Combined Spinal Epidural (CSE) Analgesia in Labor May Reduce Subsequent Efficacy of Epidural Morphine Administered for Cesarean Section
Abstract Number: 50
Abstract Type: Original Research
Introduction: Opioid-induced hyperalgesia is a well-described phenomenon in which exposure to opioid analgesics causes subsequent increased sensitivity to nociceptive stimulation. We hypothesized that the intrathecal administration of potent lipophilic opioids as part of combined spinal-epidural (CSE) analgesia in labor may reduce the subsequent efficacy of epidural morphine administered for cesarean delivery.
Methods: With approval of the IRB, we reviewed records of patients who received neuraxial analgesia for labor followed by an unplanned cesarean delivery for any indication. Patients with inadequate labor analgesia and those with a history of opioid use during pregnancy were excluded. A case-control methodology was employed, in which each patient initially receiving CSE labor analgesia was matched to the next patient who received conventional epidural analgesia and underwent cesarean delivery for failure to progress. CSE was standardized as 2.5 mg plain bupivacaine and 25 mcg fentany, followed by patient-controlled epidural analgesia (PCEA) with bupivacaine 0.125% and fentanyl 2 mcg/mL at 6 mL/hr with a 6 mL bolus and 20 minute lockout. Epidural analgesia was initiated with 20 mL 0.125% bupivacaine with fenanyl 2 mcg/mL, followed by the same PCEA regimen. Anesthesia for cesarean delivery was standardized and was achieved with lidocaine 2% with epinephrine 1:200,000 as required to achieve a T4 dermatomal level. Eight patients received 3% chloroprocaine prior to Lidocaine 2% with epinephrine 5 mcg/ml. Fentanyl 100 mcg and morphine 3 mg was administered after establishment of surgical anesthesia. Patient demographics, timing of administration of CSE or epidural analgesia, total dose of fentanyl administered during labor, physician top-ups during labor, and timing of morphine administration were recorded. Postoperative visual analogue (VAS) pain scores and supplemental analgesics were abstracted from the nursing record. Differences between CSE and Epidural groups were tested by ANOVA or chi square, as appropriate.
Results: 52 records have been reviewed to date. Age, height, gravidity, parity, gestational age, and history of prior cesarean did not differ between analgesic groups. CSE patients were slightly heavier (198 vs. 176 lb, P=.051). Duration of epidural infusion, total epidural fentanyl, and physician-administered top-ups did not differ between groups. Supplemental analgesia did not differ between groups. The use of 3% chloroprocaine in some of the patients did not significantly alter analgesic requirements. The highest recorded VAS pain score was significantly higher in the CSE group than in the epidural group (mean [95% CI], 7.0 [6.5, 7.5] vs. 5.9 [ 5.6, 6.6], P=0.018).
Discussion: In this preliminary analysis, it appears that exposure to CSE analgesia may result in greater postoperative pain and/or less effective analgesia from epidural morphine. Further investigation into this phenomenon is warranted.