DPE Technique in Labor Epidural for Morbidly Obese Women

Purpose of the study:

The primary purpose of this study is to determine if there are differences in block quality
between the DPE and standard EPL techniques for labor analgesia in the morbidly obese
patient. Establishing superiority of a technique is multifaceted and complex; therefore, the
design of the study will define a set of measureable outcomes to assess these properties,
which will be addressed in the subsequent sections. The investigators hypothesize that when
compared to the standard EPL, the DPE technique will significantly improve block quality in
this population.

The secondary purpose of the study is to find an optimal maintenance regimen for epidural
analgesia in the morbidly obese population. For the maintenance of epidural analgesia, it is
common practice to use either continuous epidural infusion or a programmed intermittent bolus
using a solution of ropivicaine 0.1% with fentanyl (2 mcg/mL). To date, there are no
randomized prospective studies that investigate maintenance regimens in the morbidly obese
parturient population. What has been shown is that super morbidly obese patients have
increased intra-abdominal and intracranial pressure which increases pressure in the epidural
space. Because of this elevated pressure, the epidural spread is increased, resulting in
higher sensory blocks than necessary for adequate labor analgesia.15 An important consequence
is that the morbidly obese parturient may experience additional undesirable side effects to a
labor epidural: increased respiratory function, increased incidence of hypotension, and
increased motor block.

Design and procedures:

The investigators propose a prospective, double-blinded, randomized trial. According to our
patient population and incidence of morbid obesity, enrollment would likely occur over a 2 to
3-year period. The investigators have a delivery rate of 3500 per year. Previous data from
our institution show that at least 11% of our patients are morbidly obese. The investigators
will therefore expect 800-900 morbidly obese women to deliver at our institution per year.
The investigators anticipate to complete enrollment for the study in 1-2 years.

Epidural technique:

Once the patient requests a labor epidural, the usual standard of care for epidural placement
will be initiated. The patient will have at least one 18g intravenous catheter and will
receive 500-1000 milliliter (mL) fluid administration. Vitals will be monitored by the labor
nurse, including continuous pulse oximetry, non-invasive blood-pressure monitoring, and
external tocodynamometry. Anesthesia time-out will be performed by the anesthesia provider
with participation from the nurse and the patient.

All patients will receive a neuraxial technique in the sitting position at L3/4 or L4/5 using
loss of resistance to saline. In the DPE group, a 25-g Whitacre needle will be used to
puncture the dura. In both groups, the epidural catheter will be threaded 5 cm in the
epidural space with an initiation dose of 15 ml of ropivacaine 0.1% with fentanyl (2 mcg/ml)
over 6 minutes as per standard practice. Labor analgesia will be maintained by programmed
intermittent bolus with 6 ml of the same solution every 45 minutes starting 30 minutes after
the initial dose. Patients will have patient-controlled epidural analgesia (PCEA) available
with an 8 ml dose per demand, every 10 minutes, for a maximum dose of 45 ml for every hour.

Assignment of Study Cohorts:

Study participants will be randomized by computer-generated sequence to EPL or DPE arms,
stratified by class of obesity (BMI ≥35<40 kg/m2, ≥40<50 kg/m2 and ≥ 50 kg/m2) and by parity
(nulliparous versus multiparous). Patients will be assigned to one of the four study arms by
computer-generated, randomized sequence in order to balance baseline characteristics across
the arms. This will be a double-blinded study. After the consented and enrolled participant
requests labor epidural, a study member will give the anesthesia provider a sealed envelope
with study assignment. The envelope will contain the instructions for placement of epidural
with wither standard EPL or DPE technique and specified maintenance regimen of either
Programmed Intermittent Epidural Bolus (PIEB) or Continuous Epidural Infusion (CEI).

Protocol for Breakthrough Pain

- If the patient has uneven or unilateral level, the provider will withdrawal catheter 1cm
from skin and bolus 5ml of epidural mix. As fetal heart rate allows for maternal
repositioning, the patient will lay lateral position with unblocked side in the
dependent position. (up to 3 catheter adjustments)

- If the patient has bilateral levels at that below T10 to ice, the patient will be
administered 5 ml off epidural pump, up to 3 times in 15 minutes.

- If the patient has pain despite T10 levels, the provider will administer Fentanyl 100
mcg via epidural.

- If analgesia continues despite these interventions up to 3 times within 30-60 minutes,
the attending anesthesiologist will determine if epidural catheter needs replacement.

Inclusion Criteria:

- Women admitted to the Duke Birthing Center for spontaneous or induced vaginal delivery
will be screened. After usual consultation with the anesthesia team is completed and
consent for anesthesia services are obtained, eligible patients will be approached to
by a member of the study team.

- ages 18-45

- singleton

- vertex fetuses at 37-41 weeks' gestation

- nulliparous and multiparous women

- cervical dilation of 2-7cm

- BMI ≥ 35 kg/m2,

- pain score > 4

- English-speaking ability.

Exclusion Criteria:

- chronic opioid use

- Major cardiac disease

- contraindications to regional anesthesia