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American Society of Anesthesiologists Classification

Editor: Emily H. Garmon Updated: 8/17/2023 9:46:47 AM


The American Society of Anesthesiologists (ASA) physical status classification system came about to offer perioperative clinicians a simple categorization of a patient's physiological status to help predict operative risk. The ASAPS originated in 1941 and has seen some revisions since that time.[1][2][3]  Unfortunately, while the ordinal classification scheme is simple, it is far from an ideal preoperative measure for assessment. Once properly reviewed, the differences that might separate any given patient from being classified in any ASAPS classification category from another patient in either a higher or lower category may be extreme from one healthcare provider, group, or system compared to another.[4]  While its utility as a simple classification is perhaps its best feature, this also portends its serious deficiencies. There is certainly a considerable body of evidence correlating ASAPS classification with a variety of useful outcomes. 

As it was neither developed nor intended to be used to predict risk with anesthesia or surgery, it is difficult to utilize it in the individual management of any patient beyond very general concepts.[5] More concerning are the great number of areas, purposes, healthcare providers, and guidelines/standards that attempt to utilize the ASAPS for an increasing plethora of purposes for which it was never intended, which will only invariably lead to a host of unintended and potentially negative consequences. This is punctuated even more so when one considers the tremendous variability and inconsistency in the classification of any one patient among non-anesthesiologists as well as even among anesthesiologists, not to mention the variability and inconsistency between anesthesiologists versus non-anesthesiologists.[6][5][4]


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Perioperative staff could utilize this classification system for perioperative outcomes management.  However, this must be considered in the larger context of the variability and inconsistency with classification between classifying entities, as meta-analyses have shown the ASAPS having a sensitivity around 0.74 (95% confidence intervals 0.73 to 0.74), specificity around 0.67 (0.67 to 0.67), and a receiver operating curve area under the summary of around 0.736 (0.725 to 0.747) in predicting mortality postoperatively.[7][8]  For robust and reliable preoperative risk assessment, one needs to consider a variety of additional factors discretely in addition to the information provided by a composite index classification:[6]

  • Age
  • Comorbidities and their relative severity and level of optimization
  • Intended surgical procedure
  • Potential additional surgical procedures that may be needed intraoperatively
  • Location, extent, and adjacent structures of the intended lesion for surgical intervention
  • Intended surgical equipment to be utilized 
  • Intended implants
  • Intended duration versus possible duration of surgical procedure and thus anesthesia administration
  • Surgical team composition, experience, ability, and skill
  • Likely need for any blood products, along with the likelihood of volume, type, and rapidity with which any blood products might be needed intraoperative
  • Intended medications that may be required along with the possibility of precise timing requirements depending on surgery type
  • Intended anesthetic technique along with the likelihood of the need for any additional rescue equipment or interventions, for the availability of any further rescue equipment or interventions
  • Anesthetic team composition, experience, ability, and skill
  • Intended anesthetic medications along with the likelihood for additional or complementary medication administration as well as the likelihood of the need for reversal or treatment of the effects of any such medications
  • Surgical facility equipment, personnel, and resources
  • Preoperative and postoperative team composition, experience, ability, and skill
  • Intended postoperative plan, location, and course, along with the likelihood of alternative postoperative plans, locations, and complications
  • Time of day, weekend versus weekday, time of the year when the surgical procedure is being performed
  • The surgical operating room location logistics related to the potential likelihood of needing transport of the patient under anesthesia intraoperatively
  • The classification of the surgery as elective, urgent, or emergent

Issues of Concern

The ASAPS is a simple and rapid assessment of a patient; however, its simplicity and rapidity ensure that it has serious issues with consistency application and determination between healthcare providers, systems, and administration in so far as classification is determined on the same patient by different entities or even by the same entity at different times.[4][6]

Clinical Significance

The ASAPS obtained in a particular patient cannot serve as a direct indicator of operative risk because (for instance) the operative risk for a high-risk patient undergoing cataract surgery under topical anesthesia is quite different than the operative risk for the same patient undergoing an esophagectomy or cardiac surgery. Also, since the ASAPS for a particular patient is based on the extent of their systemic disease (as judged by the patient’s medical history, the extent of the patient’s function limitation, etc.), technically speaking, mere physical problems such as the presence of a difficult airway by virtue of a very anterior larynx or artificial constraints such as the prohibition of a clinically necessary blood transfusion in patients who are orthodox Jehovah’s Witness do not influence the ASAPS but most definitely will strongly impact the patient’s operative risk.[5][3][9]

It has been shown that anesthesiologists sometimes vary significantly in the ASAPS classification assigned to patients, especially on factors such as age, anemia, obesity, and patients who have recovered from a myocardial infarction. Similar problems have been highlighted in a pediatric study.

Finally, note that the ASAPS classification system implicitly assumes that age is unrelated to physiological fitness, an assumption which is not true since neonates and the very elderly, even in the absence of disease, are far more “fragile” in their tolerance of anesthetics compared to young adults. However, despite these and other well-known limitations, the ASAPS classification is used ubiquitously (although sometimes uncritically) in providing a convenient description of a surgical patient’s overall condition.[10]

Other Issues

Table 1. The latest version of the American Society of Anesthesiologists (ASA) physical status classification system (ASAPS), as approved by the ASA House of Delegates on October 15, 2014, and adapted for this presentation. Note that no specific classification is assigned to patients with moderate systemic disease, just assignments for patients with mild systemic disease (ASA 2) and those with severe systemic disease (ASA 3).[4][5]

Abbreviations used: ASA: American Society of Anesthesiologists, BMI: body mass Index, CHF: congestive heart failure, COPD: chronic obstructive pulmonary disease.

ASA 1: A normal healthy patient.

Example: Fit, nonobese (BMI under 30), a nonsmoking patient with good exercise tolerance.

ASA 2: A patient with mild systemic disease.

Example: Patient with no functional limitations and a well-controlled disease (e.g., treated hypertension, obesity with BMI under 35, frequent social drinker, or cigarette smoker).

ASA 3: A patient with a severe systemic disease that is not life-threatening. Example: Patient with some functional limitation due to disease (e.g., poorly treated hypertension or diabetes, morbid obesity, chronic renal failure, a bronchospastic disease with intermittent exacerbation, stable angina, implanted pacemaker).

ASA 4: A patient with a severe systemic disease that is a constant threat to life. Example: Patient with functional limitation from severe, life-threatening disease (e.g., unstable angina, poorly controlled COPD, symptomatic CHF, recent (less than three months ago) myocardial infarction or stroke.

ASA 5: A moribund patient who is not expected to survive without the operation. The patient is not expected to survive beyond the next 24 hours without surgery—examples: ruptured abdominal aortic aneurysm, massive trauma, and extensive intracranial hemorrhage with mass effect.  

ASA 6: A brain-dead patient whose organs are being removed with the intention of transplanting them into another patient.

The addition of “E” to the ASAPS (e.g., ASA 2E) denotes an emergency surgical procedure. The ASA defines an emergency as existing “when the delay in treatment of the patient would lead to a significant increase in the threat to life or body part.”

Examples of ASAPS Classification[5][11]

Patient  1

A 20-year-old college athlete from Brigham Young University is scheduled to undergo an elective ACL repair. Non-smoker, nondrinker, no medications, BMI 23. This patient would be assigned ASAPS Class 1. 

Patient  2   

A 19-year-old college student from the University of California - Santa Barbara (a top “party school”) is scheduled to undergo emergency orthopedic surgery following a fall from his frat house roof after attending a weekly “kegger” party. The patient takes recreational medications only (mostly cannabis) and has a BMI of 29. This patient would be assigned ASAPS Class 2E by being a frequent social drinker and being scheduled as an emergency case. Note that the “full stomach” status of the patient does not figure into his ASAPS yet still adds considerably to his overall anesthetic risk.

Patient 3

A 30-year-old woman is scheduled to undergo elective surgery to remove a large ovarian cyst. Comorbidities include anemia from menorrhagia and type II diabetes treated with metformin. She is a non-smoker, an occasional social drinker, and has a BMI of 42. This patient would be assigned ASAPS Class 3.

Patient 4

A 70-year-old woman is scheduled to undergo an emergency laparoscopic appendectomy. Comorbidities include severe COPD as a consequence of a life-long smoking habit, morbid obesity (BMI 46), and type II diabetes. She gets short of breath walking more than a few meters. This patient would be assigned ASAPS Class 4E.

Patient 5

A 55-year-old man is scheduled for emergency repair of a ruptured abdominal aortic aneurysm. He is brought to the operating room with CPR in progress due to asystole. He had been intubated earlier in the Emergency Department without the need for any drugs. This patient would be assigned ASAPS Class 5E as he would not be expected to survive beyond the next 24 hours with or without surgery.

Patient 6

A 25-year-old man sustained a severe head injury in a motorcycle accident. He was not wearing a helmet. After a neurosurgical decompression procedure and numerous other interventions in the intensive care unit, it is clear that there is no hope for recovery. He is unresponsive to all noxious stimulation. Testing for brain death is carried out according to the American Academy of Neurology guidelines for Brain Death Determination, which reveals a complete absence of central nervous system function. His family agrees to make his organs available for transplantation. This patient would be assigned ASAPS Class 6.

Enhancing Healthcare Team Outcomes

All healthcare workers on the interprofessional healthcare team involved in anesthesia or procedures requiring anesthesia should have some basic understanding of the ASA classification. The American Society of Anesthesiologists (ASA) physical status classification system was developed to offer clinicians a simple categorization of a patient’s physiological status that can help predict operative risk. [Level 5]



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