Interrelationship between blood and tissue lactate in a general intensive care unit: A subcutaneous adipose tissue microdialysis study on 162 critically ill patients

Purpose The aim of the study was to study the interrelationship between blood and tissue lactate in critically ill patients with or without shock admitted in a general intensive care unit. Materials and Methods We studied 162 mechanically ventilated patients: 106 with shock (septic shock, 97; cardiogenic shock, 9) and 56 without shock (severe sepsis, 38; systemic inflammatory response syndrome, 18). A microdialysis catheter was inserted in the subcutaneous adipose tissue of the upper thigh, and interstitial fluid was collected every 4 hours for a maximum of 6 days. We assessed the relationship between tissue and blood lactate using cross-approximate entropy and cross-correlation analysis. Results Patients with shock had higher area under the curve for blood (261 vs 175 mmol/L*hours, P < .0001) and tissue lactate (386 vs 281 mmol/L*hours, P < .0001) compared with patients without shock. The interrelationship of tissue-blood lactate, as assessed with cross-approximate entropy, was more regular in patients with shock compared with patients without shock. Cross-correlation of tissue vs blood lactate yielded higher correlation coefficients in patients with shock compared with those without shock, being higher when tissue lactate preceded blood lactate by 4 hours compared with tissue vs blood lactate with no lag time. Conclusions In critical illness, the detailed dynamics between blood and tissue lactate are affected by the presence of shock. In patients with shock, microdialysis-assessed tissue lactate is higher compared with those without shock and may detect metabolic disturbances before these become evident in the systemic circulation.