The influence of a change in septic shock definitions on intensive care epidemiology and outcome: comparison of sepsis-2 and sepsis-3 definitions

BACKGROUND: Clear definitions for septic shock assist clinicians regarding recognition, treatment and standardized reporting of characteristics and outcome of this entity. Sepsis-3 definition of septic shock incorporates a new criterion, a lactate level >2 mmol/L. Differences in epidemiology and outcome of septic shock based upon both definitions were studied in an intensive care (ICU) population of septic patients. METHODS: We analyzed a prospectively collected cohort of data in the ICU of the Maastricht University Medical Centre. 632 septic patients were included. ICU mortality was compared between the patient group fulfilling Sepsis-3 definition for septic shock and those that met Sepsis-2 definition. Furthermore, association between lactate levels and ICU mortality was studied. RESULTS: Of 632 septic patients, 482 (76.3%) had septic shock according to Sepsis-2 and 300 patients (48.4%) according to Sepsis-3 definition, respectively. Patients meeting Sepsis-3 definition had a higher mortality than patients meeting Sepsis-2 definition (38.9 vs. 34.0%). Serum lactate levels between 2 and 4 mmol/L (25.0 vs. 26.2%, OR 0.94 (0.5-1.5)) and between 4 and 6 mmol/L (23.8 vs. 26.2%, OR 0.88 (0.4-1.7)) compared to levels ≤2 mmol/L were not associated with significantly higher ICU mortality. Serum lactate values ≥6 mmol/L, were significantly associated with increased ICU mortality. CONCLUSION: Patients classified according to Sepsis-3 criteria had a higher ICU mortality compared with Sepsis-2 criteria. Lactate levels <6 mmol/L were not able to identify patients with increased ICU mortality. Lactate threshold of 2 mmol/L may be too low to point out patients with actual increased ICU mortality.