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Spray Painting Them Pink

July 20, 2010

The paradigm shift in medicine is to fix the underlying problem, not its manifestation. 

When the heart stops, oxygen supply to the tissues is cut so drastically that cells have to try to survive without oxygen, a process known as anaerobic metabolism.  One of the consequences of this is an accumulation of hydrogen ions from the hydrolysis of ATP exceeding the rate of ATP production, producing a metabolic acidosis.  This can be demonstrated on an arterial blood gas sample as a low pH (i.e., less than 7.40) and a negative base excess, otherwise known as a base deficit.  It has been demonstrated that the lower the pH and the more severe the base deficit, the worse the patient will do, with death being the likely consequence for those with the most abnormal values.

We were first able to detect this clinically after the invention and development of blood gas analyzers in the late 1950s by John Severinghaus.  Physicians began to note this acidosis in the early 1960s when cardiopulmonary resuscitation (CPR) was introduced.  It was also noted that if sodium bicarbonate, a base, was administered, the acidosis could be reversed.  For decades, it became standard practice to administer “bicarb” as a routine during CPR.  The justification was that acidosis could impair cardiac performance and its response to catecholamines such as epinephrine (adrenaline).  Because of this, clinicians were instructed to correct acidosis with sodium bicarbonate before giving epinephrine during CPR.

Of course, this was all theoretical because we weren’t directly measuring cardiac performance or catecholamine responsiveness.  That was all below our radar.  In fact, there are a number of studies and reviews spanning back several years that attest to the fact that such bicarbonate is, at best, of little use or actually harmful because of the severe acidosis it can produce inside the cells (which is definitely beneath our radar).

The simplistic approach was to fix a number that was actually the result of a problem rather than the problem itself.  Correcting acidosis by giving bicarb is as effective as treating a suffocating cyanotic (blue) patient by spray painting them pink.

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