, consistent with the inattention and cognitive impairment of delirium. Per UpToDate, the cholinergic hypothesis is supported by the propensity of anticholinergic medications to precipitate delirium.

Hepatic Encephalopathy: In liver failure, ammonia — normally metabolized by the urea cycle — accumulates in the systemic circulation. Ammonia crosses the BBB and is converted to glutamine in astrocytes, causing astrocyte swelling (osmotic effect) and neuronal excitotoxicity. Inflammatory cytokines from gut-derived infection synergize with ammonia to worsen encephalopathy. The American Association for the Study of Liver Diseases (AASLD) staging (West Haven criteria: Grade 0–IV) correlates with K72.xx coding acuity.

Toxic Encephalopathy: Exogenous neurotoxins — medications (opioids, benzodiazepines, anticholinergics, immunosuppressants), industrial chemicals, heavy metals — directly impair neuronal function. Polypharmacy is a major risk factor, particularly in elderly patients. The mechanism varies: receptor blockade, ion channel disruption, mitochondrial dysfunction, or direct cytotoxicity.

Anoxic Brain Damage (G93.1): Global cerebral ischemia (cardiac arrest, asphyxia) depletes neuronal ATP within 4–6 minutes, triggering glutamate-mediated excitotoxicity, calcium influx, and apoptotic cascades. Neurological injury severity correlates with duration of anoxia and is assessed by Cerebral Performance Category (CPC) scale and EEG pattern.

Wernicke’s Encephalopathy (E51.2): Thiamine (vitamin B1) deficiency impairs the pyruvate dehydrogenase complex and transketolase enzymes, disrupting glucose metabolism in the thalamus, mammillary bodies, and brainstem. NINDS notes that without prompt thiamine replacement, the acute Wernicke’s phase can progress to permanent Korsakoff amnestic syndrome.

💊 Medication Impact / Treatment

Medications play a dual role in encephalopathy and delirium: they are among the most common precipitants, and they are also the cornerstone of targeted treatment. Documentation of medication-related causality is critical for both accurate coding and CDI query development.

Medications That Precipitate or Worsen Encephalopathy/Delirium:

• Benzodiazepines: GABA-A agonists — impair attention and arousal; paradoxical agitation in elderly; withdrawal delirium on abrupt cessation. Associated with G92.x (toxic encephalopathy) when causative.
• Opioids: CNS depression, respiratory acidosis/hypercapnia, constipation (↑ ammonia). Naloxone-reversible. Opioid-induced encephalopathy → G92.x with T40.x poisoning code.
• Anticholinergics: (diphenhydramine, tricyclics, bladder agents, antiemetics) — block central acetylcholine, worsening the cholinergic deficit in delirium. High Anticholinergic Burden (ACB) score correlates with delirium risk.
• Antiepileptics: Valproate, levetiracetam, phenytoin — can cause drug-induced encephalopathy, especially at supratherapeutic levels.
• Steroids: Steroid-induced psychosis/delirium — document as “steroid-induced delirium” → F05 with appropriate T-code for adverse effect.
• Immunosuppressants/Chemotherapy: Tacrolimus, cyclosporine, methotrexate, ifosfamide → toxic encephalopathy (G92.x); distinguish from disease-related CNS involvement.
• Antibiotics: Cefepime (cefepime-induced neurotoxicity), fluoroquinolones, metronidazole — documented toxic encephalopathy → G92.x.

Therapeutic Agents (Treatment-Focused):

• Thiamine (Vitamin B1 / J3411): First-line and emergent for Wernicke’s encephalopathy. High-dose IV thiamine (500 mg TID IV) per European Federation of Neurological Societies (EFNS) guidelines. HCPCS J3411 (thiamine HCl injection) — critical for Wernicke’s documentation and coding.
• Lactulose: Reduces intestinal ammonia absorption — mainstay of hepatic encephalopathy management (K72.xx). Available Part D; oral/enema formulations. Titrate to 2–3 soft stools/day.
• Rifaximin: Antibiotic reducing gut ammonia-producing bacteria; used as adjunct/secondary prophylaxis in hepatic encephalopathy.
• Haloperidol: Low-dose IV/IM for acute agitation in delirium (evidence-based per SCCM PADIS Guidelines); Part D. Use with caution in alcohol withdrawal (not appropriate monotherapy for DTs).
• Quetiapine / Olanzapine: Second-generation antipsychotics for hyperactive delirium; Part D. Quetiapine commonly used in ICU delirium protocols.
• Dexmedetomidine (Precedex): Alpha-2 agonist; preferred sedation in mechanically ventilated patients to reduce delirium duration per SCCM PADIS Guidelines.
• Midazolam (J2250): Benzodiazepine indicated specifically for alcohol withdrawal delirium/DTs (F10.231); monitor for respiratory depression; not first-line for non-withdrawal delirium.
• IV Acetaminophen (J0131): Non-opioid analgesic alternative to reduce delirium-precipitating opioid burden in postoperative patients.

Preview ends here. The full guide continues with FY2026 ICD-10-CM code sets, CPT surgical coding, MS-DRG mapping, reimbursement guidance, CDI query templates, and an audit checklist — all available to CCO Members.

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📘 ICD-10-CM Guidelines (FY2026)

The following official coding guidelines from CMS ICD-10-CM FY2026 and NCHS apply to encephalopathy and delirium coding. Adherence is required for compliant coding.

General Coding Principle — Etiology/Manifestation: When encephalopathy is a manifestation of an underlying condition, ICD-10-CM requires sequencing per the etiology/manifestation convention. The underlying condition is sequenced first (e.g., sepsis A41.x, hepatic failure K72.xx, uremia N18.x) with the manifestation coded as additional (e.g., G93.41), unless the tabular includes the manifestation in the code definition (as with K72.xx which includes hepatic encephalopathy).

Septic Encephalopathy — AHA Coding Clinic Q1 2017: Per AHA Coding Clinic, First Quarter 2017, when a patient has documented sepsis and the physician documents septic encephalopathy (or metabolic encephalopathy due to sepsis), code both the sepsis (A41.xx or other sepsis code) AND G93.41 as an additional diagnosis. The sepsis code is sequenced as the principal or first-listed diagnosis per sepsis guidelines (Section I.C.1.d); G93.41 is an additional diagnosis. Do NOT use R41.0 when the physician explicitly documents encephalopathy as the manifestation.

Hepatic Encephalopathy — Do Not Double-Code: ICD-10-CM codes K72.00 (acute/subacute hepatic failure without coma), K72.01 (with coma), K72.10 (chronic without coma), K72.11 (chronic with coma), K72.90 (unspecified without coma), and K72.91 (with coma) include hepatic encephalopathy in their tabular inclusion terms. Per NCHS ICD-10-CM Official Guidelines, do NOT assign a separate G93.4x code when K72.xx is already captured. The “with coma” subtype (K72.01, K72.11, K72.91) should be used when the patient meets criteria for hepatic coma (Grade III–IV West Haven).

Toxic Encephalopathy — Adverse Effect vs. Poisoning: G92.x (toxic encephalopathy) requires an additional code to identify the causative substance. If the encephalopathy results from correct administration at proper dosage (adverse effect), use the appropriate T-code adverse effect qualifier (e.g., T36–T50 with 7th character 5). If from overdose or incorrect administration, use the poisoning codes (7th character 1–4). Per ICD-10-CM Official Guidelines Section I.C.19.e, the adverse effect code is sequenced after the condition it caused.

Delirium Coding — F05 vs. Substance-Induced Delirium: F05 (Delirium due to known physiological condition) is used when delirium results from a general medical condition (metabolic, infectious, neurological) that is NOT substance intoxication or withdrawal. When delirium is substance-induced, use the specific substance use/intoxication codes in categories F10–F19 with the appropriate .x21 (intoxication with delirium) or .x31 (withdrawal with delirium) 4th/5th character extension. F10.231 (Alcohol withdrawal with delirium = delirium tremens) is an MCC.

Acute vs. Chronic Distinction: Document and code the acuity explicitly. Acute metabolic encephalopathy in an ICU patient differs fundamentally from chronic alcoholic brain degeneration (G31.2). Chronic dementia (F03.x) is not encephalopathy. Co-occurring delirium superimposed on dementia requires both a dementia code (F0x.x) and F05 as additional diagnosis per CMS coding guidance.

Uremic Encephalopathy: There is no single ICD-10-CM code for “uremic encephalopathy.” Code the underlying CKD stage (N18.1–N18.6) and, if the physician documents encephalopathy as a manifestation of uremia, also code G93.41 (metabolic encephalopathy) as an additional diagnosis — confirmed by attending physician documentation. R41.0 (altered mental status) is not used when encephalopathy is confirmed.

Anoxic Brain Damage (G93.1): G93.1 is assigned for hypoxic-ischemic encephalopathy following cardiac arrest, near-drowning, or prolonged hypoxemia. It is distinct from hypoxic respiratory failure and from neonatal HIE (P91.60–P91.63). The underlying cause (cardiac arrest, asphyxia) is coded separately. G93.1 is an MCC in most DRGs.

Wernicke’s Encephalopathy (E51.2): E51.2 is under category E51 (Thiamine deficiency). The underlying cause — alcohol use disorder, malnutrition, hyperemesis — should also be coded. If alcohol use disorder is present, code it (F10.xx) as an additional diagnosis. Note: E51.11 (Dry beriberi) and E51.12 (Wet beriberi) are distinct from E51.2 and reflect peripheral nerve vs. cardiovascular manifestations of thiamine deficiency, not encephalopathy.

🔢 ICD-10-CM Code Set (FY2026)

All codes verified for FY2026 per CMS ICD-10-CM FY2026 Tabular List.

🔎 Indexing

The ICD-10-CM Alphabetical Index provides the following pathways for encephalopathy and delirium. Coders should verify all index lookups against the FY2026 Tabular List for accuracy. Per NCHS ICD-10-CM Index:

🏥 CPT (2026)

The following CPT codes apply to evaluation, management, diagnostic workup, and procedures in encephalopathy and delirium. All codes verified for CY2026 per AMA CPT 2026.

🧾 HCPCS (2026)

The following HCPCS Level II codes are relevant to drug administration, monitoring, and supplies in encephalopathy and delirium management. All codes verified for CY2026 per CMS HCPCS 2026.

📚 AHA Coding Clinic (Recent Guidance)

The following AHA Coding Clinic advisories are directly applicable to encephalopathy and delirium coding. Coders and CDI specialists should maintain awareness of these official guidance updates.

💰 HCC / Risk Adjustment (v28)

The following HCC mappings reflect CMS HCC Model v28 (2024 implementation, applicable to 2026 payment year). HCC v28 represents a significant restructuring from v24, with new HCC hierarchies and updated RAF weights.

✍️ CDI Query Templates

The following compliant CDI query templates are designed per AHIMA Practice Brief: Guidance for Clinical Documentation Integrity Queries (2019) and ACDIS CDI best practices. All queries are non-leading, multiple-choice, and present clinically supported options without directing the provider to a specific coding-favorable answer.

🧑‍⚕️ Treatments (Clinical)

Clinical treatment of encephalopathy and delirium is etiology-directed. The following represents evidence-based management principles per major clinical societies.

Universal Principles — Non-Pharmacological (First Line for Delirium): Per SCCM PADIS 2018 Guidelines and American College of Physicians, non-pharmacological multicomponent interventions are the most evidence-supported strategy for delirium prevention and treatment: early mobilization, reorientation (lighting, clocks, familiar objects), hearing and vision aids, sleep optimization, family engagement, hydration, early removal of indwelling catheters/restraints, and pain management.

Metabolic Encephalopathy (G93.41) — Treat the Underlying Cause:

• Septic encephalopathy: IV broad-spectrum antibiotics, source control, resuscitation per Surviving Sepsis Campaign Guidelines
• Uremic encephalopathy: Urgent dialysis (hemodialysis or CRRT); dietary protein restriction; thiamine supplementation
• Hypoglycemic encephalopathy: IV dextrose (D50W bolus) — emergent; document resolution after treatment
• Hypercapnic encephalopathy: Bronchodilators, NIV/BiPAP, high-flow O2 cautiously in COPD; intubation if refractory
• Electrolyte-related encephalopathy: Careful sodium correction (hyponatremia — ≤8 mEq/L/24h to prevent osmotic demyelination), calcium normalization, magnesium repletion

Hepatic Encephalopathy (K72.xx): Per AASLD 2022 Practice Guidance: lactulose (first-line; titrate to 2–3 loose stools/day), rifaximin (secondary prophylaxis), dietary protein adjustment (do NOT restrict — 1.2–1.5 g/kg/day), zinc supplementation, treat precipitants (GI bleed, infection, dehydration, constipation). Liver transplantation evaluation for refractory cases.

Toxic Encephalopathy (G92.8) — Remove/Reverse the Toxin: Discontinue offending medication; supportive care; specific antidotes when available (naloxone for opioids, flumazenil caution in benzodiazepines, physostigmine for anticholinergic toxidrome in select cases). Activated charcoal if acute ingestion within 1–2 hours and airway protected.

Alcohol Withdrawal Delirium/DTs (F10.231): Symptom-triggered benzodiazepine protocol per CIWA-Ar score; IV lorazepam or diazepam preferred; IV thiamine before any dextrose-containing fluids; electrolyte repletion (magnesium, potassium, phosphate); seizure precautions; ICU monitoring for autonomic instability. Per NIAAA, mortality of untreated DTs is 5–15%; with appropriate treatment, <1%.

Wernicke’s Encephalopathy (E51.2): High-dose IV thiamine — 500 mg TID IV for 2–3 days (EFNS guidelines), then 250 mg/day for 5 days before transition to oral. Give BEFORE any glucose-containing solutions. MRI brain (DWI/FLAIR) for confirmation. Address malnutrition and alcohol use disorder concurrently.

Anoxic/HIE (G93.1, G93.42): Targeted Temperature Management (TTM) at 33–36°C for 24 hours in comatose post-cardiac arrest patients per AHA/ILCOR 2023 Guidelines; prognostication multimodality assessment (EEG, SSEP, NSE, brain MRI) at 72+ hours; neuroprotective supportive care; rehabilitation referral for survivors.

Hypertensive Encephalopathy (I67.4): Emergent, controlled BP reduction — target 10–20% reduction in first hour using IV agents (labetalol, nicardipine, clevidipine); avoid rapid normalization; nitroprusside if needed but monitor cyanide toxicity. Per AHA Hypertension Guidelines, radiographic resolution of PRES expected with BP control.

🎓 Patient Education / Summary

The following patient-facing education points are intended for use by CDI specialists when counseling clinical teams on documentation that supports safe care transitions, and for discharge planning documentation that supports accurate coding and readmission risk reduction.

For Patients and Families — Key Messages:

• What it is: Encephalopathy means the brain is not working normally because of a problem elsewhere in the body — such as an infection, liver disease, kidney failure, medication reaction, or low oxygen. It is usually reversible when the underlying cause is treated.
• Delirium explained: Delirium is a sudden confusion that comes and goes — different from everyday forgetfulness. Signs include not knowing where you are, seeing things that aren’t there, or being very restless or unusually sleepy. It is common in hospitals, especially in older adults and ICU patients.
• Recovery: Most encephalopathy and delirium resolves over days to weeks once the cause is treated. Some patients have prolonged cognitive recovery. Older adults may take months to return to baseline. Follow up with your primary care provider for cognitive reassessment.
• Preventing recurrence: Avoid medications that increase delirium risk (anticholinergics, sleep aids, opioids when alternatives exist). Maintain regular sleep schedule. Stay mentally and physically active. Manage chronic conditions (liver disease, kidney disease, diabetes, hypertension) proactively.
• Alcohol use disorder: If alcohol withdrawal delirium (DTs) was part of the hospital course, this represents a serious and life-threatening complication of alcohol dependence. Referral to addiction medicine and treatment programs is strongly recommended. Resources: SAMHSA National Helpline 1-800-662-4357.
• Liver disease: If hepatic encephalopathy was the cause, strict medication adherence (lactulose, rifaximin), low-sodium diet, alcohol abstinence, and regular liver specialist follow-up are essential to prevent recurrence. Know the warning signs: increasing confusion, jaundice, abdominal swelling.
• For caregivers: Hospital delirium increases falls, aspiration risk, and functional decline. Caregiver reorientation, familiar objects, and maintaining normal daily rhythms during hospitalization reduce delirium duration. Advocate for early mobility and removal of unnecessary tubes/restraints.

Documentation Note for Clinical Teams: Accurate discharge documentation of encephalopathy type and etiology is essential not only for coding and reimbursement, but for care continuity. Post-acute facilities, home health agencies, and outpatient providers rely on the discharge diagnosis to plan appropriate follow-up, medication reconciliation, and monitoring intensity. A discharge summary that reads “metabolic encephalopathy due to sepsis, resolved” communicates far more clinical utility — and supports appropriate quality metrics — than “altered mental status, improved.”

About this Guide

This Clinical Documentation Guide is published by CCO Academy and is intended for credentialed coding, CDI, and clinical documentation professionals. Content is updated for FY2026 ICD-10-CM (effective October 1, 2025). All code assignments should be verified against the official ICD-10-CM Tabular List, AHA Coding Clinic, and applicable payer-specific policies. This guide does not constitute legal, medical, or compliance advice.

Last reviewed: April 2026 · Next scheduled review: October 2026 (FY2027 update)