Research Summary

Intrathecal Nalbuphine with Adductor Canal Block Reduces Opioid Use After Total Knee Arthroplasty

Miranda Manier, BA

Key Highlights

  • Intrathecal nalbuphine (ITN) added to adductor canal block reduced postoperative morphine requirements after total knee arthroplasty.
  • Higher-dose ITN (1.2 mg) further lowered pain scores compared with control, both at rest and during movement.
  • Side effects—including nausea, vomiting, drowsiness, respiratory depression, and shivering—did not differ significantly between groups.

This prospective randomized controlled trial evaluated the role of intrathecal nalbuphine (ITN) in enhancing analgesia when combined with adductor canal block (ACB) for patients undergoing total knee arthroplasty (TKA). Results demonstrated that ITN, at both 0.8 mg and 1.2 mg doses, significantly reduced cumulative morphine consumption postoperatively, while the higher 1.2 mg dose provided additional benefit in lowering pain scores without increasing adverse effects.

TKA is associated with substantial postoperative pain that often necessitates multimodal analgesia, including regional blocks and systemic opioids. ACB is commonly used to improve postoperative pain management while preserving motor function, yet opioid use remains a concern due to side effects and risk of dependency. Nalbuphine, a mixed opioid agonist-antagonist, has demonstrated analgesic potential when used intrathecally, with a favorable safety profile. However, evidence regarding its optimal dosing in combination with ACB has been limited, providing the rationale for this investigation.

The trial was conducted at Naresuan University Hospital and included 42 patients undergoing TKA with spinal anesthesia and ACB. Participants were randomized equally into three groups: Group A (control, no ITN), Group B (ITN 0.8 mg), and Group C (ITN 1.2 mg), with 14 patients in each group. The primary endpoint was postoperative pain intensity measured by numeric rating scale (NRS) at rest and during movement across various time points. Secondary outcomes included cumulative morphine use (CMU) and incidence of side effects such as nausea, vomiting, drowsiness, respiratory depression, and shivering.

Results showed that patients in the 1.2 mg ITN group (Group C) reported significantly lower NRS pain scores at rest at 6, 12, 24, and 48 hours postoperatively compared with the control group. Group C also had lower NRS pain scores during movement at 6 and 36 hours postoperatively. However, no significant difference in NRS was observed between the 0.8 mg ITN group (Group B) and the control, nor between Groups B and C. Both ITN groups demonstrated significantly lower CMU compared with the control group at 24, 48, and 72 hours after surgery. The incidence of side effects was not significantly different across the three groups, indicating that the addition of ITN did not increase adverse event risk.

“Additional ITN, both 0.8 and 1.2 mg doses, effectively reduces CMU during the first 72 h after TKA,” Nonsri and colleagues concluded. “Given higher-dose ITN up to 1.2 mg provides benefit by further reducing pain scores, without increased side effects.”

Reference
Nonsri C, Kositanurit I, Tewaritruangsri A, Jeephet K, Rattanaprichavej P, Laoruengthana A. Intrathecal nalbuphine at two doses reduces opioid use and pain after total knee arthroplasty: a randomized controlled trial. Eur J Orthop Surg Traumatol. 2025;35(1):341. doi:10.1007/s00590-025-04459-2