Continuous assessment of local metabolism by microdialysis in critical limb ischaemia.

Objective: to investigate the feasibility of using microdialysate glucose, lactate and pyruvate concentrations for grading the severity of blood flow reduction in patients with critical limb ischaemia.
Patients and Methods: microdialysis catheters were inserted (two subcutaneously and one intramuscularly) in the symptomatic limb of ten patients. To further reduce limb perfusion, the lower leg was elevated during part of the experiment.
Results: elevation reduced ankle and toe blood pressure and transcutaneous oxygen tension. Microdialysate glucose concentration decreased at all three catheter sites, while lactate increased in the intramuscular catheter. Two patients interrupted the elevated position prematurely due to severe pain in the foot. They had among the highest lactate levels in the horizontal position and the most marked increases following provocation. Neither initial metabolite concentrations nor concentration changes during elevation were shown to correlate to conventional methods used to assess limb perfusion.
Conclusions: in patients with critical limb ischaemia microdialysis can be used without complications. A significant decrease in glucose concentration may reflect lowered blood flow in the elevated position. Metabolic response, i.e. increase in lactate concentration during profoundly reduced limb perfusion was heterogeneous, indicating an overestimation of the presence of ischaemia in some patients using current diagnostic methods.
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