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

Hand cooling is a cold pressor test, which induces general sympathetic stim ulation. This cooling procedure is often performed to investigate cold indu ced vasodilatation (CIVD) in one finger. To investigate the effects of this sympathetic stimulation on local CIVD, 12 subjects immersed either the rig ht index finger (T1), right hand (T2) or left hand and right index finger ( T3) for 30 min in water at 5 degrees C followed by 15-min recovery. Skin te mperature and skin blood flow ((Q) over dot(sk)) measured by laser Doppler flowmetry on the right index finger, as well as heart rate (f(c)) and mean arterial blood pressure (<(BP)over bar>(a)), were continuously monitored du ring the three tests. Cutaneous vascular conductance was calculated as (Q) over dot(sk)/ <(BP)over bar>(a). Concentrations of plasma noradrenaline (NA ) and adrenaline (AD) were measured at different times during the tests. Th e results showed no cardiovascular change in T1, whereas f(c) and <(BP)over bar>(a) increased significantly at the beginning of both T2 and T3. Simila rly, sympathetic stimulation was reflected in the NA concentrations, which increased significantly (P < 0.01) during T2 and T3 after 5 min of immersio n, and remained elevated until the recovery period. The AD concentration di d 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 compare d to T1 [6.38 (SEM 0.67) min], but the rewarming was lower [ + 5.40 (SEM 0. 86)degrees C in T3 and +9.10 (SEM 1.31)degrees C in T1]. These results show ed that CIVD could be altered by sympathetic stimulation but it also appear ed that the onset of CIVD could be influenced by local cooling, independent ly of the general sympathetic stimulation.