INTRAPERITONEAL VERSUS INTERPLEURAL MORPHINE OR BUPIVACAINE FOR PAIN AFTER LAPAROSCOPIC CHOLECYSTECTOMY

Background: Opioids can produce peripheral analgesic effects by activa tion of opioid receptors on sensory nerves. This study was designed (1 ) to examine a novel route of opioid administration, the intraperitone al injection; (2) to compare this to interpleural application, and (3) to compare opioid with local anesthetic effects under both conditions . Methods: At the end of laparoscopic cholecystectomy, 110 patients re ceived the following injections in a double-blind, randomized manner: Group 1 (n = 18) was given intraperitoneal morphine (1 mg in 20 ml sal ine) and 20 ml intravenous saline. Group 2 (n = 17) received intraperi toneal saline and 1 mg intravenous morphine, Group 3 (n = 15) received 20 ml 0.25% intraperitoneal bupivacaine and intravenous saline. Group 4 (n = 20) received interpleural morphine (1.5 mg in 30 ml saline) an d 30 ml intravenous saline. Group 5 (n = 20) received interpleural sal ine and 1.5 mg intravenous morphine. Group G (n = 20) received 30 ml 0 .25% interpleural bupivacaine and intravenous saline. Postoperative pa in was assessed using a visual analog scale, a numeric rating scale, a nd the McGill pain questionnaire. Pain localization, supplemental anal gesic consumption, vital signs, and side effects were recorded for 24 h. Results: Neither intraperitoneal nor interpleural morphine produced significant analgesia after laparoscopic cholecystectomy (P > 0.05, K ruskal-Wallis test), whereas interpleural bupivacaine was effective (P < 0.05, Kruskal-Wallis test, up to 6 h postoperatively) but not intra peritoneal bupivacaine (P > 0.05, Kruskal-Wallis test). Shoulder pain was not prevalent in the majority of patients during the first 6 h, By 24 h, about half of the patients complained of shoulder pain, which w as rated ''low'' by about one-third of all patients. No significant si de effects occurred. Conclusions: Interpleural bupivacaine (0.25%) pro duces analgesia after laparoscopic cholecystectomy. We attribute the l ack of effect of Intraperitoneal injections to the small dose and to a rapid dilution within the peritoneal cavity. The fact that interpleur al morphine (0.005%) is ineffective may be due to an intact perineuria l barrier in the noninflamed pleural cavity, which restricts the trans perineurial passage of morphine to opioid receptors on intercostal ner ves.