Total knee arthroplasty: epidural morphine improves postoperative analgesia

  • Meng ZT & al.
  • PLoS ONE
  • 1 Jan 2019

  • curated by Sarfaroj Khan
  • UK Clinical Digest
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Takeaway

  • Addition of low-dose epidural morphine to single-injection femoral nerve block improves moderate-to-severe pain and reduces opioid consumption within 48 hours following total knee arthroplasty (TKA).
  • It also improves the mental health-related quality of life at 30 days after surgery, without increasing adverse events.

Why this matters

  • Patients after TKA often develop moderate to severe pain.
  • Analgesic techniques have been greatly improved, however, the effect is far from optimal.

Study design

  • In a randomised, double-blind, placebo-controlled trial, 110 patients undergoing TKA were randomly assigned to receive either epidural morphine (2 mg diluted to 5 mL normal saline) or placebo (5 mL normal saline).
  • Pain severity was assessed at 6, 12, 24, 36 and 48 hours after surgery with the numerical rating scale (NRS, an 11-point scale where 0=no pain and 10=the worst pain).
  • Primary outcome: moderate-to-severe pain (NRS pain score ≥4) within 48 hours after surgery.
  • Funding: None.

Key results

  • The epidural morphine group had a significantly lower percentage of patients with moderate-to-severe pain within 48 hours than placebo (58.2% vs 76.4%; OR, 0.43 [95% CI, 0.19-0.98]; P=.042).
  • Cumulative morphine consumption within 48 hours was significantly lower in the epidural morphine group vs placebo group (18.4±6.1 mg vs 22.4±7.3 mg; P=.002).
  • The mental component summary score of quality of life (SF-12) at 30 days was significantly higher in the epidural morphine group than in the placebo group (63.8±2.9 vs 61.9±4.2; P=.008).
  • There were no significant differences in the incidence of adverse events between the 2 groups.

Limitations

  • Single-centre study.