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This study aims to determine the site of and the best sonographic method for measurement of inferior vena cava (IVC) diameter in volume status monitoring.This observational before-and-after study was performed at the intensive care unit of the emergency department. It included hypotensive adult patients with suspected sepsis who were recommended to receive at least 20 mg/kg fluid replacement by the emergency physician. The patients were fluid replaced at a rate of 1000 mL/h, and maximum and minimum IVC diameters were measured and the Caval index calculated sonographically via both B-mode and M-mode. Hence, IVC's volume response was assessed by a total of 6 parameters, 3 each in M-mode and B-mode. Freidman test was used to assess the change in IVC diameter with fluid replacement. Wilcoxon test with Bonferroni correction was used to determine which measurement method more sensitively measured IVC diameter change.Twenty-eight patients with a mean age of 71.3 were included in the final analysis.The IVC diameter change was significant with all 6 methods (P.001). The IVC minimum diameter change measured on M-mode during inspiration (M-mode i) was the only measurement method that significantly showed diameter change with each 500-mL fluid replacements. The initial and the subsequent M-mode i values after each 500 mL of fluid were 5.65 ± 3.34; 8.05 ± 3.66; 10.16 ± 3.61, and 11.21 ± 2.94, respectively (P.001, P.002, and P.003, respectively).Inferior vena cava diameter was changed by fluid administration. The M-mode i method that most sensitively measures that change may be the most successful method in volume status monitoring.

Study objective We aimed to determine the role of inferior vena cava (IVC) diameter in making a differentiation between dyspnea of cardiac (acute heart failure [AHF]) and pulmonary origin. We also attempted to determine the best sonographic method for the measurement of IVC diameter. Methods This prospective observational study was conducted at the intensive care unit of the emergency department of a training and research hospital. This study enrolled patients with the main symptom of dyspnea who were categorized into 2 groups, cardiac dyspnea and pulmonary dyspnea groups, based on the final diagnosis. All patients underwent sonographic measurement of minimum and maximum diameters of IVC, and the caval index (CI) was calculated in both M-mode and B-mode. The sensitivity, specificity, and likelihood ratios (LR) of the IVC values for the differentiation of the 2 groups were calculated. Results This study included a total of 74 patients with a mean age of 72.8 years. Thirty-two patients had dyspnea of cardiac origin, and 42 patients had dyspnea of pulmonary origin. The IVC diameter measured with B-mode during inspiration (B-mode i) was the most successful method for differentiation of the 2 groups. B-mode i values greater than 9 mm predicted dyspnea of cardiac origin with a sensitivity of 84.4% and a specificity of 92.9% (+ LR: 11.8, LR: 0.16). Conclusion Sonographic assessment of the IVC diameter may be used as a rapid, readily, nonexpensive, complication-free, and reproducible technique for the differentiation of cardiac and pulmonary causes of dyspnea. B-mode i measurement may be more successful in the differentiation of dyspnea compared with other IVC diameters and calculations.