The ASA physical status classification system is a system for assessing the fitness of patients before surgery. In 1963 the American Society of Anesthesiologists (ASA) adopted the five-category physical status classification system; a sixth category was later added. These are:
Contents
- Healthy person.
- Mild systemic disease.
- Severe systemic disease.
- Severe systemic disease that is a constant threat to life.
- A moribund person who is not expected to survive without the operation.
- A declared brain-dead person whose organs are being removed for donor purposes.
If the surgery is an emergency, the physical status classification is followed by “E” (for emergency) for example “3E”. Class 5 is usually an emergency and is therefore usually "5E". The class "6E" does not exist and is simply recorded as class "6", as all organ retrieval in brain-dead patients is done urgently. 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," but is now defined as "when [a] delay in treatment would significantly increase the threat to the patient's life or body part."
The scale they proposed addressed the patient's preoperative state only, not the surgical procedure or other factors that could influence surgical outcome. 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".
Limitations and proposed modifications
These definitions appear in each annual edition of the ASA Relative Value Guide. There is no additional information that can be helpful to further define these categories. It is logical to expect a missing class between ASA 2 and ASA 3 for a systemic disease which is neither mild nor severe, but is of moderate nature. It is also not clear what will be the ASA classification of a case who is suffering simultaneously from two, three or more systemic diseases (which might be of different severity).
An example of an ASA status classification system is that used by dental professionals. 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. Often different anesthesia providers assign different grades to the same case. The word 'systemic' in this classification creates a lot of confusion. For example, heart attack (myocardial infarction), though grave, is a 'local' disease and is not a 'systemic' disease, so a recent (or old) heart attack, in the absence of any other systemic disease, does not truly fit in any category of the ASA classification, yet has poor post-surgery survival rates. Similarly cirrhosis of the liver, COPD, severe asthma, peri-nephric abscess, badly infected wounds, intestinal perforation, skull fracture etc. are not systemic diseases. These, and other severe heart, liver, lung, intestinal or kidney diseases, although they greatly affect physical status and risk for poor outcomes, cannot be labelled as “systemic disease” (which means a generalized disorder of the whole body like hypertension or diabetes mellitus). Local diseases can also change physical status but has not been mentioned in ASA classification.
This classification system assumes that age has no relation to physical fitness, which is not true. Neonates and the elderly, even in the absence of any systemic disease, tolerate otherwise similar anesthetics poorly in comparison to young adults. Similarly this classification ignores those with malignancy (cancer). This classification system could not be improved to a more elaborated and scientific form, probably because it is often used for cost reimbursement.
Although more complex scoring systems like APACHE II exist, they are time-consuming to calculate, and do not have the same utility for ease of communication between surgeons, anesthesiologists, and insurers as well as dental professionals providing local and general anesthesia.
Some anesthesiologists now propose that like an 'E' modifier for emergency, a 'P' modifier for pregnancy should be added to the ASA score.
Also, the ASA classification does not describe the general health status when excluding the condition that indicates the surgery. In fact, there are hospitals (e.g. Uppsala University Hospital) that do exclude the condition indicating the surgery. Thus, in such hospitals, ASA 1 may still refer to a severe medical emergency, such as for example a moribund person due to a traumatic aortic rupture (which indicates the surgery) but otherwise being healthy.
Uses
While anesthesia providers use this scale to indicate one's overall physical health or "sickness" preoperatively, it is regarded by hospitals, law firms, accrediting boards and other healthcare groups as a scale to predict risk, and thus decide if a patient should have – or should have had – an operation. To predict operative risk, age and obesity, the nature and severity of the operative procedure, selection of anesthetic techniques, the competency of the surgical team (surgeon, anesthesia providers and assisting staff), duration of surgery or anesthesia, availability of equipment, medicine, blood, implants and especially the level of post-operative care etc. are often far more important than multiple ASA classification.
History
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. This effort was the first by any medical specialty to stratify risk. While their mission was to determine predictors for operative risk, they quickly dismissed this task as being impossible to devise. 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."
The scale they proposed addressed the patient's preoperative state only, not the surgical procedure or other factors that could influence surgical outcome. 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".
They described a six-point scale, ranging from a healthy person (class 1) to one with an extreme systemic disorder that is an imminent threat to life (class 4). The first four points of their scale roughly correspond to today's ASA classes 1-4, which were first published in 1963. The original authors included two classes that encompassed emergencies which otherwise would have been coded in either the first two classes (class 5) or the second two (class 6). By the time of the 1963 publication of the present classification, two modifications were made. First, previous classes 5 and 6 were removed and a new class 5 was added for moribund persons not expected to survive 24 hours, with or without surgery. Second, separate classes for emergencies were eliminated in lieu of the "E" modifier of the other classes. The sixth class is now used for declared brain-dead organ donors. Saklad gave examples of each class of patient in an attempt to encourage uniformity. Unfortunately, the ASA did not later describe each category with examples of patients and thus actually increased confusion.