title: How to perform indexing of extravascular lung water: a validation study.
abstract: BACKGROUND
  Extravascular lung water is a quantitative marker of the amount of fluid in the thoracic cavity besides the vasculature. Indexing to both predicted and actual body weight have been proposed to compare different individuals and provide a uniform range of normal.
  
  
  OBJECTIVE
  We explored extravascular lung water measured by single-indicator transpulmonary thermodilution in a large cohort of patients without cardiopulmonary instability, in order to evaluate current and alternative indexing methods.
  
  
  METHODS
  Prospective, observational.
  
  
  METHODS
  Neurosurgical ICU in a tertiary referral academic teaching hospital.
  
  
  METHODS
  One hundred and one consecutive patients requiring elective brain tumor surgery and postoperative ICU surveillance.
  
  
  METHODS
  None.
  
  
  RESULTS
  Indexed to predicted body weight, females had a mean extravascular lung water of 9.1 (SD=3.1, range: 5-23) mL/kg and males of 8.0 (SD=2.0, range: 4-19) mL/kg (p<0.001). Values indexed to predicted body weight were inversely correlated with the patient's height (p<0.001). Indexed to the traditionally used actual body weight, data showed a significant relationship to weight (p<0.001) and gender (p<0.05). In contrast, indexing to body height presented a method without dependencies on height, weight, or gender, yielding a uniform 95% confidence interval of 218-430 mL/m. Extravascular lung water increased with positive perioperative fluid balance (p=0.04).
  
  
  CONCLUSIONS
  Using either predicted or actual body weight for indexing extravascular lung water does not lead to independence of height, weight, and gender of the patient. Specifying a fixed range of normal or a uniform upper threshold for all patients is misleading for either method, despite widespread use. Our data suggest that indexing extravascular lung water to height is superior to weight-based methods. As we are not aware of any abnormal hemodynamic profile for brain tumor patients, we propose our findings to be a close approximation to normal values.
authors: Department of Neurosurgery, Klinikum Bogenhausen, Academic Hospital of the Technische Universität München, Germany. stefan.wolf@charite.de
authors: Stefan
authors: S
authors: Wolf
authors: Alexander
authors: A
authors: Riess
authors: Julia F
authors: JF
authors: Landscheidt
authors: Christianto B
authors: CB
authors: Lumenta
authors: Ludwig
authors: L
authors: Schürer
authors: Patrick
authors: P
authors: Friederich
mesh_terms: D055371:Acute Lung Injury / Q000401:mortality*; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003422:Critical Care / Q000379:methods*; D015633:Extravascular Lung Water / Q000378:metabolism*; D005260:Female; D005858:Germany; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011654:Pulmonary Edema / Q000401:mortality; D012128:Respiratory Distress Syndrome / Q000401:mortality*; D012680:Sensitivity and Specificity; D013815:Thermodilution