The duration of the analgesic effect of cryotherapy in postpartum perineal pain: a randomized controlled trial

INTRODUCTION: The ice pack, the main non-pharmacological method for relieving perineal pain, seems to be effective if applied for 10, 15 or 20 minutes. But its use is not standardized, once it lacks robust evidence on timing and frequency of applications, which hinders the effective and safe use of this therapy in obstetric practice. AIM: To evaluate if a 10 minutes ice pack application is relieving postpartum perineal pain and if its analgesic effect is maintained for up to 2 hours. METHOD: A single-blinded randomized controlled trial was performed in a birth center in Sao Paulo, Brazil. The sample size consisted of 69 primiparous women 18 years old, within 6-24hrs after spontaneous vaginal birth with perineal pain 3 by use of a numeric rating scale, who had neither received anti-inflammatory medication after childbirth nor analgesics within the previous 3hrs. The sample was stratified according to the perineal condition after childbirth into intact perineum or 1st degree laceration and 2nd degree laceration or episiotomy. Random allocation into experimental and control group occurred separately in each stratum. In the experimental group, women received a single ice pack application to the perineum for 10 minutes. In the control group, women did not receive an ice pack. The primary outcome was a reduction by at least 30% in perineal pain intensity, immediately after the application and the secondary, was the maintenance of the analgesic effect for up to 2hrs.Perineal pain was measured using the numeric rating scale (0-10, 0 = no pain and 10 = worst pain imaginable), at three points of time: before, immediately after and 2hrs after applying an ice pack. FINDINGS: Before the intervention, there were no significant differences between the experimental and control group regarding sociodemographic characteristics, facts related to childbirth and perineal pain intensity. Immediately after the intervention, pain intensity was more reduced in the experimental group (4.0 vs. 0.7, p <0.0001), and the proportion of women whose perineal pain decreased by 30% or more was also higher in this group (82.9% vs. 17.6%; p <0.001). Within two hours, there was no significant difference in the mean pain levels in both groups. However, the proportion of women whose mean pain intensity decreased by at least 30% was higher in the experimental group (82.9% vs. 44.1%; p = 0.002). The number needed to treat was 3 (95% CI 2-7). Furthermore, the percentage of women whose perineal pain intensity has not increased since the application of ice was 61.9% for the experimental group and 89.3% for the control group, respectively. For the remaining participants, levels of perineal pain were increasing after an average time of 1hr45 (95% CI 1hr34-1hr57) and 1hr56 (95% CI 1hr51-2hr01) for the experimental and control groups, respectively, with significant difference. CONCLUSION: Application of an ice pack for 10 minutes is effective for relieving postpartum perineal pain for 1hr45 to 2hrs. Moreover, it is a well-accepted method by women and allows them to better perform their daily activities.