Severe hyperlactatemia in unselected surgical patients: retrospective analysis of prognostic outcome factors

Abstract

Background: Etiology of hyperlactatemia in ICU patients is heterogeneous-septic, cardiogenic or hemorrhagic shock seem to be predominant reasons. Multiple studies show hyperlactatemia as an independent predictor for ICU mortality. Only limited data exists about the etiology of hyperlactatemia and lactate clearance and their influence on mortality. The goal of this single-center retrospective study, was to evaluate the effect of severe hyperlactatemia and reduced lactate clearance rate on the outcome of unselected ICU surgical patients.

Methods: Overall, 239 surgical patients with severe hyperlactatemia (> 10 mmol/L) who were treated in the surgical ICU at the University Medical Center Freiburg between June 2011 and August 2017, were included in this study. The cause of the hyperlactatemia as well as the postoperative course and the patient morbidity and mortality were retrospectively analyzed. Lactate clearance was calculated by comparing lactate level 12 h after first measurement of > 10 mmol/L.

Results: The overall mortality rate in our cohort was 82.4%. Severe hyperlactatemia was associated with death in the ICU (p < 0.001). The main etiologic factor was sepsis (51.9%), followed by mesenteric ischemia (15.1%), hemorrhagic shock (13.8%) and liver failure (9.6%). Higher lactate levels at ICU admission were associated with increased mortality (p < 0.001). Lactate clearance after 12 h was found to predict ICU mortality (ANOVA p < 0.001) with an overall clearance of under 50% within 12 h. The median percentage of clearance was 60.3% within 12 h for the survivor and 29.1% for the non-survivor group (p < 0.001).

Conclusion: Lactate levels appropriately reflect disease severity and are associated with short-term mortality in critically ill patients. The main etiologic factor for surgical patients is sepsis. When elevated lactate levels persist more than 12 h, survival chances are low and the benefit of continued maximum therapy should be evaluated.

Keywords: Lactate; Lactic acidosis; Outcome; Sepsis; Shock; Surgical therapy.

Fig. 1

Etiology of hyperlactatemia

Fig. 2

Distribution of measured peak lactate concentration (mmol/L) by subgroups

Fig. 3

Kaplan-Maier 90 days overall survival depending on blood lactate concentration at ICU admission

Fig. 4

Kaplan-Maier 90 days overall survival in patients with severe hyperlactatemia depending on different etiologic factors (log rank analysis)

Fig. 5

Association between 12 h lactate clearance and mortality. The black lines show 12 h lactate clearance of 0% and the cutoff having highest specificity to predict ICU mortality regarding sensitivity and specificity (12 h lactate clearance of 29.4%)