Impact of high concentrations of sevoflurane on laryngeal reflex responses.
BACKGROUND
Exaggerated defensive upper airway reflexes, particularly laryngospasm, may cause hypoxemic damage, especially in children. General clinical experience suggests that laryngeal reflex responses are more common under light levels of anesthesia, and previous clinical studies have shown an inverse correlation between laryngeal responsiveness and depth of hypnosis. However, this seems to be less obvious in children anesthetized with sevoflurane. The aim of this study was to assess the impact of high concentrations of sevoflurane on laryngeal and respiratory reflex responses in spontaneously breathing children. Accordingly, we tested the hypothesis that laryngeal and respiratory reflex responses were completely suppressed in spontaneously breathing children when anesthetized with sevoflurane 4.7% (=MACED95Intubation) as compared with sevoflurane 2.5% (=1 MAC).


METHODS
In this prospective observational study, we tested the hypothesis that the incidence of laryngospasm evoked by laryngeal stimulation is diminished under high concentrations of sevoflurane. Following Ethics approval, trial registration, and informed consent, 40 children (3-7 years) scheduled for elective surgery participated in the trial. All children received sevoflurane 2.5% (1 MAC) and 4.7% (ED95Intubation) in random order with 5-min equilibration between the states. Under both conditions, distilled water was sprayed under bronchoscopic view onto the larynx. Potential laryngeal and respiratory reflex responses were assessed offline by a blinded reviewer.


RESULTS
Laryngospasm (episodes lasting >10 s) occurred in 12/38 (32%) of the patients anesthetized with sevoflurane 2.5%, vs 7/38 (18%) in those anesthetized with sevoflurane 4.7% (difference: OR 3.5; 95% CI [0.72-16.84], P = 0.18). All other reflex responses (coughing, expiration reflexes, and spasmodic panting) were infrequent and were similar among the examined concentrations.


CONCLUSIONS
Against our hypothesis, laryngospasm could still be observed in 18% of children under the higher concentration of sevoflurane (4.7%, ED95Intubation).
Department of Anesthesia, University of Basel Children's Hospital, Basel, Switzerland.
Thomas O
TO
Erb
Department of Anaesthesia and Pain Management, Princess Margaret Hospital for Children, Perth, WA, Australia.|School of Medicine and Pharmacology, The University of Western Australia, Perth, WA, Australia.
Britta S
BS
von Ungern-Sternberg
Department of Anesthesia, University of Basel Children's Hospital, Basel, Switzerland.
Jens
J
Moll
Department of Anesthesia, University of Basel Children's Hospital, Basel, Switzerland.
Franz J
FJ
Frei
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007826:Laryngismus / Q000517:prevention & control*; D007830:Larynx / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D011446:Prospective Studies; D012018:Reflex / Q000187:drug effects; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane
anesthesia; child; laryngeal reflexes; laryngospasm; respiratory adverse events; sevoflurane