Severe sepsis is major health problem with a high mortality rate, and still its incidence continues to rise [1–5]. Lactate clearance, measurement of the lactate level at two consecutive times, is an inexpensive and simple clinical parameter that can be obtained by a minimally invasive means [6–8]. This parameter represents kinetic alteration of the anaerobic metabolism that makes it a potential parameter to evaluate disease severity and intervention adequacy. Lactate clearance early in the hospital course may indicate a resolution of global tissue hypoxia and is associated with improved outcome [7–9]. Nevertheless, the relationship between lactate clearance and short-term mortality in severe septic patients is still poorly understood. Understanding the presence of confounder factors is also important to strengthen the role of lactate clearance in the treatment of severe septic patients.