Of rare acid-base disturbances, some are inexplicably favoured by CICM examiners, and other are inexplicably neglected. For some reason pyroglutamic acidosis has been the subject of several SAQs, whereas D-lactic acidosis has never appeared in the exam.
An excellent article on this topic is available. The content below is a brief summary of this article.
- Malabsorbed carbohydrate is fermented by Lactobacillus, Bifidobacterium, Eubacterium and Streptococcus bovis in the colon, producing an excess of D-lactate.
- This has been a well-recognised problem in ruminants.
- Normally, humans have a great capacity to metabolise D-lactate (the hepatic metabolism of lactate does not discriminate between isoforms)
Implications for the diagnosis of a high anion gap metabolic acidosis
- D-lactate is not routinely measured (L-lactate levels look normal)
- Thus, the patients appear to have a high anion gap metabolic acidosis with a normal lactate
- Symptoms are neurological: confusion, slurred speech, obtundation and ataxia.
- Encephalopathy of one sort or another seems to be the most common feature
- Short gut patients are particularly at risk
- Post-pancreatectomy patients who fail to take their enzyme supplements
- Short gut hippies who ingest Lactobacillus tablets to improve their intestinal microflora
- Symptoms are exacerbated by increased food intake, and are relieved by fasting