Effects of repeated exposures to experimental cold pain stimulus on pain perception in healthy young Indian men.

Background: The influence of repeated exposures to cold pain stimulus, a surrogate of clinical pain, has remained largely unexplored. The study was planned to test the effect of repeated exposures to cold pain through cold pressor task on pain sensitivity and vascular reactivity. Methods: Single-group experimental study. Thirty-seven healthy male volunteers (18-25 years) were exposed to cold pressor tasks for seven consecutive days and on the 14th day on the nondominant hand. The same was repeated on dominant hand on first and seventh days; 31 completed the protocol. Results: Pain threshold and tolerance in the nondominant hand increased from day 1 to day 7 (p < 0.001) and were positively correlated on day 1 ( Conclusion: Habituation in pain threshold and tolerance was observed on repeated exposure to cold pain, which was not significantly retained till the 14th day. The same was not observed with subjective feeling of pain perception. The increased diastolic blood pressure response is suggestive of peripheral vasoconstriction. Increased tolerance in the dominant hand by day 7 demonstrates a systemic effect in habituation.