Epidural analgesia is widely regarding as the most effective analgesic strategy for labor
pain. Modern practice is to utilize dilute local anesthetics as a continuous infusion along
with an opioid, e.g., our common "recipe" of 12 ml/hr of 0.0625% bupivacaine with 2
micrograms/ml fentanyl, after the initial dose to maintain patient comfort until delivery.
This dose of the infusion often provides adequate comfort without interfering with the
mobility of the patient and her ability to effectively push during delivery. However, this
low dose epidural infusion strategy often results in recurrence of pain after an initial
pain free period.
This breakthrough pain is treated by administering small boluses of analgesics via the
epidural catheter. The pain occurring in labor is initially of visceral origin and is
mediated by pain fibers originating from the low thoracic and upper lumbar segments of the
spinal cord. As labor progresses to the late first phase (also known as transitional stage),
pain sensations originating from the distension of the pelvic floor, vagina and perineum
adds a somatic component to labor pain. This type of breakthrough pain is often difficult to
Although requests from patients to alleviate late stage breakthrough pain are common, no one
knows the most effective strategy for pain management in this stage of labor. This study is
designed to compare the efficacy of two treatments for controlling late first stage
breakthrough pain during labor with an epidural infusion in place: clonidine-bupivacaine
Women who have labor epidural analgesia in place will be enrolled to be randomized if and
when they present with breakthrough pain in the late first stage or second stage of labor
(≥ 8 cm dilated). They will receive 8 ml of a solution containing 10 mg bupivacaine and 75
micrograms of either fentanyl (an opioid or "narcotic") or clonidine (an "alpha-2 agonist
known to be effective as an epidural analgesic).
Pain relief, labor progress and outcome will be assessed to compare fentanyl versus
It is the hypothesis of this study that clonidine added to bupivacaine is a better analgesic
than fentanyl added to bupivacaine for breakthrough pain in advanced labor.
- women in labor at term pregnancy
- epidural analgesia in place
- breakthrough pain in advanced labor
- chronic pain syndrome
- receiving systemic opioids within 4 hours
- receiving chronic antidepressants, clonidine, opioids