Comparing Bupivacaine, Lidocaine, and a Combination of Bupivacaine and Lidocaine for Labor Epidural Activation

The most common and effective method for controlling labor pains is a local anesthetic (LA)
infusion through a lumbar epidural. To achieve adequate pain control during the first stage
of labor - onset of contractions to complete cervical dilation - nerve fibers up to the T10
dermatome must be anesthetized. When a patient is in active labor and an epidural catheter is
placed, the anesthesiologist must activate the epidural by administering LA through the
epidural to promote spread of the LA in the epidural space to anesthetize the nerve fibers
involved in the conduction of labor pains. The ideal LA to achieve this goal is one that
would allow for the fastest onset to achieve quick pain relief with the fewest side effects.

Two commonly used LA to provide labor analgesia are bupivacaine and lidocaine. When low
concentrations - 0.25% bupivacaine and 1% lidocaine - are used for labor analgesia, both of
these LA can be administered safely with very little concern of major adverse effects
associated with LA toxicity. Given that there is limited and conflicting evidence for the
usefulness of the bupivacaine and lidocaine mixture especially as it relates to labor
epidural activation, we hope to readdress these questions in an effort to determine whether
or not the LA combination offers any distinct advantage over the individual LA. The
investigators intend to determine the time it takes to achieve an adequate level (T10) for
labor analgesia, the total spread of local anesthetic, and the degree of motor block as these
factors will be important in determining the most optimal LA solution to activate a labor
epidural. With the results from this study, the investigators hope to recommend a LA solution
that will allow for the fastest pain relief in the laboring mother with the fewest side
effects.

Inclusion Criteria:

- Pregnant patients over the age of 19 who are scheduled for an induction of labor and
request an epidural are eligible for the study

Exclusion Criteria:

- age <19

- allergy to the drug or drug class

- preexisting neuropathy

- history of back pain prior to pregnancy or history of back surgery

- history of chronic opioid use

- history of hypertension or hypertensive disorders of pregnancy

- congenital or acquired cardiac disease

- contraindication to epidural placement (patient refusal, severe coagulopathy,
infection at site of epidural needle insertion, severe hypovolemia)