PURPOSE: Lactate has been shown to be a good predictor of injury severity. In contrast, hemodynamic variables have relatively poor predictive value. Current practice relies on hemodynamic variables in the pre-hospital environment for triage and treatment decisions. Therefore, we performed the first simultaneous assessment of the relative ability of standard vital signs to detect hyperlactatemia in the pre-hospital setting.
METHODS: Prospective, observational, cohort study. Setting: Pre-hospital, urban, single EMS system. Subjects: From 10/1/07 to 12/1/07, 857 subjects were enrolled. Inclusion criteria: All subjects evaluated during advanced life support transport excluding pregnancy and minors. Statistical analysis: Five hemodynamic variables [HR, SBP, DBP, MAP, and Shock Index (SI)] were evaluated upon initial, pre-hospital assessment. During the initial assessment, subjects also had point of care, whole blood lactate measured by the Lactate ProÖ analyzer. Correlation coefficients were calculated between the lactate level and corresponding hemodynamic variable. Correlation was similarly tested within lactate level tiers [normal (< 2.5 mmol/l), intermediate (2.5 - 3.9 mmo/l), high (≥ 4.0 mmol/l), occult (> 2.5 mmol/l and SBP > 90 mmHg)].
RESULTS: There was no relationship between lactate level and any hemodynamic variable measured: HR: r = 0.15 (CI 0.08 to 0.21), SBP r = −0.08 (CI −0.14 to −0.07), DBP r = −0.14 (CI −0.21 to −0.07), MAP r = −0.15 (CI −0.21 to −0.08), SI r = 0.20 (CI 0.13 to 0.26). More than 30% of lactate levels were intermediate or high; Just over 27% of all subjects could be characterized as exhibiting occult hyperlactatemia.(Table 1) Correlation did not improve within all tiered lactate subsets and their respective hemodynamic variables.
CONCLUSION: Abnormal lactate levels are common in the pre-hospital environment. Standard hemodynamic variables show no relationship with abnormal lactate levels, even at extremely high values.
CLINICAL IMPLICATIONS: Pre-hospital patient assessment, relying on traditional vital signs, may frequently underestimate elevated lactate levels. Clinical implications require further emphasis on outcome analysis.
DISCLOSURE: Kyle Gunnerson, No Financial Disclosure Information; No Product/Research Disclosure Information