title: Does indocyanine green accurately measure plasma volume early after cardiac surgery?
abstract: Potential overestimation of plasma volume (PV) determination by the conventional indocyanine green (ICG) dilution method (PV-ICG) can occur when generalized capillary protein leakage is present, because ICG binds to proteins. We recently reported that this overestimation can be recognized by simultaneous measurement of the initial distribution volume of glucose (IDVG). We examined whether overestimation of PV-ICG and further ICG-pulse dye densitometry-derived plasma volume (PV-PDD) can occur early after cardiac surgery by using the PV-ICG/IDVG ratio as an indicator. Possible overestimation was defined as a ratio higher than 0.45. Twenty-four consecutive postcardiac surgical patients were enrolled. PV-ICG, PV-PDD, and IDVG were calculated simultaneously after admission to the intensive care unit and on the first postoperative day. The mean +/- SD PV-ICG/IDVG ratio for 47 recordings was 0.38 +/- 0.05. Four had a PV-ICG/IDVG ratio higher than 0.45, and the highest was 0.48. The mean PV-PDD/IDVG ratio for a total of 47 recordings was 0.39 +/- 0.10. There were extremely high or low ratios observed in PV-PDD determinations, but they were not observed in PV-ICG determinations. Results suggest that most of the PV-ICG measurements are accurate, but inaccuracy of PV-PDD can occur early after cardiac surgery.
  
  
  CONCLUSIONS
  Overestimation of indocyanine green-derived plasma volume can occur in the presence of generalized capillary protein leakage. This overestimation was examined early after cardiac surgery by using the simultaneous measurement of the initial distribution volume of glucose. We suggest that overestimation of the traditional dye dilution method is negligible, but apparent over- or underestimation of pulse dye densitometry-derived plasma volume cannot be negligible.
authors.affiliation: Department of Anesthesiology, University of Hirosaki School of Medicine, Hirosaki-Shi, Japan. ishihara@cc.hirosaki-u.ac.jp
authors.forename: Hironori
authors.initials: H
authors.lastname: Ishihara
authors.forename: Hirobumi
authors.initials: H
authors.lastname: Okawa
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Iwakawa
authors.forename: Noriko
authors.initials: N
authors.lastname: Umegaki
authors.forename: Toshihito
authors.initials: T
authors.lastname: Tsubo
authors.forename: Akitomo
authors.initials: A
authors.lastname: Matsuki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose; D002302:Cardiac Output; D006348:Cardiac Surgical Procedures; D004396:Coloring Agents; D003720:Densitometry; D004395:Dye Dilution Technique; D005260:Female; D005947:Glucose; D006400:Hematocrit; D006801:Humans; D007201:Indicator Dilution Techniques; D007208:Indocyanine Green; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume; D013815:Thermodilution
chemical_list: D001786:Blood Glucose; D004396:Coloring Agents; D007208:Indocyanine Green; D005947:Glucose