Do lidocaine infusions reduce pain after spinal surgery?

Pain is inevitable. Suffering is optional. – Buddhist proverb

Systemic lidocaine fails to improve postoperative morphine consumption, postoperative recovery and quality of life in patients undergoing posterior spinal arthrodesis. A double-blind, randomized, placebo-controlled trial doi: 10.1093/bja/aex038

Background.

It has been shown that intravenous lidocaine has analgesic benefit in abdominal surgery, but it is inconclusive whether the perioperative administration of systemic lidocaine provides adequate postoperative analgesia and enhances recovery in major orthopaedic surgery. The authors investigate whether adolescent and adult patients undergoing posterior spinal arthrodesis would have their morphine requirements reduced.

Methods.

70 patients undergoing posterior arthrodesis were enrolled in this prospective, randomised, double-blind, placebo-controlled clinical trial. Patients received total i.v. anaesthesia with propofol and remifentanil and were randomized to an adjuvant therapy with either lidocaine [i.v.-bolus injection of 1.5 mg/kg at induction of anaesthesia, followed by an in- fusion of 1.5 mg/kg/h which was continued until six hours after arrival at the post-anaesthesia care unit] or placebo (equal volumes of saline). Postoperative pain was treated with patient-controlled i.v. morphine.

Primary endpoints of this study were morphine requirements in the first postoperative 24 h.

Secondary outcomes were:

  • The severity of pain -NRS
  • PONV-NRS
  • The inflammatory response – IL6 and IL1RA measurement at 3 points in time
  • Time to recovery of bowel function
  • Length of stay
  • QoL- 1 month before and after surgery

Results.

Systemic lidocaine did not decrease morphine requirements in the first 24 postoperative hours [lidocaine-group: 48 (23) mg (mean(SD)) vs placebo-group: 51(19) mg, P 1⁄4 0.22]. Likewise, groups were not different with respect to the severity of post- operative pain, morphine consumption after 48 and 72 h, incidence of postoperative nausea and vomiting, perioperative inflammation, time to recovery of intestinal function, hospital length of stay, and quality of life (assessed preoperatively and one month postoperatively using the SF-12 physical and mental composite scores).

 Pros:

  1. robust study design (double-blind, randomized, placebo-controlled trial)
  2. the authors account for all the enrolled subjects in the flowchart.
  3. addresses a clear, clinically relevant question
  4. extremely well defined analgesic strategies
  5. the two intervention arms have similar baseline characteristics

Cons:

  1. the study was powered only for the primary outcome.
  2. the sample size was calculated based on 10 paediatric patients aged 12 to 18. The authors, I believe, realised that it would take a long time to achieve that number and expanded the inclusion criteria to patients up to 75 year-olds. The pathophysiology and the paediatric population needing spinal surgery differs significantly from the one of the ageing patient. This might have contributed to the somewhat incongruous results of this study.
  3. some would criticise the use of Remifentanyl as it is known to produce hyperalgesia.
  4. the authors use the NRS scale to quantify pain and PONV. There is a lot of inter-patient variability in terms of pain thresholds.
  5. the measurement of plasma concentration of lignocaine would have been a welcome initiative. In contrast with similar studies, the lignocaine was given in a smaller dose. It is not known if there is a minimal plasma concentration above which Lignocaine has favourable analgesic properties.
  6. unfortunately, this study fails to provide robust evidence to sway our practice one way or another and it is a good example of what can happen in research when one deviates from an agreed protocol. ( i.e. expanding the inclusion criteria after the power calculations have been done)

Summary by Dr Stefan Sevastru

 

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