Evolution Based Medicine: A Philosophical Framework for Understanding Why Things Don't Work

An afternoon session at the ATS meeting this year about "de-adoption" of therapies which have been shown to be ineffective was very thought provoking and the contrasts between it and the morning session on ARDS are nothing less than ironic.   As I described in the prior post about the baby in the bathwater, physicians seem to have a hard time de-adopting therapies.  Ask your colleagues at the next division conference if you should abandon hypothermia after cardiac arrest and rather just treat fever based on the TTM trial and the recent pediatric trial, and see what the response is.  Or, suggest that hyperglycemia (at any level in non-diabetic patients) in the ICU be observed rather than treated.  Or float the idea to your surgical colleagues that antibiotics be curtailed after four days in complicated intraabdominal infection, and see how quickly you are ushered out of the SICU.  Tell your dietition that you're going to begin intentionally underfeeding patients, or not feeding them at all and see what s/he say(s).  Propose that you discard sepsis resuscitation bundles, etc.  We have a hard time de-adopting.  We want to take what we have learned about physiology and pharmacology and apply it, to usurp control of and modify biological processes that we think we understand. We (especially in critical care) are interventionists at heart.

The irony occurred at ATS because in the morning session, we were told that there is incontrovertible (uncontroverted may have been a better word) evidence for the efficacy of prone positioning in ARDS (interestingly, one of the only putative therapies for ARDS that the ARDSnet investigators never trialed), and it was strongly suggested that we begin using esophageal manometry to titrate PEEP in ARDS.  So, in the morning, we are admonished to adopt, and in the afternoon we are chided to de-adopt a host of therapies.  Is this the inevitable cycle in critical care and medical therapeutics?  A headlong rush to adopt, then an uphill battle to de-adopt?

Tell Them to Go Pound Salt: Ideology and the Campaign to Legislate Dietary Sodium Intake

In the March 28th, 2013 issue of the NEJM, a review of sorts entitled "Salt in Health and Disease - A Delicate Balance" by Kotchen et al can be found.  My interest in this topic stems from my interest in the question of association versus causation, my personal predilection for salt, my observation that I lose a good deal of sodium in outdoor activities in the American Southwest, and my concern for bias in the generation of and especially the implementation of evidence in medicine as public policy.

This is an important topic, especially because sweeping policy changes regarding the sodium content of food are proposed, but it is a nettlesome topic to study, rife with hobgoblins.  First we need a well-defined research question:  does reduction in dietary sodium intake:  a.) reduce blood pressure in hypertensive people?  in all people?  b.) does this reduction in hypertension lead to improved outcomes (hypertension is in some ways a surrogate marker)?  In a utopian world, we would randomize thousands of participants to diets low in sodium and "normal" in sodium, we would measure sodium intake carefully, and we would follow the participants for changes in blood pressure and clinical outcomes for a protracted period.  But alas, this has not been done, and it will not likely be done because of cost and logistics, among other obstacles (including ideology).

Falling to Pieces: Hemolysis of the Hemoglobin Hypothesis

A paramount goal of this blog is to understand the evidence as it applies to the epistemology of medical knowledge, hypothesis testing, and overarching themes in the so-called evidence based medicine movement.  Swedberg et al report the results of a large[Amgen funded] randomized controlled trial of darbepoetin [to normalize hemoglobin values] in congestive heart failure (published online ahead of print this weekend) which affords us the opportunity to explore these themes afresh in the context of new and prior data.

The normalization heuristic, simply restated, is the tendency for all healthcare providers including nurses, respiratory therapists, nutritionists, physicians, and pharmacists among others, to believe intuitively or explicitly that values and variables that can be measured should be normalized if interventions to this avail are at their disposal.  As an extension, modifiable variables should be measured so that they can be normalized.  This general heuristic is deeply flawed, and indeed practically useless as a guide for clinical care.