Extracellular metabolic alterations in critically ill septic patients studied by adipose tissue microdialysis

Introduction

Tissue metabolic alterations during critical sepsis have not been well characterized.

Objective

To investigate the tissue metabolic alterations during sepsis.

Methods

A microdialysis (MD) catheter was inserted into the subcutaneous adipose tissue of the upper thigh in 65 (39 men) septic critically ill patients upon sepsis onset. Dialysate samples were analyzed for glucose, lactate, pyruvate, and glycerol. The lactate/pyruvate (L/P) ratio was calculated. Sampling was performed six times per day for a maximum of 6 days. The daily mean values of MD measurements were calculated for each patient. Eleven (five men) critically ill nonseptic patients served as controls.

Results

Septic patients were older (66 ± 17 vs. 45 ± 20 years, P < 0.001), and had a higher APACHE II score (21 ± 5 vs. 14 ± 6, P < 0.001) along with a higher SOFA score (8 ± 3 vs. 3 ± 3, P < 0.001) compared with nonseptic patients. Septic patients had a high tissue glucose ( > 4.6 mmol/l), lactate ( > 2 mmol/l), pyruvate ( > 120 μmol/l), L/P ratio ( > 25), and glycerol ( > 200 μmol/l) during almost the entire observation period. Septic patients had higher tissue glucose (P = 0.02) and glycerol (P = 0.04) levels than nonseptic patients during the whole study period. They also tended to have higher lactate (P = 0.14) concentrations. In contrast, the two groups had similar tissue pyruvate (P = 0.35) and L/P ratios (P = 0.80).

Conclusions

Critical sepsis is characterized by an excessive release of extracellular glucose, lactate, and glycerol, with the latter reflecting probably increased lipolysis. These mirror the well-known sepsis-related blood metabolic alterations. Thus, chemical monitoring with subcutaneous MD is accurate in severely ill septic patients.