Tuesday, May 15, 2018

Root Cause Analysis: Dig Deeper, or the Weed Will Keep Growing Back

In a recent JAMA Performance Improvement piece, the authors describe the case of a man who presented to the emergency department with dizziness.  He was sedated for an MRI, his history of OSA (obstructive sleep apnea) may have been glossed over, and he arrested in the radiology department.  The subsequent "root cause analysis" traced the untoward outcome to a failure to recognize the OSA and the adverse effects that may follow sedation of a patient with this diagnosis.

The problem with this "root cause analysis" is that it assumed that the MRI, requested by a neurologist on-call, via telephone, was necessary.  It was not.  The root cause analysis got it wrong because it did not trace the roots to their deepest source:  glossing over the patient's chief complaint and considering it and its evaluation carefully and rationally.  Stroke is an uncommon cause of dizziness and the MRI was probably not indicated, especially in light of the other information provided in the case.

Here is the letter that I sent to JAMA which was not accepted/published.  It is a case of the distinction between rationality and intelligence.  Very intelligent people traced the "cause" or the "root" of the complication to a missed piece of information (OSA) and corollary ideas (he may have complications from sedation), but they failed to consider underlying assumptions:  namely that the MRI was necessary or would yield net benefit in the first place. 

Medicine is best played like chess, not like checkers.  "Intelligent people have superior performance when you tell them what to do."  A failure of a "root cause analysis" such as this will foment the regrowth of the weed.

Here is the letter:

I enjoyed the Performance Improvement case describing oversedation of a patient with obstructive sleep apnea1.  I posit that the most proximate possible root cause of the complications described was ordering an MRI with low clinical yield2, without pre-specifying what abnormality was being sought as well as its probability, and without delineating, a priori, how any resulting findings would change management3.  Presumably, the neurology consultant was looking for stroke.  What was its pre-test probability in a patient with dizziness?  Would management have changed if stroke were detected with imaging?  Were there contraindications to therapies for stroke?  Was the patient already receiving the indicated therapy for stroke?  What is the probability of a false positive finding (i.e., one that doesn’t explain the patients’ symptoms; an “incidentaloma”), and how might that finding lead to interventions which may yield net harm if stroke is not present?  What was the response to meclizine and odansetron, and how did this incremental information alter the prior probability of stroke?  Because decisions necessarily precede actions, they must always be considered as possible proximate causes of downstream complications.  Even if the other errors identified in the reported root cause analysis can be avoided in the future, injudicious testing may lead to other complications, including cascades of additional potentially harmful testing and intervention unguided by careful, rational, clinical decision making.

1. Blay E, Jr, Barnard C, et al. Oversedation of a patient with obstructive sleep apnea prior to imaging. JAMA 2018;319(5):495-96. doi: 10.1001/jama.2017.22004
2. Fakhran S, Alhilali L, Branstetter BFt. Yield of CT angiography and contrast-enhanced MR imaging in patients with dizziness. AJNR American journal of neuroradiology 2013;34(5):1077-81. doi: 10.3174/ajnr.A3325 [published Online First: 2012/10/27]
3. Pauker SG, Kassirer JP. The threshold approach to clinical decision making. The New England journal of medicine 1980;302(20):1109-17. doi: 10.1056/nejm198005153022003 [published Online First: 1980/05/15]

Confusion, Diaphoresis, and Hyperventilation Aboard a Private Airplane

This was intended to be a case report but the amount of work required to publish a case report is just too great to justify it.  The publishing landscape has been flooded with an attendant raft of predatory journals, so one must be very careful.

This will be an online interactive case report.  I will tweet this post, asking for comments and diagnoses in the comments below (preferable to twitter comments) and update with the answer and a discussion in 1-2 weeks.

A 68 year-old otherwise healthy male passenger was flying with his friend, a pilot, in a private plane from California to Montana for a fishing trip.  Within an hour after takeoff, he became confused and diaphoretic and was hyperventilating, then he lost consciousness for approximately 20 minutes.  The pilot applied supplemental oxygen and checked his passenger's arterial oxygenation via oximetry, finding it to be 95%.  The flight was diverted for a medical emergency.  During descent and landing, the passenger regained consciousness but remained confused.  In the emergency department of a nearby hospital, he had normal vital signs, and had a non-focal neurological examination, but remained confused.  Representative images from CTA of the chest are shown below (click on the images to expand).  A head CT was normal excepting for some age related atrophy.  What is the diagnosis?

Monday, November 20, 2017

Sunk Kidney Bias: A Lethal Form of Sunk Cost Bias

Hal Arkes
The heuristics and biases program of Kahneman and Tversky, once an obscure niche of cognitive psychology, became recognized among lay persons with Kahneman's Nobel prize in economics in 2002.  The popularity of the program surged with Kahneman's book Thinking Fast and Slow several years ago and several among the scores of related books about behavioral economics became best-sellers.  This year, Richard Thaler was the Nobel laureate in economics for his work in behavioral economics.   I became aware of heuristics and biases just before Kahneman's Nobel and started looking for them in medicine in 2003.  We (Aberegg, Haponik, and Terry, Chest, 2005) indeed found evidence for omission bias, and have discovered other biases along the way, some which are very intriguing but we aren't even sure what to name them (Aberegg, Arkes, and Terry, Medical Decision Making, 2006).  My point here is that these biases are useful but difficult to identify as patterns systematically operating within medical practice in predictable ways - they pop up here and there only to recede and reappear years later, if they are recognized at all.

Then there are biases about the biases.  Highly cited expositions of biases in clinical care, such as those of the insightful emergency physician Pat Croskerry (Academic Medicine, 2003), among many others) very often surmise the presence of biases in clinical care, without the kind of empirical evidence that established the biases in the first place.  Sometimes, new and probably useful biases are proposed (such as "search satisfycing"), without any empirical evidence, at all in any domain, for their existence.  They are merely postulates.  (Granted, empirical evidence is very difficult to generate, this the reason I don't do this kind of research anymore.)  Finally, the descriptions of the biases applied to medicine are often strained, or just plain wrong.  My favorite is the bastardization of "anchoring and adjustment" into a description of any time a physician seizes upon a diagnosis and discounts disconfirming evidence or fails to consider alternatives.  This is not anchoring and adjustment.  Anchoring refers to a numerical anchor, and failure to adjust away from it when providing numerical estimates.  Here is a summary of the original descriptions, from the wikipedia entry on anchoring and adjustment:

Tuesday, October 31, 2017

Applied Respiratory Physiology Vlog. Parts 1,2,3,4: Respiratory Failure Explained as Workload Imbalance

The following embedded videos are parts 1-4 of a 5 part talk I've been giving and refining on Applied Respiratory Physiology for about 10 years now.  (It is split into 5 parts because of youtube size limitations and for digestible 10-15 minute segments.)  The principles herein derive from many sources, but special credit must go to Nunn's Textbook of Applied Respiratory Physiology and The University of Chicago critical care text edited by Hall, Schmidt, and Wood.  For the majority of the ideas and applied principles herein, I have never seen them discussed in any lecture in 20 years of attending pulmonary conferences, didactics, etc.  My interest in applied physiology and Nunn's textbook indeed originated because of my frustration with the esoterica of the basic and advanced physiology that I was taught from medical school through fellowship -  I determined that much or most of it was not applicable at the bedside.  This lecture series, I hope, will be far more clinically applicable, intuitively appealing, memorable, and useful than what has been traditionally taught.  Real life examples highlighting the extremes of human respiratory performance should, I hope, make this a memorable lecture seeries.  I welcome comments and criticisms below.  Enjoy!

Tuesday, September 26, 2017

DIPSHIS: Diprivan Induced Pseudo-Shock & Hypoxic Illness Syndrome

This would be a very informative case report (and it's true and unexaggerated), but I anticipate staunch editorial resistance (even sans puns), so I'll describe it here and have some fun with it.

Background:  The author has anecdotally observed for many years that so-called "septic shock" follows rather than precedes intubation and sedation.  This raises the possibility that some proportion of what we call septic (or other) shock is iatrogenic and induced by sedative agents rather than progression of the underlying disease process.

Methods:  Use of a case report as a counterfactual to the common presumption that shock occurring after intubation and sedation is consequent to the underlying disease process rather than associated medical interventions.

Results:  A 20-something man was admitted with pharyngitis, multilobar pneumonia (presumed bacterial) and pneumomediastinum (presumed from coughing).  He met criteria for sepsis with RR=40, HR=120, T=39, BP 130/70.  He was treated with antibiotics and supportive care but remained markedly tachypneic with rapid shallow respirations, despite absence of subjective respiratory distress.  A dialectic between a trainee and the attending sought to predict whether he was "tiring out" and/or "going into ARDS", but yielded equipoise/a stalemate.  A decision was made to intubate the patient and re-evaluate the following day.  After intubation, he required high doses of propofol (Diprivan) for severe agitation, and soon had a wide pulse pressure hypotension, which led to administration of several liters of fluids and initiation of a noradrenaline infusion overnight.  He was said to have "gone into shock" and "progressed to ARDS", as his oxygen requirements doubled to 80% from 40% and PEEP had been increased from 8 to 16.  The next morning, out of concern that "shock" and "ARDS" were iatrogenic complications given considerations of temporality to other interventions, sedation and vasopressors were abruptly discontinued, diuresis of 2 liters achieved, and the patient was successfully extubated and discharged from the ICU a day later.

Conclusions:  This case provides anecdotal "proof of concept" for the counterfactual that is often unseen:  Patients "go into shock" and "progress to ARDS" not in spite of treatment, but because of it.  The author terms this syndrome, in the context of Diprivan (propofol) in the ICU setting, "DIPSHIS".  The incidence of DIPSHIS is unknown and many be underestimated because of difficulty in detection fostered by cultural biases in the care of critically ill medical patients.  Anesthesiologists have long recognized DIPSHIS but have not needed to name it, because they do not label as "shock" anesthetic-induced hypotension in the operating theater - they just give some ephedrine until the patient recovers.  DIPSHIS has implications for the epidemiological and therapeutic study of "septic shock" as well as for hospital coding and billing.

Sunday, August 27, 2017

The Number Needed Not To Treat To Harm (NNNTTTH): A Heuristic for Evaluating Trade-offs in Medical Decisions

A frequent conundrum of decision making that arises in medicine is when there is a generally indicated therapy, say, anticoagulation for atrial fibrillation, that poses unique risks in a particular patient.  CHADS2 and HAS-BLED scores are calculated, but don't quiet the hemming and hawing or quell the hand-wringing.  What is usually a simple dichotomous decision is now one laden with probabilities, risks and benefits, and compromise between competing objectives.  (See:  The Therapeutic Paradox:  What's Right for the Population May Not Be Right for the Patient.)  In order to restore nuance to the decision, we need to try to estimate the numerical values of the risks and benefits to determine if the net utility of anticoagulation is positive or negative, something the aforementioned calculators are intended to do in a semi-quantitative way.  But what if you opine that your patient has a specially enhanced risk of side effects and you're worried about falls or bleeding but ambivalent because of a concurrent fear of denying him of the benefit of stroke prophylaxis?  What if you think that he would have never been included in a trial of stroke prophylaxis and the results of those trials may have limited generalizability to him?  What if you think he has only a year to live?

The number needed not to treat to harm (NNNTTTH) is the number of patients whom you have to not treat with something beneficial in order to cause one harm from your omission.  It is numerically equivalent to the number needed to treat (NNT), but it reframes the decision from action to omission and from benefit to harm.  Ignoring bleeding altogether (because making relative utilities for bleeding and stroke is a fraught endeavor), you could ask yourself "how many patients can I withhold stroke prophylaxis from for one year before I statistically cause (or allow to happen, if you are prone to omission bias) a stroke?"  For most patients, withholding stroke prophylaxis has a NNNTTTH of about 25-30 per year (check the corresponding NNT from CHADS2 for a more "precise" estimate).  Reframing the question into "how much am I asking the patient to pay, in terms of statistical likelihood of stroke, to avoid anticoagulation and the particular side effects that cause me concern in his case?" can often provide some reassurance for the clinician and the patient alike.

Wednesday, July 19, 2017

Screening in Disguise: You Can't "Unknow" that Troponin, But You Can Dismiss It After Careful Thought

During MICU rounds last month, there were a lot of troponins ordered, and most of them should not have been.  Invariably when abnormal troponin values are reported on rounds, there is no mention of whether the patient had anginal chest pain, whether there were ischemic EKG changes, or whether this information was sought at the time the troponin was drawn.  This is because troponins are being used as a screening test, rather than as a diagnostic test.  "Not so!" exclaims the resident, eager to convince me that he has not engaged in the kind of mindless testing he knows I loathe.  I am told that because the first troponin was mildly elevated in a little old lady with cirrhosis, overdose, right heart failure and urinary tract infection, that we need to follow it to see where it "peaks".

Saturday, August 13, 2016

The Enemy of Good is Better: Maximizing versus Satisficing in Clinical Medicine

Herbert Simon, Nobel Laureate
Recently I was called to admit a little old lady with a digoxin overdose who had symptomatic bradycardia.  She was in her 70s, had Alzheimer's disease (AD) and a medication list that would not print on one page.  I immediately thought, what benefit does digoxin have that justifies even the occasional admission for toxicity?  That's a good question in its own right, but consider a partial list of her other medications:

  1. pantoprazole
  2. lisinopril
  3. gabapentin
  4. raloxifene
  5. estradiol
  6. donepezil
  7. labetolol
  8. furosemide
  9. glipizide
  10. fenofibrate
  11. memantine
  12. sitagliptin
  13. spironolactone
  14. amlodipine
  15. alprazolam
  16. aspirin
One certainly must wonder what goals her providers are trying to achieve with these and indubitably some other medications which aren't listed.  Her husband was frustrated when I told him that many of the medications she is taking are not really doing her any good.  "They why do they have her taking them?" was a question I could not answer, because it doesn't make sense to me either.  Exasperated, he offered a great analogy:  "Suppose you hire me as a contractor to build you a home, and I tell you that you need to build a 14 foot high retaining wall in the back yard, two feet thick, reinforced with rebar and containing 20 yards of concrete.  Would that be responsible unless it were absolutely necessary?  What kind of contractor would recommend something you didn't really need?"

"A physician contractor," came the ready answer in both of our minds, and we simultaneously nodded in understanding.

Thursday, August 11, 2016

Medical Decision Making as a "Patient": Pregnancy Leads to A Trip Down The Rabbit Hole - A Personal Story

My wife is pregnant.  Wanting to be a supportive spouse, I attended the first prenatal visit to see one member of her team of midwives.  (Being a "minimalist" I was, like my wife, fond of the idea of not unnecessarily "medicalizing" the [usually] natural act of labor and birth.)  I realized during that first visit that understanding the intricacies of medical decision making can be a double-edged sword when dealing with practitioners, especially outside of one's specialty.  If ignorance is bliss, 'tis folly to be wise, it is said.  I've come to wonder which is better for you when you get entangled in US healthcare, wisdom or bliss.

During the first visit, we were offered, with an air of agnosticism, a referral for genetic counseling +/- non-invasive prenatal testing (NIPT).  "How accurate is it," I naturally inquired, trying to avoid technical terms such as sensitivity and specificity.  "Something like 99%" came the reply.  So we were given the referral.  But I quickly realized that this was a classic problem of base rates.  The likelihood of a chromosomal abnormality is so low given my wife's age, that even extremely high sensitivities and specificities are inadequate to guide our decision - that is, the test is rendered practically useless because of the low base rates in our case.  And this despite the fact that the sensitivities and specificities of prenatal blood testing are inflated by the way they were derived.  But think of the decision we would have faced had we blindly proceeded with testing without this consideration - given the low base rate, the posterior probability of a chromosomal abnormality such as Down's Syndrome given a "positive" test result would be around 33%.  How would we act on this information?  Is that threshold high enough that we would consider an elective abortion (if we were morally disposed towards that as an option)?  Or would we ignore the information and proceed to term?  And if we were not ethically accepting of elective abortion as a possibility, what other remedy would we have that would justify the information from the testing?  Why would we talk about getting prenatal genetic testing before talking about the choices we may have to face after we receive the results?  Why would not a discussion of remedies, specifically abortion, precede consideration of the testing?  How many couples dive into the rabbit hole only to wonder how they got there and how they can get out?  In this case, we decided that ignorance was indeed bliss, and deferred NIPT.

At that same visit, blood was ordered to be drawn.  I had difficulty understanding why you would need to draw blood from a perfectly healthy woman at 12 weeks gestation.  Blood types and anemia and all that I guessed.  But I was particularly caught by the thyroid testing.  Why are we screening an asymptomatic woman for thyroid disease?  Is that justified by the prior probabilities?  It takes only a google search to learn that ACOG (the American College of Obstetrics and Gynecology) and an endocrine society do not recommend universal testing.  But my questioning why we were doing this was off-putting and frankly unanswerable for the midwife - she was just following the usual routine, whatever her supervisors and mentors had told her to do, without understanding....well without understanding any of this Bayesian mumbo jumbo that I was hinting at.  Alas, thyroid testing, like NIPT, was deferred.  But not for long.

Tuesday, June 14, 2016

The Lost Art of Landmarking: Right Internal Jugular Insertion Video

I have long wanted to post a video of central line insertion using the traditional landmarks method, and recently I was afforded the perfect opportunity.  The patient needed a dialysis catheter.  He had had one inserted a few months ago and it had been a disaster for him.  First, the inserting physician mistakenly installed a Cordis Introducer instead of a dialysis catheter, using ultrasound guidance and causing a good deal of pain by transecting the belly of the sternocleidomastoid (SCM) muscle, then it was rewired to a dialysis catheter that would not flow, then, finally, a working catheter was installed in a new site.  I assured the patient that this go at it would be much easier and he was very interested in having the experience recorded so he could later see it, and others could learn from it.

I previously observed that in the current training atmosphere, trainees are paying no attention to anatomical landmarks, rather they are just poking wherever they see the vein on the ultrasound image, traversing whatever structures lie between the surface and the target, without any care whatever.  It is my belief that the SCM muscle should never be split/transected with a dilator or line unless absolutely necessary.  Thus even if ultrasound is used, the landmarks ought to be identified and respected.

Several points in the video need further explication here.  (Beyond the facts that my nose did not fit under the mask, I did not wear eye protection, and that I failed to lay out the components of the tray beforehand.)

  • The importance of properly and confidently identifying the bellies/heads of the SCM cannot be overemphasized.  I will at some point do another video to go through that process specifically in detail.
  • I always keep 0.5-1.0 cc of liquid (lidocaine or flush) in the syringe during needle passes.  In my experience, it minimizes clotting in the needle and the risk of passing through the vessel without flash due to clot.
  • In contrast to what is suggested in the NEJM video for RIJ CVC insertion, I do not hold the needle at 45 degrees to the floor plane when going after the IJ.  Doing this makes you have to insert the needle much deeper, increasing the risk of pneumothorax.  I prefer an angle of 60-90 degrees.
  • In this patient, the IJ was deeper than usual and than I expected, thus I did not hit it with the "seeker" needle.
  • When the fingers of my left hand are on the neck, I am not palpating the carotid pulse.  I could care less about the carotid.  I am feeling that medial belly of the SCM as a landmark and ever so gently pushing it to the left to increase exposure of the IJ underneath of it.
  • When entering the skin with the large bore needle, I poke to and fro rapidly to keep it from "breaking through" the skin and plunging too deep.
  • Notice that each centimeter or so that I enter with the large bore needle, I pause and pull back a bit to see if I get flash in case the vessel is compressed on the forward pass.  In the video, I get flash on the second or third pull back.
  • After I get flash, I then lay the needle back to 45 degrees to facilitate guidewire passage
  • This patient's skin and subcutaneous tissue was tougher than I expected and I did not make a generous enough stab incision into the subcutaneous tissues to make a tract for the dilator.  Usually I use a regular 7.0 French triple lumen CVC kit dilator first, then the smaller of the two dilators that come with the larger 12 French dialysis catheter.  This is a new all-inclusive kit that we began using which contains only the large dilators.
  • The bleep is to protect privacy
Stay tuned for the subclavian vein CVC insertion video next!

[Formal written consent was obtained from this patient to make this video and to publish it for educational purposes.]

Special thanks to Clayton MS4 for filming this and helping with editing.  Other medical students are encouraged to participate in future web and social media initiatives.  I have several in mind.

Friday, June 3, 2016

Doctorin' with Double Effect Part II: The Devil is in the Details

In a prior post, Doctorin' with Double Effect, (a double entendre with Doctrine of Double Effect) I attempted to tease out ethical issues related to the withdrawal of life support and specifically the provision of oxygen in dying patients.  The simplest case is that of a moribund patient who is completely dependent upon life support measures such as mechanical ventilation and vasopressors.  In such a patient, withdrawal of these measures often allows a quick death to ensue.  Provision of oxygen in such a patient will not avert death, but will prolong it, so I think that while oxygen is often reflexly applied to such patients, I can say with some confidence that it should not be.  While it is mostly benign, it generally does not provide comfort and it prolongs the dying process so it is on the net futile or harmful.  I struggle to reconcile my strong pragmatic intuition about this with ethical principles such as the DDE, although I think it is consistent with the notion that I can take away something that restores a natural state to abrogate its associated discomforts or in deference to patient autonomy and a wish to have a "natural death."
But there is a very large grey area.  What about patients in whom death is not imminent?  Consider a patient who has been on the ventilator for a week with dementia and aspiration pneumonia, and who has developed weakness.  He is alert, but not oriented.  When he is extubated, it is expected that he will develop retained secretions, atelectasis, and over several days, obtundation and oxygenation and ventilation failure.  But over several days.  Should oxygen be administered in the hope that he will rally?  Does its deprivation deprive him of a chance of survival that is disproportionate to the removal of the endotracheal tube and the mechanical ventilator in terms of net costs and benefits?

Or, consider the patient who is demented and is admitted with pneumonia from aspiration and who is DNR/DNI and is given supplemental oxygen.  Does escalation of oxygen therapy to a non-rebreather mask from nasal cannula fly in the face of his DNR order?  Does the administration of peripheral vasopressors for hypotension have the same result?  Does DNR/DNI mean Do Not Respond/Do Not Intervene?

Friday, May 13, 2016

Don't Judge a Brain By It's Scan: The Importance of Actionable Information in Medical Decisions

A common and vexing problem in ICUs everywhere is posed by the patient with diffuse encephalopathy or coma - patients who are colloquially said to be "out to lunch" or "the lights are on, but nobody's home."  The underlying cause is usually a toxic, anoxic, or metabolic malady and the only available treatment is to remove the underlying insult (toxin, hypoxia, or metabolic derangement, e.g, uremia) and wait patiently to see if the neuronal injury improves or resolves.  That is perhaps the hardest part - waiting patiently, with all the attendant uncertainty and resulting anxiety, for days, or even weeks.  This, despite my knowledge that the vast majority of these patients, save for those with severe anoxic brain injury (ABI) will mostly or completely recover with supportive care and "tincture of time."  It is very difficult for me, as a physician, to watch, mostly knowing that the patient has been "out to lunch" for the past 72 or 96 hours because of drug effects, which is very common.  "Shouldn't the drugs be cleared by now?", I keep asking myself.  "Maybe I'm missing something," comes the id's reply.  This anxious uncertainty serves as an impetus for action - but what action is there to take, and is it helpful on balance?

The urge usually is to get a variety of neuroimaging tests, CT (the "donut of truth"), MRI, MRA, and probably an EEG.  But I resist this urge mightily.  These tests rarely yield actionable information - that is, data that I can act upon to change the course of care, as an alternative to waiting.  Say for example, as is often the case, the CT scan and the MRI scan are normal.  How has this helped me?  I still have a comatose patient, and I'm still stuck waiting.  (Also, without meticulous care in explaining the test's purpose and results to her family, confusion ensues.  "If the MRI is normal, why is she in a coma?" is a commonly uttered frustration.

Alternatively, the MRI can look horrible and the patient can still do very well.  I recall a case about a decade ago where we sent a patient with hepatic/toxic/metabolic/anoxic encephalopathy to "the magnet" (MRI scanner) and the neuroradiologist soon after called:  "Is this patient still alive?" he demanded.  Yes, indeed she was.  "Well she won't live long, her whole cortex is necrotic! [rotten]," he forcefully propounded.  Two days later the patient awakened.  I do not believe the radiologist's read of the MRI was in error, only that he erred in confidently inferring that function follows form.  "Don't judge a brain by it's scan" might be a useful heuristic here.  Telling this anecdote to patients' families led me to stumble upon a communication pearl:  My not getting the scan is in essence giving the patient the benefit of the doubt - because I don't want to find something that looks bad and ruins my optimism.  This is generally a very positively received explanation for families who may themselves be demanding scans, action, do something, Doc!

There are indeed cases in which radiological imaging does reveal important and undeniable information, such as stroke, hemorrhage, herniation, and swelling.  I do not impugn all scans, many times they are very useful.  I only wish to cast skeptical doubt on that large fraction of scans which are done as a pat response to non-specific encephalopathy where they are unlikely to yield actionable information.

Beyond the costs, radiation, and risks of transportation associated with the routine use of these scans, which are often not counterbalanced by the yield of actionable information, there is a psychosocial cost - in my observation, these scans increase families' anxiety.  Firstly, when you say you're going to order an MRI, false hope that we can learn what cannot yet be learned (until enough time has passed for the patient to awaken) is engendered.  The family inevitably wants to know when the MRI will be done.  The nurse says 4 PM, there are invariable delays, it gets done at 10 PM.  Anxiety pervades all of those hours.  When will it be read?  Nobody knows, but we offer "in an hour" as a guess.  More anxiety, until 1AM when the report becomes available - but it's inscrutible.  It talks of diffusion weighted this and that, and the neurologist is not available to put it into context.  Anxiety mounts.  In the morning, the neurologist attempts to explain all these little areas of this and that, or a normal scan or whatever.  But none of it tells the patient's family what they want to know, namely "Will my mom awaken?  When?"  Those questions remain unanswerable, but the family has been put on a psychic roller coaster for the past 24 hours thinking the MRI will answer them.  When it is finally done, the reason they can't divine the meaning of the scan is because there is no meaning of the scan - it is devoid of actionable information and should not have been ordered in the first place.

Monday, February 22, 2016

Procedure Meat: How Procedural Lust Imperils Patients

I'll start with a macabre anecdote of crassness, to get everyone's attention.  It is apropos because procedural lust has crass and macabre consequences.

It was about 17 years ago, while I was in training, that an attending accepted a moribund woman from a faraway place in the hinterlands.  She had multiple hepatitides and uncontrolled bleeding from esophageal varices.  A collective groan among the housestaff met notification of the incoming transfer which would keep everybody up all night with the inevitable death forestalled only briefly, and in a streak of his usual candor, the attending admitted that he accepted her not because he thought there was anything that could be done to help or save her, but because she would serve as good "procedure meat for the interns."  And the interns were like:

There are a lot of problems with that entire episode as I reflect upon it, and I won't dissect them all here.  I've been thinking about procedure meat because I so often see physicians feasting on it, to the peril of the patients.  Ideally, each and every procedure that is done ought to be done because it is in the patient's best interest to have it done.  All too often, ulterior motives and unstated goals creep into decision frameworks and lead to unnecessary procedures and therapeutic misadventures.  To combat this problem, we need to start nudging physicians to consider and patients to ask directly, "Is this procedure the best thing for me?  Are there alternatives?  Do the expected benefits outweigh the costs and risks?  Where will I be in six days, six weeks, six months, and six years as a result of the proposed procedure?  Where will I be at those times without it?"

Tuesday, January 26, 2016

They Said He Was Going to Die, So I Stopped Everything. To Save Him

It is [probably] another example of Accidental Survival From Beneficient Neglect.

A middle aged man with alcoholic liver disease with respiratory and other complications had failed extubation for secretion clearance once already, and because of this scenario and suspected but unconfirmed underlying [and incurable] cancer it was planned to terminally extubate him and let him die in peace.

He was on three antibiotics and had acquired C. difficile colitis.  He had friable esophageal varices, so it was said he cannot have a feeding tube, he must be on TPN and he was fluid overloaded as a result of this and MIVF.  He had delirium and deconditioning from his index diseases but also from being in the ICU intubated and sedated with propofol and benzodiazepines for presumed ongoing/prolonged ethanol withdrawal.  (Delirium tremens happens in the minority of abstinent alcoholics.)

One conception of reality is that on day 7 this man was succumbing to his underlying diseases.  Another is that all those have passed and he is burdened by medical interventions that are either misguided, or no longer needed.  There are many other possible realities.

But, antibiotics except flagyl for C. difficile were stopped.  Sedation except minimal propofol was stopped.  Massive diuresis was initiated.  The arm of the gastroenterologist was twisted, and an endoscopic feeding tube was placed.  TPN was stopped and enteral feedings were initiated.  Aggressive attempts to awaken the patient and reduce ventilatory support were undertaken.  Alas, he was extubated.  And so far, so good.

We are not out of the woods.  But the question is now obvious:  when did (if it did) the original disease abate and status iatrogenicus begin to reign supreme (if it did)?

In another all too familiar case, an octogenerian with a UTI was sent to the ICU for vasopressor support for flagging blood pressure.  She refuses it all.  She gets out of bed and eats a stack of pancakes the next morning.  Her lactate may still be elevated, but who would know?  It has not been checked, nor have any routine daily labs - why bother if she is "comfort measures only"?

Evolution has created powerful survival mechanisms.  To think that my TPN or my chasing lactates can outdo them is presumptuous at best, and folly and arrogance at worst.  The perspicacious but humble physician proceeds with caution, always alert that his necessarily naive suppositions and even his good intentions may have crossed that fine line from lending a helping hand, to pulling the patient into the grave.

To learn this lesson is difficult for the faint of heart (or other organs), and for the closed-minded and overconfident.  But those with the fortitude, the humility, and the interest can learn it, when pursuit of the truth for patients' sakes is guided by empiricism.

Updated 1/28/2015:  The patient is on room air, passed swallow eval, is eating and drinking and has normal labs, vital signs, and mental status examination.  He still cannot walk very far, but we're making progress.  It is anyone's guess how much of his residual weakness could have been mitigated with a more "kid gloves" approach to "caring" for him.  He will likely go home this weekend or early next week.

Monday, December 28, 2015

Book Smarts and Common Sense in Medicine - Why Highly Intelligent People Make Bad Decisions

In the presentation on Epistemic Problems in Medicine on the Medical Evidence Blog, I begin by highlighting the difference between intelligence (book smarts) and rationality (common sense).  Oftentimes thought to be one and the same, they are distinctly different, and understanding failures of common sense among very intelligent people can illuminate many problems that we see in medicine, several of which have been highlighted on this blog.

Intelligence is the ability of the mind to function algorithmically, like a computer.  Intelligent people are good at learning, through rote memorization, rules that can be applied to solve well defined problems.  They are also good at pattern recognition which allows them to recognize a problem type to know which rule applies to it.  This kind of intelligence is very precisely measured by IQ tests.  It is correlated with scores on college entrance exams like the ACT and SAT and with other entrance tests such as MCAT.  Of course, intelligent people need to devote the time to learn the rules to answer the questions on these tests which measure both aptitude and achievement.

Rationality, I think, is more closely aligned to the notion of common sense and it shows very little significant correlation to IQ in any domain in which it has been investigated.  Cognitive psychologists talk about two kinds of rationality.  The first is how well a person's beliefs map onto reality (the actual structure of the world), and it has been termed epistemic rationality (sometimes also called theoretical or evidential rationality).  Persons with epistemic rationality have beliefs that are congruent with the world around them and which are strong in proportion to the strength of the evidence supporting them.  Thus a physician who believes that bloodletting or mercury therapy cures disease in the 21st century would be considered to have suboptimal epistemic rationality, as would a person whose fear of Hantavirus while hiking in New Mexico is grossly disproportionate to the actual statistical risk.

Thursday, November 26, 2015

Jugular Venous Pulsations Video - How to Examine it Properly and not Mistake it for the Carotid Pulsations

In the video below, watch the jugular venous pulsations to know what you ought to be looking for.  In my experience, most of the time, physicians at all levels cannot identify confidently and accurately the pulsations that are clearly identified in the video.  Indeed, in many videos purporting to show the JVP on youtube, the pulsations are being shown in the external jugular veins, or carotid arterial pulsations are seen and are being mistaken for jugular venous pulsations.

In two other positions with this particular "jugular model" (keep OJ away from her!), the pulsations were not visible enough to make a compelling video image, emphasizing the finicky nature of the pulsations, the need to position the patient correctly to see them, and the general difficulty of confidently and accurately identifying the pulsations during a cardiac examination which is all too often cursory and unreliable in its findings.

The key feature of the JVP, to differentiate it from the carotid arterial pulsations is to watch to see if the most prominent feature of the "waves" is a rapid descent or a rapid ascent.  In the former case, as in the video, it is the venous X and Y descents of the venous A and V waves which are most obviously seen.  All too often, the rapid ascending waves of the carotid arterial pulses are mistaken for the JVP.  Look for rapid descents - when you find them you know you have found what you're looking for.

Tuesday, November 17, 2015

Beliefs That Dictate Evidence: Open Visitation in the ICU (Again)

The cart belongs behind the horse.
I recently blogged on idealogues who haven't any interest in the truth, rather their interest is in defending their beliefs.  For these true believers, evidence is sought selectively and strength of belief is not apportioned to strength of evidence.  Beliefs reign supreme, and evidence serves the beliefs.  The cart leads the horse.

And so let it be with open visitation in the ICU.  I'm interested in this because it is an issue of practical concern for me, and my interest was recently piqued because in nursing school, my wife was taught that open visitation is better for everyone and that ample evidence supported this contention.  Today, I came across a tweet about ICU visitation policies, a statement from the American Association of Critical Care Nurses.  So I decided to investigate a bit further the evidence upon which their policy proposals are predicated.

The very first statement in the "Supporting Evidence" section of this document is "In practice, 78% of ICU nurses in adult critical care units prefer unrestricted policies."  This statement is at odds with my personal experience working with ICU nurses for the better part of the past 20 years.  While they are patient and family advocates generally, they also recognize that the exigencies of the ICU environment require some limitation of visitation, and so does their own psychological well-being.  So I began by investigating references 7-13 which are proffered in support of this statement which for some (many?) lacks face validity.  Here are those seven references, a description, and a synopsis taken from the abstract of each:

Tuesday, November 10, 2015

Messed Up Seven Ways To Sunday: Communication About Course and Prognosis

I was reminded the other day about the importance of narrative storytelling and theory of mind in communicating with patients' families.  A good storyteller, say Stephen King, has theory of mind - he can see into the minds of his readers and anticipate how they are going to react to what he writes, to the story he's narrating to them.  He knows full well that if he uses a vocabulary that they don't understand that they can't possibly engage with his story.

So if you EVER use the word "intubation" while talking to a family, or "mesenteric ischemia" or "lumbar puncture" or similar technical jargon, you are not going to engage them with your story, and you are going to confuse and frustrate them.  You must use your theory of mind to infer what parts of your medical vocabulary that laypeople do not understand (most of them).

Next, you cannot enter the room of a patient who, say, crumped from flash pulmonary edema and was intubated, and start talking about "mitral stenosis" and "wedge pressures" and "diuresis".  They have NO IDEA what those things mean.  A better narrative would be:
"She had rheumatic fever when she was a child, right?  Well rheumatic fever injures and inflames the heart valves and over the years they can stiffen from that inflammation and injury.  It's just like a guy who injures his knee playing football in high school and then years later has arthritis in the area of that injury.  Same thing, basically.  Anyway, the heart compensates for that stiff or constricted valve over the years by building up pressure behind the valve, just like pressure builds up behind the kink in a garden hose.  You can live like that for a long time because the heart and body are good at compensating, but there comes a point where the pressure behind the kink in the hose or the stiff valve causes fluid to leak into the lungs and then it's hard to breathe with the lungs wet and heavy.  This is essentially what's happened to her - she came in with low oxygen and trouble breathing from fluid in the lungs caused by a stiff valve in the heart.  So we have to remove fluid with water pills to get her breathing without the assistance of the breathing machine, and then she's going to need surgery to replace that valve at some point, which will be determined by the surgeon."

Wednesday, September 23, 2015

Moral Heuristics in Medicine: Judge Not Lest Ye Be Judged

We often evaluate people's health choices and the resulting outcomes through a moral lens, even though many people think it is politically incorrect to do so, to "pass judgment" on others, a proscription that is especially strong within the medical profession.

But it is natural to do so.  The invocation "Thy body is thy temple" rings true from both a moral and a medical perspective.  If only people would treat their body as their temple, how the woes of humanity would melt away, and we would not have a looming physician shortage but rather a surplus!

I am not here concerned with whether or not it is appropriate to pass a moral judgment upon people for behavioral choices that affect their health.  It could be argued either way, i.e., that morality is nonabsolute and individual and that healthcare professionals have no right to make judgments based upon their conception of what is moral, or that there are certain "sins" such as sloth and gluttony that should be universally frowned upon because they are inherently bad for individual and public health.  Rather I am concerned with whether we selectively apply moral condemnation but disguise it under the veil of medical judgment, and how other choices that have health impacts are not imbued with a moral essence, also selectively.

When the alcoholic with cirrhosis is admitted with terminal liver failure, there is a collective sigh with the subtext "he did this to himself."  We condemn alcohol as a personal moral failing, and there is the everpresent lurking tendency to say, with moralistic overtones, "you reap what you sow."

I was reminded of this the other day when I admitted a woman with gastrointestinal hemorrhage who, surprisingly, was found to have esophageal varices.  Most likely, she is not an alcoholic but instead has NASH non-alcoholic steatohepatitis related to obesity, an increasingly common cause of end stage liver disease in obese people (including children).  But there is no collective sigh of exasperation with her moral failings, her gluttony of food rather than alcohol.  She's the poor woman with NASH, rather than the wretch with self-induced disease.

Pulmonologists can hardly talk about tobacco and its ills without overtones of moral condemnation.  So it would appear that while moral judgments can be made under the pretext of medical considerations, the opposite can also happen: the health impacts of a certain substance or behavior can be so dire as that the crusade against the substance or behavior can take on moral dimensions.

I'm not sure any of this is wrong.  Morality is a universal part of humanity and provides a set of intuitional guides for our daily behavior.  But I think we should be consistent.  We should separate morality from medicine or join them and consider the moral dimensions of behaviors that we don't currently have strong moral intuitions about.  Ask yourself which is worse among the following health behaviors and more importantly ask yourself why you make that judgment.  Do you have medical evidence that suggests that one behavior has worse overall holistic health impacts than another?

Are the health consequences worse from:

a.)  daily smoking of marijuana
b.)  drinking 4-5 drinks per night
c.)  being 50-100 pounds overweight
d.)  watching 3-4 hours of TV per day
e.)  not exercising (at all)
f.)  smoking 1-2 cigarettes while at the bar on weekends
g.)  working 80 hours per week
h.)  being socially isolated 
i.)  moving your family for your career every 3-4 years
j.)  using smokeless tobacco
k.)  taking prescription opioid medications chronically for pain
l.)  living in Baltimore, Maryland as compared to Salt Lake City, UT
m.)  remaining single throughout one's adult life
n.)  not reading and staying otherwise mentally active
o.)  riding a motorcycle or driving a car
p.)  owning a firearm or owning a swimming pool

My intuition is that, when we evaluate these behaviors, we utilize a heuristic based on moral intuitions about the "badness" or degree of "sin" of each of these behaviors, and that that heuristic is likely to be highly fallible.  The moral overtones of a behavior are poor surrogates for its real health effects, and moreover we can extend moral judgment to many behaviors that affect health but which we frequently overlook as important determinants of it.

Because of a comment from a former colleague on Facebook, I have modified and updated the list and will make an additional comment.  When I was attending the Johns Hopkins Bloomberg School of Public Health from 2002-2003, I would sometimes get weird looks as I showed up to class in motorcycle riding gear.  There were several group projects about mandatory helmet laws (Maryland already had one), and riding a motorcycle was considered in many ways an affront to the public health.  So was firearms ownership.  During one lecture, attended by two hundred or so students, I challenged a professor of public health who was maligning firearms ownership or motorcycle riding, I forget which, to justify why he "exposed" himself and  his family to the astronomical violent crime rate in Baltimore, Maryland, for the satisfaction of working at Johns Hopkins.  He was as speechless in that moment as I was unpopular in the School of Public Health.

This anecdote is emblematic of what I'm trying to point out in the post - that some behaviors have moral weight, and other similarly "bad for you" behaviors do not.  There is moral weight to riding a motorcycle or owning a firearm, there is no moral weight in the choice to live in Baltimore or install a swimming pool.  But, compared to living in SLC, UT, living in Baltimore statistically increases your risk of being murdered by 30 per 100,000.  That number is very close to the increase in the risk of death between riding a motorcycle and driving a car (increase of about 45/100,000).  But riding motorcycles has taken on a moral (or judgmental, if you will) character.  The choice of where you live has not.  Think very, very carefully about that.

Monday, August 17, 2015

A Poor Predictor is Worse than No Predictor: On the Superiority of Empiricism in Some Medical Decisions

John Locke, empiricist.
The moral of this story is that much maligned empiricism is sometimes (often?) both the only thing to guide you and also the best thing to guide you.

I recently received a call (at an odd hour on the weekend) from an otolaryngologist (ENT) regarding a patient from whom she had drained a large submandibular abcess.  She was calling to tell me that she planned to leave the patient intubated in the ICU overnight and she wanted "help with ventilator management" (which of course the patient does not need - he can be managed with an endotracheal tube not connected to any mechanical ventilator).  The patient did not have airway compromise or concerns thereof prior to surgery, but, she said, there was swelling noted after the case that (for her) raised concerns about the patency of the patient's airway if the endotracheal tube were to be removed.

(There is a second moral to this story: far too often, patients such as this are left intubated post-operatively not for their own safety, but rather for the convenience of surgeons and anesthesiologists who do not wish to spend the extra time awakening them from anesthesia and observing them carefully in the post-anesthesia care unit.  It is far easier to not fret over the depth of anesthesia, atelectasis, oxygen levels, fluid status, and leave the patient intubated and send them to the ICU and let somebody else sort it out.  If I had a family member undergo a relatively routine, even if urgent or emergent operation at an odd hour [holidays, weekends, after hours] and they were sent to the ICU post-op for no apparently good reason, there would be hell to pay.  Note also that for the surgeon and anesthesiologist to save an hour of their time, another physician has to drive to the hospital to take over for them spending hours of his time, and also often a nurse must be called in from home to accommodate the unexpected post-op admission [as was the case here].  The sheer arrogance and egocnetricity of this is mind-boggling.  But I digress.)

Back to the story.  I naturally inquired as to what criteria we would use the next day to determine if the patient's oropharyngeal swelling had abated sufficiently such that we could safely extubate him.  The ENT replied that she would scope (endoscopy) the patient again in the morning and if the swelling had decreased we could proceed with extubation (removing the endotracheal tube).  Well and good.  Or is it?

Monday, August 3, 2015

Accidental Survival from Beneficent Neglect: When "There's Nothing More We Can Do" Becomes Your Salvation

"There's nothing more we can do", according to this NYT article, is a terrible thing for a physician to say to a patient or his family member, even if the intention is much needed candor.

Yet sometimes, a physician's resignation or a patient's refusal becomes the patient's salvation.  There is something to be learned about the futility of many of our treatments and our arrogant ignorance of our impotence in many situations.  Several examples, I hope, will cause physicians to reflect on many of our practices.

A study showing that cancer patients choosing palliative care outlived those choosing aggressive care should have caused a lot of introspection about the possibility that many things we do harm rather than help patients.  How are we to know?  In the ICU, we have several unique opportunities to observe the futility or downright harm of many things we do.

A young woman came to the ICU with mental status changes, an EEG was ordered, and a diagnosis of "non-convulsive status epilepticus" (NCSE) was made.  She was intubated and heavily sedated and treated with every manner of anticonvulsant and CNS depressants and coma-inducing agents.  The EEG continued to show, according to the report, NCSE two weeks later.  The family was told that "there's nothing more we can do" and a decision was made to stop all therapy and withdraw care and prepare to send her to hospice.  This was done, but over the next 24 hours, she awakened and was alert and oriented. She walked out of the hospital later that week.

Tuesday, May 26, 2015

Technological Crutches and Agenesis and Atrophy of Procedural Skills

This article in the New York Times describes the possibility that with increasing reliance on technology and automation, there is atrophy of human skillsets which can lead to untoward outcomes, especially when technology fails and humans have to take back the steering wheel.  One example it called upon was a crash in 2009 of an Air France jetliner that was caused by icing over of the airspeed sensors upon which the autopilot program relied.  When the autopilot failed and the pilots took over, they were confused and ill prepared, and the plane crashed into the Atlantic Ocean.
I am no general fan of romanticizing dated technology (except for the pager) such as the physical examination when superior and ubiquitous technology supercedes it.  Spending five or ten minutes flipping the patient into different contortions trying to identify a gallop or a subtle murmur seems quixotic if an echo has been ordered or the result is pending (although if this interests you as it did me, indulge yourself, its performance and ponderment reinforces the underlying physiology poignantly).  On the other hand, if a patient in the coronary care unit crumps and you cannot identify the obvious holosystolic murmur from a chordae rupture….

I am reminded specifically of certain technological crutches graduates of internal medicine and critical care training programs have come to depend upon in the past decade such as ultrasounds for the placement of central lines and performance of thoracenteses, and fiberoptic aids for endotracheal intubations.  These devices certainly have a role in both training and patient care, and I am generally familiar with the favorable data on success and complication rates, but something is certainly lost when a trainee’s or a practitioner’s efficacy is overly dependent upon use of these technological crutches.

What to do during a Code Blue on the floor when there is no ultrasound and no intravenous access?  I recall several Code Blues where I inserted a subclavian line during brief epochs when chest compressions were held, but it is not uncommon nowadays that trainees leave a critical care fellowship with no proficiency in the subclavian approach whatsoever (or worse, that they learned erroneously that the jugular approach is generally superior to the subclavian approach).  What to do when there is a Code Blue but the Glidescope is in the ER, or there is no Glidescope, the Glidescope malfunctions, or there is a Glidescope but there is also a GI bleed or profuse vomiting and no fiberoptic visibility?  How can you know how to instinctually position the head and neck for a direct view of the larynx if you have trained almost exclusively on a device that obviates a direct view of the larynx?  How do you percuss and tap a pleural effusion when there is no ultrasound available if you have learned this procedure by the “point and poke” method?

One approach to this problem is to insist that trainees learn the tried and true methods first, and resort to the technological aids only for difficult cases or those in which the simple methods have failed.  Make an attempt with the Miller 2 blade (one brief attempt) and if that fails, proceed to the Glidescope.  Identify the internal jugular using proper patient positioning and identification of anatomical landmarks and make a pass with the finder needle before resorting to the use of the ultrasound, or use the ultrasound to confirm or refute your estimation of the jugular position prior to making a pass, rather than relying on it from the get-go.  In this way, the technology can be a way to calibrate predictions and can enhance learning of the underlying basic techniques, while also bolstering proficiency in their performance, and increasing optionality in procedural approaches.

Even with widespread availability of echocardiograms, cardiologists must be able to identify basic murmurs.  If trainees are leaving their programs where 90% or more of their procedures were performed with a technological crutch or aid, they may have rude awakenings when atrophy of basic skills (or the absence of their development) becomes apparent during exigent circumstances in real world settings.

Tuesday, February 24, 2015

Bayes' Theorem Explained, No Math Required

I was asked by a medical student to explain Bayes' Theorem.  This blog is about lack of common sense in medicine, so it follows that education about first principles will contribute to uncommon sense, and I will oblige.

Bayes' theorem is simply a long or holistic way of looking at the world, one which is more in keeping with reality than the competing frequentist approach.  A Bayesian (a person who subscribes to the logic of Bayes' Theorem) looks at the totality of the data, whereas a frequentist is concerned with just a specific slice of the data such as a test or a discrete dataset.  Frequentist hypothesis testing is where we get P-values from.  Frequentists are concerned with just the data from the current study.  Bayesians are concerned with the totality of the data, and they do meta-analyses, combining data from as many sources as they can.  (But alas they are still reluctant frequentists, because they insist on combining only frequentist datasets, and shun attempts to incorporate more amorphous data such as "what is the likelihood of something like this based on common sense?")

Consider a trial of orange juice (OJ) for the treatment of sepsis.  Suppose that 300 patients are enrolled and orange juice reduces sepsis mortality from 50% to 20% with P<0.001.  The frequentist says "if the null hypothesis is true and there is no effect of orange juice in sepsis, the probability of finding a difference as great or greater than what was found between orange juice and placebo is less than 0.001; thus we reject the null hypothesis."  The frequentist, on the basis of this trial, believes that orange juice is a thaumaturgical cure for sepsis.  But the frequentist is wrong.

Thursday, February 12, 2015

Countless Hours, Part 3: Uncalibrated Interns and Immediate and Accurate Feedback

Immediate, accurate feedback begets calibration
In this third and final installment of Countless Hours:  How to Become a Stellar Student and An Incredible Intern, I will discuss the role of immediate and accurate feedback for the refinement of a skill, prediction, or prognostication to expert levels.

Imagine you are learning to play golf, but you can't see where your balls are going - it would be very difficult, without any feedback to learn to modify your swing to improve your game.  Similarly, if the feedback you received were from an observer with poor vision, and it was not accurate, you would be trying to calibrate your swing to unreliable information and your game would not improve insomuch as the feedback was inaccurate.  Finally, if you did not receive the feedback on your swings until days later, it would be difficult to analyze it and adapt your game to it, compared with iterative feedback incorporated after each swing.

The same principles apply to learning the practice of medicine.  One of the reasons that the case study books mentioned in the previous post are so instructive is that they provide immediate, and accurate feedback - you get to know if your diagnosis was correct immediately after rendering it, and this feedback, from the experts who wrote the book (often with formal or informal peer review and editing), is presumably as accurate as you can hope for.  Thus, case based practice is a very very effective way to become an expert.

Then there is the "hands on" work you do on the wards and in clinic.  Here, feedback is, on average, less immediate, and less accurate, and this is one of the ways your learning in "real life" scenarios is compromised - but there are several things you can do about it to maximize the immediacy and accuracy of feedback in these environments.