Postoperative pain relief using intrathecal morphine for lumbar spine decompression and instrumentation surgery: A comparative study of two different doses

Background and Aims: Patients undergoing lumbar spine instrumentation surgery suffer severe postoperative pain which is difficult to treat by conventional multimodal analgesic methods. We aimed to compare the analgesic effect of two different doses of intrathecal morphine (ITM) 0.2 mg and 0.3 mg in patients undergoing lumbar spine decompression and instrumentation surgery. Design: This was a randomized, prospective, double-blinded study. Materials and Methods: After approval from the Institutional Ethics Committee, forty American Society of Anesthesiologists 1 and 2 patients of either sex aged 18 years or older undergoing lumbar spine surgery were randomly assigned to receive ITM either 0.2 mg (Group A, n = 20) or 0.3 mg (Group B, n = 20) in 2 ml saline before general anesthesia. A morphine intravenous patient-controlled analgesia (PCA) device was used for rescue analgesia in the postoperative period. Assessment parameters included hemodynamics, sedation score, pain using numeric rating scale (NRS), total consumption of PCA morphine recorded for 24 h, and patient's satisfaction score. The data were analyzed using Chi-square test for categorical variables and Student's t-test for quantitative variables. Results: NRS score was significantly low in Group B at 4, 8, 12, and 24 h as compared to Group A (P < 0.05). Group B also had decreased requirement for rescue analgesia (P = 0.001) with higher patient satisfaction. There was no significant difference between the two groups in other studied parameters. Conclusions: 0.3 mg ITM provided superior analgesia postoperatively in terms of NRS score and higher patient satisfaction compared to 0.2 mg with no significant difference in the incidence of side effects