5-Step Approach to the Markedly Elevated Lactate
- Remember your physiology: lactate is produced by most tissues in the human body, with the highest level of production in the muscle, and is cleared by the liver and a small amt by kidneys
- 2 isomers of lactate: L-lactate and D-lactate but most labs measure only L-lactate – if you want to measure D-lactate, it is a send-out test
- Step 1: Rule-out shock before you proceed:
- Lactate is a marker for tissue hypoperfusion and we also use it as an endpoint for resuscitation in patients with sepsis and septic shock
- Lactate has not been as-well studied in cardiogenic shock but it is still a useful in predicting mortality and elevated lactate in PE causing obstructive shock carries a poor prognosis
- Hypovolemic shock from trauma/hemorrhage also causes a markedly elevated lactate
- We often see the highest lactates in post-arrest patients likely from ischemia
- Step 2: Evaluate for local ischemia:
- Elevated lactate is 96% sensitive and 38% specific for mesenteric ischemia so do a careful abdominal exam in patients with markedly elevated lactate
- Also consider other local ischemia such as compartment syndrome, necrotizing fasciitis, Fournier gangrene and more
- Once you’ve ruled-out sepsis, evaluate carefully for local source & consult surgery early!
- Step 3: Evaluate for offending drugs:
- Long list of offending drugs including: Linezolid, metformin, NRTIs, valproate, theophylline, salicylates, isoniazid, propofol, epinephrine, and salicyclates
- Also consider toxidromes such as cocaine, toxic alcohols, carbon monoxide, cyanide
- Consider early call to poison control and renal for dialysis
- Remember, these patients often look well, disproportionately so to their ABGs!
- Step 4: Consider excessive muscle activity
- Excessive anaerobic muscle activity as in seizures, rhabdomyolysis, rigors can cause elevated lactate, especially with rapid clearance without intervention!
- Step 5: Look for other metabolic derangements
- You can see a very high lactate in DKA but prognosis is still not bad
- Liver dysfunction when severe can cause elevated lactate
- Rarely, inborn errors of metabolism and mitochondrial disorders can cause it
For a great summary article on approach to the highly elevated lactate, check out http://www.mayoclinicproceedings.org/article/S0025-6196(13)00555-7/fulltext