Anesthesia for the superior laryngeal nerves and tartaric acid-induced cough.
OBJECTIVE
The internal branch of the superior laryngeal nerve (ibSLN) conveys impulses for the laryngeal cough reflex, which protects the laryngeal aditus and prevents the development of aspiration pneumonia. The purpose of this study was to determine the effect of bilateral anesthesia of the ibSLN on the cough reflex after inhalation of a nebulized chemoirritant solution of tartaric acid.


METHODS
Prospective, clinical investigation.


METHODS
Outpatient.


METHODS
Nine healthy volunteers.


METHODS
Bilateral injections of 2% lidocaine solution without epinephrine into the paraglottic space containing the ibSLN.


METHODS
The tidal volume after inhalation of a nebulized 20% tartaric acid solution and forced vital capacity (FVC) were measured before and after injection. Data were analyzed using the Wilcoxon signed ranks, Mann-Whitney, and sign tests.


RESULTS
Complete anesthesia of the ibSLN abolished the laryngeal cough reflex. Postinjection tidal volumes were significantly lower than preinjection volumes (p<.01). The decrease in tidal volumes for six subjects with complete bilateral anesthesia was significantly larger than the decrease in tidal volumes for three subjects with partial anesthesia (p<.05). FVC in both the six subjects with complete bilateral anesthesia and the three subjects with partial anesthesia did not significantly change from preinjection to postinjection. None of the subjects in this study had complications or adverse respiratory sequelae.


CONCLUSIONS
Tartaric acid-induced cough may be useful in assessing the integrity of the laryngeal cough reflex after anesthesia or in patients with neurologic injury who are at risk of developing aspiration pneumonia. It may also be useful in making the decision whether to resume oral feeding.
Addington
W R
WR
Breyard Rehabilitation Medicine, Melbourne, FL 32901, USA.
Stephens
R E
RE
Goulding
R E
RE
D000280:Administration, Inhalation; D000328:Adult; D000772:Anesthesia, Local / Q000009:adverse effects*; D000779:Anesthetics, Local / Q000009:adverse effects*; D003371:Cough / Q000139:chemically induced* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007509:Irritants / Q000008:administration & dosage / Q000009:adverse effects*; D007823:Laryngeal Nerves / Q000187:drug effects* / Q000502:physiology*; D008012:Lidocaine / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012018:Reflex / Q000187:drug effects*; D013644:Tartrates / Q000008:administration & dosage / Q000009:adverse effects*; D013990:Tidal Volume / Q000187:drug effects; D014797:Vital Capacity / Q000187:drug effects
D000779:Anesthetics, Local; D007509:Irritants; D013644:Tartrates; D008012:Lidocaine; C029768:tartaric acid