Evaluation of a transcutaneous method to assess canine liver function by indocyanine green plasma disappearance rate in healthy adult Beagle dogs

- Indocyanine green disappearance rate (ICG-PDR) is a test of liver function.
- ICG-PDR can be determined using transcutaneous near infrared spectroscopy.
- We compared ICG-PDR with ICG plasma clearance rate in anesthetized and awake dogs.
- We found a good agreement between the methods in awake healthy dogs.
- Transcutaneous ICG-PDR has potential for real-time assessment of liver function in dogs.

A non-invasive, transcutaneous method using near infrared spectroscopy to assess indocyanine green plasma disappearance rate (ICG-PDR) in healthy dogs subjected to different conditions was evaluated in eight healthy purpose-bred Beagles under isoflurane-anaesthesia (Trial 1) and when they had initially recovered from anaesthesia (Trial 2). Plasma ICG concentrations (0, 5, 10, 15, 30 min after rapid ICG injection (0.5 mg/kg) into a peripheral vein were determined by high-performance liquid chromatography in parallel with transcutaneous measurements.ICG clearance (mL/min/kg) and retention rate after 15 min (R15, %) were calculated from plasma concentrations to be 3.09 ± 0.83 (mean ± SD) and 30.6 ± 8.3 in anaesthetised dogs and 3.63 ± 0.88 and 28.1 ± 7.3 in recovering dogs, respectively. ICG-PDR (%/min) and R15 (%) obtained using the transcutaneous method were 7.11 ± 3.18 and 34.6 ± 12.4 (Trial 1) and 7.79 ± 3.33 and 32.3 ± 9.2 (Trial 2). The coefficients of determination (r2) for ICG clearance and ICG-PDR were 0.14 (Trial 1) and 0.81 (Trial 2) and 0.47 (Trial 1) and 0.29 (Trial 2) for R15, respectively. The mean bias (lower, upper limit of agreement) for R15 were 5.6 (−12.3, 23.5) (Trial 1) and 3.9 (−12.4, 20.1) (Trial 2). The results suggest good agreement between the two methods in dogs recovering from isoflurane-anaesthesia and the transcutaneous method might be useful in real-time assessment of liver function in conscious dogs.