Effect of the Preoperative Intercostal Nerve Block in a Rat Model of Postthoracotomy Pain / 대한통증학회지

ABSTRACT

BACKGROUND: Chronic pain after thoracotomy has been recently reproduced in a rat model that allows investigating the effect of potentially beneficial drugs that might reduce the incidence of allodynia or alleviate pain. Local anesthetics produce antinociception in normal animals and alleviate mechanical allodynia in animals with nerve injury although their mechanisms of action may differ in these situations. Our purpose of this study was to test whether the preoperative intercostal nerve block of bupivacaine could prevent the development of allodynia in a rat model of chronic postthoracotomy pain. METHODS: All male Sprague-Dawley rats were anesthetized and the right 4th and 5th ribs were exposed surgically. The pleura were opened between the ribs to which a retractor was placed and was opened 10 mm in width. Retraction was maintained for one hour. Total 1 mg of 0.5% bupivacaine was injected at the intercostal nerves before (n = 17) or after (n = 16) surgery. A control group (n = 25) that underwent rib retraction did not receive any drug. Rats were tested for mechanical allodynia using calibrated von Frey filaments applied around the incision site during the three weeks following surgery. RESULTS: The incidence of development of mechanical allodynia in the group that received intercostal injection with bupivacaine before surgery was significantly lower than that in the control group (P < 0.05). CONCLUSIONS: Preoperative intercostal nerves block around the surgical incision before thoracotomy may decrease the incidence of postthoracotomy pain syndrome.