Measurement of indocyanine green plasma disappearance rate by two different dosages

Background and goal of study

Monitoring of organ function is often crucial for guiding therapy in critically ill patients. Most recently, the indocyanine green plasma disappearance rate (ICG-PDR) has been suggested for assessment of liver function and a transcutaneous system has been clinically introduced and validated [1]. In this study, we analyzed the agreement between ICG-PDR measured with the recommended dosage (0.5 mg/kg) and a reduced dosage (0.25 mg/kg).

Materials and methods

We studied 16 critically ill patients (five female, 11 male) who underwent monitoring of ICG-PDR for clinical indication (LiMon, Pulsion Medical Systems, Germany). For each comparative measurement, in a random fashion, either 0.5 mg/kg or 0.25 mg/kg ICG were injected and followed by the corresponding dosage 60 min later. We analyzed 31 pairs of ICG-PDR measurements by applying the recommended dosage (0.5 mg/kg, ICG-PDR 0.5) and a reduced dosage (0.25 mg/kg, ICG-PDR 0.25). Respirator settings and dosages of vasoactive drugs remained unchanged during the study. No drugs that may influence hepatic blood flow were administered during the study period. There were no changes in fluid status and the central venous pressure was unchanged at the two time points.

Results and discussions

ICG-PDR0.25 was between 2.7 and 25.0%/min and ICG-PDR0.5 between 4.5 and 24.5%/min, respectively. Linear regression analysis revealed ICG-PDR 0.25 = 1.13 and ICG-PDR 0.5 = 0.66%/min (r = 0.95, P < 0.0001) with a mean bias of 1.0%/min (standard deviation 2.5%/min). The 15-min residual rates were also highly correlated (r = 0.92, P < 0.0001) with a mean bias of 0.3%.

Conclusion

A reduced dosage of ICG (0.25 mg/kg) is sufficiently accurate for transcutaneous measurement of ICG-PDR in critically ill patients.