Laryngeal chemoreflexes induced by acid, water, and saline in nonsedated newborn lambs during quiet sleep.
Laryngeal chemoreflexes (LCR) are triggered by the contact of assorted liquids with the laryngeal mucosa. In the neonatal period, the immature LCR consist primarily of apnea and bradycardia, which at times can be life threatening. The aim of this study was to assess LCR induction in nonsedated, newborn full-term lambs by several acid solutions, compared with distilled water and saline. Twelve lambs were instrumented for recording of glottal adductor and diaphragm EMG, EEG, eye movements, heart rate, systemic arterial pressure, and respiratory movements. LCR were induced during quiet sleep by the injection (0.5 ml) of saline, distilled water or two acid solutions (HCl and citric acid, pH 2, diluted in either water or saline). A chronic supraglottal catheter was used to inject the solutions in a random order. Distilled water and acid solutions did not induce any significant decrease in heart rate or respiratory rate. However, significant lower airway protective responses (swallowing, cough, and arousal) were observed after distilled water and especially acid solution administration. In conclusion, LCR in full-term lambs, particularly with acid solutions, are merely characterized by lower airway protective responses resembling mature LCR reported in adult mammals.
St-Hilaire
Marie
M
Depts. of Pediatrics and Physiology, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
Nsegbe
Elise
E
Gagnon-Gervais
Karine
K
Samson
Nathalie
N
Moreau-Bussière
François
F
Fortier
Pierre-Hugues
PH
Praud
Jean-Paul
JP
D000143:Acids / Q000008:administration & dosage*; D000818:Animals; D000831:Animals, Newborn; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D016292:Procedural Sedation; D004305:Dose-Response Relationship, Drug; D007823:Laryngeal Nerves / Q000187:drug effects / Q000502:physiology; D007830:Larynx / Q000187:drug effects / Q000502:physiology*; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D012132:Respiratory Muscles / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D012756:Sheep; D012890:Sleep / Q000187:drug effects* / Q000502:physiology*; D012965:Sodium Chloride / Q000008:administration & dosage*; D014867:Water / Q000008:administration & dosage*
D000143:Acids; D014867:Water; D012965:Sodium Chloride