title: Comparison of three methods of extravascular lung water volume measurement in patients after cardiac surgery.
abstract: BACKGROUND
  Measurement 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.
  
  
  METHODS
  Single-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).
  
  
  RESULTS
  Seventeen 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)).
  
  
  CONCLUSIONS
  The 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.
authors: Barts and The London School of Medicine and Dentistry, Queen Mary's University of London, Royal London Hospital, London E1 1BB, UK. ben.maddison@bartsandthelondon.nhs.uk
authors: Benjamin
authors: B
authors: Maddison
authors: Christopher
authors: C
authors: Wolff
authors: George
authors: G
authors: Findlay
authors: Peter
authors: P
authors: Radermacher
authors: Charles
authors: C
authors: Hinds
authors: Rupert M
authors: RM
authors: Pearse
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006348:Cardiac Surgical Procedures; D015633:Extravascular Lung Water; D005260:Female; D006801:Humans; D007208:Indocyanine Green; D008297:Male; D008875:Middle Aged
chemical_list: D007208:Indocyanine Green