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 s itu and compared the venoconstrictor dose-response curves to locally i nfused noradrenaline at different venous congestion pressures using th e DHV compliance technique. Congestion pressure was defined as the inf lation pressure of a sphygmomanometer cuff on the ipsilateral upper ar m. Male healthy volunteers (20-45 years) participated in two experimen tal sessions. In Session I, DHV diameter was measured at congestion pr essures 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 m in(-1)) of (-)noradrenaline acid tartrate were established at congesti on pressures 30 and 45 mmHg. DHV diameter increased as a function of c ongestion pressure. The rate of increase in DHV diameter (mm/5 mmHg) d eclined at higher values of congestion pressure (e.g. 0.14mm/5 mmHg be tween 20 and 45 mmHg, and 0.04mm/5 mmHg between 45 and 70 mmHg). Norad renaline was less potent at 45 mmHg than at 30 mmHg. Mean log ED(50) w as significantly greater at 45 mmHg than at 30 mmHg congestion pressur e, while mean E(max) did not differ at the two congestion pressures. T he geometric mean ED(50) was approximately 195% greater at 45 mmHg tha n at 30 mmHg. These results show that DHV diameter is positively relat ed to congestion pressure, and that as the congestion pressure increas es, the apparent sensitivity of the vein to the venoconstrictor effect of noradrenaline decreases. This latter finding is consistent with th e physiological antagonism between congestion-induced venodilatation a nd noradrenaline-evoked venoconstriction. It is recommended that a sta ndard congestion pressure is used in order to facilitate the compariso n of results obtained in different laboratories.