- Design
- Single-centre, randomised, placebo-controlled phase 2 trial
- Population
- 120 adults having arthroscopic rotator cuff repair with interscalene block and general anaesthesia
- Primary outcome
- Rebound pain within 24 hours
- Effect
- 23.3% versus 36.7%; relative risk 0.64 (95% CI 0.36 to 1.12), P = 0.163
In a single-centre phase 2 trial, 120 adults having arthroscopic rotator cuff repair under general anaesthesia and interscalene block received intravenous lidocaine (1 mg/kg loading dose, then 2 mg/kg/h during surgery) or saline. The primary outcome was rebound pain within 24 hours.
Rebound pain occurred in 14 of 60 (23.3%) with lidocaine and 22 of 60 (36.7%) with saline (risk difference -13.3%, 95% CI -28.8% to 3.1%; relative risk 0.64, 95% CI 0.36 to 1.12). Peak movement pain scores were the same. Intraoperative remifentanil use was lower with lidocaine by about 82 micrograms per hour. Higher shoulder scores and lower central sensitisation scores with lidocaine were exploratory.
A corrected calculation showed about 82 evaluable patients per group were needed, so the trial was probably underpowered. The point estimate favours lidocaine but the interval includes no effect, and the authors say a larger trial is needed before recommending it.
- Rebound pain was 23.3% with lidocaine and 36.7% with saline, not a statistically significant difference.
- The trial had fewer patients than its corrected sample-size calculation required.
- Intraoperative remifentanil use was lower with lidocaine.
- Shoulder and sensitisation scores were exploratory outcomes.
- Wait for an adequately powered trial before adopting lidocaine infusions for this purpose.
Why it matters
Rebound pain after nerve blocks is a common early problem and drives opioid use at home.
Don't overread it
A non-significant primary result in an underpowered phase 2 trial is inconclusive, not evidence of no effect, and the secondary findings were exploratory.
The statistics, in plain English
A relative risk of 0.64 with an interval of 0.36 to 1.12 is compatible with a large benefit, no effect, or a small harm. The trial neither showed benefit nor ruled it out because it was too small.
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