Cerebral near infrared spectroscopy for the measurement of indocyanine green elimination in cirrhosis

Background: Indocyanine green (ICG) clearance is a useful indicator of hepatic function but most measurement methods are invasive. Aim: To validate a less invasive technique using cerebral near infrared spectrophotometry (NIRS) to measure ICG elimination, and to compare it with the established methods for the determination of ICG clearance in a group of normal controls and patients with cirrhosis. Method: NIRS was used to measure ICG elimination in 41 cirrhotic patients and nine healthy volunteers. The first 13 of the cirrhotic patients also had their ICG clearance measured by the conventional spectrophotometric technique. Results: NIRS ICG elimination rate (ICG-k) and spectrophotometry ICG-k values correlated strongly (r= 0.828, P < 0.001, n=13). There was a significant reduction in the mean NIRS-k in cirrhotic patients and within Child-Pugh classes A, B, and C (P < 0.001). Conclusion: Measurement of ICG elimination by the NIRS method is at least as reliable as the conventional spectrophotometric technique in normals and in patients with cirrhosis. This technique merits further development for use as a bedside, less invasive liver function test.