To explore the position and optimal pressure of blocking the superficial vein of lower extremities.

The bilateral lower limb veins of 12 healthy volunteers were selected for the study. Contrast-enhanced ultrasound was performed through the dorsalis pedis vein. Pneumatic cuffs were used to bind and apply pressure at 5 cm, 10 cm and 15 cm above the ankle joint. When the small saphenous vein (SSV) was not visible, the superficial vein blood flow of the lower extremities was effectively blocked and the pressure was recorded. In addition, the changes of diameter, flow velocity and blood flow of ipsilateral popliteal vein (POPV) before and after effective occlusion of superficial vein at 10cm of ankle were evaluated.

The pressure thresholds of supramalleolar 5 cm, 10 cm and 15 cm for effectively blocking the superficial veins of lower extremities were (66-69) mmHg, (68-71) mmHg and (73-75) mmHg (95% confidence interval), respectively. After effectively blocking the superficial veins of lower extremities at 10 cm on the ankle, the internal diameter and blood flow of ipsilateral POPV increased significantly (P<0.05), but the flow velocity did not increase significantly (P>0.05).

Different parts of the ankle require different pressure thresholds to effectively block the superficial veins of the lower extremities. CEUS can non-invasive monitor the blood flow of the superficial veins of the lower extremities effectively blocked by pneumatic tourniquet, which is helpful for the clinical treatment of deep venous thrombosis of the lower extremities.