Meperidine Compared With Nitrous Oxide for Intrapartum Pain Relief in Multiparous Patients

Intravenous meperidine and inhaled nitrous oxide have similar, limited intrapartum analgesic effects 20–30 minutes after administration in multiparous patients. OBJECTIVE: To compare the efficacy and adverse effects of intravenous meperidine and inhaled nitrous oxide for intrapartum analgesia in multiparous patients. METHODS: This randomized controlled trial was conducted in the delivery ward of a university teaching medical center in Afula, Israel. Multiparous patients with term, singleton pregnancies who were in labor were randomized in a 1:1 ratio to 50 mg intravenous meperidine or inhaled nitrous oxide. The primary outcome was pain intensity 20–30 minutes after analgesic administration, measured on a visual analog scale (VAS) from 0 to 10 cm. Secondary outcomes included the need for additional analgesia, labor length, delivery mode, patient satisfaction, and maternal and neonatal adverse effects. To detect a 1-cm (±2.6) difference in VAS score between the groups, 214 total participants were needed to achieve 80% power with an alpha of 0.05. RESULTS: From August 2016 through May 2019, 214 participants were enrolled. Fourteen were excluded after randomization. Of the 200 analyzed, 102 received nitrous oxide, and 98 received intravenous meperidine. Demographic and obstetric variables were comparable between the two groups. The VAS score 20–30 minutes after analgesic administration did not differ between the groups (7.7±2.3 cm and 7.6±2.7 cm in the nitrous oxide and meperidine groups, respectively, P=.89). There were no significant differences between the groups in the rate of additional analgesic use, labor length, delivery mode, Apgar scores, rate of breastfeeding, patient satisfaction, or maternal and neonatal adverse effects. CONCLUSION: Pain intensity was comparable in multiparous patients 20–30 minutes after administration of meperidine and nitrous oxide. Adverse effects were also comparable. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, NCT02783508.