ASA Physical Status: the backbone of perioperative risk stratification
The ASA Physical Status (ASA‑PS) classification is a simple, widely used way to describe a patient’s baseline health before anaesthesia. It improves communication and broadly correlates with postoperative complications and mortality, but it is not a complete predictor on its own. Procedure invasiveness, urgency, frailty, and functional capacity still matter.
ASA classes (I–VI) in plain language
| ASA class | Definition (summary) | Typical examples (illustrative) |
|---|---|---|
| I | Normal healthy patient | Healthy, no significant medical problems |
| II | Mild systemic disease | Well-controlled hypertension, mild asthma, pregnancy, smoker without major lung disease |
| III | Severe systemic disease | Stable angina, COPD, poorly controlled diabetes, prior MI/stroke, significant OSA |
| IV | Severe systemic disease that is a constant threat to life | Unstable angina, symptomatic heart failure, severe valve disease, ongoing sepsis |
| V | Moribund; not expected to survive without the operation | Ruptured AAA, massive trauma/hemorrhage, catastrophic intracranial bleed |
| VI | Declared brain-dead organ donor | Organ procurement procedures |
Many systems append an “E” for emergency (e.g., “ASA IIIE”). ASA VI is reserved for organ donation. Definitions vary slightly by source and local examples.
Why “ASA I cataract” is not the same as “ASA I open heart surgery”
- ASA describes the patient, not the procedure.
- Major surgery carries more bleeding, fluid shifts, pain, infection risk, and physiologic stress.
- Emergency surgery adds time pressure, incomplete optimization, aspiration risk, shock or sepsis.
Frailty and functional status
In older adults, “frailty” (reduced physiologic reserve) can be a stronger predictor of complications than age alone. It is not captured perfectly by ASA, so many clinicians combine ASA with frailty/functional assessments and procedure‑specific tools.
How to get a procedure-specific estimate
The ACS NSQIP Surgical Risk Calculator combines patient factors (including ASA class) with the planned procedure to estimate the risk of multiple complications and death within 30 days. It is among the most widely used and best validated public calculators.