Does the Volume of Medication Affect the Success of Labor Epidural Analgesia

Impact of Injected Volume on Programmed Intermittent Epidural Bolus Analgesia

The purpose of this study is to evaluate whether changing the volume and concentration of a medication affects the quality of pain relief and the side effects associated with labor epidural analgesia.

This is a randomized, single blinded trial comparing epidural pain relief for labor when medications are delivered in one of two volumes/concentrations. Patients in each arm of the study will receive the same dose of medication, but one will be half as concentrated and twice the volume. The outcome will be the number of supplemental doses of medication that patients receive during labor via their patient-controlled analgesia button.

Inclusion Criteria:

• 18 years of age or older
• Gestational age of 36 weeks or greater
• American Society of Anesthesiology physical status 2
• Induction of labor or early labor (cervical dilation < 6cm)
• Singleton gestation
• Vertex presentation

Exclusion Criteria:

• Preeclampsia
• Receiving magnesium sulfate
• Having received narcotics within 4 hours
• Multiple gestation
• Major fetal anomalies or demise
• Previous spine surgery
• Known major spine pathology
• Substance use disorder