Preoperative scar hyperalgesia is associated with post-operative pain in women undergoing a repeat Caesarean delivery.
BACKGROUND
Over 1.4 million Caesarean deliveries are performed annually in the United States, out of which 30% are elective repeat procedures. Post-operative hyperalgesia is associated with an increased risk for persistent post-surgical pain; however, there are no data on whether residual scar hyperalgesia (SHA) from a previous Caesarean delivery (CD) persists until the next delivery. We hypothesized that residual SHA may be present in a substantial proportion of women and is associated with increased post-operative pain.


METHODS
One hundred and sixty-three women scheduled for a repeat CD under spinal anaesthesia were enrolled into the study. Mechanical temporal summation (mTS) and SHA index were measured preoperatively. SHA was considered present when the index was >0. Post-operative pain scores at 12, 24 and 48 h and wound hyperalgesia (WHA) at 48 h were recorded.


RESULTS
SHA was present in 67 women 41% with a median SHA index of 0.42 (Q (25)  = 0.25; Q (75)  = 1.1, range 0.03-4.25). Women with SHA had overall higher post-operative pain scores and SHA was correlated with preoperative mTS (r = 0.164, p < 0.05), post-operative pain severity (r = 0.25, p < 0.002) and WHA at 48 h (r = 0.608, p < 0.001). Severe pain (visual analogue pain scale-S48 ≥ 7, n = 20) was predicted with a sensitivity and specificity of 60% and 62%, respectively. Positive predictive value was 18% and negative predictive value was 92%.


CONCLUSIONS
Preoperative SHA is present in 41% of women scheduled for repeat CD and is associated with increased mTS and post-operative pain. Screening for preoperative SHA may predict women at risk for increased post-operative pain, and guide post-operative analgesia to include anti-hyperalgesic drugs.
Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, USA. cortner@uw.edu
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Ortner
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Granot
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Richebé
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Cardoso
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Bollag
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Landau
D059787:Acute Pain / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology; D000293:Adolescent; D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage; D017604:Cesarean Section, Repeat / Q000009:adverse effects* / Q000706:statistics & numerical data; D059350:Chronic Pain / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology; D002921:Cicatrix / Q000453:epidemiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology; D015994:Incidence; D009020:Morphine / Q000008:administration & dosage; D010149:Postoperative Pain / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology; D059227:Postsynaptic Potential Summation / Q000502:physiology*; D011237:Predictive Value of Tests; D011247:Pregnancy; D012307:Risk Factors; D055815:Young Adult
D000701:Analgesics, Opioid; D009020:Morphine