title: Open-flow microperfusion of subcutaneous adipose tissue for on-line continuous ex vivo measurement of glucose concentration.
abstract: OBJECTIVE
  To evaluate a novel technique for on-line continuous glucose measurement in subcutaneous adipose tissue, and to investigate its accuracy for detection of hypoglycemia.
  
  
  METHODS
  The method combined an open-flow microperfusion of subcutaneous adipose tissue using a double lumen catheter and an extracorporeal sensor cell. An isotonic ion-free solution was perfused through the inner lumen of the catheter, equilibrated with the subcutaneous tissue fluid, and sampled through the outer lumen. The recovery was continuously monitored as the ratio between the measured sampled fluid conductivity and the subcutaneous tissue fluid conductivity (assumed to have a constant value of 1.28 S/m at 25 degrees C). Glucose concentration was calculated on-line from the measured glucose in the sampled fluid and the measured recovery in healthy volunteers during hyperglycemic glucose loads (n = 8), hypoglycemic hyperinsulinemic clamp (n = 6), and a 24-h monitoring period (n = 7).
  
  
  RESULTS
  Subcutaneous glucose concentrations in the fasting state were 94% of the plasma glucose concentrations in arterialized venous samples. According to the error grid analysis, 96.9% of the on-line measured subcutaneous glucose concentrations during hyperglycemia and 96.3% during hypoglycemia were in accurate or acceptable zones. The mean differences between the measured subcutaneous glucose and the actual plasma glucose concentration were -0.06-3.3 mmol/l (hyperglycemia), and -0.6-1.1 mmol/l (hypoglycemia).
  
  
  CONCLUSIONS
  By combining open-flow microperfusion, glucose sensor, and conductivity measurement, glucose concentration in the subcutaneous adipose tissue can be monitored on-line, extracorporeally, and continuously without any in vivo calibration, and gives accurate measurements during hyper- and hypoglycemia.
authors.affiliation: Department of Biophysics, Institute of Biomedical Engineering, Graz University of Technology, Austria. trajanoski@ibmt.tu-graz.ac.at
authors.forename: Z
authors.initials: Z
authors.lastname: Trajanoski
authors.forename: G A
authors.initials: GA
authors.lastname: Brunner
authors.forename: L
authors.initials: L
authors.lastname: Schaupp
authors.forename: M
authors.initials: M
authors.lastname: Ellmerer
authors.forename: P
authors.initials: P
authors.lastname: Wach
authors.forename: T R
authors.initials: TR
authors.lastname: Pieber
authors.forename: P
authors.initials: P
authors.lastname: Kotanko
authors.forename: F
authors.initials: F
authors.lastname: Skrabal
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry* / Q000378:metabolism; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002940:Circadian Rhythm; D005260:Female; D005947:Glucose / Q000032:analysis* / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000175:diagnosis; D007003:Hypoglycemia / Q000097:blood / Q000175:diagnosis*; D008297:Male; D009862:Online Systems / Q000295:instrumentation*; D009994:Osmolar Concentration; D010477:Perfusion / Q000295:instrumentation / Q000379:methods*; D011188:Potassium / Q000097:blood; D015203:Reproducibility of Results; D012867:Skin; D012964:Sodium / Q000097:blood; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D012964:Sodium; D005947:Glucose; D011188:Potassium