Absolute blood volume and hepatosplanchnic blood flow measured by indocyanine green kinetics during hemodialysis.

A technique to measure absolute blood volume and hepatosplanchnic blood flow (Q(h)) during hemodialysis (HD) is explored. The dispersion and elimination of indocyanine green (ICG) were measured using a noninvasive optical device attached to the extracorporeal system and compared with transcutaneous measurements. Distribution volume (V) and elimination rate constant (k) were determined from arterial indicator concentrations assuming standard single-pool behavior. Cardiac output (Q(c)) and access flow (Q(a)) were measured by saline dilution technique. Duplicate dilutions were available in seven subjects (two female subjects, 78.0 ± 9.66 kg dry weight). k was not different between measuring techniques (0.246 ± 0.07 vs. 0.249 ± 0.064 min⁻¹, p = n.s.). V was 4.71 ± 0.75 L (60.86 ± 10.21 ml/kg dry body weight) as anticipated for anthropometric blood volume (p = n.s). Indocyanine green half-life was 3.05 ± 0.89 min and in the range of normal liver function. Therefore, ICG clearance (K = kV, 1.14 ± 0.32 L/min) was assumed to correspond to Q(h). Systemic blood flow (Q(s)) calculated as difference between Q(c) (7.11 ± 1.47 L/min) and Q(a) (1.56 ± 0.88 L/min) was 5.55 ± 1.33 L/min. Thus, during HD 21 ± 5% of Q(s) were consumed by the hepatosplanchnic circulation. The analysis of ICG distribution and elimination using available online technology for routine HD provides plausible point-of-care information, which could be of clinical interests in extracorporeal applications.