Plasma volume estimation using indocyanine green with biexponential regression analysis of the decay curves

Abstract

We studied seven analytical methods of estimating the plasma volume from the decay curves of indocyanine green. Fifteen volunteers received 1.0 mg.kg-1 of the dye by intravenous injection and the plasma concentration was measured continuously using spectrophotometry. Plasma volumes were calculated using three single-regression methods (1-a, 1-b, 1-c) and four biexponential regression methods (2-a, 2-b, 2-c, 2-d). The means (SD) of 1-a, 1-b and 1-c were 39 (5.0), 44 (5.7) and 54 (11.5) ml.kg-1, respectively, and these were significantly different from each other (p < 0.05). The values for methods 2-b, 2-c and 2-d were similar to each other: 39 (4.6), 40 (4.1) and 40 (4.0) ml.kg-1, respectively. These required more than 3 min circulation or mixing time. When the time allowed for mixing was less than 3 min (method 2-a) the plasma volume was underestimated. We conclude that plasma volume estimation using indocyanine green and spectrophotometry is most accurate when the mixing time is adequate (3-5 min) and the decay curves are analysed using biexponential regression.

Technical and physiological background of plasma volume measurement with indocyanine green: a clarification of misunderstandings

“…At least during the first 5 min after recirculation, ICG elimination seems to consistently follow a monoexponential kinetic (48). However, beyond minute 5, the elimination kinetic inconstantly changes toward a biexponential, or even polyexponential, mode (24,45,48).…”

“…However, beyond minute 5, the elimination kinetic inconstantly changes toward a biexponential, or even polyexponential, mode (24,45,48). To avoid overestimation of the distribution space of ICG (DS ICG ), the samples used for monoexponential extrapolation should only be taken up to minute 5.…”

Impact of the time window on plasma volume measurement with indocyanine green

“…There are two possibilities to avoid misinterpretation of PV measurements with ICG-DT: (i) usage of a time window starting beyond the 5th min and applying a biexponential extrapolation technique (Sekimoto et al 1997), or (ii) usage of a time window ending before the 5th min and applying a monoexponential extrapolation. Which is the better choice for clinical needs?…”

“…Sekimoto and co-workers (Sekimoto et al 1997) measured ICG plasma concentrations in 15 volunteers during the first 30 min after dye injection and compared the PV results from mono-and biexponential regression with different time windows. To be able to perform a biexponential regression analysis to a large time window (5th to 30th min), they applied an ICG dosage four-fold higher (1.0 mg kg −1 ) than we needed to.…”

MLGA: ASASMacro to Compute Maximum Likelihood Estimators via Genetic Algorithms

“…A clear example of this last case is the bi-exponential model. It is used extensively to model drug concentrations as functions of time, for example in Sekimoto, Fukui, and Fujita (1997); Zhang, Sigmund, Rusinek, Chandarana, Storey, Chen, and Lee (2012); Williams, Buhl, and Mody (2012). This model is not identified, since the pairs (A, α1) and (B, α2) are exchangeable.…”