Comparing and Contrasting Delirium and Acute Encephalopathy

Last week I wrote about querying for the type of acute encephalopathy, and I’d like to continue this week. Please know, when I use the term “acute encephalopathy” in this article, it can include either metabolic or toxic encephalopathy, which are the most specific types of acute encephalopathy available within the applicable code set.

Additionally, I am not endorsing a definition of acute encephalopathy; instead, my goal is to offer direction on how to approach appeals if acute encephalopathy is challenged as a clinically valid diagnosis.

A lack of a standard definition for acute encephalopathy and variability in how it presents makes it extremely vulnerable to clinical validation denials. Dorland’s Medical Dictionary includes the following definitions:

• Encephalopathy is any degenerative disease of the brain.
• Hypoxic encephalopathy is “caused by hypoxia from either decreased rate of blood flow or decreased oxygen content of arterial blood; symptoms in mild cases include intellectual, visual, and motor disturbances.“
• Metabolic encephalopathy is a “neuropsychiatric disturbances due to metabolic brain disease; it may be primary resulting from conditions such as hypoxia or ischemia that affect the brain directly or it may be secondary to diseases of other organs.” 
• Septic-associated encephalopathy is “altered brain function owing to the presence of infectious agents in the blood, along with effects of accompanying fever; symptoms vary from mild to severe and may include confusion, myopathy with rigidity, and more serious conditions such as seizures and coma.”

Notably, Dorland does not have a definition for toxic encephalopathy.

The American Hospital Association (AHA) Coding Handbook defines encephalopathy as “a general term used to describe any disorder of cerebral function.” It also notes there are “more than 150 different terms” associated with encephalopathy in the medical literature, many of which cannot be captured within the ICD-10-CM code set. It includes definitions for metabolic and toxic encephalopathy as follows:

• Metabolic encephalopathy is “damage to the brain due to lack of glucose, oxygen, or other metabolic agents, or caused by organ dysfunction. Symptoms include an altered state of consciousness, usually characterized as delirium, confusion, or agitation, and changes in behavior or personality.”
• Toxic encephalopathy is “caused by exposure to toxic substances or as an adverse effect of medication. It is characterized by an altered mental status, and symptoms can include memory loss, small personality changes, lack of concentration, involuntary movements, nausea, fatigue, seizures, arm strength problems, and depression.”

With definitions that are mostly dependent on subjective data, what are we to do, as clinical documentation integrity (CDI) professionals? To me, the most important feature of acute encephalopathy is acute change in mental status, with a return to baseline by discharge. This standard can be used in a patient with or without dementia, which is a discussion for another time.

Another key concept is “transient,” which is often used when defining encephalopathy, because it is usually reversible. Using an artificial intelligence (AI) tool, I could not find any reference that symptoms must persist for a particular amount of time to clinically validate a diagnosis of acute encephalopathy. Sometimes, like in the case of low glucose or low oxygen, recovery can occur quickly. In contrast, when acute encephalopathy is related to an infection or toxin, it may take longer for the body to recover and mental status to return to baseline. A quick return to baseline, following treatment of the underlying condition, does not exclude a diagnosis of acute encephalopathy if it meets criteria for reporting.

Why do we query for acute encephalopathy? Documentation of altered mental status (AMS) requires clarification because it maps to R41.82, a symptom code. All too often, patients present to the emergency department for AMS. The problem is determining the appropriate associated diagnosis or diagnoses that represent the clinical scenario (and should, thereby, be offered as query response choices).

Most queries for clarification of AMS include the choices of metabolic encephalopathy, toxic encephalopathy, or delirium. I purposely did not include “encephalopathy” because it is a less specific diagnosis, as noted in my last article. It is also unlikely that both metabolic and toxic encephalopathy need to be offered as choices, unless the patient is experiencing kidney or liver failure, in which case either could be appropriate, depending on the provider’s perspective. Remember that the Guidelines for Achieving a Compliant Query Practice (2022 Update) state:

“Multiple choice query formats should include clinically significant and reasonable option(s) as supported by clinical indicator(s) in the health record, recognizing that occasionally there may be only one reasonable option. . . There is no mandatory or minimum number of choices necessary to constitute a compliant multiple-choice query (p. 9).

Should delirium always be included as an option when querying for acute encephalopathy? Both acute encephalopathy and delirium can have similar presentations.

Dorland’s Medical Dictionary defines delirium as “an acute, transient disturbance of consciousness accompanied by a change in cognition and having a fluctuating course.” It is characterized by a reduced ability to maintain attention to external stimuli and disorganized thinking, as manifested by rambling, irrelevant, or incoherent speech; there may also be a reduced level of consciousness, sensory misperceptions, disturbance of the sleep-wake cycle and level of psychomotor activity, disorientation to time, place, or person; and memory impairment.

Like acute encephalopathy, delirium can be caused by conditions that result in derangement of cerebral metabolism, including systemic infection, poisoning, drug intoxication or withdrawal, seizures or head trauma, and metabolic disturbances.

The primary difference between acute encephalopathy and delirium is that symptoms associated with delirium fluctuate. The DSM-5-TR (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision) notes that the course of delirium often fluctuates and is more pronounced later in the day and at night, when there are fewer external orienting stimuli. In contrast, encephalopathic patients typically do not exhibit this fluctuation.

Additionally, acute encephalopathy is unlikely to be responsive to antipsychotic medications that are often used to treat delirium.

What can be problematic is that delirium is often an indicator of acute encephalopathy. Even worse, many providers use the terms delirium and acute encephalopathy interchangeably. A recent article on ICU Delirium (Mohammed, A. and Cascella, M. (March 2024), equates delirium with “acute confusional state, “toxic or metabolic encephalopathy,” or “acute brain failure.” Another important feature of delirium, which is also true for acute encephalopathy, is that these are diagnoses of exclusion.

Although delirium and acute encephalopathy may be clinically similar, they are not equal in terms of the code set – and therefore, do not equally represent the clinical scenario or patient acuity. Delirium without further specificity maps to R41.0, disorientation, unspecified, with an inclusion term of confusion. Why replace one symptom code, R41.82 altered mental status, with another one if there is evidence of a definitive diagnosis?

Additionally, the terms acute and subacute are nonessential modifiers, meaning the code set does not have a different code for “acute delirium;” it will also be reported as R41.0, disorientation, unspecified.

To report a diagnosis code, delirium must be associated with alcohol or other substances or a known psychological condition. Unlike metabolic encephalopathy, as discussed last week, use of F05, delirium due to known physiological condition includes a code-first note, because it is part of an etiology/manifestation pair, so the etiology must be reported. Additionally, F codes are assigned to mental, behavioral, and neurodevelopmental disorders.

Some may be hesitant to query if delirium is documented because they don’t want to lead the provider, since a response of acute metabolic or toxic encephalopathy will add a major complication/comorbidity (MCC) to the claim. If there are clinical indicators that support acute encephalopathy as a reportable diagnosis, it is not leading to query for additional clarification. It is also possible for a patient to have both delirium or delirium due to a known psychological condition and acute encephalopathy. There are no Excludes 1 notes (don’t code together) associated with codes that represent either of these conditions. Next week, I’ll continue my series on acute encephalopathy by discussing why it’s not necessary and it could be problematic to include coma scores as clinical indicators of acute encephalopathy.