Please confirm that an ethics committee approval has been applied for or granted: Yes: I’m uploading the Ethics Committee Approval as a PDF file with this abstract submission

Background and Aims Sequentially, open and combined anterior-posterior lumbar spine interbody fusion (APLF) involves: an abdominal incision a longitudinal lumbar incision and changing patient position from supine to prone or vice versa. Pain intensity and postoperative rescue morphine dose are higher compared with posterior approach only. Our study aims to evaluate whether the use of intrathecal morphine (ITM) significantly improves acute postoperative pain without increasing adverse effects or length of hospital stay (LOS).

Methods Retrospective analysis of 6 patients who underwent APLF in 2023 at our center. All patients underwent general anesthesia and multimodal analgesic regimen. Postoperatively, the paracetamol, dexketoprofen and use of IV morphine by patient-controlled analgesia pump was administered. We made 2 groups: patients without ITM and patients with 200 μg of isobaric ITM. We analyzed: use of ultrasound-guided interfascial blocks, visual analogue scale (VAS), postoperative rescue morphine dose and incidence of adverse effects and LOS.

Results Six patients were included. In the Control group, all patients reported a VAS ≥6, while all ITM Group patients reported a VAS<3. A higher dose of postoperative rescue morphine was also observed in the Control Group (median of 46 mg/24h) compared to the MIT Group (median of 1 mg/24h). In Control group, 2 patients received ultrasound-guided interfascial blocks, none of ITM group. There were no other clinically significant adverse effects and LOS.

Conclusions ITM administration has reduced VAS after APLF without increasing adverse effects or LOS. Based on our results, we will carry out a prospective study to establish the appropriate dose of ITM in APLF patients.