Subcutaneous Microdialysis for Metabolic Monitoring in Abdominal Aortic Surgery

Abstract

Microdialysis, that is the sampling of interstitial fluid via semi-permeable tubes, has been shown to be suitable for detecting ischemic changes e.g. in brain and heart tissue. The purpose of the present study was to investigate the possibility of monitoring with subcutaneous microdialysis peri-operative metabolic sequelae of elective abdominal aortic surgery. In 22 patients microdialysis catheters were inserted subcutaneously in the lower leg as well as the shoulder serving as a reference topographic region. Lactate, pyruvate and glycerol, which indicate ischemia or reperfusion, were measured. We observed severe metabolic changes within the interstitial fluid of the lower extremity during ischemia followed by normalization during reperfusion. Despite high interstitial concentrations of lactate and glycerol indicating severe ischemia during clamping of the abdominal aorta these parameters returned to pre-operative values within 2 hrs after declamping and all patients recovered completely. Objective.Information about the metabolic state of the lower extremity during and after infrarenal aortic aneurysm repair should modify peri-operative treatment. The aim of the study was to evaluate whether microdialysis of the subcutaneous tissue reflects metabolic changes during ischemia and reperfusion. Lactate, pyruvate and glycerol concentrations were measured in the subcutaneous tissue of the lower extremity and compared to the microdialysis measurements from shoulder subcutaneous tissue. Method.In 22 patients microdialysis catheters were inserted preoperatively in the subcutaneous space of the left shoulder and the left calf. Samples were taken at timed intervals before, during and after clamping of the abdominal aorta. Results.The subcutaneous glycerol concentration of the calf was increased during the clamping period from initially 68 ± 11 µM up to 182 ± 27 µM (p< 0.05); the lactate/pyruvate (L/P) ratio was increased eightfold. After declamping these values normalized to baseline. Microdialysis measurements of the shoulder showed no prominent changes during the entire course of observation. Conclusions.Subcutaneous microdialysis was able to detect metabolic changes due to ischemia during clamping of the abdominal aorta as well as reperfusion there after. It is a suitable technique to monitor the peri-operative course of the dependent tissue after abdominal aortic vascular surgery.