Artifactual lactic acidosis from point of care analysis: mind the gap

Introduction

A patient presented with severe acidosis, point-of-care (POC) lactate of 42 mmol/l. This led to suspicion of mesenteric ischemia and potential need for laparotomy. However, plasma lactates were <4 mmol/and ethylene glycol (EG) ingestion was subsequently diagnosed. We therefore wished to determine why discrepant lactates occur and whether this lactate gap (that is, the difference between lactate measured using two common methods) could be clinically useful.

Methods

We phlebotomized blood, added various concentrations of EG metabolites, and tested with the five most common lactate analyzers.

Results

Glycolate caused massive artifactual lactate elevation with the Radiometer 700 POC analyzer even at low concentrations. Another major EG metabolite, glyoxylate, but not oxalate (or formate), caused similar elevation. The iSTAT and Bayer POC analyzers and Beckman and Vitros laboratory analyzers caused minimal lactate elevations. The lactate gap was determined by comparing the Radiometer with any of the other analyzers.

Conclusions

We demonstrated how inappropriate laparotomy or delayed-therapy might occur if clinicians are unaware of this phenomenon (now dubbed the lactate gap) or if hospitals only have access to a single analyzer. We also showed how the lactate gap can be exploited: to expedite treatment, diagnose late EG ingestion, and terminate dialysis. By comparing lactate results from the iSTAT or Bayer versus the Radiometer, EG ingestion can be diagnosed at POC, thereby further expediting diagnosis and treatment ahead of plasma EG.