Once Bitten, Twice Try: Failed Trials of Extubation

“When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.”                                                                                   – Clark’s First Law

It is only fair to follow up my provocative post about a “trial of extubation” by chronicling a case or two that didn’t go as I had hoped.  Reader comments from the prior post described very low re-intubation rates.  As I alluded in that post, decisions regarding extubation represent the classic trade-off between sensitivity and specificity.  If your test for “can breathe spontaneously” has high specificity, you will almost never re-intubate a patient.  But unless the criteria used have correspondingly high sensitivity, patients who can breathe spontaneously will be left on the vent for an extra day or two.  Which you (and your patients) favor, high sensitivity or high specificity (assuming you can’t have both) depends upon the values you ascribe to the various outcomes.  Though these are many, it really comes down to this:  what do you think is worse (or more fearsome), prolonged mechanical ventilation, or reintubation?

What we fear today we may not seem so fearsome in the future.  Surgeons classically struggled with the sensitivity and specificity trade-off in the decision to operate for suspected appendicitis.  “If you never have a negative laparotomy, you’re not operating enough” was the heuristic.  But this was based on the notion that failure to operate on a true appendicitis would lead to serious untoward outcomes.  More recent data suggest that this may not be so, and many of those inflamed appendices could have been treated with antibiotics in lieu of surgery.  This is what I’m suggesting with reintubation.  I don’t think the Epstein odds ratio (~4) of mortality for reintubation from 1996 applies today, at least not in my practice.

Bite the Bullet and Pull It: The NIKE approach to extubation.

I was very pleased to see McConville and Kress' Review article in the NEJM this week (December 6, 2012 issue) regarding weaning patients from the ventilator. I have long been a fan of the University of Chicago crew as well as their textbook and their pioneering study of sedation interruption a decade ago.

In their article, they provide a useful review of the evidence relating to the discontinuation of mechanical ventilation (aka weaning , liberation, and various other buzz words used to describe this process.) Yet at the end of the article, in describing their approach to discontinuation of mechanical ventilation, they provide a look into the crystal ball that I think and hope shows what the future may hold in this area. In a nutshell, they push the envelope and try to extubate patients as quickly as they can, ignoring inconvenient conventional parameters that may impede this approach in select instances.

Much of the research in this field has been dedicated to trying to predict the result of extubating a patient. (In the case of the most widely cited study, by Yang and Tobin, the research involves predicting the result of a predictor of the ultimate result of interest. This reminds me of Cervantes' Quijote - a story within a story within a story....but I digress.) And this is a curious state of affairs. What other endeavor do we undertake in critical care medicine where we wring our hands and so helplessly and wantonly try to predict what is going to happen? Don't we usually just do something and see what happens, making corrections along the way, in silent acknowledgment that predicting the future is often a fool's errand? What makes extubation so different? Why the preoccupation with prediction when it comes to extubation? Why not "Just Do It" and see what happens?