Required volume for color flow injection test to confirm the intravascular placement of a peripheral venous catheter.

Background: Confirmation of adequate peripheral intravenous catheter placement is essential before using venous catheters. The color flow injection test has been reported as a method with high sensitivity and specificity for this purpose. The technique involves administrating saline through the peripheral venous route to observe changes in the color flow pattern around the same vein at a more central location. However, the required volume of saline remains uncertain. This study aims to determine the appropriate dosage for conducting the test in pediatric patients and explore any potential correlations between dosage and patient characteristics.

Methods: A prospective study was conducted in children under 6 years of age with American Society of Anesthesiologists Physical Status 1-2 presenting for general anesthesia. After an intravenous cannula was placed in the forearm under general anesthesia, normal saline was injected at a speed of approximately 1 mL/s while the axillary artery and vein were observed with color flow Doppler imaging. The volume of normal saline required to induce a change in the color flow pattern around the vessels was measured. Measurements were performed twice and averaged for comparison with patient characteristics and other factors.

Results: The study cohort included 30 patients aged from 0.3 to 5.5 (2.6 ± 1.6) years. The change in color flow Doppler imaging was noted in all the patients, and the average volume was 1.40 ± 0.36 mL (95% confidence interval (CI), 1.27-1.54; p < 0.001), which was significantly correlated with age, with a correlation coefficient of 0.435 (95% CI, 0.09-0.69; p = 0.02).

Conclusions: The required volume for the color flow injection test is small; therefore, the test is easy to perform and minimally invasive in pediatric patients.