Should intrathecal narcotics be used as a sole labor analgesic? A prospective comparison of spinal opioids and epidural bupivacaine - Original Research

Journal of Family Practice, July, 2002 by Patricia Fontaine, Patricia Adam, Kenneth H. Svendsen

KEY POINTS FOR CLINICIANS

* Stand-alone intrathecal morphine and fentanyl (intrathecal narcotics [ITNs]) are associated with significantly higher pain levels than continuous epidural analgesia with bupivacaine and fentanyl.

* Intrathecal narcotics provide excellent pain relief for women who deliver within 2 to 3 hours of receiving them.

* Lower pain levels are significantly correlated with greater satisfaction with labor pain management.

* Women receiving ITNs were subjectively more satisfied with their ability to walk during labor.

* There was no difference in overall side effect severity between groups.

* OBJECTIVE Intrathecal narcotics (ITNs) are being used in some settings as a sole labor analgesic. However, they have not been directly compared to epidural analgesia.

* STUDY DESIGN We used a prospective observational design.

* POPULATION Eighty-two women with uncomplicated full-term pregnancies were enrolled upon analgesia request during spontaneous labor with cervical dilation 3 to 7 cm. Sixty three chose ITNs (morphine and fentanyl), and 19 chose epidural analgesia (continuous infusion of bupivacaine and fentanyl).

* OUTCOMES MEASURED Pain scores were documented using a visual analog scale. Satisfaction and side effects were rated with Likert scales during a structured interview on the first postpartum day. Outcomes were analyzed with multivariate regression techniques.

* RESULTS Intrathecal narcotics were associated with significantly higher pain scores than was epidural analgesia during the first and second stages of labor and on an overall postpartum rating. The median effective duration of action for ITNs was between 60 and 120 minutes; however, ITNs provided excellent analgesia for a subgroup of women who delivered within 2 to 3 hours of receiving them. Although women in both groups were satisfied with their pain management, women receiving ITNs had statistically lower overall satisfaction scores.

* CONCLUSIONS within the limitations of a nonrandomized study, a single intrathecal injection of morphine and fentanyl has a shorter duration of action and provides less effective pain control than a continuous epidural infusion of bupivacaine and fentanyl. However, ITNs may have a role in settings with limited support from anesthesiologists or for women whose labors are progressing rapidly.

* KEYWORDS Analgesia, obstetric; injection, intrathecal; analgesia, epidural. (J Fam Pract 2002; 51:630-635)

**********

The subarachnoid injection of opioids, a technique termed "intrathecal narcotics" (ITNs), was first adapted to obstetric practice in the early 1980s (1) and has since been achieving increasing acceptance as a safe and effective method for managing labor pain. Compared to epidural local anesthetics, ITNs are easy to administer, provide rapid onset pain relief, and do not cause motor blockade. (2-4) Compared to parenteral opioids, ITNs provide better pain control and are less likely to result in neonatal respiratory depression. (5) Despite these advantages, there is uncertainty as to whether ITNs are an analgesic option that deserves wider acceptance, or whether they have a role distinct from the combined spinal epidural technique.

Studies of ITNs given as pan of a combined spinal epidural have documented a rapid onset of profound pain relief during the first stage of labor. (2-4,6) However, in these studies, when the initial dose of subarachnoid opioid wore off, epidural drugs were administered either immediately or within 1 to 3 hours. Therefore, these studies fail to provide information about the effectiveness of stand-alone ITNs during advanced first- and second-stage labor.

Existing studies of stand-alone ITNs have in fact been favorable to the technique. (7,9) However, these studies used patients' retrospective assessments or nurses' comments in the medical record rather than pain scores obtained during labor. No prospective studies have documented pain scores during the second stage of labor in women receiving ITNs as a sole labor analgesic. Nor have there been direct comparisons of second-stage pain scores involving women receiving ITNs and women receiving continuous infusion epidural drugs. This prospective study was therefore undertaken to compare the effectiveness of stand-alone ITNs to that of epidural analgesia in the first and second stages of labor, as well as to compare women's satisfaction with their pain management and their subjective experiences with side effects.

METHODS

Setting and subjects

Fairview University Medical Center is a merged community-university teaching hospital with more than 4000 births per year. In 1999, 50% of women undergoing spontaneous vaginal delivery received ITNs and only 6% had epidural analgesia. Although both methods are available to patients, institutional culture has historically favored ITNs, perhaps because a managed care environment favors a simple, cost-effective method. (2,10) The Labor Pain Management Study was approved by the University of Minnesota's Committee on Human Subjects.