Episode Transcript
Hello everybody. My name is Dr. Robb Wasserman. I am an assistant professor at the University of North Carolina who specializes in general anesthesiology. Today, I would like to talk to you about ASA physical status. Over the next 15 minutes, we will go over a brief history of the ASA physical status classification system and how the classification system is currently used today. After that, we will follow a single fictional patient as he goes through every ASA physical status as well as dive deep into how every patient should be assigned their status. By the end of this podcast, you should be able to correctly assign ASA physical status to your future patients. Let’s get started.
I would like to start by taking you back in time. The year is 1941 and the American Board of Anesthesiology has asked Drs. Saklad, Rovenstine, and Taylor to come up with a way to collect and tabulate data in anesthesiology. Their solution was the creation of a system that was broken down into 6 classes of physical status. Class 1 was defined as no organic pathology with classes 2 through 4 being defined as moderate, severe, and extreme systemic disturbances respectively. Each one of these classes had multiple examples listed to assist in the provider’s ability to correctly classify their patient. The final two classes, 5 and 6, were used for emergencies. At some point (the exact timing and method has been lost to time) a class 7 was added. This class represented a patient who was expected to die within 24 hours regardless of whether they had an operation of not.
The next changes to the classification system came in 1961 by Dr. Dripps and colleagues. Specifically, they eliminated the classes 5 and 6 and placed an E for emergency after the other 5 classes. What was previously the class 7 moribund patient not expected to survive for 24 hours now became class 5. Also, of note, they removed all of the clinical vignettes of each physical class previously provided by Dr. Saklad as they believed this would help with the objectivity of assigning ASA physical status. Fast forward 18 years to 1980, and we see a sixth class added. This class 6 physical status was for brainstem dead organ donors. It wouldn’t be until 2014 when we would see a return of the clinical vignettes, and finally in December of 2020 both pediatric and obstetric patient examples were added to each category giving us the ASA physical status classification system we have today.
Despite the original purpose of this classification system not to be used to estimate “operative risk”, it absolutely morphed into exactly this. In two studies, one by Vacanti and colleagues in 1970 and one by Marx and colleagues in 1973, it was shown that ASA physical status correlated well with overall surgical mortality. I do want to note here, however, that even though there is a correlation between surgical mortality and ASA physical status, the correlation between anesthetic mortality and ASA physical status is much weaker. Nowhere in the definitions of ASA physical status does is estimate the risk of difficult intubation or difficult mask ventilation. Nowhere does it talk about the risk of malignant hyperthermia or the risk of machine malfunction causing hypoxia. Despite these shortcomings, a patient’s ASA physical status is still one of the best predictors we currently have for surgical mortality. It is the only classification system that we use consistently to express the preoperative condition of a patient. As such, its main purposes today (which have gone beyond the original intent of the ASA classification system) are for both billing and case reimbursement, as well as stratifying case complexity in order to triage decisions regarding inpatient versus ambulatory care, transferring patients to other facilities, assigning appropriate anesthesia providers to cases, and determinizing appropriate anesthesia staffing ratios. Of note it has also been used by non-anesthesiologists for decisions regarding need for anesthesia professionals in out-of-operating room procedures when sedation is needed.
Now that we have gone over the history and purpose on the ASA physical status classification system, let’s shift our focus and talk about our hypothetical patient and practice assigning ASA physical status together. Our patient’s name is Tommy. Tommy is a healthy 13-year-old male with no significant past medical history. Unfortunately, Tommy fell while skateboarding down a hill the day prior and broke his humerus. Today, he presents to the operating room for operative repair. So, what would Tommy’s ASA physical status be? Considering that Tommy has no significant past medical history and is healthy, this is someone who would be classified as having an ASA physical status of 1. According to the current iteration of the ASA physical status, a patient with an ASA physical status of 1 is defined as a “normal healthy patient”. The example given on the ASA’s website is “healthy, non-smoker, and no or minimal alcohol use”. Clearly this patient fits this definition.
Let’s now follow Tommy 10 years into the future. He now goes by Tom and unfortunately has picked up the habit of daily cigarette smoking. He takes no medications, has no other diseases diagnosed, and works out for an hour a day at his local gym. He presents to the hospital to repair a hernia he obtained while weight lifting. What would his ASA physical status be? The fact that Tom is now a current smoker has increased his ASA physical status to a 2. The ASA defines a physical status of 2 as “a patient with mild systemic disease”. The examples listed are “mild disease only without substantive functional limitations such as current smoker, social alcohol drinker, pregnancy, obesity with BMI greater than 30 and less than 40, well controlled diabetes or hypertension, and mild lung disease”. I want to take a second here to point out that a person with no significant past medical history except obesity with a BMI between 30 and 40 is a patient with ASA 2 status. I also want to point out the fact that a completely healthy patient with an uncomplicated pregnancy is also considered an ASA 2.
Now let’s shift our focus back to Tom. Unfortunately, Tom continues to smoke a pack per day for the next 20 years. He is now 43 years old and has been diagnosed with COPD. He also had a myocardial infarction the prior year. He no longer works out and has mild shortness of breath while walking up a flight of stairs but denies chest pain with activity. For the last 24 hours he has had intense abdominal pain, so he presents to the hospital and is diagnosed with acute appendicitis. What is Tom’s current ASA physical status? Both the diagnosis of COPD and a myocardial infarction greater than three months ago have increased his ASA physical status to a
3. The ASA physical status of 3 is defined as “a patient with severe systemic disease”. The examples given by the ASA are “substantive functional limitations and one or more moderate to severe diseases such as poorly controlled diabetes or hypertension, COPD, morbid obesity with a BMI greater than or equal to 40, active hepatitis, alcohol dependence or abuse, implanted pacemaker, moderate reduction of ejection fraction, end stage renal disease undergoing regularly scheduled dialysis, and history of MI, stroke, TIA, or coronary artery disease/stents greater than 3 months ago”. Again, I would like to take a moment stress the point about obesity here. A patient with a BMI greater than or equal to 40 is classified as an ASA 3.
Ok, back to Tom. After Tom had his appendix removed, he continues to smoke. He has also been eating poorly and has developed type 2 diabetes. A few more years pass and unfortunately Tom has not been compliant with his diabetes medication. Due to his poorly controlled diabetes, he suffers a second myocardial infarction. Two months after suffering this MI, while frying some food, Tom accidently spills the hot grease on his chest and presents to the hospital with severe burns. He is brought to the operating room for debridement of this burn. Tom is now an ASA 4. This is due to the fact that he suffered an MI less than three months prior to presenting for an operation. Per the ASA, an ASA 4 patient is defined as “a patient with severe systemic disease that is a constant threat to life”. The examples given are “recent (less than three months ago) MI, stroke, TIA or CAD/stents, ongoing cardiac ischemia or severe valve dysfunction, severe reduction of ejection fraction, shock, sepsis, DIC, acute renal dysfunction or end stage renal disease not undergoing regularly scheduled dialysis”. Here I would like to stress the point that a patient who is currently septic or had an MI and or stroke less than three months prior is considered an ASA 4.
Now back to the unfortunate case of Tom. He has left the hospital against medical advice two days after his burn debridement and decides to try and walk home across a busy highway. He is struck by a car at high velocity and rushed back to the hospital and operating rooms with massive internal bleeding as well as various other injuries. His blood pressure when he arrives is 60/30 with a heart rate of 150. Tom is now an ASA 5E, with the E denoting an emergency surgery where a “delay in treatment of the patient would lead to a significant increase in the threat to life or body part”. An ASA 5 is defined as “a moribund patient who is not expected to survive without the operation”. Examples given on the ASA website are “ruptured abdominal/thoracic aneurysm, massive trauma, intracranial bleed with mass effect, ischemic bowel in the face of significant cardiac pathology or multiple organ/system dysfunction”. With the massive trauma Tom clearly fits this definition. The anesthesia and surgical team get Tom through the emergency surgery and bring him to the ICU. Unfortunately, the next day he is declared brain dead. Tom was an organ donor, however, so he is brought to the operating rooms for an organ harvest. Tom is now an ASA 6 defined as “a declared brain-dead patient whose organs are being removed for donor purposes”.
Now that we have reviewed the case of Tom going though all 6 ASA physical classification statuses, I would like to review a few more hypothetical cases to really reinforce our ability to correctly assign ASA physical status.
Our next patient is Sandra. Sandra is a 58-year-old female with a past medical history of end stage renal disease due to poorly controlled hypertension. She presents to the hospital for AV fistula placement for dialysis access. Previously, she had been undergoing nightly peritoneal dialysis and states she “never misses a session”. What would Sandra’s ASA physical status be? Sandra would be considered an ASA 3. She receives this status of an ASA 3 for two specific reasons. The first is due to her poorly controlled hypertension. The second is due to her end stage renal disease undergoing regularly scheduled dialysis. I would like to note here this if Sandra was not undergoing regularly scheduled dialyses, this would make her have an ASA physical status of 4.
The final patient we will go over today is Maria. Maria is an 88-year-old female with a past medical history of severe aortic stenosis, well controlled hypertension, and history of a stroke 10 years prior. She states she gets light-headed and short of breath often when walking around her house. She presents for a transcatheter aortic valve replacement. What would Maria’s ASA status be? Maria would be considered an ASA 4. She receives the status of ASA 4 due to severe valve disfunction. Of note, just having a history well controlled hypertension would give a patient an ASA status of 2 while just having a history of a stroke 10 years prior would give a
patient an ASA status of 3.
I would like to end this talk by briefly going over a potential limitation of the ASA physical status classification system. In the past few years, there has been a growing acknowledgment of the significance of patient frailty in surgical outcomes. In fact, on its own, frailty could be deemed akin to a “serious systemic disease” and therefore give a patient ASA 3 status. Despite this, however, there lacks formal guidance regarding its inclusion within the ASA physical status classification system.
Now that we have gone over all 6 ASA physical statuses as well as talked briefly about their history and purpose, I would like to thank you all for taking the time to listen to this Anesthesia Toolbox Podcast on ASA Status. I hope everyone will find this podcast useful.
