Oxygen saturation of brachial venous blood correlates with fingertip temperatures between 11 and 39 degrees C

The relationships between fingertip skin temperature (Tfin), brachial venous hemoglobin oxygen saturation (SVO2), and plasma catecholamines were studied by exposing 15 semi-nude men to 30 min of 5 degrees C and 48 degrees C ambient air temperature extremes. After 30 min of cold air, norepinephrine (NE) increases from 2.01 +/- 0.26 to 7.15 +/- 0.64 nmol/L, and epinephrine (Epi) increases from 201 +/- 25 to 295 +/- 34 pmol/L. In contrast, after 30 min of hot air exposure, Epi rises from 161 +/- 32 to 348 +/- 43 pmol/L, while NE rises slightly from 2.07 +/- 0.26 to 2.57 +/- 0.64 nmol/L. Heat elevates SVO2 from 68.8 +/- 0.72 to 93.3 +/- 0.66% and Tfin from 29.5 +/- 1.09 to 39.4 +/- 0.56 degrees C. Cold lowers SVO2 to 32.1 +/- 0.70% and Tfin to 11.5 +/- 0.55 degrees C. SVO2 correlates with Tfin (r = 0.895, p less than 0.0001). We conclude that exposure to an environmental temperature of 5 degrees C decreases Tfin with concurrent decreases in blood flow and SVO2 in the extremity by the vasoconstrictive action of NE. Exposure to 48 degrees C increases Tfin with increases in blood flow and SVO2 in the extremity by vasodilation of peripheral vascular beds, which may be related to the rise in the plasma concentration of Epi.