Measurement of indocyanine green plasma disappearance rate by two different dosages

Objective: While using a transcutaneous system for assessment of liver function by indocyanine green plasma disappearance rate (ICG-PDR) in critically ill patients, we compared the agreement between ICG-PDR obtained by the recommended standard ICG dosage (0.5 mg/kg) and a reduced dosage (0.25 mg/kg). Design: Clinical study. Setting: Intensive care unit of a university hospital. Patients: Critically ill patients (n=16, 5 female, 11 male) who underwent liver function monitoring by ICG-PDR for clinical indication. Measurements and results: We analyzed 31 pairs of ICG-PDR measurements by applying the recommended dosage (0.5 mg/kg, ICG-PDR0.5) and a reduced dosage (0.25 mg/kg, ICG-PDR0.25). For each comparative measurement either first 0.5 mg/kg or 0.25 mg/kg of ICG was injected in a random fashion and followed by the corresponding dosage 60 min later. All patients were sedated and mechanically ventilated via a tracheal tube. Each patient was monitored by an ICG finger clip which was connected to a liver function monitoring system (LiMon, Pulsion Medical Systems, Germany). ICG-PDR0.25 was 2.7-25.0%/min and ICG-PDR0.5 4.5-24.5%/min, respectively. Linear regression analysis revealed ICG-PDR0.25=1.13.ICG-PDR0.5-0.66%/min (r=0.95, p<0.0001) with a mean bias 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.