ANALGESIA IN LABOR

I. Narcotics

  1. Side f/x for mom include: respiratory depression, orthostatic hypotension, nausea and vomiting; may slow labor in latent stage but speed active labor (prob. due to decreased pain)
  2. Demerol: peak analgesia 40-50min after IM (50-100mg) or 5-10min after IV (25-50); lasts about 3h
  3. Morphine Sulfate: Gives more neonatal respiratory depression per degree of analgesia than meperidine (Demerol)
  4. Fentanyl: may cause rapid respiratory depression in mom but seems not to affect neonate too much; IM 50-100 micrograms gives analgesia by 10min & duration 1-2h; IV 25-50 micrograms gives immediate analgesia with duration 30-60min
  5. Butorphanol (Stadol) may increase pulmonary vascular resistance; low risk of maternal respiratory depression; 1-2mg IM; pharmacokinetics comparable to meperidine (Demerol)
  6. Naloxone (Narcan-An opiate analgesic antidote): ADULTS 0.4mg IV; BABY 0.1mg/kg IV or IM

II. Benzodiazepines: for sedation & anxiolysis; f/x in neonate include hypotonia, lethargy, & hypothermia, but rare at low doses

  1. Valium: limit dose to <30mg total or the baby will have it around for a long time!
  2. Ativan: shorter t-1/2 but more resp. depression in baby than valium
  3. Versed: short duration, rapid onset; can cause anterograde amnesia

III. Phenergan: anxiolytic/antiemetic; no apparent neonatal depression

IV. EPIDURAL ANESTHESIA

  1. Although some retrospective cohort studies have suggested an association with subsequent low back pain, one prospective nonrandomized study (BMJ 312:1384, 1996--JW) and one secondary analysis of patients in a randomized trial (BMJ 325:357, 2002--JW) failed to show any such association.
  1. Obs. Gyn. 86:783, 1995-AFP
  1. 1300 women with singleton, uncomplicated pregnancies presenting at <5cm dilation randomized to epidural (bupivacaine + fentanyl) vs. meperidine IV.
  2. Women assigned to epidural reported sig. less pain during labor and were more likely to retrospectively rate satisfaction with analgesia as excellent or very good (80% vs. 22%)
  3. However, epidural group was more likely to
  1. Receive augmentation of labor
  2. Show evidence of chorioamnionitis
  3. Have a 2nd stage > 2h
  4. Have total time from admission to delivery be > 10h
  5. Deliver by low forceps
  6. Deliver by c/s (RR 2.0)
  1. Associated with longer labors & possibly higher risk of c/s
  1. See study cited just above
  2. Retrospective study of 3,200 nulliparous pts pts before and 3,700 after on-demand epidural analgesia became available at a hospital showed no sig. diff. in c/s rates between the groups; however, in "after" group, women requiring c/s for dystocia were more likely to have had epidural than those requiring c/s for other indication, suggesting a possible common cause for dystocia and severe labor pain (Am. Soc. Anesthesiologists meeting 1998--AFP)
  3. In a randomized trial of 459 healthy nilliparous patients with singleton cephalic presentations randomized to epidural vs. IV meperidine, active labor was sig. longer in the epidural gropu (6h vs. 5h) but stage 2 was not sig. different in length (Obs. Gyn. 100:46, 2002--JW)
  4. In a meta-analysis of data from seven randomized trials comparing low-dose epidural analgesia with parenteral opioids in primigravida in labor, there was no sig. diff. in incidence of cesarian section, though epidural analgesia was ass'd with RR 1.63 for instrumental delivery (sig.) (BMJ 328:1410, 2004--JW)
  5. In a study in 449 nulliparous women in active labor at > 36wks gstation, with cervical dilataion 3cm or less and cervical effacement of 80% or more randomized to early (up to 3cm dilatation) or late (4-5cm dilatation) epidural analgesia; the incidence of cesarian delivery was not sig. diff in the two groups; the early-epidural group had sig. SHORTER first stage of labor (5.9h vs. 6.6h) (Am. J. Obs. Gyn. 194:600, 2006--AFP)
  1. Associated with maternal fever and neonatal sepsis evaluations
  1. 1047 women who had epidurals (self-selected) compared to 610 women who didn't. Average labor 6h longer with epidurals. Intrapartum fever (>100.4) occurred in 14.5% of epidural vs. 1% of non-epidural group. Neonatal sepsis evaluations occurred in 34% of epidural vs. 9.8% of non-epidural group; difference applied even to neonates who didn't have fever. "Held up after mult. regression analysies" (Pediatrics 99:415, 1997--JW)
  1. Epidural vs. IV or IM opioid analgesia
    1. A meta-analysis of 10 randomized trials with total 2369 pts (JAMA 280: 2105, 1998) found:
      1. Nonsig. increased incidence of c/s in epidural pts (8.2% vs. 5.6%)
      2. Sig. longer 1st and 2nd stages of labor (42 and 14 min, respectively)
      3. Sig. more likely instrumented delivery (OR 2.19)
      4. Sig. lower pain scores and greater satisfaction with epidural
  1. Low-dose "walking" epidurals
    1. In a randomized study of 1,054 women requesting epidural analgesia randomized to "traditional" epidural, low-dose combined local-opioid epidural, and low-dose infusion epidural, vaginal delivery rate was sig. higher in the "low-dose" groups vs. traditional group (43% vs. 35%); the rate of instrumental vaginal deliveries was correspondingly lower; no sig. diff. in c/s rates; no diff.in pain relief (Comparative Obstetric Mobile Epidural Trial," Lancet 358:21, 2001--AFP) 

V. Combined Spinal-Epidural analgesia

  1. 761 nulliparous women randomized to either standard epidural or combined spinal-epidural. No sig. diff. in rate of c/s, dystocia, pain scores, or frequency of maternal or fetal complications. However, fewer women in the combined group required instrumental delivery (30% vs. 40%). Cesarean more likely if epidural given with vtx at station < 0 or cervical dilation < 4 (NEJM 337:1715, 1997--JW)