Review Of: Francis G, Suffoletto B, Castillo J, et al. Prehospital serum lactate as a predictor of outcomes in trauma patients: A retrospective observational study. J Trauma. 2011;70(4):782–786.
The Science: This is an observational study of the use of serum lactate as a predictor of morbidity and mortality of trauma patients transported by an air medical EMS system to a level 1 trauma center. The study acquired lactate data (samples were from venous or capillary blood) on consecutive trauma over an 18-month period; 1,168 patients were included for analysis. The primary outcome was mortality with secondary outcomes being: emergent surgery and multiple organ dysfunction. The results showed that lactate was associated with mortality (OR 1.23), surgery (OR 1.13), and multiple organ dysfunction syndrome (OR 1.14). The investigators concluded that prehospital lactate could help identify patients who require more aggressive resuscitation efforts in the hospital setting.
Medic Marshall: Despite any downfalls this study may have, I believe it has tremendous implications for EMS. Point-of-care testing of serum lactate, in my humble opinion, is definitely poised to become a pervasive practice throughout the U.S. Furthermore, this study also helps to demonstrate the value of obtaining serum lactates in the field.
The Doc and I reviewed a previous article about EMS obtaining serum lactates in the field, but that was for sepsis. The authors of that study were able to demonstrate that lactate was very useful in determining if patients were in septic shock. Is anyone starting to see a trend here? Serum lactate is an indicator of distributive shock. And it can be identified before it’s too late.
So why aren’t more systems implementing this? It’s as simple as obtaining a blood glucose reading, albeit serum lactates take 60 seconds versus glucometers that take less than 30 seconds. I believe EMS providers and medical directors need to start pushing their agencies to look at the obvious benefits of this. I hope that within the next three to five years, obtaining prehospital serum lactate becomes a common practice.
Doc Wesley: I agree with Marshall that point-of-care (POC) testing for serum lactate levels has the potential to change our practice and improve patient care. The challenge, however, is to interpret these studies to determine the best method of incorporating this new science into our toolbox.
Marshall alluded to this study’s shortcomings that I believe should be reviewed. Primarily, it suffers from selection bias. The prehospital patients tested were trauma patient transported from the scene and inter-facility transport by an air medical service. Therefore, all the patients had been triaged as being at high risk of significant injury and complication. In order for serum lactate POC testing to be validated as a triage tool, it needs to be studied in a ground ambulance operation to determine if it can correctly identify those patients most likely in need for care at a regional trauma center.
But more importantly, this test needs to have sufficient negative predictive value (that is when the test is negative it indicates the patient is not at risk). Unfortunately, POC lactate testing misses about 8–10% of patients later found to be at risk. Is there a role for this test in trauma? I don’t know yet. It appears to have promise, but it’s not ready for primetime until additional studies are performed.