Rinaldo Bellomo is here to cause some trouble! He says that critical care physiology in resuscitation has problems! Whilst the rest of the medical field has advanced and evolved over time (we no longer routinely prescribe oxygen for an acute myocardial infarction), critical care resuscitation still relies on malfunctioning physiological paradigms. Critical care clinicians can change physiology with a number of tools. They can repeatedly, often, and mercilessly change physiological variables. Blood pressure, cardiac output, cardiac filling pressures, glucose levels, positive fluid balance and countless other physiological parameters can be increased and decreased at will. This kind of “numerology” is attractive because the outcomes can be immediate, and clinicians feel powerful and effective. However, outside the obvious situations where physiology is so dangerously abnormal as to threaten life, such physiological manipulations have an unproven relationship with outcome. Importantly, patients do not care whether their cardiac output has been increased from 5L/min to 6 L/min. They only care whether they live or die, get out of hospital intact and return to their previous life. Thus, physiological gain is not patient centred. Moreover, all research focusing of the physiology of a specific intervention inevitably deals with the effect on a specific set of variables. For example, a fluid bolus may or may not increase cardiac output in the short term. However this effect is not sustained much past 20 minutes. Similarly, no studies examine the effect of such fluid bolus on anything other than haemodynamics. No one measures what the effect is on the immune system, cerebral oedema, the glycocalyx, interstitial oxygen gradient, pulmonary congestion, body temperature, haemoglobin, or white cell function. Thus, all physiological studies are “blind” to the broader effects of their intervention. Rinaldo claims that in critical care resuscitation physiology, the measurable is made important but the important may not be measured. Clinicians need to reflect on this before they become seduced by physiological manipulation. Rinaldo’s challenge to you? Look at the literature, consider biological plausibility, follow evaluated evidence, balanced, accept doubt with a smile and practice known medicine of the time whilst understanding that today’s medicine will be the source of derision in the future.
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