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Publication AbstractsSuppression of the reactive hyperemic response in the forearm due to local hand cooling.Kilgour RD, Carranza A, Findlay RAviat Space Environ Med 1997; 68:46-50 AbstractMethods: Forearm blood flow (FBF) was measured by electrical impedance plethysmography in order to identify the influence of local cooling of the contralateral hand after 3 min of arterial occlusion. Ten volunteers (six females, four males) were randomly assigned to the following three experimental conditions on separate days: a) 6 min of local hand cooling (5 - 7 C); b) 3 min of arterial occlusion of the forearm; and c) combined arterial occlusion and local cooling. Results: All subjects experienced the typical pressor response during 6 min of hand cooling as evidenced by the significant increase (p < 0.05) in heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP). The FBF responses demonstrated an immediate increase (p < 0.05) within the first 30 s of hand submersion and then progressively declined over the next 5 min. The forearm vascular resistance (FVR = MAP/FBF) made an initial drop during the first 30 s of cooling and then gradually rose to reach peak levels between 5 - 6 min of cooling. With respect to the hyperemic response, FBF significantly increased (p < 0.05) from baseline (mean ± SEM; 1.09 ± 0.18 ml · 100 ml-1 · min-1) and achieved peak levels (6.75 ± 0.64 ml · 100 ml-1 · min-1) within the initial 30 s of the post-occlusion period. Thereafter, FBF declined rapidly by 30 - 60 s (1.67 ± 0.29 ml · 100 ml-1 · min-1) and 60 - 90 s (1.26 ± 0.33 ml · 100 ml-1 · min- 1) of the post-occlusion period. Conclusion: When the reactive hyperemic response was coupled with hand cooling, FBF increased above baseline values and reached peak levels during the initial 30 s of the post-occlusion period. However, the magnitude of the hyperemic response was significantly lower in the cold condition compared to the hyperemia alone (3.20 ± 0.42 vs 6.75 ± 0.64 ml · 100 ml- 1 · min-1; p < 0.05). Clearly, the overall sympathetic response to local cooling had an overriding effect on the factors that promote peripheral vasodilation following brief periods (3 min) of arterial occlusion.
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