Reactive hyperemia increases forearm vein area

PURPOSE: To determine the effect of reactive hyperemia on human forearm vein area. METHODS: After obtaining ethics approval and informed consent, an automatic tourniquet was applied to the forearms of 20 healthy subjects for one, two, and three minutes, at pressures of 25 mmHg, 200 mmHg, then 25 mmHg. A blinded radiographer measured the cross-sectional area of the cephalic vein at the wrist using ultrasonography. Measurements were recorded prior to tourniquet application and every minute thereafter for ten minutes, at each pressure setting and each time interval. RESULTS: The mean vein cross-sectional area (mm2) increased from 8.22 +/- 3.09 to 10.77 +/- 3.50 after one minute of ischemia, from 8.31 +/- 2.78 to 10.61 +/- 2.77 after two minutes of ischemia, and from 8.39 +/- 3.34 to 10.94 +/- 3.46 after three minutes of ischemia (P < 0.05 for all). A tourniquet inflated to 25 mmHg for 13 min produced a mean vein cross-sectional area of 10.71 +/- 3.25 mm2. CONCLUSIONS: Reactive hyperemia causes human forearm vein cross-sectional area to increase. A low pressure tourniquet will also increase forearm vein area, but veins dilate more quickly during reactive hyperemia. This may have important clinical implications for attempting venous cannulation in patients with difficult venous access.