Chapter 39: Low-Concentration Labor Epidural Analgesia

BACKGROUND

Of the pharmacologic and nonpharmacologic options for labor analgesia, neuraxial analgesia is the gold standard with the highest efficacy in terms of visual analog scale pain scores and patient satisfaction.¹ Historically, high concentration local anesthetic solutions (0.25-0.5% bupivacaine) were used to induce and maintain epidural analgesia. However, these epidural solutions resulted in significant hypotension, fetal bradycardia, maternal lower extremity motor blockade, and subsequent impaired second stage of labor.¹ More recently, dilute local anesthetic solutions (≤0.1% bupivacaine or equipotent ropivacaine) have gained favor due to decreased maternal motor block, increased maternal mobility, shorter second stage of labor, and decreased need for assisted vaginal delivery compared to more concentrated solutions.^1,2 Dilute local anesthetic solutions have been demonstrated to yield the same length of labor and rate of assisted vaginal delivery and cesarean delivery as nonepidural analgesic options.³ Maternal satisfaction with labor analgesia has been shown to be equivalent with lower concentration epidural solutions compared to more concentrated solutions.^2,4

GOALS

• To provide adequate labor analgesia while minimizing side effects (e.g., maternal motor block, hypotension, nausea/vomiting, pruritus, prolonged second stage of labor, need for assisted vaginal delivery, and fetal distress)

CLINICAL PRACTICE

Larger volumes of dilute local anesthetic solutions can safely be administered than of more concentrated solutions, which leads to enhanced analgesia via improved dermatomal spread in the epidural space.¹ The addition of a lipophilic opioid (e.g., fentanyl or sufentanil) to a dilute local anesthetic solution maximizes labor analgesia while reducing the required local anesthetic concentration.¹ Fentanyl and sufentanil have similar analgesic efficacy when administered in equipotent doses. Methods of administration include continuous epidural infusion of a fixed rate and a programmed intermittent epidural bolus (PIEB) in which a set volume is delivered by pump followed by a programmed pause. Both methods should be accompanied by a patient-controlled demand function (PCEA) to reduce the frequency of breakthrough pain.

The “Walking Epidural” solution from our tertiary care academic medical center is provided in Table 39-1.⁵ This solution has been in continuous practice since the early 1990s. Table 39-2 lists variations of low-concentration to high-concentration (0.125%) schemes in common practice.