title: Membrane cut-off does not influence results regarding the measurement of small molecules - a comparative study between 20- and 100-kDa catheters in hepatic microdialysis.
abstract: BACKGROUND
  Microdialysis is a method used to monitor hepatic tissue metabolism. Membranes with a molecular cut-off of 20 kilodalton (kDa) are currently used to measure the small metabolites glucose, glycerol, lactate and pyruvate. Using membranes with higher cut-off such as 100 kDa allows the possibility of measuring larger molecules but may affect results regarding small molecules. The aim was to compare microdialysis catheters with a cut-off of 20 and 100 kDa in the measurement of small molecules in a pig liver model.
  
  
  METHODS
  Four microdialysis catheters were inserted into the liver of each pig used in the experiment (n = 6). Two catheters with cut-off of 20 kDa were perfused with Ringer acetate, and two catheters with cut-off of 100 kDa: one perfused with Ringer acetate and one with hydroxyethyl starch (Voluven) at a flow rate of 0·3 μl min(-1). Dialysate samples were collected at 40-min intervals and analysed for glucose, glycerol, lactate and pyruvate.
  
  
  RESULTS
  Compared to the other catheters, the 100-kDa catheters perfused with Ringer acetate tended to measure higher dialysate concentrations of the small molecules, the difference reaching statistical significance in the case of pyruvate. Concentrations measured by the 100-kDa catheters perfused with Voluven were, however, comparable to the 20-kDa catheters.
  
  
  CONCLUSIONS
  Microdialysis catheters with membrane cut-off of 20 and 100 kDa can be used equally in hepatic microdialysis for the monitoring of glucose, glycerol, lactate and pyruvate, and lactate/pyruvate ratio if a high osmotic solution (Voluven) is used to perfuse the 100-kDa catheters.
authors: Division of Surgery, Department of Clinical Science, Intervention, and Technology (CLINTEC), Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
authors: Melroy A
authors: MA
authors: D'souza
authors: Anna
authors: A
authors: Ravn
authors: Carl
authors: C
authors: Jorns
authors: Greg
authors: G
authors: Nowak
authors: Bengt
authors: B
authors: Isaksson
mesh_terms: D000818:Animals; D057785:Catheters; D004867:Equipment Design; D005260:Female; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006895:Hydroxyethyl Starch Derivatives; D019344:Lactic Acid / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008567:Membranes, Artificial; D017551:Microdialysis / Q000295:instrumentation*; D023421:Models, Animal; D008970:Molecular Weight; D010477:Perfusion / Q000379:methods; D016062:Porosity; D019289:Pyruvic Acid / Q000378:metabolism; D013552:Swine; D013997:Time Factors
chemical_list: C485123:HES 130-0.4; D006895:Hydroxyethyl Starch Derivatives; D008567:Membranes, Artificial; D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose; D005990:Glycerol
keywords: liver metabolism; membrane cut-off; microdialysis; microdialysis catheter