the effects of regional analgesia on the progress and outcome of labor
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The Effects of Regional Analgesia on the Progress and Outcome of Labor. Marissa Lazor, M.D. In 1847, the Scottish obstetrician, James Simpson administered ether to a woman during labor to treat the pain of childbirth.

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the effects of regional analgesia on the progress and outcome of labor

The Effects of Regional Analgesia on the Progress and Outcome of Labor

Marissa Lazor, M.D.

In 1847, the Scottish obstetrician, James Simpson administered ether to a woman during labor to treat the pain of childbirth.
  • “It will be necessary to ascertain anesthesia’s precise effect, both upon the action of the uterus and on the assistant abdominal muscles; it’s influence, if any, upon the child; whether it has a tendency to hemorrhage or other complications.”
Approximately 60 percent of women, or 2.4 million each year, choose epidural or combined spinal-epidural analgesia for pain relief during labor.
stages of labor
Stages of Labor
  • First Stage - start of regular uterine contractions until the completion of cervical dilation (latent and active)
  • Second Stage - from complete cervical dilation to delivery of the fetus
  • Third Stage - from delivery until placenta and membranes are expelled
labor pain pathways
Labor Pain Pathways
  • Labor pain is transmitted through lower thoracic, lumbar, and sacral nerve roots
  • Afferent pain impulses from the cervix and uterus are carried by sensory nerve fibers that accompany sympathetic nerve endings and enter the neuraxis at T10-L1
  • Pain pathways from the perineum travel to S2-S4 via the pudendal nerve
benefits of epidural analgesia are obvious
Benefits of Epidural Analgesia are Obvious
  • superlative pain relief
  • high patient satisfaction
  • minimal effect on fetal well-being
  • contributing factor to overall decline in maternal mortality from anesthetic causes (failed intubation and aspiration)
controversy still remains over the effects of epidural analgesia
Controversy Still Remains Over the Effects of Epidural Analgesia
  • rate of c-section delivery
  • rate of instrument-assisted delivery (vacuum extraction and forceps)
  • prolongation of labor
  • effects on the fetus
retrospective studies
Retrospective Studies
  • Most show an association between epidural analgesia and a higher c-section rate
  • It is not possible to draw definitive conclusions from studies comparing women who select epidural analgesia from those who did not
characteristics of patients who select epidural analgesia
Characteristics of Patients Who Select Epidural Analgesia
  • earlier stage of labor at admission
  • higher fetal station at admission
  • greater use of oxytocin
  • smaller pelvic outlets and larger babies
  • more fetal malpresentation
  • more likely to be primagravid
  • more likely to have private insurance
  • more likely to “accept” medical intervention
pain in labor itself
Pain In Labor Itself
  • Pain early in labor is associated with a slower labor resulting in an increased rate of c-section and instrumental deliveries
  • More pain in labor is associated with a higher likelihood of selecting epidural analgesia
natural experiment studies
“Natural Experiment” Studies
  • The rates of c-section delivery is compared immediately before and after a rapid change in the availability of epidural analgesia to a certain population of women
  • A total of 8 such studies show that a rapid increase in epidural analgesia availability had no effect on the overall rate of c-section delivery
advantages of natural experiment design
Advantages of “Natural Experiment” Design
  • Less selection bias than retrospective studies
  • All patients included, not just an uncharacteristic subset, who agree to participate in a randomized trial
  • Data analysis not complicated by by crossover and protocol non-compliance
  • Large sample sizes are easily studied
methodologic limitations
Methodologic Limitations
  • Impossible to control for changes in obstetrical practice style that may occur
  • A stable patient population is important
  • Other external factors (peer review or practice guidelines) that might have been put into effect during the study period
segal 2000
Segal (2000)
  • Meta-analysis of 37,000 patients in a variety of different practice settings and time periods in several different countries showed:
  • No significant change in
    • overall c-section delivery rate
    • rate of c-section deliveries for dystocia
    • rate of forceps delivery
prospective randomized trials
Prospective, Randomized Trials
  • 11 clinical trials since 1990 have assessed the effect of epidural analgesia on c-section rates by randomizing women to opiod versus epidural analgesia
  • Epidural analgesia associated with an increase in c-section delivery rate in only one study
problems with prospective randomized trials
Problems With Prospective, Randomized Trials
  • Patients who consent to such a trial may not represent the general parturient population
  • Unblinded - obstetrician bias
  • Many studies are severely underpowered
  • Protocol non-compliance and cross-over between groups make data difficult to interpret (30%)
  • Variable results depending on how data is analyzed – “intent to treat” is correct but problematic with large cross-over
thorp 1993
Thorp (1993)
  • Randomized 93 nulliparous women at term to epidural analgesia or iv meperidine
  • crossover of only one patient in each group
  • large increase in c-section rate with epidural analgesia (16.7 % vs. 2.2 %)
  • longer 1st and 2nd stages of labor
  • more malpositions
  • more need for oxytocin
sharma 2002
Sharma (2002)
  • Randomized 459 nulliparous women in active labor to receive epidural analgesia or parenteral meperidine with only 8% cross-over rate
  • no significant difference in the c-section rate between groups (6 percent in the epidural and 7 percent in the meperidine group)
  • Significant increase in rate of forceps delivery in epidural group (13% vs 7%)
  • Longer 1st and 2nd stages of labor with epidural (40 minutes and 11 minutes)
  • Significant increase in maternal fever in epidural group
it is not clear why these two studies had such different results
It Is Not Clear Why These Two Studies Had Such Different Results
  • Obstetrical practice styles
  • Small sample size in Thorp’s study - only one more c-section in the control group would have eliminated statistical significance
  • Earlier administration of epidurals in Thorp’s study
  • Lower use of forceps in Thorp’s study
segal 1999
Segal (1999)
  • Studied the c-section rates of 110 obstetricians while controlling for known patient risk factors for c-section
  • Obstetrical practice style is a major determinant of rates of c-section
  • C-section rates for dystocia varied tremendously among practitioners (3% - 17%)
halpern jama 1998
Halpern (JAMA, 1998)
  • Meta-analysis of 2400 patients randomized to receive either epidural or iv opiods
  • epidural analgesia assoc. with prolongation of first stage of labor by 42 minutes, second stage of labor by 14 minutes
  • no significant difference in c-section rate between groups (8.2% epidural vs. 5.6% opiod)
  • doubling of the rate of forceps delivery in the epidural group
sharma 2004
Sharma (2004)
  • Individual meta-analysis of 2700 nulliparous women
  • No difference in overall c-section rate (10.5% vs. 10.3%) or rate for dystocia
  • Significant increase in forceps deliveries (13% vs. 7%) in epidural group
  • Epidural analgesia was associated with prolongation of 1st and 2nd stages of labor, increased need for oxytocin, and maternal fever
  • One and 5 minute apgar scores significantly worse in the intravenous meperidine group
  • Significantly lower pain scores and greater satisfaction both stages of labor in epidural group
consistent finding of increased instrument assisted deliveries
Consistent Finding of Increased Instrument-Assisted Deliveries
  • Motor blockade may prevent the mother from pushing
  • Epidural analgesia is associated with a higher frequency of occiput-posterior presentation
  • Presence of epidural may decrease the obstetrician’s threshold for performing instrument-assisted deliveries
  • Epidural analgesia does lengthen the duration of labor by approximately one hour
  • Epidural analgesia probably does not increase the risk of cesarean delivery
  • Most studies show a significant increase in forceps delivery with epidural analgesia
  • Epidural analgesia results in more frequent use of oxytocin
  • Patient satisfaction and neonatal apgar scores are better after epidural than intravenous opiods
factors known to be associated with an increased c section rate


multiple gestation

fetal distress


previous c-section

young or advanced maternal age

pregnancy induced hypertension

low or high birth weight

pre or post-term infants

induction of labor

obstetrical practice style

Factors Known to be Associated with an Increased C-section Rate
reported complications of epidural analgesia
Reported Complications of Epidural Analgesia
  • Association between use of epidural analgesia and maternal fever - demonstrated in observational and randomized studies
  • No increase in the rate of neonatal sepsis but but more work-ups for sepsis and greater antibiotic use in these infants
  • No relation between new onset of back pain and epidural analgesia
3 percent incidence of dural puncture during placement of an epidural with severe headache occuring in up to 70 percent
  • fetus more often in occiput posterior position at delivery with epidural analgesia
timing of epidural analgesia during labor
Timing of Epidural Analgesia During Labor
  • Observational studies show higher rates of c-section with early epidurals
  • Randomized trials of early vs. late epidurals show no difference in rate of c-section, forceps delivery
  • Recent randomized trial of early CSE (2cm) vs. iv narcotics plus late epidural (4cm) showed no increase in c-section rate or instrumental deliveries and faster progress of labor with early CSE (Wong, NEJM, 2005)
acog asa joint statement 2002
ACOG/ASA Joint Statement (2002)
  • Maternal request for pain relief during any stage of labor is sufficient medical indication for its use
advantages of combined spinal epidural analgesia
Advantages of Combined Spinal-Epidural Analgesia
  • More rapid onset of analgesia – (6-8 min)
  • Profound, reliable sensory block
  • High maternal satisfaction
  • Minimal motor blockade - ability to ambulate
  • Negligible systemic absorption of medications
disadvantages of cse
Disadvantages of CSE
  • Pruritus (80%)
  • Maternal hypotension (20%) - frequency equal to standard epidural
  • Fetal bradycardia (5%) – frequency equal standard epidural
  • Respiratory depression (.01-.1%)
  • Rate of PDPH similar to standard epidural
  • Delay in identifying a poorly working epidural catheter
  • No increased rate of SA catheter migration
potential advantages of cse over epidural
Potential Advantages of CSE over Epidural
  • When analgesia must be achieved rapidly (late, rapid labor in multiparous women)
  • Analgesia with minimal motor block (ambulation during labor) – but no difference in in c-section or instrumental deliveries in ambulating vs. non-ambulating patients
  • Progression of labor more rapid in patients given early CSE vs. traditional epidural or iv narcotics
agents used for labor cse
Agents Used For Labor CSE
  • Fentanyl – 10-25 ug
  • Sufentanil – 2-10 ug
  • Bupivicaine – 2.5 mg (1cc of 2.25%)
  • +/- epinephrine 200ug – may extend duration of action by 30 minutes
combined spinal epidural analgesia and the rate of c section delivery
Combined Spinal-Epidural Analgesia and the Rate of C-Section Delivery
  • Gambling (1998) - Randomized trial of CSE vs. intravenous demerol showed no increase in c-section rate for dystocia or for non-reassuring fetal heart rate tracings
  • Nageotte (1997) - Randomized trial of CSE vs. epidural showed no difference in c-section rate or frequency of dystocia but decreased instrumental deliveries with CSE