Intravenous meperidine infusion for obstetric analgesia

To provide safe, satisfying obstetric analgesia when epidural analgesia was unavailable.

Randomized, controlled study of women in labor.

A regional hospital offering primary- and secondary-level obstetric care.

Thirty-nine women with low-risk, single, term pregnancies and anticipated vaginal delivery.

Women in the intermittent intramuscular (IM) injection group received meperidine 50-100 mg, every 2 hours, as required. Those in the intravenous (IV) infusion group received an initial bolus of meperidine 25 mg, a basal infusion rate of 60 mg/h, and intermittent boluses of 25 mg/h as required. Each participant had a maximum of 200 mg of meperidine available to her during labor.

Pain intensity was measured on a 10-cm visual analogue scale. Pain ratings were recorded when analgesia was initiated and every 30 minutes thereafter, until delivery.

Women who received IV meperidine reported significantly lower levels of pain (p = .0015) than women in the IM group. However, women in the IV group received significantly higher doses of meperidine (mean = 121 mg) than those in the IM group (mean = 82 mg; p = .0007). When pain scores were compared on a smaller group of participants (n = 18) who received similar doses of meperidine (100-150 mg), women in the IV group still reported lower pain scores (p = .0092). No significant differences were found between the groups in length of labor, maternal vital signs, fetal heart rate, Apgar scores, level of maternal sedation, or patient-reported side effects.

IV meperidine infusion was superior to intermittent IM injections for pain relief during labor.