Association between prehospital lactate categories with short- and long-term mortality: a prospective, observational multicenter study

Background Lactate is an already recognized biomarker for short-term mortality in emergency medical services (EMS). However, how different levels of lactate are associated with short-, mid- and long-term outcomes should be unveiled. Aim To determine how different categories of hyperlactatemia are associated with mortality. We also aim to clinically characterize hyperlactatemia groups. Design A multicenter, prospective, observational study performed between January 2019 and February 2022, considering 48 basic life support units and 5 advanced life support units referring to 4 tertiary care hospitals (Spain). Patients were recruited from phone requests for emergency assistance in adults, evacuated to emergency departments. The primary outcome was in-hospital mortality from any cause within the first to the 365-day period following EMS attendance. The main measures were demographical and biochemical variables, prehospital advanced life support techniques used and patient condition categorized in 24 diseases. Methods Univariate and Cox regression analysis. Results A total of 5072 participants fulfilled inclusion criteria. Group #1 (non-hyperlactatemia) was composed of 2389 subjects (47.1%), Group #2 (mild hyperlactatemia) of 1834 (36.1%), Group #3 (hyperlactatemia) of 333 (6.6%) and, finally, Group #4 (severe hyperlactatemia) of 516 (10.2%). The 1-day mortality was 0.2%, 1.1%, 9% and 22.3% in the four lactate groups, respectively. Long-term mortality (365 days) was 10.2%, 22.7%, 38.7% and 46.7% in the four lactate groups, respectively. Differences between patients' conditions of lactatemia groups were also found. Conclusions Our results demonstrated that prehospital lactate categories were associated with short- and long-term outcomes in a different manner. These results will allow EMS to establish different risk states according to the prehospital lactate categories.