DETERMINATION OF PLASMA-VOLUME WITH INDOCYANINE GREEN IN MAN

We investigated the feasibility of using indocyanine green (ICG) for p lasma volume (PV) determination in man. Duplicate PV measurements were carried out in 23 healthy subjects to test repeatability. ICG (0.25 m g/kg) was injected intravenously into one arm and venous blood was wit hdrawn from the opposite arm. Optical density of plasma samples from m inute 3 to 9 was measured in a densitometer. ICG concentration at inje ction time was determined by monoexponential extrapolation. The mean ( SD) difference (MD) was -23 ml (183) or -0.6% (5.7%). Linear regressio n revealed PV2=0.92.PV1+226 (r=0.92). The PV values corresponded well with data from other studies. In 26 surgical patients PV was determine d using two methods: 1) the same as in healthy subjects and 2) using a modification of this method in whole blood (PVB). For PVB measurement blood was drawn through a cuvette-densitometer from an arterial line. Calculations were the same as in PV determination except for the use of hematocrit to achieve plasma concentrations of ICG from whole blood . In patients MD were -53 ml (144) or -1.3% (4.3) for PV and -19 ml (1 61) or -0.3% (5.1) for PVB. Comparing PVB and PV revealed MD = -113 ml (149) or -3.3% (4.2). The whole blood method is easier to perform and reduces blood waste to almost zero. In conclusion, ICG is a suitable tracer for PV determination.