Surgery

ASA Physical Status Classification Calculator

ASA Physical Status Classification system for perioperative risk assessment

Primary source: American Society of Anesthesiologists Physical Status Classification

Aleksandr A. Aulov, MD, internal medicine Last clinical review: April 28, 2026

Online calculation

ASA class

About this score

The ASA scale (American Society of Anesthesiologists Physical Status Classification) is a standard assessment of a patient's physical status before anesthesia and surgery. It has been in use since 1941, with the latest revision in 2020.

Classes: I — healthy patient with no systemic disease; II — mild systemic disease without functional limitation (controlled hypertension, mild diabetes, class I obesity, smoking); III — severe systemic disease with functional limitation (decompensated diabetes, stable coronary artery disease, moderate COPD, BMI ≥ 40, CKD on dialysis); IV — severe systemic disease that is a constant threat to life (unstable angina, MI < 3 months prior, severe heart failure, sepsis); V — moribund patient not expected to survive without the operation, death expected within 24 hours; VI — declared brain-dead (organ donor).

The suffix E (Emergency) denotes an emergency operation and increases risk. The scale is applied by the anesthesiologist during the preoperative assessment and documented in the anesthesia record. The 2020 ASA classification remains the primary tool for perioperative risk stratification.

When to use

Preoperative assessment before any procedure requiring anesthesia.
Risk stratification within the anesthesia protocol.
Estimating perioperative mortality (approximate: I — 0.1%, II — 0.4%, III — 4.5%, IV — 25%, V — > 50%).
Deciding on the level of postoperative monitoring (ward vs ICU).

Parameters in detail

ASA class

ASA class I through VI, assigned by the anesthesiologist at preoperative assessment based on the severity of systemic disease and functional limitation.

Clinical example

Case

67-year-old man scheduled for elective cholecystectomy. Coronary artery disease with stable angina, functional class II, MI 5 years ago, heart failure NYHA class II with EF 50%, stage 2 hypertension on three medications. Able to climb one flight of stairs without symptoms.

Calculation

Severe systemic disease (coronary artery disease, heart failure, prior MI), stable, with functional limitation but not life-threatening → class III.

Interpretation and management

ASA III. Approach: preoperative cardiology consultation, RCRI (Revised Cardiac Risk Index) assessment, echocardiography; reassess the plan if decompensation is suspected. Anesthesia: prefer a regional/combined technique where feasible, invasive hemodynamic monitoring, intraoperative preload optimization, postoperative monitoring with extended surveillance. Continue beta-blockers and statins; antiplatelet therapy decided individually with the surgeon.

Limitations and cautions

Subjective — two anesthesiologists may assign different classes; reproducibility is moderate.
Does not account for the type and complexity of the operation — for the same ASA class, risk varies substantially between procedures.
Does not capture functional reserve in detail (use METs or cardiopulmonary exercise testing for this).
Classes II and III are poorly distinguished — most patients end up classified as III, which limits the discriminative value of the scale.

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Frequently asked questions

What does the “E” in ASA III E mean?

Emergency — an emergency operation. It can be appended to any class I–IV. Emergency status roughly doubles perioperative risk.

What ASA class applies to pregnancy?

Pregnancy itself is usually classified as ASA II (a physiologic change). With preeclampsia or gestational diabetes with complications, it is III. With severe preeclampsia or HELLP syndrome, it is IV.

Does smoking justify class II?

Active smoking is classified as ASA II (per the 2014 update). Previously, smoking alone did not preclude class I.

How does ASA relate to RCRI?

ASA is a general assessment of physical status, while RCRI is a specific cardiac risk stratification tool for noncardiac surgery. The two are used in parallel.

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Aleksandr A. Aulov Physician, internal medicine, Sechenov School — independent medical education platform. Calculators are compiled from the original publications and current clinical guidelines. Interpretation thresholds follow the source study unless stated otherwise.

This calculator is intended for healthcare professionals. Do not use it for self-diagnosis or self-treatment. Management decisions are made by the treating clinician based on the full clinical picture of the individual patient.