A high lactate level, which is usually defined as an arterial lactate level > 2 mmol/L, is a notorious predictor of negative outcome with regard to organ dysfunction and mortality in various subgroups of critically ill patients. Vellinga et al. aimed to examine the importance of a single-spot arterial lactate measurement and simultaneous in vivo microscopy in a heterogeneous Intensive Care Unit population recruited from 36 ICUs around the world.
This study was a post hoc analysis of a prospective observational point prevalence study of the prevalence and significance of microcirculatory alterations in a heterogeneous ICU population. Lactate levels were measured within a maximum of 4 hours before or after sublingual sidestream dark-field (SDF) imaging. For this substudy, patients with an arterial lactate level ≤ 2 mmol/L were included.
Analysis was focused on associations between lactate levels, mortality, organ dysfunction, and microcirculatory alterations. Increases in ICU mortality were observed for every lactate quartile, and similar trends were observed for hospital mortality.
Abnormal microcirculatory flow was defined as a microvascular flow index (MFI) < 2.6. MFI is a semiquantitative score ranging from 0 (no flow) to 3 (continuous flow). Associations between microcirculatory flow abnormalities, single-spot lactate measurements, and outcome were analyzed.
Patients with a capillary microvascular flow index (MFI) < 2.6 (14%) had slightly but nonsignificantly higher lactate levels than patients with a higher MFI (1.11 [0.90–1.60] vs. 1.00 [0.80– 1.40] mmol/L, P = 0.117). A nonsignificant trend toward a higher prevalence of an abnormal microcirculation in the highest lactate quartile was observed (P = 0.169).
In this study, a single-spot arterial lactate level > 1.5 mmol/L was associated with increased mortality as well as with microcirculatory abnormalities and organ dysfunction. Lactate levels on admission as low as 1.1 mmol/L already appeared to be associated with adverse outcome.
This article was written by Vellinga et al. and published in 2017 in Critical Care
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Mildly elevated lactate levels are associated with microcirculatory flow abnormalities and increased mortality: a microSOAP post hoc analysis