Analgesic effects and hemodynamic mechanisms of perpendicular and transverse needling at Sanyinjiao(SP 6) in patients with primary dysmenorrhea: A randomized controlled trial

Objective: To explore the analgesic effects and uterine hemodynamics of perpendicular needling(PN)and transverse needling(TN) at SP 6 in patients with primary dysmenorrhea(PD).Methods: In this randomized controlled trial, patients with PD diagnosed with cold-dampness congealing pattern were randomly assigned in a ratio of 1:1 to receive PN or TN at bilateral SP 6 for 10 min.Acupuncture was performed when the menstrual pain score was over 40 mm on the first day of menstruation, as measured using the visual analog scale for pain(VAS-P). The primary outcome was average menstrual pain(VAS-P). Secondary outcomes included the pulsatility index(PI), resistance index(RI), and systolic-diastolic peaks ratio(S/D) in uterine arteries as measured using color Doppler ultrasonography; anxiety as assessed using the Hamilton Anxiety Rating Scale(HAMA), blood pressure(BP),and heart rate(HR).Results: Forty-eight patients completed the study. The TN group exhibited a significant reduction in VAS-P scores(-5.71 mm, 95% confidence interval(CI): -8.78, -2.63, P =.001), RI values(-0.05, 95% CI:-0.09, -0.01, P=.015), and HAMA values(-2.50, 95% CI: -4.78, -0.22, P=.032) when compared with the PN group. No significant differences in PI, S/D, BP, or HR values were observed between the two groups(P >.05).Conclusion: TN at SP 6 was superior to PN in alleviating menstrual pain and anxiety in patients with PD.This analgesic effect of TN may be due to its better ability to improve uterine arterial blood flow via decreases in RI values.