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To the Editor,
We thank Drs Basaran, Yilbas, and Kutahya for their interest1 in our report describing the effects of inflating endotracheal tube (ETT) cuffs with air, lidocaine, or ropivacaine on postoperative sore throat (POST) and for their thought-provoking comments.2 Our sample size calculation assumed the 50% rate of POST described in control groups from a systematic review of intracuff lidocaine.3 We agree, our observed rates of POST 24 h following surgery in the control (4/20 [20%]), ropivacaine (6/21 [29%]), and lidocaine (6/19 [32%]) groups were lower than expected. While lower than anticipated, we chose to see this as positive for our patients. These low POST rates may be due to our ETT cuff inflation protocol using the stethoscope-guided inflation technique described by Kuman and Hirsch.4
As Dr. Basaran correctly points out, we did not report the duration of intubation amongst our study patients. Our median [interquartile range] intubation duration was 145 [105–219], 180 [105–225], and 180 [105–225] min for air, ropivacaine, and lidocaine, respectively (P = 0.84). A report describing the association of POST with duration of anesthesia indicated the mean (standard deviation) duration was 180 (88) min in those experiencing POST and 158 (77) min in those who did not experience POST.5 The patients in our control group experienced generally shorter intubations. Nevertheless, the duration of intubation in our patients for ropivacaine and lidocaine were between these two medians, making definitive comment regarding the possibility of our data set underrepresenting long procedure times difficult. That said, the same study showed only a weak positive correlation between the intensity of sore throat and the duration of anesthesia (Spearman’s r = 0.12) and the odds ratio (OR) of sore throat as a function of anesthesia time had only a moderate effect (OR, 1.27).5 We agree it remains possible that intracuff local anesthetic may reduce POST for longer cases, although a significant clinical benefit is unlikely.
References
Basaran B, Yilbas AA, Kutahya E. Comment on: Intracuff local anesthetic to reduce postoperative sore throat: a randomized clinical trial. Can J Anesth 2020. DOI: https://doi.org/10.1007/s12630-020-01690-9.
McLachlan M, Gamble J, O’Brien JM, McKay WP, Bajwa JS. Intracuff local anesthetic to reduce postoperative sore throat: a randomized clinical trial. Can J Anesth 2020; 67: 495-7.
Lam F, Lin YC, Tsai HC, Chen TL, Tam KW, Chen CY. Effect of intracuff lidocaine on postoperative sore throat and the emergence phenomenon: a systematic review and meta-analysis of randomized controlled trials. PLoS One 2015; DOI: https://doi.org/10.1371/journal.pone.0136184.
Kumar RD, Hirsh NP. Clinical evaluation of stethoscope-guided inflation of tracheal tube cuffs. Anaesthesia 2011; 66: 1012-6.
Biro P, Seifert B, Pasch T. Complaints of sore throat after tracheal intubation: a prospective evaluation. Eur J Anaesthesiol 2005; 22: 307-11.
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This submission was handled by Dr. Gregory L. Bryson, Deputy Editor-in-Chief, Canadian Journal of Anesthesia.
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McLachlan, M., Gamble, J. & O’Brien, J. In reply: Does length of intubation explain the failure of intracuff local anesthetic to reduce postoperative sore throat. Can J Anesth/J Can Anesth 67, 1303–1304 (2020). https://doi.org/10.1007/s12630-020-01691-8
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DOI: https://doi.org/10.1007/s12630-020-01691-8