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Intrathecal Morphine Reduces Wound Hyperalgesia in Women Undergoing an Elective Cesarean Delivery
Abstract Number: F-35
Abstract Type: Original Research
Wound hyperalgesia is associated with acute post-cesarean pain (1) and chronic post-surgical pain (2). In addition, opioid-induced hyperalgesia (OIH) has been suggested to occur when intrathecal (IT) fentanyl is added to the spinal solution in women undergoing elective cearean deliveries (3). This study was designed to evaluate whether IT morphine affects wound hyperalgesia.
At the time of a clinical practice change in our hospital of adding IT morphine (100mcg; M) to a standard spinal solution containing bupivacaine (12mg; B) and fentanyl (20mcg; F) for elective cesarean deliveries, we decided to prospectively enroll all consecutive women between March and December 2013. According to day allocation, women either received BF&M on Monday-Tuesday-Wednesday, or BF only on Thursday. Breakthrough pain was treated with paracetamol 1g q8h, ibuprofen 600mg q12h, dipyrone 1g q4h. Outcome measures included: average post-op pain scores (verbal numeric rating score; 0-100) at rest, upon movement, uterine cramping at 24h and 48h, and number of analgesic requests. Extent of wound hyperalgesia was evaluated with a von Frey filament (180g of pressure) 48h post-op around the area of the scar as previously described (1), by an investigator blinded to the IT solution. Statistical analysis included t-test for equality of means (p<0.05).
Out of the 185 enrolled women during the study period, 36 received BF only and 149 BF&M. Adding M to the IT solution not only significantly reduced pain severity at 24h and the number of analgesic requests as expected, but also reduced the wound hyperagesia index (Table).
IT morphine added to IT fentanyl reduced post-operative wound hyperalgesia at 48h. Further studies are needed to evaluate whether this measurable decrease in post-operative wound hyperalgesia correlates with overall better long term outcomes. Within the setting of this study design, there was no evidence for OIH in women receiving IT morphine.
1. Eur J Pain 2013;17:111-23
2. Anesh Analg 107:2008:948-57
3. Int J Obstet Anest 2012;21:29-34