Limits in Medicine

Where are the limits in medicine?

Take laboratory tests. First- or second-year medical students are taught "normal values." There are dozens to absorb: how many times "should" someone's heart beat per minute? (60-100 beats per minute for an adult.) What is the definition of a fever? (T greater than 100.4F or 38C.) When is a white blood cell count too low or too high? (Less than 4,400 cells/microliter or more than 11,000 [4.4-11.0 x 10^9/L].) There are very few absolutely good or bad numbers in medicine, as natural human variation ensures that such measurements plot out to a bell curve, with most values falling in the middle and only a few being quite high or quite low. Convention, general consensus, and expert opinion have decreed where the limits of "normal" aka average fall, such that most patients are healthy with those values. As clinical neophytes, junior students are developing a physiological framework by which to determine sick/not sick. Not infrequently a measurement that is juuust outside normal will indicate illness in practice questions or on exams, as a way to judge their knowledge of common test ranges. A result reported in red, or with a telling arrow, alerts them to a critical result.

Third and fourth-year students begin to learn that the cut-offs that were so firm on Step 1 are actually fuzzy. For instance, a WBC count of 15 is abnormal...unless the patient just had surgery. Or, an alanine aminotransferase of 70 IU/L is technically abnormal but in the absence of other signs or symptoms may merely represent a normal variant. Not to mention that different laboratories often have different cut-off points, so a sodium of 134 mMol/L might be normal at one lab but abnormal at another. Senior students have to absorb these medical and technical qualifications in the process of refining their understanding of pathophysiology. The goal is to develop enough clinical acumen to recognize a critical value in the absence of an accompanying H or L ("High" or "Low"), and to appreciate an abnormal but unconcerning result, nagging red font to the contrary.

As an intern, I am getting increasingly comfortable with laboratory values that are consistently out of the normal range. This month I am treating a number of patients with both heart and kidney failure. At baseline, their creatinine ("kidney number") is higher than the upper limit of normal (1.0 mg/dL), sometimes much higher. I know that the treatment for their fluid overload is diuresis with "water pills" or IVs, and that these drugs can elevate their creatinine. The trick is not to freak out when I get the admission labs showing a Cr of 2.5 mg/dL--or when subsequent tests show a "bump" to 2.9mg/dL. Each value needs to be interpreted in the context of the previous one rather than observed in a vacuum. Also, maybe their diuretics need to be scaled back for a day to give their kidneys a rest. Like many things in medicine, there is a delicate balance between effect and side effect, and I am learning to push the limits of my comfort with discomfort.

One of the reasons being the intern on the team is so hard is that there are thousands of such decisions to be made every shift, at the same time that you are continuing to learn and understand which results are actionable and which are not. What test(s) should I order? What am I expecting to find? If I find it, what if anything will I do about it? Does this patient usually have abnormal values? If so, how abnormal is significant for them? A typical morning after sign-out involves at least an hour of "chart review," in which every patient's vital signs and test results are reviewed. That's a minimum of 20 numbers per patient x 5-8 patients = 100-160 decisions by 8am alone. Of course many patients have more or more obscure test results as well.

At some point decision fatigue sets in. The first time I worked more than 80 hours in a row (as scheduled, with a lighter week before and after that), I reached my limit. By the time I signed out the evening of the seventh day, I just could not make any more decisions. My brain was fried. I was done. So of course, while I was waiting my turn to speak with the night intern, a nurse paged me about a patient whose blood pressure had been difficult to control for the last couple of days, since he was put on steroids. She pointed out that the order for his rescue medication only specified that she should give it if his systolic blood pressure (top number) was greater than 160mmHg. However, his most recent reading was something like 155/105. Now, a diastolic blood pressure (bottom number) greater than 100mmHg is also abnormal and arguably actionable. She was right to ask me to change the order. However, I could not motivate myself to care enough to do it. I was moments away from signing over my pager for 24 hours of freedom. I was frustrated that nothing we had tried seemed to have worked. I rationalized that maybe such a high blood pressure wouldn't be so bad, and that it would come down now that the steroids had been stopped. I told her I would sign it out to the night intern--who, in the face of my abdication of responsibility, also chose to do nothing. The patient's blood pressure did eventually come down, but I can still hear the disappointment in the nurse's voice at my inaction, and I count it as a low moment thus far in my term as an intern.

These kinds of limits on a new clinician's ability to evaluate and synthesize data are one reason I oppose the proposed relaxation of duty-hour regulations for first-year resident physicians. The Accreditation Council for Graduate Medical Education (ACGME) would like to change the maximum number of hours interns can work in a row from 16 to 28 (24 hours of active duty + 4 hours to sign-out, finish notes, etc.). They argue that the best way to learn about the progression of disease is to observe it in person. Also, that more hand-offs--for instance, between the day team and the night team--means more opportunities for error in communication. They are probably right about the first point, but they are definitely wrong about the second one. Practically speaking, how many 24+-hour shifts can a single intern work in a week? At most 4, assuming s/he is granted 24 hours off in between. Even putting aside the exhaustion factor, there would be fewer handoffs of more information. The historian of medicine in me wishes to remind you that hospitals today take care of more and sicker patients--with more and more complicated test info--than ever before. So prior generations of doctors cannot extrapolate from their training experiences to ours.

It's true that mental and physical stamina differ among trainees, but we all have limits to our ability to transmit and receive information, even when well-rested. When the intern under the proposed rule leaves the hospital, s/he must communicate 24 hours worth of data to the new team--and that, at a time when s/he is likely thinking most of getting home for a shower, some food, and finally sleep. Then, when the intern comes back, s/he will have to absorb a whole day's worth of data rather than only 8-12 hours'. This could leave large gaps in his or her experience of the patient's illness, as the nuances of changes in vital signs or lab values are glossed over in an effort to assimilate what has happened with what should happen next. (It is almost 9 o'clock and time to start morning rounds.) Whether there are more sign-outs with less information or fewer sign-outs with more information, the way to improve patient hand-offs is to improve patient hand-offs.

The last thing I will say on the subject is that the farther into residency I go, and the more discussions we have about better ways to structure the labor of physicians in training, the more I think of the socialist slogan "eight hours labor, eight hours recreation, eight hours rest."* Interns do not need to be restricted to eight-hour shifts, as three hand-offs per day is an invitation for communication errors, but constantly working 12+ hours per day leads inevitably to physical and mental fatigue. It is possible to work both too little and too much to learn, which is purportedly our most important job. Moreover, no resident's job is done when s/he leaves the hospital. We are expected to check in on our clinic patients, to complete administrative paperwork and learning modules, and to study alone and in groups. The margin between (supervised) work and sleep need not be eight hours, but it should be acknowledged as part of both our work day and our personal lives.

Where are the limits in medicine? They lie at either end of the bell curve of "normal" laboratory values. They are at the edge of our ability to synthesize data and recognize patterns in it that could be classified as sick or not sick. And they come at the point of exhaustion and burnout, which is different for every individual but almost certainly lies on this side of the proposed duty-hour modifications. None of these limits should be treated as hard and fast boundaries, and they change over time. An infant's respiratory rate is generally much faster than that of an adult, and a resident in the last year of training is typically more adept at processing patient information than an intern is. Limits in medicine are more often blurry than not, and they are almost always up for discussion. But let us not ignore common sense and sleep physiology in the name of "learning" or "safety," especially when one outcome of the proposed extension of duty hours will be permission to exploit new trainees as cheap labor.



*I was quite sure I had read this lyrical phrase in Karl Marx, perhaps in Das Kapital: "Eight hours for work, eight hours for rest, and eight hours to do with as he pleases." But an internet search for the actual quotation was fruitless, and my copy of DK is in a box in a closet, so I am using Richard Owen's formulation instead.