Originally published at Pediatric EM Morsels on December 19, 2014. Reposted with permission.

Follow Dr. Sean M. Fox on twitter @PedEMMorsels

Patients’ families often present to us requesting “bloodwork” to make sure that the child is not “sick” or to tell them “what’s wrong.”  While we all know that no lab can be used to proclaim complete certainty of a patient’s health or to make a definitive diagnosis on its own, often we perpetuate the myth by ordering labs that do not necessarily direct our actions.  By now, most of you know of my disdain for the ubiquitous WBC count (The Last Bastion of the Intellectually Destitute – Amal Mattu), but there is another often ordered test that may also fall into that category — the Lactate Level.

The Lactate Level has grown in popularity over the past decade, particularly in the Adult EDs.  Certainly, there is literature that supports its utility with respect to evaluation of SEPSIS and trauma, but this often becomes extrapolated to all patients who “may be sick” as a means to find the covertly ill.  This  approach (often in a “shotgun” fashion) has steadily crept into the Pediatric EDs as well.  What is the known utility of Lactate Level in children? [Thank you @ErnestoAlarco12 for inspiring the question].

Lactate Level – Basic BioChem

• Just in case you don’t recall BioChem class as well as you used to…
• During Glycolysis glucose is converted into Pyruvate.
  • Through AEROBIC metabolism, pyruvate is used to generate 2 Acetyl-CoA and eventually many ATPs, H2O, and CO2 (remember the Krebs cycle?).
  • When there is not enough Oxygen around (ANAEROBIC metabolism), then pyruvate is converted into Lactate.
  • Lactate can be converted back to pyruvate once the oxygen deficit has been corrected.
  • Well that was a fun walk down memory lane.
• With this in mind, elevated lactate levels would potentially reflect tissue oxygen deficit.

• Under normal conditions, lactate is rapidly cleared by the liver, with some assistance from the kidneys. (Anderson, 2013)
• There is no standardized levels:
  • Most studies use cutoff values of 2.0 to 2.5 mmol/L.
  • Many define “High” as a Lactate level > 4.0 mmol/L. (Anderson, 2013)

Lactate Level – Some Causes of Lactate Elevation

Most often elevated Lactate Levels conjure thoughts of tissue hypoperfusion with diminished access to oxygen (SHOCK), but there are others causes to consider. (Anderson, 2013)

• Global ischemia (SHOCK)
• Regional ischemia (ex, mesenteric ischemia, burns, trauma, compartment syndrome)
• High Metabolic States (ex, seizures, heavy exercise, increased work of breathing)
• Drugs (ex, Metformin, epinephrine, propofol, acetominophen, beta-2-agonists)
• Toxins (ex, Cocaine, Cyanide, Carbon monoxide, alcohols)
• Malignancies
• Liver Disease (can’t clear the lactate)
• Diabetic Ketoacidosis
• Thiamine Deficiency (w/o thiamine, anaerobic metabolism predominates)
• Inborn Errors of Metabolism and Mitochondrial Diseases

Lactate Level – Elevation in Kids

• In the PICU:
  • Studies of SEPSIS have shown increased mortality in the setting of elevated lactate levels. (Jat, 2011)
  • Monitoring serial lactate levels in patients following surgery for congenital heart disease can help discriminate patients at high risk. (Schumacher, 2014; Agrawal, 2012)
  • Poor lactate clearance (< 30% at 6 hours) has been associated with increased risk of mortality. (Munde, 2012)
  • High lactate level upon admission to the PICU is associated with in-hospital mortality. (Bai, 2014)
• In the ED:
  • High lactate levels can be useful to help “rule-in” severe bacterial infection in children in the ED. (Vorwek, 2011)
  • High lactate levels identify a population at higher risk for severe outcomes amongst the kids with SIRS in the Peds ED. (Scott, 2012)
  • After Return of Spontaneous Circulation following a resuscitation, higher lactate levels are associated with higher likelihood of death, although don’t predict outcomes. (Topjian, 2013)
  • Elevated lactate levels obtained in pediatric trauma patients during prehospital transport are associated with increased need for critical care. (Shah, 2013)

Lactate Level – Did it Help You?

• Thus far, we see that, like in adults, an elevated lactate can help identify those patients who are potentially sicker than others, although not perfectly.
• One issue is that, often, an astute clinician would generate a similar assessment of clinical severity. (Scott, 2012)
  • That being said, it is known that signs of SHOCK can be under-appreciated in children (see subtle signs of heart failure and palpation of pulse).
  • Hypotension is also, generally, a late finding in pediatric patients.
• Another issue is that, when obtained in the “shotgun” approach of obtaining labs, often the confounders (see above) are not taken into account.

• It is only helpful if it alerts you to severe illness presenting subtly or helps direct your resuscitation efforts… which, again, require the astute clinician to determine.

References