Calculation of maximal removal rate of indocyanine green to measure hepatic functional mass in dogs by use of the nine-hour method

Abstract

Abstract Objective To establish a versatile and reliable procedure for the determination of indocyanine green maximal removal rate (ICG Rmax) to measure hepatic functional mass in dogs within 9 hours (9-hour method). Design Relation between 9-hour and standard 3-day methods was examined. Animals 101 healthy dogs. Procedure On investigation of the optimal technical conditions allowing completion of all procedures in a day, the appropriate IV administered doses of ICG were 0.125, 0.5, and 2.0 mg/kg of body weight, and the best blood sample collection times for obtaining plasma half-life at these 3 doses were before and 3, 6, and 9 minutes after ICG administration. Results Comparison of the 9-hour with 3-day method yielded a correlation coefficient (r) of 0.84, indicating close (P < 0.01) correlation. In the 9-hour method, mean ± SD of ICG Rmax in healthy dogs was 0.24 ± 0.09 mg/kg/min in male (n = 62) and was 0.23 ± 0.06 mg/kg/min in female (n = 21) Beagles, and was 0.21 ± 0.10 mg/kg/min in male (n = 11) and 0.20 ± 0.07 mg/kg/min in female (n = 7) mixed-breed dogs. In Beagles treated orally with carbon tetrachloride (0.1 ml/kg in gelatine capsules) thrice weekly during a 10-week period, plasma alanine transaminase activity plateaued at a high value (> 2,000 IU/L) on day 5, and remained at this value until the end of the study. The ICG Rmax changed accordingly: day 5, 0.17; day 10, 0.11; day 40, 0.05; and day 60, 0.06 mg/kg/min. Conclusion The 9-hour method for determination of ICG Rmax correlates favorably with the 3-day method. Clinical Relevance This procedure may be practically applied in veterinary clinics in terms of prediction of hepatic functional mass, and for diagnosis of hepatotoxicosis induced by certain compounds. (Am J Vet Res 1996;57:803–806)