Efficacy and safety of intrathecal morphine for pain control after spinal surgery: a systematic review and meta-analysis

OBJECTIVE: This study aimed to assess the efficacy and safety of intrathecal (IT) morphine for postoperative pain control in adults undergoing spinal surgeries. We searched the electronic databases of PubMed, Embase, and CENTRAL up to 1st January 2021 for randomized controlled trials (RCTs) or controlled clinical trials (CCTs) comparing IT morphine with placebo or other analgesics. Twelve studies were included. Eleven were RCTs and one was a CCT. Our meta-analysis indicated a statistically significant reduction of pain scores with IT morphine at 2 hours, 4 hours, 6 hours, 8 hours, 12 hours, and 24 hours; but no significant difference at 48 hours. Meta-analysis indicated a statistically significant reduction in analgesic consumption with IT morphine as compared to control. Pooled analysis indicated that IT morphine had no statistically significant effect on length of hospital stay. Our analysis indicated no statistically significant difference in the risk of nausea, vomiting, sedation, respiratory depression, headache, and urinary retention between IT morphine and control groups. The incidence of pruritis was significantly increased in the IT morphine group. The certainty of the evidence was judged to be "moderate" for pain scores at 12 hours, 24 hours, and analgesic consumption. To conclude, our review indicates that IT morphine results in significantly better pain control in the first 24 hours after spinal surgery. The risk of pruritis is significantly increased with the use of IT morphine but not for other opioid-related adverse events. Future RCTs should focus on finding the most optimal dose of IT morphine for spinal surgeries.