Estimation of circulating blood volume in infants using the pulse dye densitometry method

Summary Background:  Estimation of hemodynamics is important for critically ill infants. Pulse dye densitometry (PDD) using indocyanine green (ICG), which enables measurements of circulating blood volume at the bedside, has recently been developed for adults. Methods:  We conducted a basic investigation to determine whether this method can be applied to infants and measured circulating blood volume in 25 infants whose gestational ages ranged from 24 to 40 weeks (median, 32 weeks). At first, to validate the accuracy of measurements, arterial ICG concentrations determined by blood sample measurements were compared using a spectrophotometer ([ICG blood]) and by noninvasive measurement using PDD ([ICG pdd]) in seven infants. Next, blood volumes in 25 infants were estimated by the PDD method. Results:  There was a positive relationships between [ICG blood] and [ICG pdd] (r = 0.913, P < 0.0001). Using Bland Altman analysis, the bias between the two methods was 0.24 ± 0.30 mg·l−1 (95% confidence interval: 0.39–0.09 mg·l−1) and the limits of agreement (2 sd) were −0.36  and 0.84 mg·l−1, respectively. Mean (sd) blood volume was 94.9 ml·kg−1 (24.3). The values obtained by this study are almost the same as previously reported values obtained by using other methods. Conclusions:  PDD using ICG can be used to monitor of hemodynamics in infants.