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

Abstract

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.

Diameter, pressure and compliance relationships in dorsal hand veins

“…It thus depends strongly on baseline constriction, as well as on sensitivity to drug, drug dose and distending pressure, as others also have shown. 9 The diameter at the selected distending pressure both limits the constriction possible and serves as the reference point for measures of per cent constriction. These points are illustrated in Figure 4.…”

“…Parameters of fitted model curves before and after an intervention also provide a more concise description than that which has been published previously. 9 The entire range of the diameter-pressure relationship can be characterized by two parameters. For example, 50 ng/min of norepinephrine changed P 50 (shifted the pressure axis of the diameter-pressure relationship) by 15 mmHg without significantly changing the midpoint slope.…”

“…Where others have shown the effects of distending pressure on a norepinephrine dose-response curve, 9 we have examined the effects of norepinephrine on a diameterpressure curve. We believe that our results complement those of others, 9 allowing greater prediction of the interactions of distending pressure and drug dose. Model fitting and parameter comparison provides a clear description of drug effects on venous diameter-pressure relationships.…”

“…This has not been done, although others have looked at the effects of pressure on the doseresponse to a constricting agent. 9 To investigate the diameter-pressure relationship in superficial hand veins under control conditions (saline infusion) and after infusion of norepinephrine we fitted the arctangent model to the data. It was hypothesized that norepinephrine would either shift the midpoint of the curve to higher distending pressures, increasing P 50 at constant slope, or change the midpoint slope or both.…”