Anesthesiology: From Patient Safety to Population Outcomes

Abstract

OCTOBER 16, 1846, marked a dramatic day in the history of humankind, with the first public demonstration of anesthesia (fig. 1A).1If the reduction of human suffering is medicine's primary goal, it could be argued that anesthesiology has contributed more to humankind than any other field of medicine. In its first issue in 2000, the editors of The New England Journal of Medicine published an editorial on a millennium in medicine, in which they presented the 11 most important advances in medicine in the past 1,000 years.2Anesthesiology was, of course, on the list. However, because information was published in chronological order, anesthesiology did not appear first, its rightful position of importance in my opinion. Although none of us can take credit for this advance, we can clearly be proud of our heritage and what we do every day in reducing pain and suffering for millions of people.During the past 164 yr, the field of anesthesiology has rapidly progressed, with many developments that have improved the quality and safety of anesthesia care and enabled tremendous advances in the surgical disciplines. During this lecture, I will focus on two “points of inflection” in the field of which I am familiar: the development of noninvasive monitoring of oxygenation (and monitoring standards, in general) and the development of perioperative anesthesia information management systems (AIMS). I believe many of the older members of this audience will agree that there was a significant change in the practice of anesthesiology between 1980 and 1990. I hope to convince you that we are in the midst of another change that will dramatically affect the way we practice in the next decade as we first implement information systems as a routine and then use the data derived from those systems to make another dramatic change in the way medicine is practiced, not only in our field but in other disciplines.As I review the progress of anesthesiology for greater than the past 150 yr, I see striking similarities in the progress of the aviation industry. This may make even more sense for me. Having a father who was a test pilot and having soloed my first plane at the age of 17 years, I felt a remarkable déjà vu “soloing” my first anesthetic. What do we actually do to patients? (1) We suspend consciousness. (2) We counterbalance painful stimuli. (3) We maintain normal physiology during a planned trauma. (4) We frequently produce nausea and vomiting. We are a lot like pilots. Both of us have a fun job taking people places. We place people in a dangerous situation. We try to make people feel at ease and allay their fears. We really do not provide complete information for consent. If we were to inform the patient of what we actually plan to do to him or her, we would have to tell the patient the following. We will give you a drug that will cause you to stop breathing, and your oxygen concentration will start to decrease. In case you attempt to breathe, we prevent even the slightest possibility of that occurring by giving you a second drug that paralyzes your muscles. Then, during the next critical few minutes, we manage to control your airway and place you “safely” on a ventilator. This is similar to what a pilot would have to say to passengers before starting down the runway. Before the plane takes off, the pilots do not state that the liftoff speed is 180 mph and that if that speed is not reached half-way down the runway the plane will end up in a pile of flames and most likely all will perish. The pilot should also state that during the first few minutes of maximum thrust, if for some reason the plane should lose power, again it will fall to the earth in a pile of flames and most likely all will perish. This type of informed consent, as with detailed information regarding anesthesia, would not help the passengers (or patients) undergo their “flight” at ease. Therefore, neither pilots nor anesthesiologists inform their patients nor passengers with accurate details of what is about to happen. A formal informed consent does not seem necessary because everyone has a general understanding that being up in the air is not safe and could potentially be lethal. The same could be said regarding anesthesia but in a more vague way (i.e. , most patients know that anesthesia is an abnormal state with inherent danger, but the alternative seems much worse).Next, both anesthesiologists and pilots have a flight plan A and plans B and C, should the unforeseen occur. Again, most of the risk is during the takeoff and the landing (i.e. , the induction and emergence); during the flight, both of us look at electronic devices to see where we are. Finally, we both tend to make some people experience nausea and vomiting.As with pilots, anesthesiologists have short and long flights, with long ones requiring more planning and preparation. We may be flying young “healthy” planes, or we may be flying elderly planes with more “comorbidities.” We may need to fly under extreme conditions. The advances in anesthesiology in improving safety have given us the ability to care for more elderly patients undergoing more complex surgical procedures.On December 17, 1903, the Wright brothers (Orville and Wilbur Wright, Dayton, Ohio) made history by flying the first heavier-than-air aircraft (fig. 1B). Approximately 4 yr later, on September 7, 1908, LT Thomas Selfridge climbed aboard an early Wright brothers aircraft with Orville Wright for a test flight as part of an evaluation for a military contract. Several minutes into the flight, a propeller broke and fell to the ground, and the plane soon followed, seriously injuring Orville Wright and making the 26-yr-old lieutenant the first aviation fatality (fig. 2A).3Although this disaster devastated the Wright brothers, there was a thorough investigation by the military that absolved Orville Wright of any blame, noting the crash was the result of a mechanical failure. Ultimately, Orville Wright was awarded the first military contract for $30,000 to further develop a military aircraft.Similarly, 2 yr after the demonstration of ether anesthesia in Boston, Massachusetts, a 15-yr-old girl named Hannah Greener (who died on January 28, 1848) underwent chloroform anesthesia for the removal of a toenail. According to Thomas Nathaniel Meggison, M.D., who administered the chloroform, the girl did not take the anesthetic well. She died despite all resuscitative efforts, including “dashed water in her face,”“gave her some brandy,” and “opened veins in her arm and jugular” (fig. 2B).4Unfortunately, as anesthesia became more popular and expanded throughout the world, there continued to be significant mortalities. The first intravenous anesthetic, thiopental, was associated with problems when it was first made available in a 5% concentration.5The first major study6of anesthetic mortality noted that anesthesia was associated with a mortality of 1 in 1,560 individuals and was estimated to cause more deaths than polio during the height of the epidemic. Ironically, 50 yr later, in an Institute of Medicine report,7anesthesiology was highlighted as a leader in patient safety and recognized for notably reducing errors by using a “combination of technological advances and standardized equipment.” This reduced anesthesia-associated mortality to approximately 1 in 200,000 individuals.How did this dramatic improvement in anesthesia safety occur? It was probably started with the efforts of Harvey Cushing, M.D. (a neurosurgeon born in Cleveland, Ohio, in 1869), considered by many as the father of neurosurgery, with his use of an anesthetic record to document pulse and respiration and, later, blood pressure.8For the first time, this allowed tracking of the physiologic course of anesthetic care. During the next 80 yr, anesthesia machines were developed and incorporated vaporizers, gas flow meters, ventilators, and carbon dioxide absorbers. However, the monitoring remained relatively unchanged, with the manual cuff, pulse rate, and auscultation of respirations (fig. 3A). This is what I would refer to as the visual flight rules era of anesthesia, equivalent to that of a 1930s aircraft; pilots were required to have exquisite “clinical skills” to assess the status of the aircraft and navigate simultaneously (fig. 3B). It was not until the early 1980s that the course of anesthesia changed with the nearly simultaneous availability of three monitoring devices: a noninvasive automatic blood pressure cuff, a capnometer, and a pulse oximeter.In this section, I will briefly review the fascinating history of the development of pulse oximetry; more than any other device, the pulse oximeter signifies the point of inflection in the history of anesthesia. It is a monitor that was developed and promoted by anesthesiologists but has been adopted by all those in acute-care medicine. As with many innovations, the development of pulse oximetry involved a host of individuals. Most would agree that the first functional oximeter was developed by Glenn Alan Millikan, Ph.D. (a physiologist working for the Johnson Research Foundation; University of Pennsylvania, Philadelphia, Pennsylvania) during World War II as part of a series of physiologic experiments to determine when aviators (another aviation connection) would require supplemental oxygen.9Millikan was the son of Robert A. Millikan, Ph.D. (1868–1953), the Nobel Prize–winning physicist and cofounder of the California Institute of Technology, Pasadena.10Per previous data, the color of living tissue could change with the desaturation of hemoglobin and the color change was measured by light absorption or reflection. Millikan demonstrated that this change could be detected by shining light through the earlobe and measuring the change in the transmitted light intensity. Two modifications of the device were required to detect a signal related to arterial hemoglobin. Because light is absorbed by the blood and tissue in the ear, he had to zero the device by squashing the ear to eliminate blood and zero the light transmission to that of bloodless tissue. After the device was zeroed, he then released the pressure to allow blood to return to the ear, but this blood was a combination of arterial, venous, and capillary blood. To obtain a signal that was primarily arterial, he heated the device to 42°C to make the ear hyperemic and thereby arterialized the blood sensed by the oximeter. This device was successfully used in experiments during the next decade and was cited as a clinical monitoring device in Anesthesiology in 1951 by Stephen et al. 11Although the oximeter was useful in detecting desaturation that was undetectable clinically, this early device was difficult to maintain. If left in the same site, it would cause a burn. In 1974, a Japanese electrical engineer, Takuo Aoyagi, Ph.D. (Faculty of Engineering, Niigata University, Niigata Prefecture, Japan), made an insightful observation.12He was working on a technique to noninvasively estimate cardiac output by using a Millikan-type oximeter and intravenous dye. He detected this dye by placing a Millikan ear oximeter on his subjects and then attempted to measure a dye dilution curve as the intravenously injected dye perfused the ear, hoping that the ear blood flow could be related to the total cardiac output. During these experiments, he noted oscillations in the red and infrared signals of the ear oximeter. He came up with the ingenious idea that if he assumed that the pulsatile signal must be arterial blood, he could then derive a signal related to arterial hemoglobin saturation without first calibrating by compressing the ear and then heating the ear. Although he did not publish this as a pulse oximeter, it soon became known as the pulse oximeter because it analyzed the pulsatile light absorption signal in red and infrared light. This idea was soon adopted by Scott Wilber, B.E. (an engineer and founder of Biox Technology, Boulder, CO), and modified by using light-emitting diodes as light sources and photo diodes as light detectors, which allowed for a lightweight clip-on ear or finger probe.13The modern pulse oximeter was developed by an anesthesiologist, Bill New, M.D., Ph.D. (Engineer and Clinical Assistant Professor of Anesthesiology, Stanford University, Palo Alto, California).13He saw the tremendous application of the device in anesthesia and ingeniously decided to make the pulse beep tone change with saturation. With its easy-to-use sensor that needed no calibration to provide beat-to-beat arterial saturation and pulse, this generation of pulse oximeter was greeted with nearly instantaneous acceptance. The first publication documenting the accuracy of the pulse oximeter appeared in Anesthesiology in 1984 by Yelderman and New.14It was only 2 yr later that the American Society of Anesthesiologists (ASA) published standards for monitoring that recommended pulse oximetry.*It is impressive that it was only 2 yr from the introduction of the device to its consideration as a standard of care by the ASA.I refer to the combination of pulse oximetry and capnography as the “dynamic duo” for acute-care monitoring. Pulse oximetry ensures beat-to-beat oxygen saturation and pulse while capnography ensures breath-to-breath ventilation and pulmonary blood flow (cardiac output). It is difficult to image a life-threatening situation in which these two devices remain in the normal range. I believe that most would agree that the significant reduction in anesthetic-related mortality in the 1990s was because of the routine adoption of oximetry and capnography. Once the value of pulse oximetry was noted by anesthesiologists, it progressively spread to all acute-care areas of medicine, including intensive care units, step-down units, and emergency departments.Before we leave the historic portion of this lecture, I would like to bring up other analogies between aviation and anesthesiology. Just as W. T. G. Morton, M.D. (1819–1868), a dentist, tried to obtain commercial value from his discovery by attempting to market ether as a new substance (i.e. , “letheon”), the Wright brothers also filed a series of patents on their flying machine in the hopes of obtaining commercial success.15,16Both attempts were to no avail. Morton's attempt to disguise ether as another substance was discovered, disgracing him; although he is well recognized for his public demonstration of anesthesia, he never profited from it and died destitute. The Wright brothers also failed to profit substantially from their efforts. After years of litigation with Glenn H. Curtiss (aviator and founder of the US Aircraft Industry, 1878–1930), the federal government forced a resolution and suspended their patents. This was because World War I was approaching and the litigation was preventing development of aircraft for the war effort.17Again, the Wright brothers are noted in history for developing the first heavier-than-air flying machine but had to settle for a relatively small monetary reward. Other similarities between the two fields are the preflight aircraft walk-around inspection and the pre–take off checklist. These are analogous to the anesthesia machine checkout. As we heard at last year's Rovenstine lecture, given by Peter Pronovost, M.D., Ph.D. (Professor, School of Medicine, Department of Anesthesiology, Critical Care Medicine, and Surgery, Johns Hopkins University, Baltimore, Maryland), preprocedure checklists and recently adopted time-outs, now routine before surgical procedures, can be valuable.18,19Each of these processes was adopted in the aviation industry well before its “discovery” in medicine. The analogies go on and on. Filing a flight plan before the flight has been routine, just as the anesthesia workup with an anesthetic plan is a required part of our practice. Aircraft between the 1930s and 1970s progressively developed in complexity and dramatically increased the number of gauges and monitoring devices to alert the pilot about the status of the aircraft. During anesthesia, starting in the 1980s, the number of monitoring devices progressively increased to allow for close monitoring of patient status. Flight time restrictions on pilots were adopted in 1978, and anesthesia work hour restrictions for trainees were adopted in the United States in 2001.†20The Federal Aviation Agency was established in 1950 to improve safety and apply uniform standards to the aviation industry; the ASA established the Anesthesia Patient Safety Foundation to improve safety in 1986.‡21The National Transportation Safety Board started an aviation accident database in 1962, and the ASA developed a closed-claim investigation task force in 1991.§∥Finally, last but not least, flight simulators for training and certification and anesthesia simulators for training and ultimately certification were developed. Because our fields seem to be so similar, it might be useful to see what the aviation industry has done in the past 25 yr to predict what we most likely will be doing in the next 25 yr.If you look at the progression of aircraft instrumentation, aircraft became more complex (i.e. , more gauges and dials appeared using simple high- and low-threshold alarms with little integration or intelligence) (fig. 4, A and B). Unfortunately, as the number of gauges increased, the ability for a human to monitor those gauges actually decreased.22Human factors research has demonstrated that when multiple high- and low-alert limits are used from multiple gauges, the normal response is to either silence the alarm limits or place them at such wide thresholds that they become nonfunctional.22If something does happen immediately and multiple monitors are in range at the same time, the alarms become distracting and prevent the pilot from focusing on the most important problems first. Thus, the designers of cockpits integrated alarms and prioritized those alarms; today, aircraft have three screens (i.e. , navigation [radar], primary flight display, and multifunction display) (fig. 5, A and B).#With the advent of global positioning system, the navigator has been replaced by a navigation screen that tracks the whereabouts of the aircraft along its planned course. The primary flight display linked to the multifunctional display produces an integrated system tracking the status of the aircraft and alerting the pilot to issues of concern, whether related to the mechanical function of the aircraft or its flight status.When looking at a current anesthesia machine, with its monitors and a paper record, it looks much like an aircraft shortly after World War II: many dials with high/low alarms, navigation by pen and paper (the anesthetic record), and no integration of information that could be considered a primary flight display equivalent. With the advent of AIMS, providing electronic “navigation,” integrated monitoring systems, and electronic anesthesia machines, we have the opportunity to mimic the aircraft industry by integrating these information sources. This will allow us to manage patients more specifically by using data from current physiologic monitors and the anesthesia machine and from the patient's medical history and laboratory data to develop the “multifunctional display” and “primary flight display”; in medicine, this is called decision support. There are many examples of automatic decision support being used, such as reminders for antibiotic timing (either pop-up displays on an information system or α-numeric pages), alerts for abnormal laboratory values, and alerts for the potential of awareness during anesthesia.23–25The integration of these multiple sources of data provides us with the opportunity to move into a new era of perioperative care. We may have the opportunity to reduce our anesthetic-related mortality to lower than 1 in 200,000 individuals, but we may also have the opportunity to reduce the postoperative complications (e.g. , myocardial infarction, renal failure, and stroke) by optimizing and individualizing our perioperative care based on patient- and procedure-specific personalized care plans.An AIMS is composed of several components: an electronic anesthesia history and physical (H&P) examination findings, an intraoperative record, and procedures and postoperative documentation. In addition, these systems usually have interfaces with the hospital's electronic medical record. They have interfaces with the admission/discharge, the operating room scheduling, and the laboratory systems; in addition, they have an interface to be more functional with the e-mail and paging systems. Originally, when they first appeared, AIMS were called anesthesia record keepers because all they did was replicate the handwritten intraoperative record. Unfortunately, the companies who developed these systems did not survive because there was little value in replacing an inexpensive process (paper and pen) with an expensive electronic system, other than what was considered to be more accurate documentation.26,27For this reason, the electronic medical record, in most institutions, has progressed while most anesthesia departments have stayed with paper. As a society, we have not mandated these systems because they have been expensive and difficult to justify. Although there have been various attempts to develop a return on investment for an AIMS, I believe the most compelling reason to implement an AIMS is that the entire medical record will become electronic and that we (the field known for its advances in technology) should not be left out of the electronic age. Of the components of an AIMS, I believe the most important part is the electronic anesthesia workup (H&P). I hope to demonstrate why this part of an AIMS may allow us, as a specialty, to make a significant contribution to medicine.An anesthesia H&P, or a preoperative evaluation, is unique among H&Ps in traditional medicine. In the paper world, an anesthesia evaluation is usually one sheet of paper with a variety of boxes that are checked to enable someone to quickly review the key organ systems and assess their status. Our evaluations are quick and focused. A traditional H&P, as we learned in medical school, has the following components: chief complaint, history of present illness, medical history, review of systems, impression, and plan. If you look up H&Ps in the electronic medical record of most institutions, you will find that the H&Ps follow this general format and are dictated and transcribed, therefore providing a readable “story” describing patients' problems and concluding with an impression and plan. The benefit of transcribing this into an electronic data repository enables the H&P to be viewed by multiple people and multiple places at any time. Unfortunately, it is still a text story. It does not allow us to perform outcomes research, which would require specific fields to be completed or picked, as opposed to transcribing text. Attempts have been made to make smart word searches to extract specific comorbidities or conditions from text H&Ps, but these are fraught with problems, as you can imagine (fig. 6). Although the patient in figure 6has a written history of coronary artery disease, it could easily state “patient does not have a history of coronary artery disease” or “father has history of coronary artery disease.” The number of word combinations to try to determine whether this patient has coronary artery disease is endless. Because of the limited value, from a clinical research perspective, of these text electronic records, most large clinical research databases require trained researchers to read the text and extract the pertinent history and comorbidities and enter them into a relational database, which can then be queried. An example of a system like this in our field is the Multicenter Study of Perioperative Ischemia Research; and in surgery, it is the National Surgical Quality Improvement Project (NSQIP).**28These clinical research databases with patient information in queriable data fields have been extremely useful in outcomes research, examples of which I will describe later.Now, I will contrast an anesthesiology H&P with a traditional medical H&P. For example, a patient is being scheduled for a cholecystectomy. The surgical H&P describes this patient as having the chief complaint of postprandial periepigastric pain. The history of present illness describes this “40-yr-old woman was previously in good health until several months ago, when she noted increasing symptoms of colicky pain after eating fatty foods.” The history of present illness describes in more detail what aggravated the symptoms, what alleviated the symptoms, and what the patient had done about those symptoms. This was followed by a medical history in which the patient states that she took “birth control pills and has occasional back pain for which she takes Aleve.” She also had a history of postpartum depression after her first child, 15 yr ago. She had taken some over-the-counter medications to help curb her appetite. After this descriptive story of chief complaint, history of present illness, and medical history; the surgical workup briefly lists a review of systems. In contrast, we, as anesthesiologists, really do not care about much of this story.Cholecystitis has been diagnosed, and the treatment plan (cholecystectomy) has been chosen. Therefore, from an anesthesiology viewpoint, we have little interest in how the patient got to the operating room; we only want to know what surgical procedure is planned. On the other hand, we have a serious interest in the review of systems (i.e. , the patient's comorbidities, how they affect the patient's physical status, and how they will affect our plan). Our chief complaint, history of present illness, consists of the following: “has gallbladder, doesn't want it.” The end. We actually do not ask a patient his or her medical history because it is too time-consuming to have the patient describe his or her version of the medical history; it is much more efficient for us to immediately go to a review of systems. In actuality, an anesthesia H&P is a detailed review of systems in which the pertinent history, the pertinent signs and symptoms, and management are documented (fig. 7). What we really do is review the patient's physical status, organ system by organ system, for risk stratification. In fact, we are the original risk stratifiers (i.e. , ASA physical status is the oldest and most recognized risk stratifier).29By the way, who do you think developed ASA physical status? E.A. Rovenstine, M.D. (1895–1960, Emery A. Rovenstine, Professor and Chair, Bellevue Hospital and New York University School of Medicine, New York) with two other colleagues.29Risk stratification is our primary concern as we try to assess the patient regarding suitability to undergo the planned procedure, tests that may be needed to further evaluate organ systems at risk, and how to plan the anesthetic to minimize damage to any organ system, allowing the patient to undergo the procedure as safely as possible. Interestingly, risk stratification (risk adjustment) is a key element of all of clinical outcomes research.28,30It is meaningless to compare outcomes of various groups unless they have been risk stratified. This was the primary conclusion when the Veterans Administration started their surgical outcomes project more than 20 yr ago.30Clearly, patients with more comorbidity would have a worse outcome when undergoing the same procedure. Unfortunately, the clinical databases being developed by other specialties, NSQIP, the society thoracic surgeons, and others (of which there are many) all require manual entry of data extracted from the medical record or an interview with the patient by a trained researcher.28,30This process would be prohibitively expensive to apply to all patients. In addition, because these data fields are designed by research groups in advance and implemented through many institutions, the research data fields are relatively static. They do not change with time (i.e. , they do not add fields regularly because it would be too disruptive to many data collectors at many institutions). On the other hand, anesthesiologists provide this risk stratification with the anesthesia H&P on every patient. If done so in an AIMS with data fields, we are populating our “clinical research database” as part of our standard care. Thus, it is actually “free”; we do this with our preoperative H&P, intraoperative documentation, and postoperative documentation.As an example, I will describe the first simple study we conducted using our AIMS at the University of Michigan, Ann Arbor. In 2003, while attempting to mask ventilate a patient after the induction agent was given, I asked Richard Han, M.D. (a first-year anesthesia resident at the University of Michigan, 2003) how difficult it was for him to ventilate the patient. As he attempted to explain this to me, we realized it would be easier if we graded his ability to mask ventilate as follows: easy, medium, hard, or impossible. After the case, we reviewed the literature and found an excellent article that had been published on the topic by Langeron et al. 31Langeron et al. had an observer classify 1,502 cases as easy, difficult, or impossible (with specific descriptor definitions of each); the incidence of difficult was 5%, and only 1 of the 1,502 cases was classified as impossible. The independent predictors of difficult mask ventilation were as follows: a beard, body mass index more than 26 kg/m2, lack of teeth, older than 55 years, and history of snoring. We took the idea of Langeron et al. and decided to make the following scale: 0, mask ventilation was not attempted; 1, ventilated easily by mask; 2, ventilated by mask but required an oral airway, relaxant, or another adjuvant; 3, difficult mask ventilation (described as inadequate, unstable, or requiring two providers); and 4, unable to ma