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]:
Summary
- 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.
Resources:
(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.
(3) Lactic Acidosis Updated: Mar 07, 2017 Author: Kyle J Gunnerson, MD from emedicine.medscape.com.
(4) Mind The Gap: Anion gap acidosis DECEMBER 17, 2013 BY DR ROB ORMAN of ERCAST.
(5) The Anion Gap Posted on May 22, 2012 by Tom Wade MD
