title: Sonographic evaluation of intravascular volume status in the surgical intensive care unit: a prospective comparison of subclavian vein and inferior vena cava collapsibility index.
abstract: BACKGROUND
  Traditional methods for intravascular volume status assessment are invasive and are associated significant complications. While focused bedside sonography of the inferior vena cava (IVC) has been shown to be useful in estimating intravascular volume status, it may be technically difficult and limited by patient factors such as obesity, bowel gas, or postoperative surgical dressings. The goal of this investigation is to determine the feasibility of subclavian vein (SCV) collapsibility as an adjunct to IVC collapsibility in intravascular volume status assessment.
  
  
  METHODS
  A prospective study was conducted on a convenience sample of surgical intensive care unit patients to evaluate interchangeability of IVC collapsibility index (IVC-CI) and SCV-CI. After demographic and acuity of illness information was collected, all patients underwent serial, paired assessments of IVC-CI and SCV-CI using portable ultrasound device (M-Turbo; Sonosite, Bothell, WA). Vein collapsibility was calculated using the formula [collapsibility (%) = (max diameter - min diameter)/max diameter × 100%]. Paired measurements from each method were compared using correlation coefficient and Bland-Altman measurement bias analysis.
  
  
  RESULTS
  Thirty-four patients (mean age 56 y, 38% female) underwent a total of 94 paired SCV-CI and IVC-CI sonographic measurements. Mean acute physiology and chronic health evaluation II score was 12. Paired SCV- and IVC-CI showed acceptable correlation (R(2) = 0.61, P < 0.01) with acceptable overall measurement bias [Bland-Altman mean collapsibility difference (IVC-CI minus SCV-CI) of -3.2%]. In addition, time needed to acquire and measure venous diameters was shorter for the SCV-CI (70 s) when compared to IVC-CI (99 s, P < 0.02).
  
  
  CONCLUSIONS
  SCV collapsibility assessment appears to be a reasonable adjunct to IVC-CI in the surgical intensive care unit patient population. The correlation between the two techniques is acceptable and the overall measurement bias is low. In addition, SCV-CI measurements took less time to acquire than IVC-CI measurements, although the clinical relevance of the measured time difference is unclear.
authors.affiliation: Department of Surgery, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA.
authors.forename: Alistair
authors.initials: A
authors.lastname: Kent
authors.forename: David P
authors.initials: DP
authors.lastname: Bahner
authors.forename: Creagh T
authors.initials: CT
authors.lastname: Boulger
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Eiferman
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Adkins
authors.forename: David C
authors.initials: DC
authors.lastname: Evans
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Springer
authors.forename: Jayaraj M
authors.initials: JM
authors.lastname: Balakrishnan
authors.forename: Sebastian
authors.initials: S
authors.lastname: Valiyaveedan
authors.forename: Sagar C
authors.initials: SC
authors.lastname: Galwankar
authors.forename: Chinedu
authors.initials: C
authors.lastname: Njoku
authors.forename: David E
authors.initials: DE
authors.lastname: Lindsey
authors.forename: Susan
authors.initials: S
authors.lastname: Yeager
authors.forename: Geoffrey J
authors.initials: GJ
authors.lastname: Roelant
authors.forename: Stanislaw P A
authors.initials: SP
authors.lastname: Stawicki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001811:Blood Volume Determination / Q000379:methods* / Q000592:standards; D003422:Critical Care / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D019095:Point-of-Care Systems; D011183:Postoperative Complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011446:Prospective Studies; D015203:Reproducibility of Results; D012151:Resuscitation; D013350:Subclavian Vein / Q000000981:diagnostic imaging* / Q000502:physiology; D014463:Ultrasonography / Q000379:methods* / Q000592:standards; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging* / Q000502:physiology; D055815:Young Adult
keywords: Hemodynamic resuscitation; Inferior vena cava; Intravascular volume status assessment; Point-of-care testing; Portable ultrasound; Subclavian vein; Surgical intensive care unit; Venous collapsibility index