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?

The obvious problem with this approach is that we have no iota of an idea what is the sensitivity and specificity of the endoscopy for determining the patency of the airway as regards respiration without obstruction.  No idea whatsoever.  This neophyte ENT could practice for the next thirty years leaving patients intubated when there is swelling and extubating them when it abates with "great success" and arrive at the confident and firm conclusion that swollen patients need the tube and it can safely be removed only when the swelling abates.  But it could also be that every one of those patients could breathe without obstruction or the need for an endotracheal tube and she arrives at the wrong conclusion because she never tried it the other way.  She would be 100% sensitive and 0% specific in her calls.  Alternatively, she could wait until patients with airway swelling have life-threatening airway compromise such that a "slash trach" (emergency tracheostomy) is needed before she intervened with a "protective airway" in which case she would have low sensitivity for detecting airway compromise but 100% specificity.  The sensitive approach seems "safer" than the specific approach, especially for the ego of the ENT which is not bruised by failure to recognize patency, but which is badly bruised by failure to recognize compromise, and especially if you consider leaving patients unnecessarily intubated overnight (or longer) in the ICU to be a cost- and risk-free endeavor.

So what to do?  Empiricism is the only thing to do.  This ENT has no demonstrably reliable criteria for evaluating airway patency except observing for airway patency without the endotracheal tube.  This should have been done in the operating room with ENT and anesthesia present and properly equipped with all tools necessary for dealing with any airway crisis.  The patient should have been extubated and observed for an hour and if he was fine, as almost surely he would have been, he could have been sent to the ICU (or the medical floor) for observation.  If he was not, he could have had the endotracheal tube replaced under the best, most controlled circumstances.  Sending him to the ICU if he does not need the airway just increases morbidity, and extubating him in the ICU the next day regardless of the appearance of his airway on endoscopy simply increases his risk.

And here's the final kicker - when practitioners are this wrongheaded in their approach to these kinds of problems, or guided consciously or subconsciously by ulterior motives (the devil on the left shoulder says "I want to go home and sleep and not receive any more calls about this case tonight"), there really is no diplomatic way to discourage them acutely, as I learned in this case and so many others before it.  But I do think that calling them out may have chronic effects, by demonstrating that not everybody is going to play along in the charade.

So I encourage you to be the child that cries out "The ENT has no clothes!" - for your patients' sakes.


  1. Thank you for this thoughtful article.

  2. How does this compare to looking for a "cuff leak" in patients with airway edema/ compromised airway?

  3. It could be argued that it's about the same thing, given the imperfections of the available predictors.


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