CONTINUOUS MONITORING OF LACTATE IN SEPSIS AND SHOCK WITH SUBCUTANEOUS MICRODIALYSIS: EXPERIMENTAL AND CLINICAL STUDIES

Abstract

We evaluated a new method for continuously monitoring lactate concentrations with subcutaneous microdialysis sampling and continuous flow analysis in an experimental model of fatal septic shock in rats and in human shock patients. A microdialysis probe was placed subcutaneously, and dialysate lactate concentrations were compared with mixed central venous plasma lactate concentrations. After intra peritoneal injection of E. Coli bacteria in 4 rats, plasma lactate concentrations and subcutaneous dialysate lactate concentrations increased until death. The increase in plasma and dialysate lactate concentration were linearly correlated. However, in the terminal phase of shock, the dialysate lactate concentration increased relatively less as plasma lactate. This probably results from decreased subcutaneous blood flow. We also measured the subcutaneous microdialysis lactate concentration in 4 shock patients for periods ranging from 4 to 24 hours, admitted to the intensive care unit. The microdialysis lactate concentrations were significantly correlated to the plasma lactate concentrations in two patients. Plasma lactate concentrations also reflected the severity of illness. Our results also suggest that cardiac output is critical for plasma lactate levels to correlate with subcutaneous dialysate lactate levels. These experimental and clinical results indicate that subcutaneous microdialysis may be clinically useful to monitor the plasma lactate concentration in critically ill and shock patients. However, it remains to be eluciated how peripheral blood flow influences subcutaneous dialysate lactate concentrations.