Comparison of three methods of extravascular lung water volume measurement in patients after cardiac surgeryReport as inadecuate

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Critical Care

, 13:R107

First Online: 06 July 2009Received: 25 June 2009Accepted: 06 July 2009


IntroductionMeasurement of extravascular lung water EVLW by using the lithium-thermal Li-thermal and single-thermal indicator dilution methods was compared with the indocyanine green-thermal ICG-thermal method in humans.

MethodsSingle-center observational study involving patients undergoing cardiac surgery with cardiopulmonary bypass. Paired measurements were taken 1, 2, 4, and 6 hours after surgery. Bland-Altman analysis was used to calculate bias and limits of agreement. Data are presented as mean SD or median IQR.

ResultsSeventeen patients were recruited age, 69 years 54 to 87 years; Parsonnet score 10 0 to 29. Sixteen ICG-thermal measurements were excluded after blinded assessment because of poor-quality indicator dilution curves. EVLW volume as measured by the ICG-thermal technique was 4.6 1.9 ml-kg, compared with 5.3 1.4 ml-kg for the single-thermal method. Measurements taken with the Li-thermal method were clearly erroneous -7.6 7.4 ml-kg. In comparison with simultaneous measurements with the ICG-thermal method, single-thermal measurements had an acceptable degree of bias, but limits of agreement were poor bias -0.3 ml-kg 2.3. Li-thermal measurements compared poorly with the ICG-thermal reference method bias, 13.2 ml-kg 14.4.

ConclusionsThe principal finding of this study was that the prototype Li-thermal method did not provide reliable measurements of EVLW volume when compared with the ICG-thermal reference technique. Although minimal bias was associated with the single-thermal method, limits of agreement were approximately 45% of the normal value of EVLW volume. The Li-thermal method performed very poorly because of the overestimation of mean indicator transit time by using an external lithium ion electrode. These findings suggest that the assessment of lung water content by lithium-indicator dilution is not sufficiently reliable for clinical use in individual patients.

AbbreviationsCOcardiac output

EVLWextravascular lung water

GEDVglobal end-diastolic volume

IQRinterquartile range

ICGindocyanine green

ITBVintrathoracic blood volume


MTTmean transit time.

Electronic supplementary materialThe online version of this article doi:10.1186-cc7948 contains supplementary material, which is available to authorized users.

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Author: Benjamin Maddison - Christopher Wolff - George Findlay - Peter Radermacher - Charles Hinds - Rupert M Pearse


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