In 1963 the American Society of Anesthesiologists (ASA) adopted the five-category physical status classification system; a sixth category was later added.
The original definition of emergency in 1940, when ASA classification was first designed, was "a surgical procedure which, in the surgeon's opinion, should be performed without delay,"[1] but is now defined as "when [a] delay in treatment would significantly increase the threat to the patient's life or body part.
[4] Many include the 'functional limitation' or 'anxiety' to determine classification which is not mentioned in the actual definition but may prove to be beneficial when dealing with certain complex cases.
[11] For predicting operative risk, other factors – such as age, presence of comorbidities, the nature and extent of the operative procedure, selection of anesthetic techniques, competency of the surgical team (surgeon, anesthesia providers and assisting staff), duration of surgery or anesthesia, availability of equipment, medications, blood, implants and appropriate postoperative care – are often far more important than the ASA physical status.
[citation needed] In 1940–41, ASA asked a committee of three physicians (Meyer Saklad, Emery Rovenstine, and Ivan Taylor) to study, examine, experiment and devise a system for the collection and tabulation of statistical data in anesthesia which could be applicable under any circumstances.
[12] While their mission was to determine predictors for operative risk, they quickly dismissed this task as being impossible to devise.
[citation needed]They state: "In attempting to standardize and define what has heretofore been considered 'Operative Risk', it was found that the term ... could not be used.
It was felt that for the purposes of the anesthesia record and for any future evaluation of anesthetic agents or surgical procedures, it would be best to classify and grade the person in relation to his physical status only.
They hoped anesthesiologists from all parts of the country would adopt their "common terminology," making statistical comparisons of morbidity and mortality possible by comparing outcomes to "the operative procedure and the patient's preoperative condition".
Examples: This includes patients suffering with fractures unless shock, blood loss, emboli or systemic signs of injury are present in an individual who would otherwise fall in Class 1.
Infections that are localized and do not cause fever, many osseous deformities, and uncomplicated hernias are included.
Pulmonary tuberculosis that, because of the extent of the lesion or treatment, has induced vital capacity sufficiently to cause tachycardia or dyspnea.