Hypohydration effect on finger skin temperature and blood flow during cold-water finger immersion

This study was conducted to determine whether hypohydration (Hy) alters blood flow, skin temperature, or cold-induced vasodilation (CIVD) during peripheral cooling. Fourteen subjects sat in a thermoneutral environment (27°C) during 15-min warm-water (42°C) and 30-min cold-water (4°C) finger immersion (FI) while euhydrated (Eu) and, again, during Hy. Hy (−4% body weight) was induced before FI by exercise-heat exposure (38°C, 30% relative humidity) with no fluid replacement, whereas during Eu, fluid intake maintained body weight. Finger pad blood flow [as measured by laser-Doppler flux (LDF)] and nail bed (Tnb), pad (Tpad), and core (Tc) temperatures were measured. LDF decreased similarly during Eu and Hy (32 ± 10 and 33 ± 13% of peak during warm-water immersion). Mean Tnb and Tpad were similar between Eu (7.1 ± 1.0 and 11.5 ± 1.6°C) and Hy (7.4 ± 1.3 and 12.6 ± 2.1°C). CIVD parameters (e.g., nadir, onset time, apex) were similar between trials, except Tpad nadir was higher during Hy (10.4 ± 3.8°C) than during Eu (7.9 ± 1.6°C), which was attributed to higher Tc in six subjects during Hy (37.5 ± 0.2°C), compared with during Eu (37.1 ± 0.1°C). The results of this study provide no evidence that Hy alters finger blood flow, skin temperature, or CIVD during peripheral cooling.