Hepatic Vein Microdialysis is not Equivalent to Intrahepatic Microdialysis Monitoring for the Detection of Metabolic Changes Induced by Arterial Ischemia in a Pig Liver Model

Background: Intrahepatic (intraparenchymal) microdialysis is a well-established method used to monitor liver metabolism. A less invasive alternative would be to use a transjugular approach to place a microdialysis catheter in the middle hepatic vein and measure these metabolites intravenously in the liver. The aim was to study whether these two methods would be comparable for metabolic monitoring in a pig liver model. Methods: Three microdialysis catheters with molecular cut-off 20kDa were inserted into the liver, middle hepatic vein and subcutaneously in 8 pigs used in the experiment. The flow rate was 0.3 μl/min in the intrahepatic and subcutaneous (reference) catheters and 1 μl/min in the hepatic vein catheter. During a 2-hour period of equilibration, a steady state was reached after 1 hour. The hepatic artery was then clamped for a period of 4 hours to induce ischemia. Dialysate samples were collected at 15-minute intervals from the hepatic and intravenous catheters and 30-minute intervals from the reference catheter and analysed for glucose, glycerol, lactate and pyruvate. The lactate/pyruvate ratio was calculated. Results: Lactate and pyruvate levels in the intrahepatic and subcutaneous catheters showed significant changes after hepatic arterial clamping. Glycerol and the lactate/pyruvate ratio in the intrahepatic catheter showed increases, which were not significant, but spontaneously normalized despite persistent clamping. There were no changes in the metabolites measured by the hepatic vein catheter throughout the experiment. Conclusion: Hepatic vein microdialysis cannot be used equally as compared to direct intrahepatic (intraparenchymal) placement regarding the monitoring of glucose, glycerol, lactate and pyruvate.