A comparative study of reactive hyperemia in human forearm skin and muscle

Reactive hyperemia (RH) in forearm muscle or skin microcirculationhas been considered as a surrogate endpoint in clinical studies ofcardiovascular disease. We evaluated two potential confoundersthat might limit such use of RH, namely laterality of measurementand intake of non-steroidal anti-inflammatory drugs (NSAIDS).Twenty-three young non-smoking healthy adults were enrolled. InExperiment 1 (n=16), the RH elicited by 3 min of ischemia wasrecorded in the muscle (strain gauge plethysmography, handexcluded) and skin (laser Doppler imaging) of both forearms. InExperiment 2 (n=7), RH was determined in the dominant forearmonly, one hour following oral acetylsalicylic acid (1 g) or placebo. InExperiment 1, peak RH was identical in both forearms, and so werethe corresponding durations of responses. RH lasted significantlyless in muscle than in skin (p=0.003), a hitherto unrecognized fact.In the skin, acetylsalicylate reduced duration (43 vs. 57.4 s forplacebo, p=0.03), without affecting the peak response. In muscle,duration tended to decrease with acetylsalicylate (21.4 vs. 26.0 swith placebo, p=0.06) and the peak increase in blood flow wasblunted (27.2 vs. 32.4 ml/min/100 ml tissue with placebo,p=0.003). We conclude that, when using RH as a surrogateendpoint in studies of cardiovascular disease, a confounding bylaterality of measurement need not be feared, but NSAIDS mayhave an influence, although perhaps not on the peak response inthe skin.