Femoral Vein Diameter as a Predictor for Intravascular Volume Status

Background The central venous pressure (CVP) is used as a tool for assessing volume status in hypotensive patients. Ultrasonographic inferior vena cava (IVC) measurement has been accepted as a surrogate measure of CVP. But IVC visualization is occasionally cumbersome. Hence our study attempts to assess the correlation of femoral vein diameter (FVD) and CVP. Methods The study is a prospective observational study conducted among the hypotensive Emergency Department patients of a tertiary care centre in Kerala. Based on an earlier study sample size calculated was 27. Pregnant females, patients with deep vein thrombosis (DVT), patients with acute heart failure and patients who did not consent were excluded. IVC diameter and FVD were measured ultrasonographically. CVP was measured using a transducer. Pearson's correlation coefficient between FVD and CVP was computed. Results There is a strong positive correlation between FVD and CVP (r=0.919, p<0.001). The regression equation of CVP on FVD was CVP = 0.535+9.275*FVD. FVD of 1.2cm had a sensitivity of 90% and specificity of 94.4% in predicting CVP >12mm of Hg (high CVP). FVD less than 0.8cm had a sensitivity of 25% and specificity of 100% in predicting CVP <8mm of Hg (low CVP) and had a positive predictive value of 100%.  Conclusion The study had concluded a strong linear correlation between CVP and FVD. Hence FVD can be used as a surrogate marker of CVP to predict the volume status. FVD <0.8 cm is specific in detecting the low CVP group. FVD is of good statistical quality in predicting the high CVP group. Hence the complications of unwanted fluid resuscitation can be avoided.