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Pre-operative scar hyperalgesia in women undergoing repeat Cesarean section
Abstract Number: 1
Abstract Type: Original Research
In the US, 1.2 Mio cesarean sections (CS) are performed annually out of which 30% are elective repeat CS (1). Acute post-CS pain and wound hyperalgesia remain an under-recognized problem that may result in chronic post-surgical pain (2). Repeat CS represents a unique pain model as few surgical procedures are actually repeated following the same exact incision and surgical protocol. To the best of our knowledge, scar mapping to assess pre-op hyperalgesia has not been evaluated in this constantly growing surgical population. We hypothesized that a substantial proportion of women have abnormal scar mapping prior to their repeat CS, and that this otherwise unsuspected scar hyperalgesia may be associated with increased post-CS pain.
165 women scheduled for repeat CS were enrolled in the study. Recall of persistent pain at previous CS was assessed. Mechanical temporal summation (mTS) & scar mapping to evaluate hyperalgesia (Fig) were tested pre-op. Spinal anesthesia was standardized (bupivacaine 12mg, fentanyl 25µg & morphine 100µg). Post-op pain scores (12, 24, 48h) and wound hyperalgesia at 48h were recorded. Statistical analysis included t-test for equality of means and Pearson correlation (p<0.05).
Recall of persistent pain at previous CS was present in 13 women (8%). Pre-op scar hyperalgesia was found in 67 women (40%) with a median hyperalgesia index (HI)=0.42 (Q25=0.25;Q75=1.1, range 0.03-4.25). Women with pre-op hyperalgesia had higher pain scores at 12, 24 and 48h post-CS (Fig) and HI was correlated with pain severity (r=0.29, p<0.001), 48h post-op hyperalgesia (r=0.594, p<0.001) and pre-op mTS (r=0.164, p< 0.05).
We report a rather high incidence of pre-op scar hyperalgesia in women scheduled for repeat CS. In addition, pre-op hyperalgesia was associated with abnormal pre-op mTS, higher post-op pain scores and post-op wound hyperalgesia. The combination of several quantitative sensory tests that all substantiate central sensitization (hyperexcitation) suggests abnormal pain modulation in these women. Pre-op wound mapping may allow predict women at higher risk for severe acute and possibly persistent pain that would justify anti-hyperalgesic drugs in addition to standard multimodal analgesia. Such an approach has already been suggested; intra-op iv ketamine was most effective in women with abnormal pre-op temporal summation (3).
1 Zhang, AJOG 2010
2 Lavandhomme, IJOA 2010
3 Lavand’homme, SOAP 2009 (A258)