Secondary hyperalgesia is not affected by wound infiltration with bupivacaine

The purpose of this study was to determine the effects of wound infiltration with bupivacaine on incisional pain and the zone of secondary hyperalgesia. Twenty-eight healthy parturients were studied in a double-blind randomized trial. At the time of Caesarean section one wound edge was infiltrated with saline 0.9% and the other with bupivacaine 0.25%. After 24 hr, visual analogue scores were obtained for incisional pain and the zone of secondary pain around the incision was measured. Patients served as their own controls. Visual analogue scores for the bupivacaine side of the wound were less than for the saline side (P < 0.05). The zone of secondary pain was similar overall for both sides of the wound. It is concluded that the bupivacaine-infiltrated side of the wound was less painful than the saline-injected side 24 hr postoperatively. The zone of pain measured around the wound edges was unaffected by bupivacaine or saline.