Emergency department bedside ultrasonographic measurement of the caval index for noninvasive determination of low central venous pressure.

STUDY 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%).

CONCLUSION: 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.