Sympathetic stimulation induced by hand cooling alters cold-induced vasodilatation in humans.

Hand cooling is a cold pressor test, which induces general sympathetic stimulation. This cooling procedure is often performed to investigate cold induced vasodilatation (CIVD) in one finger. To investigate the effects of this sympathetic stimulation on local CIVD, 12 subjects immersed either the right index finger (T1), right hand (T2) or left hand and right index finger (T3) for 30 min in water at 5°C followed by 15-min recovery. Skin temperature and skin blood flow (Q˙sk) measured by laser Doppler flowmetry on the right index finger, as well as heart rate (fc) and mean arterial blood pressure (\(\)), were continuously monitored during the three tests. Cutaneous vascular conductance was calculated as Q˙sk/\(\). Concentrations of plasma noradrenaline (NA) and adrenaline (AD) were measured at different times during the tests. The results showed no cardiovascular change in T1, whereas fc and \(\) increased significantly at the beginning of both T2 and T3. Similarly, sympathetic stimulation was reflected in the NA concentrations, which increased significantly (P < 0.01) during T2 and T3 after 5 min of immersion, and remained elevated until the recovery period. The AD concentration did not change during the three tests. During T2, the CIVD appeared later and slower in comparison with T1 [CIVD onset: 12.81 (SEM 2.30) min in T2 and 5.62 (SEM 0.33) min in T1] . During T3, the CIVD onset was not delayed compared to T1 [6.38 (SEM 0.67) min], but the rewarming was lower [+5.40 (SEM 0.86)°C in T3 and +9.10 (SEM 1.31)°C in T1]. These results showed that CIVD could be altered by sympathetic stimulation but it also appeared that the onset of CIVD could be influenced by local cooling, independently of the general sympathetic stimulation.