CARDIAC-OUTPUT AND CIRCULATING BLOOD-VOLUME ANALYSIS BY PULSE DYE-DENSITOMETRY

Objective. Pulse dye-densitometry (PDD) is a newly developed method fo r monitoring the indocyanine green (ICG) concentration in an artery wi th which cardiac output (CO) and circulating blood volume (CBV) can be determined. We evaluated its accuracy for clinical use. Methods. In 7 patients under general anesthesia, ICG-sensitive optical probes (805 and 890nm) were attached to a finger. Following injection of ICG, the arterial concentration of dye was recorded optically by the non-invasi ve test instrument and sampled arterial blood ICG concentration was al so measured photometrically for comparison. In order to validate the P DD analysis, CO was also measured by both the dye dilution cuvette met hod and by thermodilution in 8 patients scheduled for coronary artery bypass grafting. In 30 other patients, CBV assessed by PDD was compare d with its value estimated from body size. Results. The blood dye conc entration correlated well with the values obtained by PDD (r = 0.953, p < 0.01). Mean bias for the test PDD CO was +0.15 +/- 0.72 min l(-1) (not significant (n.s)) compared with the cuvette method while the mea n bias of the thermodilution method vs the cuvette method was +0.79 +/ - 0.84 min l(-1) (p < 0.0001.). The average value of CBV obtained by P DD was 3.81 +/- 1.39 L compared with that estimated value, 3.72 +/- 0. 77 L (n.s). Conclusions. CO determined by PDD agrees well with cuvette densitometry, and somewhat less well with CO by thermodilution. The n ew method, by not requiring a pulmonary arterial catheter, is less inv asive than either older method, and yields in addition a value of CBV.