Accuracy of the caval index and the expiratory diameter of the inferior vena cava for the diagnosis of dehydration in elderly.

PURPOSE: Dehydration is a very common condition among elderly people. Till date there is not yet a fast and easy method to determine a state of dehydration in the emergency department. In the literature there are some exploratory studies that have tried to establish the relationship between some widely used laboratory values and ultrasound for the purpose of diagnosing dehydration. The primary aim of this study is to verify the correlation between two measures derived by ultrasound (caval index and expiratory diameter of inferior vena cava) and blood urea nitrogen (BUN)/creatinine ratio. The relationship between vital signs and BUN/creatinine ratio has also been explored.

METHODS: An observational cohort study of patients aged 70 years or more, all examined in our ED. The population was divided on the basis of the BUN/creatinine ratio greater or lower than 20.

RESULTS: A total of 270 patients have been considered. No vital sign correlated with an increased BUN/creatinine ratio. Both the diameter of the inferior vena cava in expiratory and the percentage of its collapsibility in inspiratory (caval index) have revealed a correlation with a BUN/creatinine ratio greater than 20. Areas under the curve are, respectively, 76 % (95 % CI 70-82) and 80 % (95 % CI 75-86). Sensitivity, specificity, positive predictive value and negative predictive value are, respectively, 85.5 % (95 % CI 79.4-90.4); 100 % (95 % CI 97-100); 100 % (95 % CI 97.5-100); 82.9 % (95 % CI 75.9-88.7) and 99.3 % (95 % CI 96.3-99.9); 100 % (95 % CI 97-100); 100 % (95 % CI 97.5-100); 99.2 % (95 % CI 95.6-99.9).

CONCLUSIONS: Ultrasound has proved to be useful to diagnose dehydration in elderly people while in the emergency department. Vice versa the vital signs have shown to be unrelated to the hydration state of elderly patients.