Figure 1. The recirculatory pharmacokinetic model used to analyze indocyanine green and alfentanil concentration-time relations. The parts in the dashed boxes represent the model for indocyanine green, the intravascular part of the model. The complete model is used to describe the alfentanil pharmacokinetics. Cl^ND_f = fast nondistributive; Cl^ND_s = slow nondistributive clearances; Cl^T_f = fast peripheral tissue clearance; Cl (^T)_s = slow peripheral tissue clearance; C.O. = cardiac output; V^C_f = fast central volume; V^C_s = slow central volume; V^ND_f = fast nondistributive volume; V^ND_s; slow nondistributive volume; V^T_f = fast peripheral tissue volume; V^T_s = slow peripheral tissue volume.