Equis ISSN 2398-2977

Blood: biochemistry - indocyanine green

Contributor(s): Prof Michael J Day, Graham Munroe


  • Indocyanine green is a dye which when injected intravenously into an animal is rapidly bound to blood proteins (principally albumin) and them removed from the plasma and excreted into the bile by the liver. It is not in any way metabolized by the hepatocytes.
  • Its rate of disappearance from the blood can be measured and allows hepatic function and blood flow to be assessed. Compromised hepatic function results in delayed systemic clearance.
  • It is an alternative to the bromosulphalein (BSP) test which is now obsolete.


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  • Insert jugular catheter for specimen sample collection   Blood: collection  .
  • Collect initial blood sample.
  • 0.5-1 mg/kg bodyweight of dye solution is administered intravenously into contralateral jugular vein.
  • Take 3 blood samples from jugular vein at any time within 3-15 min post-injection of the indocyanine green.
  • The blood is centrifuged.
  • The serum is placed into a spectrophotometer which reads at wavelengths in the infrared range.
  • The serum dye concentrations are read directly at 805 nm wavelength.
  • The dye concentrations are plotted on a graph with semi-logarithmic co-ordinations and the half-life value calculated directly (T½).
  • The fractional clearance K or % removed per minute is calculated from the equation K=In2/T½ where In2=0.693.


  • IC-GREEN (Akorn, Inc. Lake Forest, IL 60045, USA).
  • Sterile lyophilized green powder containing 25 mg indocyanine green plus sterile water to mix for sterile intravenous injection.
  • Unstable solution which must be used within 6 h.

Result Data

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Parry B W, Bayly W M & Tarr B (1989) Indocyanine green clearance and estimation of plasma volume in the normal horse. Equine Vet J 21 (2), 142-144 PubMed.
  • Engelking L R et al (1985) Hepatobiliary transport of indocyanine green and sulfobromophthalein in fed and fasted horses. Am J Vet Res 46 (11), 2278-2284 PubMed.