title: Indocyanine green R15 ratio depends directly on liver perfusion flow rate.
abstract: BACKGROUND
  Indocyanine green (ICG) is a synthetic dye that is widely used to evaluate liver function in critically ill patients, before liver resection or after liver transplantation. Controversy still exists about the impact exerted on the ICG ratio after 15 min (ICG R15) by differences in liver perfusion rates, hyperdynamic states, or patient cardiac output. We studied the role of different liver perfusion rates on the ICG R15 ratio in a normothermic extracorporeal liver perfusion system under standardized conditions.
  
  
  METHODS
  Livers from landrace pigs (40-50 kg) were perfused with fresh porcine blood. Normal and high perfusion rates were defined as 1 ml and 2 ml/g liver/min, respectively. Perfusate pressure of the hepatic artery and portal vein were within the physiological range in both groups. According to manufacturer's instructions, 0.5 mg of ICG per kg was applied and the ICG R15 was calculated. Calculations were based on fifteen experiments in five liver perfusions. Bile production, liver function and histology were analyzed.
  
  
  RESULTS
  All perfusions were characterized by physiological bile production, lack of hepatocellular damage and normal histology. ICG R15 ratio in group I, perfused with 1 ml/g liver, was 18.9 +/- 6%. In group II, perfused with 2 ml/g liver, the ICG R15 ratio was 7.2 +/- 3%. The difference between groups 1 and 2 was statistically significant (p < 0.05).
  
  
  CONCLUSIONS
  ICG R15 is reliable within one group at defined perfusion rates. Doubled perfusion rates contribute to higher ICG clearance. For clinical application we would like to suggest considering cardiac output of the patient for interpretation of ICG ratios.
authors.affiliation: Department of Surgery, University of Leipzig, Leipzig, Germany. MWWJanssen@web.de
authors.forename: Martin W W
authors.initials: MW
authors.lastname: Janssen
authors.forename: Karl T
authors.initials: KT
authors.lastname: Druckrey-Fiskaaen
authors.forename: Leyla
authors.initials: L
authors.lastname: Omidi
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Sliwinski
authors.forename: Christine
authors.initials: C
authors.lastname: Thiele
authors.forename: Bernd
authors.initials: B
authors.lastname: Donaubauer
authors.forename: Nina
authors.initials: N
authors.lastname: Polze
authors.forename: Udo X
authors.initials: UX
authors.lastname: Kaisers
authors.forename: Joachim
authors.initials: J
authors.lastname: Thiery
authors.forename: Christian
authors.initials: C
authors.lastname: Wittekind
authors.forename: Johann P
authors.initials: JP
authors.lastname: Hauss
authors.forename: Michael R
authors.initials: MR
authors.lastname: Schön
mesh_terms: D000818:Animals; D004396:Coloring Agents / Q000493:pharmacokinetics*; D004195:Disease Models, Animal; D005260:Female; D007208:Indocyanine Green / Q000493:pharmacokinetics*; D008099:Liver / Q000098:blood supply / Q000378:metabolism; D008102:Liver Circulation / Q000502:physiology*; D017093:Liver Failure / Q000378:metabolism / Q000503:physiopathology / Q000601:surgery; D016031:Liver Transplantation; D008657:Metabolic Clearance Rate; D010477:Perfusion / Q000379:methods*; D011379:Prognosis; D013552:Swine
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green