Effects of Interpleural Morphine on Severity of Post-Thoracotomy Pain

Thoracotomy is one of the most painful surgical procedures because of the extent of surgical insult. The aim of this study was to evaluate the effect of interpleural morphine on pain after thoracotomy. An experimental and a randomized double-blind study were designed to assign 31 patients in Masih Daneshvari Hospital, Tehran, Iran. In 16 patients, 0.2 mg/Kg morphine sulfate in 40 mL of 0.9% normal saline (N/S) was injected via interpleural (IP) catheter, after surgery. Meanwhile, 10 mL of 0.9% normal saline was administered intravenously (IV) [interpleural morphine (Ipm) group]. In 15 patients, 40 mL of 0.9% N/S IP and concurrently morphine sulfate 0.05 mg/kg in 10 mL of N/S IV were injected [interpleural sulfate (Ips) group]. After the first injection in the operating room, infusion of the aforementioned solutions was repeated every four hours, for 24 hours in ICU. The severity of pain was measured according to the facial pain scale (FPS), before drug injection and 30 minutes after it was evaluated. The results of the proportional odds marginal regression model showed significant difference between the opium and Ips groups (P = 0.024), adjusting for baseline pain scores, sex, age and time of the measurements. The reported odds ratio of the group variables was 4.18, showing that the odds of having no pain in the Ipm group were 4.18 times of the same odds in the Ips group. The negative estimation for the variable of time showed that the severity of pain decreased over time in these patients. In general, our findings revealed that administration of interpleural morphine can cause effective and favorable analgesia after thoracotomy.