American Society of Anesthesiologists Physical Status Classification System

Excerpt

The American Society of Anesthesiologists (ASA) physical status classification system was introduced in 1941 to provide perioperative clinicians with a standardized method to evaluate a patient's medical comorbidities and help predict perioperative risk. This classification system has undergone several revisions since its inception, with its most recent amendment in 2020. Though the classification system is far from a perfect tool for preoperative assessment, its limitations are outweighed by its simplicity and high predictive accuracy for postoperative outcomes. It consists of 6 ordinal scoring categories (and one additional designation for emergencies) to succinctly communicate a general assessment of underlying physiologic status, ranging from completely healthy (ASA Class I) to brain-dead awaiting organ procurement for donation (ASA Class VI). Though it has high validity and predictive accuracy for postoperative mortality, the ASA physical status classification system cannot be used alone to determine anesthesia or surgical risks because other factors (such as procedure invasiveness and patient frailty) also contribute to perioperative risk for poor outcomes.

Additional limitations in the ASA classification system include its nonbinary nature, which introduces high interrater variability when determining a range of disease severity rather than disease presence or absence. The same comorbidity may be present in more than one classification score, and judgment regarding comorbidity severity can vary significantly between healthcare providers, groups, or systems. Notably, age does not appear in the ASA physical status classification system, though neonates and older adults may be more sensitive to the effects of anesthesia than children and young adults, even in the absence of disease. Despite these limitations, the ASA physical status classification system remains one of the most widely used assessment and communication tools to describe a surgical patient's overall condition.