Cough: why care?

Although often minor, common post-operative complications have by definition a broad impact on the perioperative experience. Some common complications, such as coughing on extubation, can also have significant surgical consequences such as for neurosurgical or ophthalmic procedures.

Both coughing on extubation (reported incidence 15-94%) and post-operative sore throat (21-72%) are very common among surgical patients.

What did they do?

Yang and team performed a high-quality meta-analysis of RCTs investigating the effect of intravenous lidocaine/lignocaine on coughing at extubation. Many of these trials also looked at further secondary effects, such as post-operative sore throat. They included 16 trials, totalling 1,516 subjects. Although the trials demonstrated significant heterogeneity, subgroup analyses still confirmed the study's findings.

And they found...

There was significant reduction in cough RR 0.64 (0.48-0.86 & NNT=5), and post-operative sore throat RR 0.46 (0.32-0.67), though no difference in laryngospasm, adverse events or time to extubation with modern volatile agents.

Analysing various lidocaine timings (pre-operative vs intra-operative) and dose ranges (low <1.5mg/kg or high >1.5 mg/kg) yielded no evidence of clear advantage. Nonetheless the findings are consistent with previous reviews, such as from Clivio et al. (2019) showing lidocaine 1.5 mg/kg reduced cough (RR: 0.44; 0.33–0.58), and that the effect is probably dose responsive.

Ok, but how does lidocaine work?

The mechanism of action reducing cough is not understood, although several possibilities have been proposed, including...

"...the suppression of airway sensory C fibres, the reduction of neural discharge of peripheral nerve fibres, and the selective depression of pain transmission in the spinal cord."

Bottom-line

Peri-operative intravenous lignocaine effectively reduces coughing on extubation and reduces post-operative sore throat, without any increase in adverse events.

summary

• Stephen S Yang, Ning-Nan Wang, Tatyana Postonogova, Grace J Yang, Michael McGillion, Francois Beique, and Thomas Schricker.
• Department of Anesthesia, McGill University, Montreal, QC, Canada. Electronic address: stephen.yang@mail.mcgill.ca.
• Br J Anaesth. 2020 Mar 1; 124 (3): 314-323.

BackgroundIn surgical patients undergoing general anaesthesia, coughing at the time of extubation is common and can result in potentially dangerous complications. We performed a systematic review and meta-analysis to assess the efficacy and safety of i.v. lidocaine administration during the perioperative period to prevent cough and other airway complications.MethodsWe searched Medical Literature Analysis and Retrieval System, Excerpta Medica database, and Cochrane Central Register of Controlled Trials for RCTs comparing the perioperative use of i.v. lidocaine with a control group in adult patients undergoing surgery under general anaesthesia. The RCTs were assessed using risk-of-bias assessment, and the quality of evidence was assessed using Grading of Recommendations, Assessment, Development and Evaluations (GRADE).ResultsIn 16 trials (n=1516), the administration of i.v. lidocaine compared with placebo or no treatment led to large reductions in post-extubation cough (risk ratio [RR]: 0.64; 95% confidence interval [CI]: 0.48-0.86) and in postoperative sore throat at 1 h (RR: 0.46; 95% CI: 0.32-0.67). There was no difference in incidence of laryngospasm (risk difference [RD]: 0.02; 95% CI: -0.07 to 0.03) or incidence of adverse events related to the use of lidocaine.ConclusionsThe use of i.v. lidocaine perioperatively decreased airway complications, including coughing and sore throat. There was no associated increased risk of harm.Copyright © 2019 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

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