BACKGROUND
In various situations such as pain, exposure to hot or cold, and mental stress, where physiological stress occurs, the increased excitatory response in the sympathetic efferent neurons leads to an increased return of blood flow from the peripheral veins to the right atrium. The cold pressor test (CPT) is based on the effects of a cold stimulus that activates afferent sensory pathways to trigger a sympathetic response, resulting in an increase in blood pressure. This study aimed to evaluate the effects of the cold pressor test on popliteal vein diameter, flow velocity, and blood flow in the lower limbs in 60 healthy individuals.
MATERIAL AND METHODS
We included 30 men and 30 women age 18-40 years. Baseline vein diameter, flow velocity, and blood flow of the left popliteal vein were measured by Doppler ultrasound, then the left hand was immersed in a bucket of cold water. After immersing the hand in cold water for 1 minute (CPT-1), 3 measurements of vein diameter, flow velocity, and blood flow were taken again, and their averages were calculated.
RESULTS
In the study, data obtained from the individuals were statistically analyzed. At CPT-1, venous diameter and flow values showed significant increase compared to baseline (P=0.001, P<0.001, respectively).
CONCLUSIONS
In healthy volunteers, CPT increases venous flow in the popliteal veins. However, our study did not provide evidence for the hypothesis that the increase in venous return is due to venoconstriction mechanisms.

Keywords: Sympathetic Nervous System; Ultrasonography, Doppler, Color; Popliteal Vein