Cardiac output and circulating blood volume analysis by pulse dye-densitometry

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Abstract
Objective. Pulse dye-densitometry (PDD) is a newly developed methodfor monitoring the indocyanine green (ICG) concentration in an artery withwhich cardiac output (CO) and circulating blood volume (CBV) can bedetermined. We evaluated its accuracy for clinical use. Methods. In 7patients under general anesthesia, ICG-sensitive optical probes (805 and 890nm) were attached to a finger. Following injection of ICG, the arterialconcentration of dye was recorded optically by the non-invasive testinstrument and sampled arterial blood ICG concentration was also measuredphotometrically for comparison. In order to validate the PDD analysis, CO wasalso measured by both the dye dilution cuvette method and by thermodilutionin 8 patients scheduled for coronary artery bypass grafting. In 30 otherpatients, CBV assessed by PDD was compared with its value estimated from bodysize. Results. The blood dye concentration correlated well with thevalues obtained by PDD (r = 0.953, p < 0.01). Meanbias for the test PDD CO was +0.15 ± 0.72 minl−1 (not significant (n.s.)) compared with the cuvette methodwhile the mean bias of the thermodilution method vs thecuvette method was +0.79 ± 0.84 min l−1 (p < 0.0001.). The average value of CBV obtained by PDD was 3.81± 1.39 L compared with that estimated value, 3.72 ± 0.77 L (n.s.).Conclusions. CO determined by PDD agrees wellwith cuvette densitometry, and somewhat less well with CO by thermodilution.The new method, by not requiring a pulmonary arterial catheter, is lessinvasivethan either older method, and yields in addition a value of CBV.