title: Inferior vena cava diameters and collapsibility index reveal early volume depletion in a blood donor model.
abstract: BACKGROUND
  Changes of volume status can be readily inferred from variations in diameter of the inferior vena cava (IVC) measured by ultrasound. However the effect of IVC changes following acute blood loss are not fully established. In this study, three different approaches to measuring IVC variables were compared in healthy blood donors, as a model of acute volume depletion, in order to establish their relative ability to detect acute blood loss.
  
  
  METHODS
  Inspiratory and expiratory IVC diameters were measured before and after blood donation in hepatic long axis, hepatic short axis and renal short axis views using a 2-5 MHz curvilinear probe. All measurements were recorded and examined in real-time and post-processing sessions.
  
  
  RESULTS
  All windows performed satisfactorily but the renal window approach was feasible in only 30 out of 47 subjects. After blood donation, IVC diameters decreased in hepatic long axis, hepatic short axis and renal short axis (expiratory: -19.9, -18.0, -26.5 %; CI 95 %: 14.5-24.1; 13.1-22.9; 16.0-35.9, respectively) (inspiratory: -31.1, -31.6, -36.5 %; CI 95 %: 21.3-40.1; 18.8-45.2; 23.4-46.0, respectively), whereas the IVC collapsibility index increased by 21.6, 22.6 and 19.3 % (CI 95 %: 11.6-42.9; 18.5-39.5; 7.7-30.0). IVC diameters appeared to return to pre-donation values within 20 min but this was only detected by the hepatic long axis view.
  
  
  CONCLUSIONS
  IVC diameter and collapsibility index variations, as measured in M mode, consistently detect volume changes after blood donation. The longitudinal mid-hepatic approach performed better by allowing a panoramic view, avoiding anatomical aberrancies at fixed points and permitting to identify the best possible perpendicular plane to the IVC. In addition, it was able to detect time-dependent physiological volume replacement. In contrast, in our hands, the renal window could not be visualized consistently well.
authors.affiliation: Department of Medical Sciences, University of Turin, Corso AM Dogliotti 14, 10126, Turin, Italy. paolopasquero@libero.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pasquero
authors.affiliation: Department of Medical Sciences, University of Turin, Corso AM Dogliotti 14, 10126, Turin, Italy. albani.aosta@gmail.com.
authors.forename: Stefano
authors.initials: S
authors.lastname: Albani
authors.affiliation: Department of Medical Sciences, University of Turin, Corso AM Dogliotti 14, 10126, Turin, Italy. elena.sitia@gmail.com.
authors.forename: Elena
authors.initials: E
authors.lastname: Sitia
authors.affiliation: Department of Medical Sciences, University of Turin, Corso AM Dogliotti 14, 10126, Turin, Italy. annataulaigo@gmail.com.
authors.forename: Anna Viola
authors.initials: AV
authors.lastname: Taulaigo
authors.affiliation: Department of Medical Sciences, University of Turin, Corso AM Dogliotti 14, 10126, Turin, Italy. lorenzo.borio@mclink.net.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Borio
authors.affiliation: Department of Clinical and Biological Sciences, University of Turin, Turin, Italy. paola.berchialla@unito.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Berchialla
authors.affiliation: Blood Bank, AOU Città della Salute e della Scienza, Turin, Italy. fcastagno@cittadellasalute.to.it.
authors.forename: Franco
authors.initials: F
authors.lastname: Castagno
authors.affiliation: Department of Medical Sciences, University of Turin, Corso AM Dogliotti 14, 10126, Turin, Italy. massimo.porta@unito.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Porta
keywords: Blood loss; Collapsibility index; Inferior vena cava; Ultrasound; Volume depletion