ASA Classification Transition in the Course of Time and Depiction in the Literature

The American Society of Anesthesiologists classification of physical status (ASA PS) is a widely used system for categorizing the preoperative status of patients. The ASA class is a good independent predictor of perioperative morbidity and mortality. The definitions of the ASA classes have been amended several times since 1941, resulting in inconsistent and confusing usage in the current literature. Conflicting definitions of ASA PS exist, particularly for classes III, IV and V. The high variability of individual classifications by different anesthesiologist, however, can be explained by the previous lack of examples for diagnoses. In 2014, the ASA has added a catalogue of examples for a simplified definition for classification of the ASA PS. This has so far received limited attention in German-speaking countries. This article describes the transition of the ASA classification over the past 75 years und summarizes the currently valid definitions.