American Society of Anesthesiologists (ASA) Physical Status Classification

The American Society of Anesthesiologists (ASA) Physical Status Classification System is a risk-stratifying system used mainly by anesthesiologists to help predict preoperative risks; it has been in use for more than 60 years. This system is used to assess a patient’s preoperative comorbid conditions and assigns a class ranging from I to VI. It is used in conjunction with other assessments (eg, type of surgery, frailty, and level of deconditioning) for predicting perioperative risks. ^[1]

Assigning a physical status classification level is a clinical decision based on multiple factors. Whereas the physical status classification can be assigned anytime during the preoperative assessment, the final physical status classification is assigned on the day of the procedure by the anesthesiologist. ^[1]

The ASA has updated its classification system with a number of disease examples. As of January 2026, the system includes the following definitions, with selected examples from adults. ^[1]  (Examples specific to pediatric and obstetric patients are also provided by the ASA. ^[1] )

ASA I - A normal healthy patient, as follows:

• Healthy
• Nonsmoker
• No or minimal alcohol consumption

ASA II - A patient with mild systemic disease without significant functional limitation or end-organ involvement, including but not limited to the following:

• Active smoking
• Social alcohol consumption
• Pregnancy
• Obesity - BMI >30 but < 40
• Controlled diabetes mellitus (DM) or hypertension (HTN)
• Mild lung disease
• New York Heart Association (NYHA) class 1 congestive heart failure (CHF)
• Mild cognitive dysfunction
• Isolated mild-to-moderate obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) compliance

ASA III - A patient with one or more severe systemic diseases causing substantive functional limitation, including but not limited to the following:

• Chronic obstructive pulmonary disease (COPD)
• Morbid obesity - BMI ≥40
• Active hepatitis
• Compensated cirrhosis
• Alcohol dependence or abuse
• Functional implanted pacemaker
• Moderate reduction of ejection fraction (EF) or NYHA class 2 or 3 CHF
• End-stage renal disease (ESRD), undergoing regular scheduled dialysis
• History (>3 mo) of myocardial infarction (MI), cerebrovascular accident (CVA), transient ischemic attack (TIA), pulmonary embolism (PE), or coronary artery disease (CAD)/stents
• Significant cognitive dysfunction
• Isolated severe OSA ^[2] regardless of CPAP compliance, or any severity of OSA with CPAP noncompliance
• Poorly controlled DM or HTN with or without end-organ dysfunction.

ASA IV - A patient with severe systemic disease that poses a constant threat to life, including but not limited to the following:

• Recent (< 3 mo) MI, CVA, TIA, or CAD/stents
• Ongoing cardiac ischemia or severe valve dysfunction
• Severe reduction of EF or NYHA class 4 CHF
• Shock
• Sepsis
• Disseminated intravascular coagulation (DIC)
• Acute respiratory distress syndrome (ARDS)
• ESRD, not undergoing regular scheduled dialysis
• Uncompensated cirrhosis
• Severe cognitive dysfunction

ASA V - A moribund patient not expected to survive without the operation, including but not limited to those with the following:

• Ruptured thoracic or abdominal aneurysm
• Massive trauma
• Intracranial bleeding with mass effect
• Ischemic bowel with significant cardiac pathology
• Multiple organ or system dysfunction

ASA VI - A declared brain-dead patient whose organs are to be removed for donation.

The addition of “E” after the classification signifies emergency surgery; an emergency is considered to be present in cases where delaying treatment of the patient would result in a significantly increased threat to life or a body part.

Apart from the common examples provided by ASA for the six classes, other conditions not specifically mentioned can be assigned an ASA class on the basis of the general principles underlying each classification. 

The subjective nature of the ASA classification makes it challenging for clinicians to assign the correct class, and this has led to some criticism of the system for inconsistent status assignments. Updates to the ASA classification and the addition of examples have reduced these inconsistencies. ^[3]

For better prediction of perioperative risk, other essential factors besides ASA class should be considered, including but not limited to the following ^[1] :

• Age
• Other comorbidities
• Home medications
• Duration and extent of the operative procedure
• Anesthetic choice and medications administered
• Surgical team skills and technique
• Blood products required
• Implants needed
• Expected postoperative care

The classification system can be used preoperatively to identify patients who are at high operative risk. Depending on the type of procedure, there is a variable trend toward increasing likelihood of complications and mortality with increasing ASA class. ^{[4, 5, 6]}