Comparison of PIEB vs CEI for Labor Analgesia

Labor pain during childbirth is regarded as one of the most painful experiences in a woman's
life with the potential to cause lasting emotional and psychological effects. Childbirth has
also been associated with the development of chronic pain with the prevalence of between
4-10% after cesarean section and 6-18% after vaginal delivery. Hence, effective management of
labor pain is instrumental in preventing the development of life altering chronic pain in
women of childbearing age. Maintaining epidural analgesia with combined local anesthetic and
an opioid is considered extremely safe and leads to superior neonatal and maternal short and
long-term outcomes. Historically, maintenance of epidural analgesia involved intermittent
provider-administered bolus injections, patient controlled epidural analgesia (PCEA) and
continuous epidural infusions (CEI) with or without PCEA for breakthrough pain or discomfort.
CEI has been shown to provide consistent analgesia in addition to improved patient
satisfaction and reduced workload for the anesthesia providers. However, CEI is associated
with greater local anesthetic consumption and increased maternal motor blockade. Increased
motor block is associated with reduced mobility, decreased pelvic muscle tone and impaired
ability for the parturient to adequately Valsalva during the second stage of labor. Motor
blockade is also associated with increased incidence of shoulder dystocia and instrumental
deliveries, which precipitate birth trauma to the fetus and the mother. Achieving adequate
analgesia during labor, without compromising motor function is critical for optimizing both
short-term and long-term outcomes for the mother and the neonate.

A more novel approach to labor analgesia involves the administration of small, programmed
intermittent epidural boluses (PIEB) with PCEA dosing for breakthrough pain. Preliminary
studies have indicated that PIEB could be a superior method of labor analgesia compared to
current standard of care, CEI. A randomized double-blind study by Wong et al. compared CEI
and PIEB incorporating the use of PCEA for breakthrough pain in healthy parturients with
singleton pregnancies. Results suggested that the cohort receiving PIEB required less local
anesthetic use, had similar analgesia and improved patient satisfaction when compared with
CEI. Additionally, a subsequent study by Wong et al found that in healthy, term, nulliparous
women in spontaneous labor, extending the PIEB interval and increasing volume decreased local
anesthetic consumption, PCEA requests or rescue analgesia requirements without increasing
patient discomfort or compromising satisfaction. Two subsequent studies allocating women to
receive either PIEB or CEI in nulliparous parturients and women terminating pregnancy
suggested PIEB recipients experienced less motor blockade when compared to those receiving
CEI.

The investigator has recently performed a systematic review and meta-analysis of studies
comparing the effects of labor analgesia with either PIEB or CEI with or without PCEA in
laboring women. The meta-analysis included 9 studies and evaluated various primary outcomes
including: patient satisfaction, required manual anesthesia interventions, labor progression
and mode of delivery (vaginal, instrumental or cesarean delivery). Secondary outcomes
included: degree of motor blockade, degree of sensory blockade, time to first anesthetic
intervention, local anesthetic dose delivered per hour, pruritus, shivering, maternal fever,
nausea and vomiting, neonatal Apgar scores at 1 minute and 5 minutes, and umbilical artery
and vein pH. PIEB dosing of local anesthetic was associated with reduced local anesthetic
consumption, decreased required anesthetic interventions, and an improvement in maternal
satisfaction in comparison to laboring women receiving CEI. Pooled results indicated that
PIEB and CEI were comparable with regard to the duration of first stage labor, but there was
a statistically significant 22 min reduction in the length of stage two of labor with PIEB.
Similarly, this review did not suggest statistically significant differences in cesarean
delivery rate or required anesthetic intervention between CEI and PIEB. There were several
limitations to these preliminarily studies. While, each of the 9 studies reported at least
one primary outcome listed in the systematic review, none of the studies included all primary
outcomes. Additionally, most studies only involved nulliparous women, which may limit the
ability to apply results to multiparous women. Furthermore, many of these studies involved
the use of two pumps, one to deliver CEI or PEIB and another to deliver PCEA in a research
setting, or involved the use of non-commercially available research pumps.

Currently the CADD solis v 3.0 pump system has been upgraded to allow the co-administration
of epidural anesthesia with PIEB or CEI and PCEA. This new technology has been available on
the labor and delivery unit of Duke University Medical Center as the standard of care since
March 2015. This new pump differs from those used in the preliminary studies, which utilized
a two-pump approach to administer PIEB or CEI and PCEA for labor pain relief. Preliminary
studies have not identified optimal PIEB settings, bolus volumes, lock out intervals, or drug
concentrations, which represents a gap in literature at the present time. The investigator
performed a retrospective study to explore whether PIEB was associated with reduced LA use,
PCEA use and rescue analgesia in comparison to CEI in laboring women. The investigator also
assessed whether PIEB decreased the number of instrumental deliveries and reduced motor
blockade, which serves as an impediment to the progression of labor. The study divided
patients into three groups. The first received CEI 5mL/hour, the second received PIEB 5mL
every 60 min, the third used PIEB of 3mL every 30 min. Each group had access to PCEA set to 5
mL boluses with an 8-minute lockout period and maximum of 35mL per hour. The results of the
study did not suggest what was expected as the study revealed no statistically significant
difference between the LA consumption, amount of motor blockade or mode of delivery for
patients receiving CEI or PEIB when using the single pump system instead of two-pump system
employed by prior studies. However, this study did suggest patients who received PIEB regimen
of 3mL every 30 minutes used a lower PCEA volume than patients receiving CEI. Patients
receiving PEIB regimens had more attempts/PCEA given than the CEI patients and the PIEB
3ml/30 minute group had more unsuccessful PCEA attempts/hour than CEI recipients.

This study, unlike prior studies comparing PIEB vs. CEI with PCEA, used more concentrated
solutions consisting of double the concentration and half the volume of bupivacaine. One of
the investigators speculations is that larger boluses of a more dilute LA may have improved
dissemination in the epidural space and thus improved analgesia. This study interpreted PCEA
attempts/given and the number of unsuccessful PCEA attempts/hour as reflections of patient
pain or discomfort, as an attempt is interpreted as an effort to achieve better pain relief.
Another way to interpret the aforementioned PCEA attempts is as representation of the amount
of time a patient "locked out" or prevented from receiving additional boluses of PCEA. Hence,
a limitation of this study is the fact that patient satisfaction scores were not collected as
they could help distinguish whether attempts reflect the lockout period or inadequate
analgesia. Other limitations of this retrospective study include the fact that explicit
instructions about how to properly use the PCEA was not standardized, and the fact that
patient satisfaction or pain scores were not garnered due to the study's retrospective
nature. Probably one of the most significant limitations of this study was the fact that
patients were not randomized to treatment groups. Hence, the providers chose the analgesia
received. On the other hand, another retrospective study utilizing a more dilute
concentration of local anesthetic reported reduced need for physician interventions with PIEB
compared to CEI. The investigators have recently switched the local anesthetic in our
practice from bupivacaine 0.125 % to a more dilute concentration of ropivacaine 0.1% mixed
with fentanyl 2 mcg/ml. The investigator therefore aims to prospectively study if the use of
PIEB with the new epidural solution would be associated with improved analgesia compared to a
regimen using CEI.

Inclusion Criteria:

- American Society of Anesthesiology (ASA) class 2 and 3 women

- Nulliparous

- Age > 18 yrs

- gestational age > 36 weeks

- singleton pregnancies

- vertex pregnancies

- spontaneous labor or scheduled induction of labor

- cervical dilatation 2-5 cm at time of epidural placement

- Pain score > 5

Exclusion Criteria:

- BMI > 50 kg/m2

- history of past or current intravenous drug or chronic opioid abuse

- chronic analgesic use

- allergy or contraindication to any study medications

- any maternal or fetal condition requiring planned assisted stage 2 delivery