Cutoff Value Of Serum Lactate Level At Diagnosis Of Septic Shock; Question About Its Validity.

Background: 

According to new definition of septic shock, vasopressor therapy and hyperlactatemia are essential for diagnosis of septic shock. However, there were many debates to determine cutoff value of serum lactate level, and prognostic factors in patients with septic shock and hypolactatemia remain unclear. Therefore, this study evaluated the prognostic significance of the cutoff value of lactate level in septic shock patients.

Methods: 

The study prospectively enrolled 933 patients aged ≥ 18 years with severe sepsis from November 2007 to March 2016 at a 2,000-bed university hospital. Only patients who meet the revised definition of septic shock were included. Clinical outcome of patients with hyperlactatemia was compared with hypolactatemia.

Results: 

A total of 912 patients were eligible for this study. 510 and 402 had serum lactate level > 2 mmol/L and ≤ 2 mmol/L, each. In high lactate group, proportion of male gender (59 % vs 43.8 %, p <0.001), incidence of diabetes mellitus (37.1 % vs 26.9 %, p <0.001) and median C-reactive protein/albumin ratio (45.1 mg/dL vs 39.6 mg/dL, p =0.027) were greater than low lactate group. The other way, mean serum albumin level (3.1 g/dL vs 3.3 g/dL, p <0.001), and median estimated glomerular filtration rate (40.0 mL×min^-1×1.73 m^-2 vs 52.0 mL×min^-1×1.73 m^-2, p <0.001) were lower than low lactate group. In clinical outcome, more patients in high lactate group suffered from renal failure (42.5 % vs 27.1 %, p <0.001), liver failure (14.3 % vs 3.2 %, p <0.001), heart failure (5.9 % vs 2.5 %, p =0.013), and disseminated intravascular coagulation (13.9 % vs 2.2 %, p <0.001). 28-days mortality (10.9 % vs 3.7 %, p <0.001) was higher in high lactate group. A subgroup analysis of risk factors affecting mortality in low lactate group was performed. On multivariate regression analysis, hypoxemia (p =0.002), high APACHEⅡ score (p =0.006), high alanine aminotransaminase (ALT) level (p =0.007), and hypoalbuminemia (p =0.026) were independently associated with 28-days mortality.

Conclusion: In this study, serum lactate level is very reliable parameter of diagnosis and prognostic predictor of septic shock. However, there were not inconsiderable cases of mortality in patients without hyperlactatemia, and high APACHEⅡ score and decreased liver function affect mortality rate in this subgroup. Further studies are needed to distinguish high risk case of septic shock without hyperlactatemia.