In resource (1), Drs. Helman, Claybo, and Grewal discuss a great case of metabolic acidosis and propose a new mnemonic for anion gap metabolic acidosis, GOLDMARK, to replace the old one we all learned in medical school, MUD PILES [See resource (4)].
In the course of their discussion, the speakers state that L in GOLDMARK stands for lactate and the D stands for d-lactate.
So what is the difference between lactate (which, for example, we would order in a sepsis workup) and d-lactate?
Well, it turns out that lactate comes in two stereoisomers, l-lactate and d-lactate. And when we order a serum lactate, the lab is actually measuring l-lactate.
What follows is the summary from resource (2) [The complete article is very much worth reading]:
- Lactate exists in nature in two stereoisoforms: L-lactate and D-lactate
- The predominant form in humans is L-lactate – blood contains approximately 100 times more L-lactate than D-lactate
- D-lactate is the predominant form of lactate produced by some bacterial species
- Pathological significance of lactate is almost entirely confined to the L-lactate isoform and it is specifically this isoform that is routinely measured at the point of care and in the laboratory
- Short-bowel syndrome is the only condition to be associated with increase in D-lactate of sufficient severity to cause symptoms and acidosis (D-lactic acidosis)
- Blood L-lactate is typically normal in those with D-lactic acidosis
- Measurement of D-lactate should be considered in all patients with unexplained metabolic acidosis (i.e. normal lactate) presenting with symptoms of encephalopathy. In such patients a past history of bowel surgery is highly suggestive of D-lactic acidosis.
- It must be emphasized that short-bowel syndrome is a rare condition and that D-lactic acidosis does not necessarily occur in all those with the condition so that the clinical demand for measurement of D-lactic acid is extremely low. In practically all cases of lactic acidosis it is only the L-lactic acid isomer (i.e. the isomer measured in blood gas machines) that is clinically significant.
(1) Best Case Ever 56 Anion Gap Metabolic Acidosis March 28, 2017 from Emergency Medicine Cases.
(2) L-lactate and D-lactate – clinical significance of the difference Oct 2011 by Chris Higgins of acutecaretesting.org.
(5) The Anion Gap Posted on May 22, 2012 by Tom Wade MD