What is the role of prehospital lactate testing in emergency medical services (EMS)?

From the Guidelines

Prehospital lactate testing is a crucial diagnostic tool that should be utilized for early identification of critically ill patients, particularly those with suspected sepsis or shock, as it provides valuable information on tissue hypoperfusion and guides timely interventions to improve patient outcomes. The test measures blood lactate levels, which rise when tissues receive inadequate oxygen, serving as an early indicator of poor perfusion before vital signs deteriorate 1. According to the European guideline on management of major bleeding and coagulopathy following trauma, blood lactate has been used as a diagnostic and prognostic marker of haemorrhagic shock since the 1960s and is considered to reflect the severity of haemorrhagic shock 1.

Key Points to Consider

• Portable handheld devices allow emergency medical services (EMS) personnel to obtain lactate results from a small blood sample within minutes, typically requiring only 0.5-1.0 mL of blood.
• Normal lactate values are below 2.0 mmol/L, with levels above 4.0 mmol/L indicating severe illness and potential need for aggressive resuscitation.
• Implementation requires minimal training for EMS personnel, and the test can be performed during transport without delaying care.
• The clinical value of prehospital lactate testing lies in its ability to identify occult hypoperfusion in patients who appear stable but have underlying tissue hypoxia, allowing for earlier intervention with fluid resuscitation, vasopressors, or antibiotics as needed 1.

Clinical Implications

• This early recognition facilitates appropriate triage decisions, preparation of receiving facilities, and has been associated with reduced mortality in septic patients by enabling earlier goal-directed therapy.
• The cost-effectiveness of prehospital lactate testing is supported by its relatively low expense compared to the benefits of earlier intervention and potentially reduced hospital stays.
• As noted in the Surviving Sepsis Campaign guidelines, serum lactate is not a direct measure of tissue perfusion, but increased lactate levels are associated with worse outcomes, making lactate-guided resuscitation a valuable strategy in managing septic shock 1.

From the Research

Prehospital Lactate Testing

• Prehospital lactate testing has been explored as a potential tool for early recognition of sepsis and septic shock 2
• A study published in 2016 found that paramedics can accurately measure lactate levels in the prehospital setting, with a correlation of 0.57 between prehospital and emergency department lactate values 2
• However, the study also found that elevated prehospital lactate levels were not significantly associated with increased risk of admission to the intensive care unit or diagnosis of sepsis 2

Prognostic Value of Lactate Levels

• Lactate levels have been shown to have prognostic value in patients with sepsis and septic shock, with higher levels associated with increased mortality 3, 4
• A retrospective cohort study published in 2021 found that 6-hour lactate levels were more accurate in predicting 30-day mortality than 6-hour lactate clearance or initial lactate levels 4
• The study also found that a lactate level of ≥3.5 mmol/L was the optimal cut-off value for predicting 30-day mortality 4

Utility of Lactate Levels in Diagnosis and Prognosis

• Lactate levels have been recognized as a useful biomarker for diagnosis and prognosis of septic shock, particularly in pediatric patients 5
• A study published in 2015 found that fluid resuscitation guided by lactate clearance rate and central venous oxygen saturation was more effective than guidance by central venous oxygen saturation alone in patients with septic shock 6

Limitations and Controversies

• The use of lactate monitoring in sepsis diagnosis and management has generated controversy and concerns, including the potential for unnecessary broad-spectrum antibiotic use and fluid overload 3
• More research is needed to fully understand the role of lactate testing in prehospital settings and to determine the optimal strategies for using lactate levels to guide diagnosis and treatment of sepsis and septic shock 2, 4