Background <p>Postoperative (PO) pain management after spine surgery is challenging. For such surgeries, erector spinae plane block (ESPB) and intrathecal morphine (ITM) may offer effective PO analgesia. However, the lack of availability of US machines in low-resource settings and proper dose of ITM that confine the side effects may limit the use of either. Nalbuphine presents an effective approach for managing opioid-induced pruritus without diminishing PO pain relief. In first 24&#xa0;h after lumbar fusion operations under general anesthesia, the researchers examined effectiveness of bilateral ultrasound (US)-guided ESPB on PO pain and analgesic intake in comparison with ITM.</p> Methods <p>One hundred twenty patients premedicated with 4&#xa0;mg intravenous ondansetron were randomized into group E; bilateral US-guided ESPB, group M; ITM (0.2&#xa0;mg) or group C; control group. Time to first rescue analgesic (ketorolac) was the primary outcome while parameters of PO analgesic regimen and side effects were considered as secondary outcomes.</p> Results <p>Compared to C group, E &amp; M groups had longer duration to first rescue analgesic and reduced analgesic consumption within 24&#xa0;h postoperatively (<i>P</i> &lt; 0.001). Twenty-four hours after surgery, the M group had lower pain scores (<i>P</i> &lt; 0.001) and higher rates of nausea and pruritus (<i>P</i> &lt; 0.001) than the other two groups without any cases of respiratory depression.</p> Conclusions <p>The analgesic effect of 0.2&#xa0;mg intrathecal morphine after lumbar fusion operation under general anesthesia provided lower pain scores and lower analgesic demands than erector spinae plane block at the expense of a higher incidence of manageable side effects of intrathecal morphine within the first 24&#xa0;h postoperatively.</p> IRB <p>FMASU MD 102/2022.</p> Trial registration <p>ClinicalTrials.gov Identifier: NCT05338320. The date that the clinical trial was registered in the ClinicalTrials.gov. : April 14, 2022.</p>