Cold-induced vasodilatation is not homogenous or generalizable across the hand and feet

Cold-induced vasodilatation (CIVD), a paradoxical cyclical increase in finger temperature upon cold exposure, is assumed to serve against cold injury. Most existing research has focused on hand and finger responses, yet most cold injuries occur in the feet. We investigated if CIVD responses of one finger can predict the responses of other fingers, and also whether the fingers could predict CIVD responses of the feet and toes. Ten subjects immersed their left hand up to the wrist in 8°C water for 30 min. They passively rewarmed for 15 min, followed by immersion of the left foot to the ankle in 8°C water for 30 min. Digit temperature at the edge of the nail bed was recorded on all fingers and toes and on the hand and feet. In all subjects, toe and foot temperature gradually decreased exponentially from ∼31 to ∼9°C. No subject exhibited CIVD in any toe or on the foot itself. Eight subjects exhibited CIVD (>1°C temperature increase) in at least one digit of the hand, but no consistent pattern existed in finger response to cold. No subject had strong (>2.0°C) CIVD in all fingers. Five had strong CIVD in some but not all digits, with magnitudes ranging 1.4–7.5°C, while three had weak (<2°C) CIVD in some but not all digits. Four exhibited asynchronous CIVD in the fingers, with cycles beginning at different times. We conclude that CIVD is highly variable across the fingers, and is not a generalizable response across digits or limbs.