Elevated adipose tissue lactate to pyruvate (L/P) ratio predicts poor outcome in critically ill patients with septic...

Sepsis is a disease affecting tissue metabolism; in vivo microdialysis (MD) is a bedside technique enabling researchers to monitor tissue metabolic changes. We conducted this study aiming to evaluate the relationship between lactate to pyruvate (L/P) ratio, a sensitive marker of tissue oxygenation and perfusion, and mortality in critically ill septic patients.

We enrolled 105 patients with septic shock hospitalized in the mixed intensive care unit of a tertiary hospital. A MD catheter was inserted in the subcutaneous adipose tissue of the upper thigh and interstitial fluid samples were collected and analyzed for glucose, lactate, pyruvate, and glycerol.

Multivariate regression analysis showed that among variables registered on day 1, APACHE II and SOFA scores, blood lactate and microdialysis-assessed tissue L/P ratio were independently associated with 28-day mortality. Even in patients with normal (<2 mmol/L) blood lactate, adipose tissue L/P ratio showed a strong trend to statistical significance. During the 6-day study period, non-survivors had significantly higher L/P ratios compared to survivors (P=0.001) and mixed model analysis revealed a different pattern of evolution in time with non-survivors experiencing an increase while survivors had a late decline in their L/P ratio. The AUC for L/P ratio was similar to that of APACHE II (P=0.67) and SOFA score (P=0.73). Comparison of the Kaplan-Meier 28-day survival curves of patients with normal (≤ 25) versus elevated (>25) L/P ratios showed that the latter survived significantly less (P=0.02; log-rank test).

Elevated adipose tissue L/P ratio is associated with poor outcome in critically ill patients with septic shock. Microdialysis deserves to be further studied as a research tool in the multi-modal monitoring of septic critically ill patients.