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Interpretation of serum lactate levels in septic hyperlactatemic patients with acute respiratory distress syndrome

Introduction

Increased serum lactate levels are used as a surrogate marker of tissue hypoxia in critically ill patients [1]. The aim of this study was to define the significance and the origin of hyperlactatemia in septic acute respiratory distress syndrome (ARDS) patients.

Methods

We prospectively observed 21 consecutive septic ARDS patients (standardized criteria) with a hyperlactatemia for a period of 24 months in a general ICU (17 beds, Pirogov Emergency Institute, Sofia, Bulgaria). Parameters of oxygen transport, haemodynamics and metabolism were defined with the aid of pulmonary artery catheterization and indirect calorimetry for a 10-day period. In addition, the transpulmonary lactate gradient (LACTtp = LACT(v) - LACT(a) (mmol/l)) and transpulmonary lactate flux (LACTtf = LACTtp × COtd (mmol/min, mmol/hour)) were calculated to assess the presence of intrapulmonary lactate production/consumption.

Results

We found positive values of transpulmonary lactate flux and transpulmonary lactate gradient in all patients, which determines the pulmonary lactate kinetics as pulmonary lactate production. There were statistically significant epidemiological differences in pulmonary lactate kinetics. The mortality in this study was 47%, higher in patients with direct lung injury. We did not observe pathological supply dependency of oxygen consumption using the method of indirect calorimetry.

Conclusion

These results define the lung as the main lactate-producing organ in septic hyperlactatemic patients with ARDS, which in the absence of a pathological supply dependency of oxygen consumption outlines the risk of wrong interpretation of serum lactate levels as a surrogate marker of tissue hypoxia in these patients.

References

  1. 1.

    Leverve XM, et al.: Lactate: a key metabolite in the intercellular metabolic interplay. Crit Care 2002, 6: 284-285. 10.1186/cc1509

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Milanov, S., Georgiev, G., Todorova, V. et al. Interpretation of serum lactate levels in septic hyperlactatemic patients with acute respiratory distress syndrome. Crit Care 12, P452 (2008). https://doi.org/10.1186/cc6673

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Keywords

  • Lactate
  • Oxygen Consumption
  • Surrogate Marker
  • Acute Respiratory Distress Syndrome
  • Lactate Production