Microdialysis: Reducing the Delay in Detection of Shift in Molecular Composition a Laboratory Study

Abstract

Introduction: Microdialysis is one of the methods used clinically for the detection of ischemia. Although microdialysis is reliable, in most clinical settings there is a delay of 1-2 hours before the information is available. Objective:The aim of this study was to evaluate whether an increase in the Microdialysis per fusion rate from 0.3 to 1.0 or 2.0 µl/min was capable of reducing the delay in the detection of a shift in molecular composition. Methods and material:Microdialysis was performed in a container with 3 catheters per fused with 0.3, 1.0 and 2.0 µl/min. The molecular composition in the container regarding glucose and lactate was initially as follows: C Glucose =6.0 mmol/L and C Lactate =2 mmol/L. At T=90 min the composition was changed to C Glucose =1 mmol/L and C Lactate =12 mmol/L. Dialysates were harvested from the three catheters and were analysed regarding the concentration of glucose and lactate. For calculation of the relative recovery, samples were harvested directly from the liquid. The relative recovery and the delay before new steady state were calculated for each of the 3 catheters. The experiment was performed 8 times.Results: A decrease in relative recovery was found with the higher perfusion rate. For glucose, the relative recovery was 100, 88, and 69% at perfusion rates of 0.3, 1.0 and 2.0 µl/min. For lactate, the corresponding values were 103, 93, and 77%. An increase in the lactate/glucose ratio was found with the higher perfusion rate. The delays in detection of shift in molecular concentration were found to be 60, 20, and 10 minutes for catheters 0.3, 1.0 and 2.0, respectively.Conclusion: Using microdialysis it is possible to significantly reduce the delay while still detecting a shift in the concentration of glucose and lactate when the perfusionrate is increased.