Measurement of blood volume using indocyanine green measured with pulse-spectrophotometry: its reproducibility and reliability.

OBJECTIVE: To systematically investigate the reproducibility and reliability of a newly developed, less invasive approach of estimating blood volume (BV), using indocyanine green (ICG) measured with pulse-spectrophotometry.
DESIGN: Prospective, clinical study.
SETTING: Surgical unit at a university hospital. PATIENTS: Twenty-two patients undergoing general anesthesia for elective surgery and seven healthy volunteers.
INTERVENTIONS: Catheters were inserted into the forearm veins of healthy volunteers for the administration of ICG and blood sampling for the measurement of hemoglobin concentration.
MEASUREMENTS AND MAIN RESULTS: The distribution volumes of ICG in seven healthy volunteers were estimated repetitively following three or four consecutive intravenous administrations at 30-min intervals. A low intrasubject coefficient of variation of 3.94 +/- 2.03 (SEM) % and a reasonable intersubject coefficient of variation of 13.3 +/- 5.52% (in mL/kg) for the BV measurements were obtained. In addition, ICG was administered to 22 patients, first under general anesthesia by a bolus, and then by a bolus with a constant-rate infusion. The ICG blood concentration was noninvasively measured with pulse-spectrophotometry. The blood concentration time courses following both bolus and constant-rate infusion were well fitted by the one-compartment model, indicating that the distribution equilibrium of ICG is instantaneous. The distribution volumes estimated following bolus injection correlate closely with the distribution volume estimated based on constant-rate infusion administration (r2 = .90).
CONCLUSIONS: The BV estimation with a bolus injection of ICG and pulse-spectrophotometry is reliable, as reflected by the reproducible BVs estimated in the same subject. The integrated pulse-spectrophotometry monitoring system offers a less invasive and useful tool for bedside estimation of BV.