Analgesic effects of adding lidocaine to morphine pumps after orthopedic surgeries

Background: Opiate is used in patient-controlled intravenous analgesia pumps (PCIA) for controlling pain in post-surgical patients. Other drugs are remarkably added to opioid pumps to enhance quality, lengthen analgesia, and reduce side eff ects. Lidocaine, a local anesthetic which inhibits sodium channels, has anesthetic and analgesic eff ects when injected locally or intravenously. Th e objective of this study is to evaluate the analgesic eff ects of adding lidocaine 1% to diff erent doses of morphine via IV pump to patient-controlled analgesia (PCA) after orthopedic surgeries. Materials and Methods: In a randomized clinical trial, 60 patients who had undergone orthopedic surgery of lower extremities were divided into three equal groups to control postoperative pain. Intravenous pump with 5 ml/h fl ow rate was used as the analgesic method. Th e solution consisted of lidocaine 1% plus 20 mg morphine for the fi rst group, lidocaine 1% plus 10 mg morphine for the second group, and only 20 mg morphine for the third group (control group). Patients were checked every 12 h, and Visual Analog Scale (VAS), extra opioid doses, nausea/vomiting, and sedation scale were examined. Results: Pain score was lower in the fi rst group compared to the other two groups. Mean VAS was 2.15 ± 0.2, 2.75 ± 0.2, and 2 ± 0.25 on the fi rst day and 1.88 ± 0.1, 2.74 ± 0.3, and 2.40 ± 0.3 on the second day, respectively, in the three groups and the diff erence was statistically signifi cant (P < 0.01 and <0.05, respectively). Also, 10% of patients in the fi rst group needed extra opioid doses, while this fi gure was 30% in the second group and 25% in the third group (P < 0.01). Nausea/vomiting and sedation scores were not statistically diff erent among the three groups. Conclusion: Compared to lidocaine 1% plus 10 mg morphine or 20 mg morphine alone in PCIA, adding lidocaine 1% to 20 mg morphine decreases the pain score and opioid dose after orthopedic surgeries without having side eff ects.