Base excess, lactate cut-off value, and early vasopressors initiation for predicting in-hospital mortality in septic shock patients on emergency department arrival: A retrospective observational study

Background: Sepsis and septic shock are conditions characterized by systemic infection and tissue hypoperfusion. Septic shock is defined by the requirement for vasopressor to maintain a mean arterial pressure ≥65 mmHg, or the presence of hyperlactatemia (lactate >2 mmol/L) in the absence of hypovolemia. These patients face a markedly higher risk of death, and the Sequential Organ Failure Assessment (SOFA) scale serves as a valuable tool for quantifying this risk. Due to its medical complexity and associated mortality rates, numerous clinical and laboratory variables have been proposed to predict mortality outcomes. Among these variables, gasometric parameters—such as lactate and base excess—accurately reflect the degree of tissue hypoperfusion and, consequently, the severity of shock. Methods: This retrospective observational study included patients admitted to Hospital Universitario San Ignacio between January 1, 2017, and December 31, 2019. Receiving operating characteristic curves and the Youden Index were used to identify new cut-off values for lactate and base excess in predicting mortality. Sensitivity and specificity for lactate and base excess were then calculated, with 28-day in-hospital mortality as the outcome. Results: The average lactate level was 3 mmol/L with a base excess of -6.1 mmol/L, indicative of tissue hypoperfusion. Lactate levels were significantly higher in patients who died compared to survivors, highlighting their prognostic value. Similarly, base excess levels showed a significant trend towards more negative values in non-survivors compared to survivors. Lactate levels >3.5 mmol/L and base excess values <-7.5 mmol/L were associated with increased 28-day mortality rates. Conclusion: Patients with septic shock had an average lactate level of 3 mmol/L and a base excess of –6.1 mmol/L on admission, indicating a higher risk of hemodynamic instability requiring vasopressor support. Elevated blood lactate levels >3.5 mmol/L and base excess levels <-7.5 mmol/L were strongly associated with increased in-hospital mortality rates.