ASA physical status classification

Assessment

A six-level scale that describes how ill a patient is before an anaesthetic, from healthy (I) to brain-dead organ donor (VI).

Updated Nov 13, 2026

What it is

The ASA physical status classification, from the American Society of Anesthesiologists, is a simple scale that describes the patient's overall health before an anaesthetic. It has six classes: ASA I, a normal healthy patient; ASA II, mild systemic disease without functional limitation; ASA III, severe systemic disease that limits activity; ASA IV, severe systemic disease that is a constant threat to life; ASA V, a moribund patient not expected to survive without the operation; and ASA VI, a brain-dead patient whose organs are being removed for donation. The letter «E» is added when the operation is an emergency, meaning a delay would increase the threat to life or a body part. The class describes the patient, not the operation, so it does not by itself predict the risk of a given procedure; it is combined with the surgical risk, the airway and specific scores. It is quick, widely understood and correlates with complications and mortality, but different clinicians often assign different classes to the same patient, so the society publishes examples for each class.

What to assess

Overall health of the patient before anaesthesia, not the size of the operation.
How well each disease is controlled and whether it limits daily activity.
Whether a disease is a constant threat to life (recent myocardial infarction or stroke, ongoing ischaemia, sepsis, severe valve disease).
Whether the operation is an emergency, which adds «E».
Smoking, alcohol, pregnancy and body mass index, which move a healthy person into ASA II or higher.

How it is done (and why)

List the patient's diseases and how each one is controlled — control, not the diagnosis alone, decides the class.
Ask how each condition limits daily activity — functional limitation separates mild (II) from severe (III) disease.
Look for conditions that threaten life right now — recent ischaemia, sepsis or decompensated organ failure define ASA IV.
Use the society's published examples when in doubt — they reduce disagreement between clinicians.
Add «E» if delay would increase the threat to life or a body part — emergency surgery carries extra risk at any class.
Combine the class with surgical risk and specific scores — ASA alone does not predict the risk of a particular operation.

ASA physical status classes, with typical adult examples

Class	Definition	Examples
ASA I	Normal healthy patient	Healthy non-smoker, little or no alcohol
ASA II	Mild systemic disease, no functional limitation	Current smoker, social drinker, pregnancy, obesity, well-controlled diabetes or hypertension, mild lung disease
ASA III	Severe systemic disease with functional limitation	Poorly controlled diabetes or hypertension, COPD, morbid obesity, dialysis, myocardial infarction or stroke more than three months ago, pacemaker
ASA IV	Severe systemic disease that is a constant threat to life	Myocardial infarction or stroke within three months, ongoing cardiac ischaemia, severe valve dysfunction, sepsis, severely reduced ejection fraction
ASA V	Moribund, not expected to survive without the operation	Ruptured abdominal aortic aneurysm, massive trauma, intracranial bleed with mass effect
ASA VI	Declared brain-dead, organs removed for donation	Organ donor

Findings that change the plan

ASA III or higher: plan closer monitoring, consider invasive monitoring and a higher postoperative care level.
ASA IV: weigh benefit against risk with the surgeon and the patient, and plan intensive care beforehand.
ASA V: surgery is usually the only chance of survival; involve the most senior team and discuss goals of care.
Many day-case and office procedures accept only ASA I–II, or stable ASA III, patients.

Next step

Record the ASA class with the reason (the disease that sets it) in the pre-anaesthetic note.
Discuss ASA IV and V patients with a senior anaesthetist and the surgeon before starting.
For ASA III or higher, confirm the postoperative bed (ward, high dependency or intensive care) before the day of surgery.
Reassess the class if the patient's condition changes between the visit and the operation.

Test yourself

Think of the answer, then tap the question to see it.

What is the difference between ASA II and ASA III?

ASA II is mild systemic disease without functional limitation; ASA III is severe systemic disease that limits activity, such as poorly controlled diabetes or COPD.

What does the suffix «E» mean in the ASA classification?

The operation is an emergency: delaying it would increase the threat to life or to a body part.

Why is the ASA class not a complete surgical risk score?

It describes only the patient's overall health; it ignores the size and type of operation, the airway and specific risks, so it is combined with other tools.

Which ASA class is a patient with a myocardial infarction two months ago?

ASA IV: a recent myocardial infarction (within about three months) is severe systemic disease that is a constant threat to life.

Add to my cards (4)

Elsewhere in DurgiPedia

Preoperative care: assessment, teaching, fasting, skin preparation and the checklist

Connections

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: American Society of Anesthesiologists Physical Status Classification System (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.