It remains unclear to what extent intravenous lidocaine prevents cough and whether there is dose-responsiveness and risk of harm.
We searched electronic databases to January 1, 2017 for randomized trials comparing intravenous lidocaine with placebo for the prevention of cough in surgical patients. Primary outcome was the incidence of cough. Data were analyzed using a random-effects model and were expressed as risk ratio (RR) and number needed to treat (NNT) with 95% confidence interval.
In 20 trials in adults (n = 3062) and 5 trials in children (n = 445), intravenous lidocaine 0.5-2 mg·kg was tested for the prevention of intubation-, extubation-, or opioid-induced cough. Twenty-two trials included only American Society of Anesthesiologists I or II patients; 3 trials (n = 99) also included American Society of Anesthesiologists III patients. Lidocaine was associated with a lower incidence of cough compared to placebo in adults and children, irrespective of dosage and cough etiology. Data from adults suggested dose-responsiveness; with 0.5 mg·kg, RR was 0.66 (0.50-0.88) and NNT was 8 (5.4-14.3); with 1 mg·kg, RR was 0.58 (0.49-0.69) and NNT was 7 (4.6-8.9); with 1.5 mg·kg, RR was 0.44 (0.33-0.58) and NNT was 5 (3.3-5.2); and with 2 mg·kg, RR was 0.39 (0.24-0.62) and NNT was 3 (2.0-3.4). Adverse effect reporting was sparse.
Within a range of 0.5-2 mg·kg, intravenous lidocaine dose dependently prevents intubation-, extubation-, and opioid-induced cough in adults and children with NNTs ranging from 8 to 3. The risk of harm in high-risk patients remains unknown.