Effect of high local temperature on reflex cutaneous vasodilation

TLDR

The study investigated whether raising local forearm skin temperature to 42 °C alters reflex cutaneous vasodilator responses during whole‑body heat stress. By locally warming one forearm to 42 °C while leaving the other at ambient, the authors monitored forearm blood flow under two protocols—raising whole‑body skin temperature 30 min after local warming and raising both temperatures simultaneously—to assess reflex vasodilation. Local warming to 42 °C for 35–55 min abolished or markedly attenuated reflex forearm vasodilation during whole‑body heat stress, with the warmed arm showing minimal blood‑flow changes while the normothermic arm increased, indicating that maximal cutaneous blood flow is achieved at this temperature and basal arteriolar tone is suppressed.

Abstract

We examined the effect of high local forearm skin temperature (Tloc) on reflex cutaneous vasodilator responses to elevated whole-body skin (Tsk) and internal temperatures. One forearm was locally warmed to 42 degrees C while the other was left at ambient conditions to determine if a high Tloc could attenuate or abolish reflex vasodilation. Forearm blood flow (FBF) was monitored in both arms, increases being indicative of increases in skin blood flow (SkBF). In one protocol, Tsk was raised to 39–40degrees C 30 min after Tloc in one arm had been raised to 42 degrees C. In a second protocol, Tsk andTloc were elevated simultaneously. In protocol 1, the locally warmed arm showed little or no change in blood flow in response to increasing Tsk and esophageal temperature (average rise = 0.76 +/-1.18 ml X 100 ml-1 X min-1), whereas FBF in the normothermic arm rose by an average of 8.84 +/- 3.85 ml X 100 ml-1 X min-1. In protocol 2, FBF in the normothermic arm converged with that in the warmed arm in three of four cases but did not surpass it. We conclude that local warming to 42 degrees C for 35–55 min prevents reflex forearm cutaneous vasodilator responses to whole-body heat stress. The data strongly suggest that this attenuation is via reduction or abolition of basal tone in the cutaneous arteriolar smooth muscle and that at a Tloc of 42 degrees C a maximum forearm SkBF has been achieved. Implicit in this conclusion is that local warming has been applied for a duration sufficient to achieve a plateau in FBF.