Relation between indocyanine green (ICG) plasma disappearance rate and ICG blood clearance in critically ill patients

Objective: In contrast to indocyanine green (ICG) blood clearance, the plasma disappearance rate (PDR) of ICG does not require absolute ICG blood concentrations and today can be assessed transcutaneously. In this study, we analyzed the relation between ICG disappearance rate and ICG blood clearance as parameters of liver function in critically patients. Design: Observational, clinical study. Retrospective analysis. Setting: Operative intensive care unit of a university hospital. Patients: 209 patients (139 male, 70 female, age 10-88 years, 53 +/- 19 years) who underwent liver function monitoring for clinical indication. Patients suffered from sepsis (n = 99), acute respiratory distress syndrome (n = 31), severe head injury (n = 38), hemorrhagic shock (n = 19), intracranial hemorrhage (n = 19), and cerebral infarction (n = 3). All patients were sedated and mechanically ventilated via an endotracheal tube. Measurements and results: All patients were monitored by the transpulmonary double-indicator (thermo-dye dilution) technique using a thermistor and calibrated fiber-optic system (Pulsiocath 4F, PV 2024L, Pulsion Medical Systems, Munich, Germany). For each measurement, a dosage of 0.3 mg/kg ICG was injected central-venously. Transpulmonary ICG concentration curves were analyzed automatically using a computer system (COLD-Z021, Pulsion Medical Systems, Munich, Germany). By using the first ICG measurement in each patient after admission to the ICU, we analyzed 209 pairs of ICG disappearance rate and ICG blood clearance. Linear regression analysis revealed a correlation of r(2) = 0.77 between ICG-PDR and ICG blood clearance. Conclusion: ICG-PDR does reflect ICG blood clearance with sufficient accuracy in critically ill patients and may be used as a surrogate.