Identification of the hydration state in emergency patients: correlation between caval index and BUN/creatinine ratio

Abstract

Background: Dehydration is a frequent clinical problem. No single laboratory value has been found to be accurate; however, the BUN/Creatinine Ratio appears the most sensitive parameter. The respiratory variation (Caval Index, CIn) in the diameter of the inferior vena cava has been investigated as a non-invasive marker for the intravascular volume status.

Aim: The present study is performed with the aim to explore the relationship between CIn and BUN/creatinine ratio.

Patients and methods: This prospective, observational study was conducted at Emergency Department (ED) of San Paolo Hospital (Savona, Italy), in October 2011.

Results: 113 patients were considered eligible (mean age of 63 years). We found a good correlation between CIn and BUN/Cr Ratio (Pearson Index 0.76, p < 0.001). Receiver operator characteristic curve (ROC) analyses indicated that the maximum value was 0.884 (p < 0.0001) and corresponded to CIn 60.7%, (sensitivity 79%, specificity 89%). CIn was a good predictor for patients with BUN/Cr ratio greater than 20, and was particularly strong in determining patients with lower BUN/Cr ratio.

Discussion: Our study suggests that inferior vena cava could provide indications on the state of hydration of the patients: we found that a caval index greater than or equal to 60% was associated with a BUN/Cr Ratio over 20, which is considered an important marker for dehydration. Therefore, bedside sonography can give emergency physicians immediate information on patient volume status long before obtaining laboratory findings.

Conclusions: Our study seems to support the hypothesis that CIn can be a useful bedside marker to predict dehydration in Emergency Department (ED) patients.