Changes in the blood flow velocity test (V-test)
The mean blood flow velocity was calculated for each 5-s period before and after NS injection; each 5-s period included 500 separate data measurements. Subsequently, the absolute difference between the mean velocity values before and after injection was obtained. The difference between mean velocity values was classified as positive when the difference was ≥ 1 cm/s (V-test). The cut-off value of 1 cm/s was based on the validation results of a previous study