Trial of Onset of Epidural Pain Relief With Low Dose Bupivacaine and Different Doses of Fentanyl in Laboring Women

Onset of Labor Epidural Analgesia With Low Dose Bupivacaine and Different Doses of Fentanyl: a Randomized Double Blinded Clinical Trial.

Epidural analgesia is the most effective form of labor pain relief. Low doses of local anesthetic (freezing solutions) in combination with opioids (narcotics) are commonly used as epidural solutions to provide pain relief. Low dose local anesthetic solutions with opioids for labor have been shown to decrease motor block (leg weakness or temporary paralysis), without affecting labor pain relief. However, onset of pain relief can be delayed with these low dose solutions. The standard epidural solution used at Victoria Hospital is a low dose of local anesthetic called bupivacaine mixed with fentanyl, an opioid, for labor epidural pain relief.

There is some evidence that the addition of more fentanyl to the epidural bolus dose of bupivacaine at the start of labor epidural analgesia can speed onset of pain relief. Both medications are safe for you and your baby.

This study will investigate whether the addition of different doses of fentanyl (20 mcg, 50 mcg and 100 mcg) to the epidural bolus dose speeds onset of pain relief.

The study hypothesis is that the onset of epidural labor analgesia will be shortest with the larger fentanyl epidural bolus.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status 1 or 2
• Pregnant women in early labor (cervical dilation <5cm)
• Singleton fetuses
• Gestational age more than 36 weeks
• Normal fetal heart rate tracing

Exclusion Criteria:

• Severe pre-ecclampsia
• Antepartum hemorrhage
• ASA >3
• Chronic pain
• Substance abuse
• Language barrier between patient and investigator
• Contraindications to epidural analgesia
• Allergies to local anesthetics or fentanyl
• Morbid obesity
• Previous administration of opioid analgesia