title: Emergency department bedside ultrasonographic measurement of the caval index for noninvasive determination of low central venous pressure.
abstract: OBJECTIVE
  Among adult emergency department (ED) patients undergoing central venous catheterization, we determine whether a greater than or equal to 50% decrease in inferior vena cava diameter is associated with a central venous pressure of less than 8 mm Hg.
  
  
  METHODS
  Adult patients undergoing central venous catheterization were enrolled in a prospective, observational study. Inferior vena cava inspiratory and expiratory diameters were measured by 2-dimensional bedside ultrasonography. The caval index was calculated as the relative decrease in inferior vena cava diameter during 1 respiratory cycle. The correlation of central venous pressure and caval index was calculated. The sensitivity, specificity, and positive and negative predictive values of a caval index greater than or equal to 50% that was associated with a central venous pressure less than 8 mm Hg were estimated.
  
  
  RESULTS
  Of 73 patients, the median age was 63 years and 60% were women. Mean time and fluid administered from ultrasonographic measurement to central venous pressure determination were 6.5 minutes and 45 mL, respectively. Of the 73 participants, 32% had a central venous pressure less than 8 mm Hg. The correlation between caval index and central venous pressure was -0.74 (95% confidence interval [CI] -0.82 to -0.63). The sensitivity of caval index greater than or equal to 50% to predict a central venous pressure less than 8 mm Hg was 91% (95% CI 71% to 99%), the specificity was 94% (95% CI 84% to 99%), the positive predictive value was 87% (95% CI 66% to 97%), and the negative predictive value was 96% (95% CI 86% to 99%).
  
  
  CONCLUSIONS
  Bedside ultrasonographic measurement of caval index greater than or equal to 50% is strongly associated with a low central venous pressure. Bedside measurements of caval index could be a useful noninvasive tool to determine central venous pressure during the initial evaluation of the ED patient.
authors: Department of Emergency Medicine, Warren Alpert Medical School of Brown University, Providence, RI 02903, USA.
authors: Arun D
authors: AD
authors: Nagdev
authors: Roland C
authors: RC
authors: Merchant
authors: Alfredo
authors: A
authors: Tirado-Gonzalez
authors: Craig A
authors: CA
authors: Sisson
authors: Michael C
authors: MC
authors: Murphy
mesh_terms: D000368:Aged; D002496:Central Venous Pressure / Q000502:physiology; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007022:Hypotension / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging* / Q000503:physiopathology