Effects of different congestion pressures on the diameter of the dorsal hand vein and on its apparent sensitivity to noradrenaline.

We have measured the diameter of the human dorsal hand vein (DHV) in situ and compared the venoconstrictor dose-response curves to locally infused noradrenaline at different venous congestion pressures using the DHV compliance technique. Congestion pressure was defined as the inflation pressure of a sphygmomanometer cuff on the ipsilateral upper arm. Male healthy volunteers (20-45 years) participated in two experimental sessions. In Session I, DHV diameter was measured at congestion pressures of 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 mmHg. In Session II, venoconstrictor dose-response curves to six doses (0.1-33.33 ng min-1) of (-)noradrenaline acid tartrate were established at congestion pressures 30 and 45 mmHg. DHV diameter increased as a function of congestion pressure. The rate of increase in DHV diameter (mm/5 mmHg) declined at higher values of congestion pressure (e.g. 0.14 mm/5 mmHg between 20 and 45 mmHg, and 0.04 mm/5 mmHg between 45 and 70 mmHg). Noradrenaline was less potent at 45 mmHg than at 30 mmHg. Mean log ED50 was significantly greater at 45 mmHg than at 30 mmHg congestion pressure, while mean E(max) did not differ at the two congestion pressures. The geometric mean ED50 was approximately 195% greater at 45 mmHg than at 30 mmHg. These results show that DHV diameter is positively related to congestion pressure, and that as the congestion pressure increases, the apparent sensitivity of the vein to the venoconstrictor effect of noradrenaline decreases. This latter finding is consistent with the physiological antagonism between congestion-induced venodilatation and noradrenaline-evoked venoconstriction. It is recommended that a standard congestion pressure is used in order to facilitate the comparison of results obtained in different laboratories.