title: Bedside sonographic measurement of the inferior vena cava caval index is a poor predictor of fluid responsiveness in emergency department patients.
abstract: OBJECTIVE
  Sonographic measurement of the inferior vena cava (IVC) caval index predicts central venous pressure in ED patients. Fluid responsiveness (FR) is a measure of preload dependence defined as an increase in cardiac output secondary to volume expansion. We sought to determine if the caval index is an accurate measurement of FR in ED patients.
  
  
  METHODS
  We conducted a prospective, observational trial at an urban, academic, adult ED with an annual census >105 000. Included patients were clinically suspected of eu- and hypovolemia. Excluded patients were <18 years old, pregnant, incarcerated, sustained significant trauma or unable to consent. Supine IVC diameter was measured by bedside ultrasonography (M-Turbo; Sonosite, Bothwell, WA, USA). Caval index = [(expiratory IVC diameter - inspiratory IVC diameter)/expiratory IVC diameter] × 100. FR was defined as an increase in the cardiac index by >10% by impedance cardiography (BioZ; Sonosite) following passive leg raise. The primary outcome was analysed using Spearman correlations for non-parametric data and the area under the receiver operating characteristics curve by Wilcoxon method.
  
  
  RESULTS
  Thirty patients were enrolled; four were excluded because of incomplete data collection. Thirty-one per cent (95% CI 13-48) of the patients were FR. The mean initial caval and cardiac index were 15.8% (95% CI 9.5-22) and 2.9 L/min/m(2)  (95% CI 2.6-3.2), respectively. Caval index did not predict FR (receiver operating curve = 0.46, 95% CI 0.21-0.71, P = 0.63).
  
  
  CONCLUSIONS
  Bedside sonographic measurement of IVC caval index does not predict FR in a heterogeneous ED patient population. Further research using this technique in targeted patient subsets and a variety of shock etiologies is needed.
authors.affiliation: Department of Emergency Medicine, Warren Alpert School of Medicine, Brown University, Providence, Rhode Island, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Corl
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Napoli
authors.forename: Fenwick
authors.initials: F
authors.lastname: Gardiner
mesh_terms: D000328:Adult; D002496:Central Venous Pressure; D016001:Confidence Intervals; D004636:Emergency Service, Hospital; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D014463:Ultrasonography; D014481:United States; D014505:Urban Population; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging*; D014882:Water-Electrolyte Balance