British Journal of Anaesthesia, Vol 82, Issue 6 857-860, Copyright © 1999 by The Board of Management and Trustees of the British Journal of Anaesthesia
A. P. Hall, A. J. Fox, J. H. Raphael, N. Nandwani and G. Smith
Patients presenting for elective anaesthesia and surgery may be suffering
with, or recovering from, a recent upper respiratory tract infection.
Airway reflexes are heightened and these individuals may be more likely to
suffer airway complications on administration of general anaesthesia. We
have examined the effect of nebulized lidocaine on upper airway reflexes in
such subjects. Using dilute ammonia as a chemical stimulus to the upper
airway, we measured upper airway reactivity in 15 volunteers (aged 22-43
yr) with symptoms of an upper respiratory tract infection for 4 days or
less. The threshold concentration of ammonia producing a brief reduction in
inspiratory flow was determined. Measurements were made before and after
administration of a nebulized solution of 4% lidocaine 4 ml or saline.
After a 2-h interval the procedure was repeated with the alternative
solution. The order of administration was randomized. The observer was
blind to the solution given. Ammonia threshold was found to increase in
subjects after nebulized lidocaine, from a median value of 327 (range
76-878) ppm to 878 (251-1620) ppm (P = 0.0007, Wilcoxon); there was no
significant change after nebulized saline. After a convalescence period of
at least 4 weeks, with no return of symptoms in the preceding 2 weeks,
ammonia threshold was reassessed. It was found to be increased in all 15
subjects. Comparison of the five different times of measurement showed a
highly significant difference (P < 0.001, Friedman). Subsequent analysis
showed significant differences (P < 0.05, Wilcoxon) between convalescent
ammonia threshold and both baseline and post-saline nebulizer values. There
was no significant difference between convalescent and post-lidocaine
ammonia threshold. We conclude that in adult subjects, nebulized lidocaine
attenuated the heightened airway reflex sensitivity associated with
symptoms and signs of upper respiratory tract infection.
CLINICAL INVESTIGATIONS
Upper airway reactivity and upper respiratory tract infection: effect of nebulized lidocaine
University Department of Anaesthesia, Leicester Royal Infirmary, Leicester LE1 5WW, UK
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