Purpose: Hyperlactatemia may occur for a variety of reasons and is a predictor of poor clinical outcome. However, only limited data are available on the underlying causes of hyperlactatemia and the mortality rates associated with severe hyperlactatemia in critically ill patients. We therefore aimed to evaluate the etiology of severe hyperlactatemia (defined as a lactate level >10 mmol/L) in a large cohort of unselected ICU patients. We also aimed to evaluate the association between severe hyperlactatemia and lactate clearance with ICU mortality.
Methods: In this retrospective, observational study at an University hospital department with 11 ICUs during the study period between 1 April 2011 and 28 February 2013, we screened 14,040 ICU patients for severe hyperlactatemia (lactate >10 mmol/L).
Results: Overall mortality in the 14,040 ICU patients was 9.8 %. Of these, 400 patients had severe hyperlactatemia and ICU mortality in this group was 78.2 %. Hyperlactatemia was associated with death in the ICU [odds ratio 1.35 (95 % CI 1.23; 1.49; p < 0.001)]. The main etiology for severe hyperlactatemia was sepsis (34.0 %), followed by cardiogenic shock (19.3 %), and cardiopulmonary resuscitation (13.8 %). Patients developing severe hyperlactatemia >24 h of ICU treatment had a significantly higher ICU mortality (89.1 %, 155 of 174 patients) than patients developing severe hyperlactatemia ≤ 24 h of ICU treatment (69.9 %, 158 of 226 patients; p < 0.0001). Lactate clearance after 12 h showed a receiver-operating-characteristics area under the curve (ROC-AUC) value of 0.91 to predict ICU mortality (cut-off showing highest sensitivity and specifity was a 12 h lactate clearance of 32.8 %, Youden Index 0.72). In 268 patients having a 12-h lactate clearance <32.8 % ICU mortality was 96.6 %.
Conclusions: Severe hyperlactatemia (>10 mmol/L) is associated with extremely high ICU mortality especially when there is no marked lactate clearance within 12 h. In such situations, the benefit of continued ICU therapy should be evaluated.
Keywords: Circulatory shock; Critical care; Hyperlactatemia; Intensive care unit; Lactate; Sepsis.