Beyond arterial gases: the role of lactates in risk stratification in pulmonary embolism

Background and aim: Lactic acid is a well established early marker of tissue hypoperfusion and it can be used as a therapeutical target. It usually measured on every patient with suspicion of acute pulmonary embolism. However, its prognostic significance in this setting is unknown. We aimed to determine whether arterial lactate was associated with in-hospital mortality in patients with PE. Methods: We retrospectively analyzed 193 patients (mean age 72.63±16.64 years; 47.2% male) admitted to our emergency department with acute PE between January and December 2010. Arterial blood was immediately collected after patient admission and the sample was processed within 15 minutes. Clinical, laboratorial and follow-up data was collected; the endpoint was in-hospital mortality. Results: Mean lactate level was 1.91±1.73. The best cut-off value (2.5 mmol/L) had an area under the ROC curve of 0.758 and a sensitivity of 57.1% and a specifity of 86.6%. Regarding the demographic and clinical data, we haven't found any significant difference between patients with lactate levels > 2.5 mmol/L and patients with lactate levels ≤ 2.5 mmol/L. Nevertheless, patients with lactate levels > 2.5 mmol/L had higher levels of BNP (570 vs. 221, p < 0.001), troponin (0.82 vs. 0.24, p < 0.001) and LDH (189 vs. 164, p=0.031). A value over 2.5 mmol/L was associated with an increased hazard ratio of 1.294 (95% CI: 1.052 – 1.590, p = 0.015) of in-hospital mortality. Conclusion: An only slighlty elevated arterial lactate level, collected immediately after admission, is a specific predictor of in-hospital mortality and may help in early triage of higher-risk patients.