Nalbuphine versus morphine: an adjuvant to spinal anesthesia for controlling pain after total knee arthroplasty: a propensity score-matched analysis

Nalbuphine, a synthetic k-agonist and µ-antagonist, provides efficient pain relief while reducing opioid-related adverse effects. This study aims to compare the efficacy of intrathecal nalbuphine (ITN) with intrathecal morphine (ITM) for post-TKA pain.

A retrospective cohort analysis of 131 patients who underwent TKA with spinal anesthesia (SA), a single shot of adductor canal block, and periarticular injections was conducted. The patients were divided into 2 groups, Group N received 0.8 mg nalbuphine, and Group M received 0.2 mg morphine as an adjuvant to SA. Propensity-score matching was employed to compare the visual analog scales (VAS) of postoperative pain intensity, cumulative morphine use (CMU), maximum knee flexion angle, straight leg raise (SLR) ability, incidence of postoperative nausea and vomiting (PONV), and length of hospital stay (LHS).

The mean VAS of group M were significantly lower than group N at 6, 12, 18, and 24 h (P < 0.01). Group M had lower CMU than group N at 24 h (P < 0.01) and 48 h (P < 0.01), while there was no significant difference between groups in terms of knee flexion angle and SLR at any time point. Additionally, 29.3 and 57.9% of patients in group N and M experienced PONV, respectively (p = 0.04), and group N had significantly shorter LHS compared to group M (P < 0.001).

Although, intrathecal morphine (ITM) still provides better pain control particularly in the first 24 h, patients who received intrathecal nalbuphine (ITN) had significantly fewer incidence of PONV, and shorter LHS.