Endotracheal lactate reflects lower respiratory tract infections and inflammation in intubated patients

Abstract

The aim of this study was to assess L‐lactate and D‐lactate in endotracheal aspirate from intubated patients hospitalized at the intensive care unit and explore their use as diagnostic biomarkers for inflammation and lower respiratory tract infections (LRTI). Tracheal aspirates from 91 intubated patients were obtained at time of intubation and sent for microbiological analyses, neutrophil count, and colorimetric lactate measurements. We compared the concentration of lactate from patients with microbiological verified LRTI or clinical/radiological suspicion of LRTI with a control group. In addition, associations between inflammation and the lactate isomers were examined by correlating L‐lactate and D‐lactate with sputum neutrophils and clinical assessments. The concentration of L‐lactate was increased in aspirates with verified or suspected LRTI (p < 0.001) relative to the control group at Day 0. Connections between L‐lactate and inflammation were indicated by the correlation between neutrophils and L‐lactate (p < 0.001). We found no increase in sputum D‐lactate from patients with verified or suspected LRTI relative to the control group and D‐lactate was not correlated with neutrophils. L‐lactate was found to be a potential indicator for inflammation and LRTI at the time of intubation. An association was found between neutrophil count and L‐lactate. Interestingly, the increase of L‐lactate in the control group after intubation may suggest that intubation challenges the host response by inflicting tissue damage or by introducing infectious microbes.

“The Standard Procedure” for Investigation of Oral Neutrophils in Oral Diseases

“…The instrument was calibrated using BD™ Cytometer Setup and Tracking Beads (642412, BD Bioscience). We have previously used the same antibody combination to quantitate exudated human neutrophils [ 17 – 19 ] and the specificity for the leukocyte subtypes has been verified in peripheral human blood where the identity of leukocyte subtypes was validated according to the morphology as determined by the light scatter. Gating of the fluorescence and the light scattering was set according to similarly stained human peripheral blood samples.…”

“…Gating of the fluorescence and the light scattering was set according to similarly stained human peripheral blood samples. The concentration of neutrophils was calculated from the ratio of recorded neutrophils and counting beads as previously described [ 17 – 19 ].…”