Abstract
Background: Labor pain perception has been demonstrated to exhibit a circadian rhythm with lower pain scores during the day compared with the night. This study aimed to determine and compare the median effective dose (ED50) of ropivacaine in parturients having epidural labor analgesia during the day vs. during the night.Methods: The study group consisted of 60 nulliparous healthy parturients who were assigned to one of two groups according to the time they requested labor analgesia: Day Group (7:01 am to 7:00 pm) and Night Group (7:01 pm to 7:00 am). A bolus of.15% ropivacaine was administered epidurally and effective analgesia was defined as the attainment of a visual analog scale (VAS) pain score ≤ 10 mm within 30 min. The dose of ropivacaine for the first parturient in each group was 18 mg. The dose for each subsequent parturient was varied with increments or decrements of 3 mg based on the response of the previous subject. The ED50 was calculated using up-down sequential analysis. Probit regression was used to estimate the relative mean potency of ropivacaine between groups.Results: The ED50 (mean [95% CI]) of ropivacaine was lower in the Day Group (17.9 [16.5–19.4] mg) than in the Night Group (20.9 [19.2–22.7] mg) (P = 0.003). The estimate of relative potency for ropivacaine for the Night Group vs. the Day Group was 0.85 (95% CI:0.56–0.98).Conclusions: Under the conditions of this study, the dose requirement for epidural ropivacaine for labor analgesia was ~ 15% greater during the night than during the day.Clinical Trials Registration: Chinese Clinical Trial Registry (No.: ChiCTR1900025269. http://www.chictr.org.cn/showprojen.aspx?proj=36993).
Highlights
Chronobiology, the circadian variation in biological rhythms, can influence many biological functions [1,2,3,4]
The calculated value for ED50 of ropivacaine was lower in the Day Group (17.9 mg [95% CI, 16.5–19.4]) compared with the Night Group (20.9 mg [95% CI, 19.2–22.7]) (P = 0.003)
The ED50 values calculated using probit regression were 17.9 mg in the Day Group and 21 mg in the Night Group
Summary
Chronobiology, the circadian variation in biological rhythms, can influence many biological functions [1,2,3,4]. Labor pain perception has been demonstrated previously to exhibit a Circadian Variation in Labor Analgesia circadian rhythm with lower pain scores during the day compared with the night [5, 6]. We hypothesized that the dose requirement for ropivacaine would differ depending on whether epidural labor analgesia was administered during the day vs the night. We designed the present study to determine and compare the median effective dose (ED50) of ropivacaine given for epidural labor in healthy parturients during the daytime vs the night. Labor pain perception has been demonstrated to exhibit a circadian rhythm with lower pain scores during the day compared with the night. This study aimed to determine and compare the median effective dose (ED50) of ropivacaine in parturients having epidural labor analgesia during the day vs during the night
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