American Society of Anesthesiologists Classification (ASA Class)

Article Author:
Daniel John Doyle
Article Editor:
Emily Garmon
Updated:
10/6/2017 12:39:20 PM
PubMed Link:
American Society of Anesthesiologists Classification (ASA Class)

Introduction

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 be helpful in predicting operative risk. The ASAPS originated in 1941 and has seen some revisions since that time. 

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 his or her 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 a 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.

It has been shown that anesthesiologists sometimes vary significantly in the ASAPS classification assigned to patients, especially on the influence of factors such as age, anemia, obesity, and with 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 simply 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.

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 there is no specific classification assigned to patients with a moderate systemic disease, just assignments for patients with mild systemic disease (ASA 2) and those with severe systemic disease (ASA 3). 

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 a 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 is a cigarette smoker).
  • ASA 3: A patient with a severe systemic disease that is not life-threatening. Example: Patient with some functional limitation as a result of 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: 

Patient  1 A 20-year-old college athlete from Brigham Young University is scheduled to undergo an elective ACL repair. Nonsmoker, 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 3A 30-year-old woman is scheduled to undergo elective surgery for removal of a large ovarian cyst. Comorbidities include anemia from menorrhagia and type II diabetes treated with metformin. She is a non-smoker, occasional social drinker, and has a BMI of 42. This patient would be assigned ASAPS Class 3.

Patient 4A 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 5A 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 6A 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 reveals a complete absence of central nervous system function, and his family agrees to make his organs available for transplantation. This patient would be assigned ASAPS Class 6.