Preparation vs. Improvisation

Everything in its place

I have a new partner who called me obsessive once.

“Eh?” I asked.

“Everything has to be just so. When you come in you make sure the collars are organized and facing the same direction, you fold over the ends of the tape and stack it in a certain order, you make sure the handles on the bags are easy to grab…”

“I’m not obsessive… have you seen my car?”

“Well, you are here.”

And it’s true. When I show up in the morning, I do my damnedest to ensure that all of our equipment is as stocked, ready, and prepared as possible. I’m the guy who checks the integrity of the air-filled gaskets on the BVM masks, and considers two spare O2 tanks one and one none. If my blood pressure cuffs aren’t labeled, I label them, and I ensure my map book is turned to the correct page.

And all of that may sound funny, because everybody knows that one of the hallmarks of EMS is improvisation, the ability to adapt to unusual situations and “make do.” If you’re juking around at a chaotic scene and discover that you haven’t got any splints, or your stretcher strap is broken, or your patient is dangling over the side of a balcony and needs to be boarded, you see what you have and use your noodle and make it work. Not long ago I saw somebody apply pressure to a laceration on top of a patient’s head by tying a bandage to both stretcher rails and rubber-banding it over their skull like a bow-and-arrow. Why not?

We find a way. So why am I so anal about being prepared while we’re still standing on solid ground?

The fact is, in this job, things are going to go wrong. They just are. And you’re going to handle them the best you can. But if too many things go wrong, the situation may reach a breaking point — your capacity to “adapt and overcome” is not infinite.

Have you ever read a book or watched a show about a major disaster? Plane crashes, reactor meltdowns, bridge collapses. What they have in common is that numerous intelligent people usually foresaw the possibility of such an event, and so they designed systems and safeguards to prevent it from happening. When disaster happens nonetheless, it isn’t because one thing went wrong. It’s because five, six, twelve things went wrong. The backups to the backups to the backups failed. More problems occurred simultaneously than anybody expected..

In this job, too, the only time when feces hit fans is when problems accumulate. It’s not that the patient was sicker than you expected. Or that the stairs were rickety and covered in snow. Those are a nuisance. It goes from whoopsie to trainwreck when you didn’t bring your stairchair and your suction. Then when you go back, the chair falls open while you’re walking, and as you try to fold it you trip over your untied laces, and when you finally get inside you realize the suction canister is missing a cap and won’t hold pressure. And then once you get the patient extricated they’re already unconscious, but you can’t find any Yankauer tips in the truck, and by the time you do they’ve stopped breathing…

See? With this job, even at the best of times, the line between well-in-hand and circling-the-drain can be pretty slim, and once you’re on that slope it’s hard to recover. The only way to stay safely in control is to create a buffer, and that means doing everything you can to prepare yourself when you have the chance, because you won’t always have a chance. If you don’t bother dotting your I’s and crossing your T’s before you enter the mix, then when things inevitably go wrong, the sum of those unhingings may be too much to handle.

Consider your emergency responses. It’s a safe bet that you’re going to drive past the address, or turn the wrong way, or get caught behind the world’s slowest schoolbus. Something is going to cause problems, whether it’s your dyslexic partner who confuses Gable Street with Bagel Street, or you forgetting the apartment number three times in a row. But that’s just a small delay. It won’t be a real problem unless you also stopped to pee before leaving the base, or forgot where your boots were, or had to spend five minutes backing out of where you parked. In that case, you already burned through your margin for error, and now when the unexpected (but inevitable) comes along, you’ve got no slack left.

In short, you can be the best in the world at rolling with the punches, and in this job, you ought to be. But that doesn’t mean you shouldn’t also try to be prepared to the point of obsessiveness. One lays a foundation for the other, and when you habitually have both to work with, you can handle whatever comes your way; if you’ve only got one, you’ll be lucky to get through your shift.

Staying in Place: Compensation and Endpoints

Red queen running


Man’s leaning against a wall. He doesn’t move for hours. Just stands there not moving. Finally, someone says, “You been here all day — don’t you have anything to do?”

“I’m doing it,” he answers.

“Doing what?”

“Holding up the wall.”


And who’s to say he’s not? Maybe he’s working as hard as he can to make sure that wall doesn’t fall down.

In this situation, the man is a compensating mechanism. He is struggling to prevent changes in the wall; keeping that wall upright is an endpoint he cares to maintain, to sustain, to keep intact.

How do we know that the wall isn’t holding up the man? Because we don’t care about the man. Whether he leans or falls doesn’t matter much to anybody. But it would be a terrible thing if the wall collapsed. So we’ll let the man lean or shift in order to prop up the wall when it starts to totter — we’ll use him, adjust him, to compensate for any wall-changes. That’s why he’s there.

If the wall gets weak enough or tilts too far, though, he won’t be able to keep it up. He’ll try, but he’s not infinitely strong, and then maybe the wall begins to tilt or collapses completely. Since we know that under normal circumstances, he’s doing his best to prevent this, if we walk in and see that the wall is tilting, that is not a good sign. It may mean that despite his best efforts, the man has exhausted his strength and is no longer able to resist further wall-changes; or it may mean that, for some reason, the man isn’t doing his job properly. Either way, any further tilting will be unopposed, and will probably happen rapidly and uncontrollably.


Compensators and endpoints

This same dynamic plays out within the human body. As we know, living organisms seek to maintain a certain homeostatic equilibrium. We put our vital metabolic processes in motion and we don’t want them to halt or change, despite any insults or fluctuations imposed upon us by our surrounding environment. So our bodies struggle to keep all of our complex systems at an even keel, using a diverse and powerful array of knobs, dials, and other regulatory tools. Not too hot or too cool, not too acid or too basic, not too fast or too slow. Just right.

The kicker is this, however. Some of our physical parameters are more important than others. In other words, while some parameters have room to adjust, others aren’t negotiable, can’t change much, without derailing our basic ability to function and survive. Things like blood pressure (or at least tissue perfusion, for which blood pressure is a pretty good surrogate measure) are essential to life; your pressure can fluctuate a little, but if it drops too low, you are unquestionably going to suffer organ damage and then die. And yet there are many insults that could potentially lower our blood pressure if we let them: if we bleed a little, or pee a little, or don’t drink enough water, or sweat, or even just stand up instead of sitting down. How do we preserve this vital parameter despite such influences?

By compensating, of course. Our body gladly modulates certain processes in order to preserve other, more important parameters. So in order to maintain blood pressure, perhaps we accelerate our heartrate. In an ideal world, it might be nice if the heart were thumping along at — let’s say — a mellow 80 beats per minute. It’ll use little less energy and less oxygen than if it were beating faster. But it’s really important to keep our blood pressure up, and speeding up the heart can increase the pressure, so we gladly make that trade and induce tachycardia. (Many of these compensatory systems are linked to the sympathetic nervous system, our body’s standard “all hands on deck” response to stress and crisis.)

So imagine we find a patient who’s bleeding and notice that he’s tachycardic, with a normal blood pressure. This suggests a compensated shock; the body is using tachycardia to maintain that normal pressure we see; although his volume is lower than usual, the critical endpoint of adequate blood pressure is still intact.

But what if instead, we found him tachycardic and hypotensive? Well, that’s not good. We see that the body is trying to compensate, but we also see that the important endpoint — blood pressure — is falling nonetheless. The body would never intentionally allow that; BP is too important. So we recognize this as decompensated shock. The hypovolemia has progressed so far, and volume is now so low, that he can’t make up the difference anymore — the compensatory slack has run out — and any further decreases in volume will probably lead to an immediate and unopposed drop in pressure. There’s nothing more the body can do on its own; it’s out of rope.

The skilled clinician — or “homeostatic technician” as Jeff Guy says — uses this predictable progression to understand what’s happening in almost any crisis. Because primary insults are initially covered up by compensatory mechanisms, they may not be immediately apparent, and the earliest and most detectable signs of physical insult are usually nothing more than the footprints of the answering compensation. Thus, when when we encounter those, we know to suspect the underlying problem even if it’s not obvious yet. It’s like seeing brakelights flash from cars on the road ahead; even if you can’t see an obstacle yet, you know people are slowing down for something.

Obvious signs of decompensation usually show up late. Once the primary, underlying problem is revealed by failure of the corrective mechanisms, it’s often progressed so far that it’s too late to address. If you wait to brake until you can see the wreck itself, you might not be able to stop in time.


Two signposts for decompensation

There are two great ways to recognize which signs and symptoms connote decompensation.

The first is to understand which physical parameters are endpoints — which functions the body tries to preserve at all costs. These processes are only compromised as a last resort, so if you see them deteriorate, things are in the end-game; the body doesn’t intentionally sacrifice these for the benefit of anything else.

The second clue is more subtle. In this case, you observe a compensatory mechanism (not an endpoint), but find that it’s no longer successfully compensating — it’s failing, and starting to unwind and scale back, rather than doing its job. The changes in the compensatory system are inappropriate, resulting in less of what we need, not more. This happens when our systems are so damaged that they can’t even fix problems and pursue homeostasis anymore; our infrastructure, maintenance, and repair systems are breaking down. Consider this: we saw how tachycardia could be compensatory, but could bradycardia ever be beneficial in shock? Probably not. So if we found a shocked patient with bradycardia (and likely hypotension, the failing endpoint), we should be very alarmed indeed. There’s nothing helpful, compensatory, or beneficial about bradycardia in the setting of shock, so we recognize that the body would never go there on purpose. It’ll only happen when the machinery itself is falling apart.

Consider, for instance, Cushing’s Triad, the collection of signs often encountered after severe traumatic brain injury, when intracranial pressure has increased enough to squeeze the brain out from the skull like toothpaste. The triad includes hypertension, bradycardia, and irregular or slow respirations. What’s interesting is that, while all are a result of increased ICP, one of these is compensatory, while the others are merely the result of damage. Hypertension is the body’s compensatory attempt to force blood into the brain despite the elevated pressure in the skull. But bradycardia and bradypnea simply result from pressure upon the regulatory centers of the brain tasked with maintaining breathing and heart-rate. That’s why hypertension may be seen earlier, while the other two signs won’t usually manifest until the brain is actively herniating. One signals compensation, the other two decompensation.

Of course, there can be other reasons why compensatory mechanisms might fail, or at least exhibit lackluster performance. Some medications or other aspects of a medical history (potentially unrelated to the current complaint) might throw a wrench in the system. For instance, beta blockers (such as metoprolol and other -olol drugs) limit heart-rate as part of their basic mechanism, so patients with beta blockade often have trouble mustering compensatory tachycardia during shock states. That doesn’t mean they’re any less shocked; in fact, it means they’re more susceptible to hypotension, and that you must be especially on the lookout, because you won’t see one of the red flags (a rapid heart-rate) you might usually expect. Elderly patients with many comorbidities are generally not able to muster up effective compensation for anything, so they can deteriorate quickly, and without much fanfare. Ironically, healthy pediatric patients are the opposite: since they’re so “springy” and smoothly functioning, they compensate very well, with few changes in observable endpoints, until suddenly running out of slack and crashing hard because they’re already so far from shore.

Here are a few important compensatory signs, breakdowns of compensatory systems, and vital physical endpoints:


Appropriate signs of compensation

  • Tachycardia — increases cardiac output
  • Vasoconstriction (cool, pale skin) — raises blood pressure
  • Diaphoresis (sweatiness) — decreases temperature when necessary, but is often just a side effect of sympathetic stimulation
  • Tachypnea — increases oxygenation, CO2 blowoff, and cardiac preload
  • Fever — part of the immune system’s response to infection
  • Shivering — warms a hypothermic body

Inappropriate changes in compensatory mechanisms

  • Bradycardia — reduces cardiac output, rarely useful in illness; as a chronic finding may be the result of high levels of cardiovascular fitness (in healthy young patients) or medications (in sick old patients); but acutely, it is an ominous finding
  • Bradypnea — reduces oxygenation, CO2 blowoff, and cardiac preload
  • Hypothermia (or normothermia when a fever is expected) — suggests a failure of temperature regulation

Inviolable endpoints

  • Blood pressure — can elevate in stress states, but should not drop below resting levels
  • Mental status — except in the presence of a drug or similar agent directly affecting cognition, maintaining appropriate alertness and mentation are always a top priority for the body
  • Blood glucose — kept at normal levels in almost all situations, except when the regulatory systems fail, as in diabetes mellitus
  • pH — most of the cellular machinery fall apart if significant acidosis or alkalosis occurs
  • Low O2 saturation or cyanosis — although oxygen saturation can dip briefly without harm, and in some patients (particularly those with COPD, or long-time smokers) it may run low at baseline, a significant acute drop — or the clinical equivalent, which is frank cyanosis — is always inappropriate.

Missing your Manners


“Hi, my name is Brandon. I’m an EMT with Save-a-life Ambulance. Can I help you?”

Anybody remember that? I think it was on page 6 of the EMT textbook.

I suppose it’s about communicating your name, which is nice. And it’s about obtaining consent, which is important, although in reality, consent in EMS is usually handled the same way as consent in sexual activity — you just go until someone says stop.

But mainly it’s about courtesy and professionalism. It’s gauche to swoop into a room and just start playing with somebody’s lesions without so much as a how-do-you-do.

The trouble is that the formal intro is so hokey nobody actually uses it. Or uses anything remotely similar. And I think that’s a shame, because although it’s silly, it’s getting at something important.

We understand that people call us mainly to bring some order to their crisis. Obviously, that involves Doing Medicine. But the medicine is just a means to an end.

Why do we call plumbers? When your sink starts flooding water into the kitchen, you don’t know what to do. This situation is alien; it’s outside of your expertise. You may be very good at many things in life, such as fueling your car, tying your shoes, and making cherries jubilee, but you don’t know what to do about this.

You know that there are people who have the answers, though; they’re called plumbers. So you call a plumber, and say, make it right.

We’re the same way. People don’t know what to do when they get chest pain or crash their car. But they know that if they call 911, professionals will come who know what to do. So they call us. That’s why people sometimes ask 911 to fetch cats out of trees or ask when the circus is coming to town. It’s why the first reaction of so many motorists after a crash is to call their spouse or their dad.

The thing is, when we walk in and our first reaction is to Do Medicine, it’s not helping the problem. All that medicine is just more strangeness, unless your patient is a fellow clinician. So now their distress is going to continue until you can finally tell them what’s wrong. Except you won’t, because you don’t think you’re qualified for that. So now they’ll stay confused and scared until they get to the hospital. And on and on.

Throw them a rope!

The fastest way to restore normality to a situation is to reintroduce a familiar activity. And social courtesies are very familiar to everyone.

When you introduce yourself and shake someone’s hand, they’re transported from the confusing world of a medical crisis to something much more comfortable. They know how to do this. Smile, shake, say your name. It’s easy. They’re good at it.

Sometimes patients are visibly shocked when you do this, and seem to reset; you can literally watch them change channels. Now they’re a little calmer, a little happier, and you can work with that. With enough balls, you can pull this off in the most outrageous circumstances. Sing praise for the EMT who can walk in on the triple traumatic amputation and say “Hi! I’m Jim. What’s going on?”

Now, of course, you don’t want to minimize the patient’s distress. In an emergent situation, it can be galling and obnoxious for their freak-out to be met by your apparent apathy or boredom. That’s why you have to find a middle ground between projecting calm confidence and acknowledging the seriousness (perceived or real) of the patient’s situation. Don’t let them drag you along into panic, but don’t try to abruptly pull them to a halt either; strike a balance, pace them, and then gradually slow them back down. The point is that introducing yourself like a regular person is a powerful tool for restoring normality to a crazy situation: use that tool liberally, but intelligently.

I’ve had patients tell me I was the only Medical Person they could remember introducing themselves. That’s a damned shame. People greet each other and make a introduction when they meet. And aren’t patients people?

Clinical Judgment: How to Do Less


It was around 11:00 AM when we were called to a local skilled nursing facility for a hip fracture. The patient was a 61-year-old male with mild mental retardation and several other issues, who’d fallen last night while walking to the bathroom. He was helped back to bed with moderate hip pain, and the staff physician stopped by to check him out. A portable X-ray was performed, which the physician interpreted as showing a proximal femur fracture as well as an associated pelvic fracture. This was communicated to us via a scrawled note and a cursory report.

The patient was found resting comfortably in bed, semi-Fowler’s and alert. He had no complaints at rest, although his pelvis and left femoral region were mildly tender and quite painful upon movement. No deformity was notable and there was no obvious instability. His vitals were stable and he was generally well-appearing, in no apparent distress. He denied bumping his head and had no pain or tenderness in the head or neck.

We gently insinuated a scoop stretcher underneath him, filled the nearby voids with towels and other linen, and bundled him into a snug, easily-movable package. Then we gave him the slow ride to his requested emergency department, a teaching hospital in town just a few minutes away.

We rolled into the ED and were lifting him into bed on the scoop when a young man entered the room, bescrubbed and serious-looking. I gave a brief report. As the words “pelvic fracture” left my lips, his mental alarms started visibly beeping and flashing, and he hurriedly asked, “What kind of pelvic fracture?”

“We don’t know. All we’ve got is the radiology note, which doesn’t say much.”

“Okay, but pelvic fractures can be a big deal. It could be … ” he sucked in air, “… open-book. There could be a lot of bleeding.”

I stared at him. “Well, sure. But he’s been stable since last night, and has a basically normal physical with no complaints at rest. He’s not exactly circling the drain.”

He didn’t seem to hear me as he briskly approached the patient and began poking him and asking questions. While we pulled our stretcher out of the room, he asked, “Does your neck hurt at all?”

Now that the patient had been stuck on a scoop stretcher for over twenty minutes, he thought for a moment and then shrugged. “Sure.” The doctor immediately ordered the placement of a cervical collar.

As we escaped, he was on the phone to the SNF, and the last thing I heard was him berating them with his urgent need to know exactly what type of pelvic calamity the patient had suffered.


What was the failure here? It was a failure of clinical judgment.

Clinical judgment is a phrase which means different things to different people, and often its meaning is so nebulous (much like “patient advocacy“) that it sounds good while saying nothing. But most would agree that it means something like this: the ability to combine textbook knowledge and personal experience, applying them intelligently to the current patient’s situation to yield an accurate sense of the possible diagnoses and the costs vs. benefits of possible treatments. In other words, it means knowing what the patient’s probably got and what to do about it, which is the heart of medicine anyway. So what’s all the fuss about?

In reality, when clinical judgment is mentioned, what’s often meant is something specific: the wisdom to know when something’s not wrong. Much of medicine is about planning for the worst, ruling out the badness, and looking for the unlikely-but-possible occult killer that nobody wants to miss. As a result, we often act as if nearly everybody is seriously ill, even when they probably aren’t.

On a practical level, most complaints — from chest pain to the itchy toe — could conceivably represent a disaster. Anything’s possible. So if we want to truly adopt perfectly mindless caution, we should be intubating every patient and admitting them directly to the ICU so that we’re ready when their skin melts off and their eyes turn backwards.

But we can’t do that, and we shouldn’t. So how do we know when to do a little less? Clinical judgment.

Clinical judgment is the acumen to assess a patient and say, “I think we’re okay here. Let’s hold off on that.” It’s what you develop when you have both the knowledge and experience to understand that a person is low-risk, and that certain tests or treatments are more likely to harm than to hurt them. That doesn’t mean that nothing will be done, or that more definitive rule-out tests will not occur, but it means you’re not freaking out in the meanwhile. It’s a triage thing.

Put another way, imagine the patient who you’re placing in spinal immobilization, or providing with supplemental oxygen, or to whom you’re securing a splint. They ask, “Look, I don’t much like this; do I really need it?” Well, I don’t know, rockstar — does he? If you’re simply acting on algorithms, reflexively doing x because you found y, then you really don’t know. How important is that oxygen? To answer that, you’d need to truly understand the benefits versus the potential harms, which means having a strong grasp of the mechanism of action, familiarity with the relevant literature (including the pertinent odds ratios, NNT and so forth), prior experience with similar patients, et cetera… only with that kind of knowledge do you really understand what’s happening. In essence, the patient is asking for the informed element of informed consent, something he’s entitled to, and you can’t provide it if you don’t have it yourself.

But when you do develop that depth and breadth of knowledge, you gain a special ability. It’s the ability to do less. When you truly understand what you’re dealing with, and more importantly, what you’re not dealing with, you can titrate medicine to what’s actually needed and stop there. Along with the knowledge comes the confidence, because you don’t merely know, you know that you know; in other words, you don’t need to take precautionary steps merely because you’re worried there might be considerations you don’t understand.

When it comes to withholding anything, even the kitchen sink, you might ask, “isn’t there risk here?” And strictly speaking, there is risk. But you can set that bar wherever you want. The important thing to grasp is that “doing everything for everyone” is not the “safe” approach; overtriage and overtreatment are not benign. All those things you’re doing have a cost. They may cause real harm. Even at best, they cost time and money, and subject the patient to unnecessary discomfort and inconvenience. We’d like to minimize all that whenever possible.

So, we return to the gentleman with the pelvic fracture. Strictly speaking, fracture of the pelvis has the potential to be life-threatening; certain types of unstable fracture can cause massive bleeding, along with damage to nervous, urinary, and other structures. So a textbook response to “pelvic fracture?” might be to treat it as a high-risk trauma.

But a patient with an unstable, severely hemorrhaging open-book pelvic fracture probably wouldn’t look like that. It would be evident; it would cause a number of apparent effects, such as pain and distress, shock signs, altered vitals, deformity or palpable instability. Except in bizarre cases or in patients who are clinically difficult to evaluate, big problems create big changes. While it’s true that we don’t know exactly what the X-ray showed, so one could theoretically argue for any conceivable pathology, there’s no question that the patient appeared stable, had remained unchanged for many hours, and had apparently been judged low-acuity after evaluation and imaging by his own doctor. In other words, let’s take it easy.

The question of spinal immobilization is another example. Strictly speaking, could we rule out the possibility of a cervical spine fracture? Well, no. Not without CT and MRI and even then who knows. But the fall was many hours ago, the patient was freely mobile and turning his head throughout that period, had no peripheral neurological deficits, denied striking his head or loss of consciousness, and quite frankly, had no pain until he spent twenty minutes with his head against a metal board.

It’s not often that you find a doctor more concerned about C-spine than an EMT. How did it happen here?

Despite the fact that we delivered the patient to a major tertiary center, it was nevertheless a teaching hospital, and the new interns had just hit the wards. While this particular clinician was undoubtedly smart and well-educated, at this stage he had about two weeks of experience behind him, and that is not conducive to providing judicious (rather than applied-by-spatula) care. He had neither the experience to know when to take it easy, nor the confidence in that experience to stand by such a decision.

We don’t want to take this concept to its extreme, which would involve doing very little for most of our patients. In the end, this is still emergency medicine, and emergency care will always involve screening for the deadly needle in the benign haystack. There’s also danger in simply becoming lazy and burned-out, and using Procrustean application of cynical “street smarts” to justify never bothering with anything. The real goal is to do the right things for the right reasons, no more, no less. And to get to that point, you have to put in some time.

The Curious Incident of the Dog in the Diagnosis


“Is there any point to which you would wish to draw my attention?”

“To the curious incident of the dog in the night-time.”

“The dog did nothing in the night-time.”

“That was the curious incident,” remarked Sherlock Holmes.

Sir Arthur Conan Doyle, Silver Blaze

We can learn a lot from Sherlock Holmes.

If there’s anybody who better personifies the ultimate diagnostician, I don’t know who. Sir Arthur Conan Doyle, creator of the Holmes canon, was himself a physician and purportedly based his famous detective on Dr. Joseph Bell — who, it was said, could glean a dozen esoteric facts of a patient’s background, history, and complaints from a single glance. (Holmes himself, of course, was not a medical man; that role was played by Watson, the earnest physician who carried his stethoscope wrapped inside his hat.)

Holmes didn’t diagnose illness. Instead, he diagnosed crimes. But the methods were the same, so much so that among the countless fictional characters based upon the Holmesian archetype, some have been crime-solvers (cf. Monk), yet others have been medical doctors (House is the best). Perhaps we shouldn’t model ourselves after the man, who was a single-minded addict and misanthrope, but when it comes to diagnosis — something we can’t escape in medicine — he knows whereof he speaks.


The diagnostic method

Holmes tells us in The Sign of Four that detection involves nothing more than three skills: observation, deduction, and knowledge. Let us consider what he means when faced with, for example, a complaint of chest pain.

Observation: we perceive a middle-aged male, alert and seated upright, rubbing at his sternum with a pained expression. His skin is slightly pale, his respiratory rate is slightly elevated, and he is hypertensive. He complains of “tight” 4/10 chest pain whenever he breathes. Upon auscultation we detect diffuse, bilateral, biphasic wheezing. We note a history of coronary artery disease, diabetes, and COPD.

Knowledge: Chest pain in adults indicates a high risk for acute coronary syndromes. Pallor, tachypnea, and hypertension are consistent with this diagnosis. Sharp, mild, pleuritic pain is not, nor is wheezing, all of which are more consistent with a primarily respiratory etiology. But we also know that MI often presents atypically, particularly in diabetics.

Deduction: Both cardiac (ACS) and respiratory (COPD exacerbation) diagnoses top our differential. An ECG and biomarkers are needed to further evolve the odds.


So what just happened? We observed using our medical assessment — the history, physical, and diagnostic tests — thus yielding a collection of facts and data. We took the set of background knowledge we already possessed, regarding pathophysiology, epidemiology, and hazard ratios, and used it to “fill in the blanks” and provide context to our assessment findings. Finally, we connected the dots together and used deduction to decide what we’re dealing with.

Holmes knew this method well. He might observe your tattered boots, and using knowledge he possessed of typical wear patterns in the various trades, deduce that you make your living as a longshoreman. Simplicity itself.

Why is this a useful model for diagnosis? Because it highlights the fact that these three skills are entirely distinct, though all quite essential. Observation requires skill with the physical exam, the ability to take a nuanced history, the acumen to interpret diagnostics — it’s simply the trait of being aware. (Holmes, succinctly: “Data, data, data! I can’t make bricks without clay.”) Knowledge is knowledge: it’s memorized facts, what you learn in school or from books, and it gives us the basis to understand the raw material we discover in our assessment. Finally, deduction is the mental capacity to analyze, discover patterns, weigh odds, use your imagination, and extract from the vast pool of observation and knowledge the particular pieces that are actually relevant. (Holmes: “… to recognize out of a number of facts which are incidental and which are vital.”)


The hidden danger

Here’s the rub: we’re almost too good at deduction. Humans are excellent at finding patterns in anything. If I leave you my tea-cup for long enough, you’ll undoubtedly find an image revealed in the leaves.

That’s good — but it’s an error. Because there’s not really any image in the tea leaves. But if you’re good at observing details, and have a strong imagination, you’ll still “deduce” many wonderful things from it. Call it apophenia: people want to connect the dots, even when there aren’t any. So we create connections that may be true, but are not always true. We develop stereotypes. Simplifications. False associations.

In medicine, we’re especially prone to this. Because we do know that the human body is interconnected, and that patterns are the rule rather than the exception. Indeed, a large part of developing experience and clinical judgment is increasing your catalog of mental connections. Crackles mean CHF. Irregular pulses mean A-fib. People with Foley catheters have UTIs. Homeless people are drunk. Toe pain is a nonsense complaint. We can’t avoid making the connections, because just like when Holmes examines your boots, those connections are essential to doing our job. But at the same time, we need to learn when to reign them in, or we enter an inescapable diagnostic tunnel after the first moments of patient contact.

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.

A Scandal in Bohemia

What’s the secret? Knowledge.

Sure, we gather the pieces from our assessment, and we automatically start to connect them together. We can’t help that; patterns jump out at us, we’re natural pattern-finding machines. But using our knowledge, we can look past those simplistic, eye-catching patterns, because knowledge tells us something more subtle: what’s missing.

She’s all false positives. See, that’s the trouble with naturals. They don’t see what’s missing.

Lie to Me, “Moral Waiver”

Okay, Friday night, a “man down” call for a homeless guy on the sidewalk. You’re already thinking: drunk. And the initial observations confirm it: he rouses sluggishly, slurs his speech, and pushes you away as he rolls back over. But then you open the mental box that you filled with this sort of thing in your training, and you reflect: where’s the bottle? And this is a strange spot — it’s cold, wet, public and unsheltered. And come to think of it, is that a medical alert bracelet? We should probably check this guy out a little more. Maybe take his blood sugar, look for any trauma, shake him awake and ask some questions.

The initial pattern recognition is there, but you don’t have to be a slave to it, because you know what else to look for. Even if five clues say one thing, if we don’t see five others that ought to be there, that tells us something different. Pertinent negatives, they call ’em in the business.

Maybe there’s nothing else; maybe the drunk is just drunk. But we’re too smart to make that kind of assumption. Because we know that getting it right doesn’t just mean registering the hits — it means checking off the misses, too.

Holmes would expect no less.