Canadian Journal of Anaesthesia

, Volume 43, Issue 1, pp 39–43 | Cite as

Differential effects of propofol, thiamylal and ketamine on the cricothyroid and posterior cricoarytenoid muscles of the canine larynx

  • Hiroshi Iwasaki
  • Hideya Ohmori
  • Masanori Yamauchi
  • Akiyoshi Namiki
Laboratory Investigations



To measure the electromyographic (EMC) responses of the phasic discharge in the cricothyroid (CT; a tensor muscle of the vocal folds) and the posterior cricoarytenoid (PCA; sole abductor muscle of the vocal folds) following intravenous infusion of propofol 1.0 mg · kg−1 · min−1, thiamylal 1.0 mg · kg−1 · min−1, or ketamine 0.5 mg · kg−1 · min−1 for five minutes.


Prospective, nonrandomized, controlled animal study. Setting: University research laboratory. Subjects: Fifteen mongrel dogs, including three groups of five animals in each group.


Under 0.2–0.3% halothane and oxygen anesthesia with spontaneous ventilation, phasic EMG activities of the CT and PCA muscles were recorded in an identical manner after the administration of each drug.

Measurements and main results

Propofol infusion produced almost equal suppression of EMG activity of the CT and the PCA with lime and three minutes after the start of infusion of propofol there was a significant depression of the phasic activities in the both muscles; EMG activity of the CT and the PCA was 33.8 ± 21.2 and 36.6 ± 22.9% (% of control, mean ± SD) respectively P < 0.05). Thiamylal selectively reduced rhythmic discharges in the CT muscle during spontaneous breathing and significant depression of discharge in the CT muscle was observed three minutes after the drug (47.3 ± 24.9%, P < 0.05). In contrast, both phasic EMG activities of the CT and the PCA were rhythmically active and the differential sensitivity between the CT and the PCA muscles was not observed after ketamine, even after ten minutes of administration.


This study confirms a difference in sensitivity between the CT and the PCA muscles, demonstrating that the intrinsic laryngeal muscles do not behave similarly after the administration of conventional intravenous anaesthetic agents.

Key Words

anaesthetics, intravenous: propofol, thiamylal, kelamine larynx: anatomy, vocal cords 



Mesurer la réponse électromyographique (EMG) de la décharge phasique du muscle cricothyrodien (CT: un des muscles tenseurs des cordes vocales) et la cricoaryténodien postérieur (CAP: le seul muscle abducteur des cordes vocales) après une perfusion intraveineuse de propofol 1,0 mg · kg−1· min−1, de thyamilal 1,0 mg · kg−1 · min−1 ou de kétamine 0,5 mg · kg−1 · min−1 pendant cinq minutes.

Organisation de l’étude

Prospective, non aléatoire, contrôlée, sur des animaux.


Laboratoire de recherche universitaire.


Quinze chiens de race commune divisés en trois groupes de cinq.


Sous anesthésie en ventilation spontanée à l’halothane 0,2–0,3% en oxygène, l’activité phasique EMG des muscles CT et CAP est enregistrée de manière identique après l’administration de chaque agent.

Mesures et principaux résultats

La perfusion de propofol produit une suppression presque identique de l’activité EMG du CT et CAP avec le temps. Trois minutes après le début de la perfusion de propofol, on constate une dépression importante de l’activité phasique des deux muscles; l’activité phasique du CT et du CAP est respectivement de 33,8 ± 21,2 et 36,6 ± 22,9 (% du contrôle, moyenne ± ET, P < 0,05). Par contre, l’activité EMG phasique du CT et du CAP était en harmonie et une différence de sensibilité entre les muscles CT et CAP n’a pas été observée avec la kétamine, même après dix minutes d’administration.


Cette étude confirme la différence de sensibilité qui existe entre les muscles CT et CAP et démontre que les muscles intrinseques du larynx ne se comportent pas de la même façon après l’administration des anesthésiques intraveineux usuels.


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Copyright information

© Canadian Anesthesiologists 1996

Authors and Affiliations

  • Hiroshi Iwasaki
    • 1
  • Hideya Ohmori
    • 1
  • Masanori Yamauchi
    • 1
  • Akiyoshi Namiki
    • 1
  1. 1.Department of AnesthesiologySapporo Medical University, School of MedicineSapporoJapan

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