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American Society of Anesthesiologists Staging

Editor: Brian M. Fitzgerald Updated: 1/29/2023 9:21:10 AM


In 1963, the American Society of Anesthesiologists instituted a system to assess a patient's physical health status and clinical risk during anesthetic administration and surgical operation. Pre-operatively, the patient is subjectively assigned a score according to their physical status, which is determined by the anesthesiologist after considering patient presentation, history, and functional limitations. Assigning this score, ranked ASA I through ASA VI, would thereby attempt to categorize the patient's risk of perioperative complications based on their physical status and overall health. Patients assigned to higher numerical categories have increased risk of perioperative adverse events. The goal of creating the ASA Physical Status Classification System (ASA-PS) was to improve patient outcomes and predict perioperative risk.[1] Despite its setbacks, it has since become a standard practice during perioperative encounters and plays a key role in preventative medicine associated with anesthesia.

Issues of Concern

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Issues of Concern

A topic of concern commonly encountered with assigning ASA scores is that there is often significant variation with how providers may classify the same patient. Assessment and evaluation of patients can vary between providers in different specialties compared to the staff anesthesiologists, causing a significant increase in standard deviation even when participants had access to the same medical records. This situation proves to be a problem that is more prevalent outside the specific specialty, posing a potential threat to the success of healthcare teams composed of multiple providers from multiple specialties.[2] Studies have shown that adding examples for each respective score aided both anesthesia and non-anesthesia providers consistently classifying patients accurately.[3] In 2014, the ASA provided access to a catalog of examples for simplification when assigning an ASA score, increasing accuracy and decreasing inter-observer variation.[4]

Clinical Significance

Using the ASA Physical Status Classification System to evaluate and prepare for possible adverse events remains one of the most widely used pre-operative screening methods for all providers worldwide[5]. The ASA Physical Status Classification System has been shown to predict the frequency of perioperative morbidity and mortality. Research has shown that the implementation of the classification system correctly predicts the frequency and severity of adverse events, which improves patient outcomes[5]. The ASA score is assigned based on the presence and severity of systemic disease in a patient. Examples of some disease processes commonly encountered are listed with their respective score assignment. The letter E may be added onto any category (i.e., ASA IIE) to denote an emergency.

ASA I: a healthy patient with no evidence of active or chronic disease processes, non-smoker, and BMI under 30.[6]

ASA II: a patient with mild systemic disease. Examples include a patient who has no functional limitations and well-controlled disease, BMI under 35, is a social drinker or smokes cigarettes, or has well-controlled hypertension.[6]

ASA III: a patient with severe systemic disease that is not life-threatening. Examples include patients with functional limitations as a result of systemic disease, poorly treated hypertension or diabetes, renal failure, morbid obesity, stable angina, or pacemaker.[6]

ASA IV: A patient with severe systemic disease that is a constant threat to life. Examples include patients with functional limitations as a result of severe systemic disease such as unstable angina, poorly controlled COPD, symptomatic CHF, recent MI, or stroke less than three months prior.[6]

ASA V: A moribund patient who is not expected to survive without surgical intervention. Examples include ruptured abdominal aortic aneurysm, massive trauma, or extensive intracranial bleeding with mass effect.[6]

ASA VI: A patient declared brain-dead, who is a transplant donor. 

Nursing, Allied Health, and Interprofessional Team Interventions

During perioperative care, the actions of the nurse contribute not only to patient outcomes but also in preventing and monitoring for adverse events. Nurses should not only understand what may place a patient in a specified category but also should be able to interpret any complications each patient may face as a result of their assigned score and/or illness. With the education and utilization of the ASA Physical Status Classification System, a nurse can intervene when necessary and collaborate with other providers to ensure the best possible clinical outcome. Interpretations of a patients’ categorization are important to nursing staff as they will use the complete clinical evaluation to guide their monitoring of the patient and to communicate effectively with other members of the anesthesia care team.[7] This categorization also applies to pharmacists and other health professionals who may be contributing to a patient's care plan. Studies have shown that interprofessional team communication failures continue to be a leading cause of adverse outcomes.[8] Therefore, an increased effort toward improving collaboration between nurse and physician anesthesia providers ultimately improves patient care.[9][10] [Level 3]

Nursing, Allied Health, and Interprofessional Team Monitoring

Nurses will provide pre- and post-operative care in addition to monitoring changes in the anesthetic plan. As stated previously, it is essential that nurses understand the ASA Physical Classification System and what conditions a patient may have that might increase their chance of adverse outcomes during the perioperative period. Nurses play a vital role in perioperative care as they closely monitor patients in the PACU for possible adverse outcomes. Nurses should integrate the patient's ASA categorization into their perioperative care plan and monitor for any adverse outcomes that may be associated with their illness. 



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Level 2 (mid-level) evidence


Torgersen KA,Chamings PA, Examining collaborative relationships between anesthesiologists and certified registered nurse anesthetists in nurse anesthesia educational programs. AANA journal. 1994 Apr     [PubMed PMID: 8085417]

Level 2 (mid-level) evidence


Canales C,Strom S,Anderson CT,Fortier MA,Cannesson M,Rinehart JB,Kain ZN,Perret D, Humanistic medicine in anaesthesiology: development and assessment of a curriculum in humanism for postgraduate anaesthesiology trainees. British journal of anaesthesia. 2019 Oct 5;     [PubMed PMID: 31591019]