Les pressions élevées du masque laryngé, causées par le protoxyde d’azote, n’augmentent pas les lésions muqueuses chez les chiens

Abstract

P Pu ur rp po os se e: : During general anesthesia, nitrous oxide (N 2 O) diffuses rapidly into the air-filled laryngeal mask airway (LMA) cuff, increasing intracuff pressure. There is no clear correlation between LMA intracuff pressure and pressure on the pharynx. We have studied the effects of high LMA intracuff pressures secondary to N 2 O on the pharyngeal mucosa of dogs.M Me et th ho od ds s: : Sixteen mongrel dogs were randomly allocated to two groups: G1 (intracuff volume, 30 mL; n=8) breathed a mixture of O 2 (l L·min 1 ) and air (l L·min 1 ) and G2 (intracuff volume, 30 mL; n=8) a mixture of O 2 (l L·min 1 ) and N 2 O (l L·min 1 ). Anesthesia was induced and maintained with pentobarbitone. LMA cuff pressure was measured at zero (control), 30, 60, 90 and 120 min after #4 LMA insertion. The dogs were sacrificed, and biopsy specimens from seven predetermined areas of the pharynx in contact with the LMA cuff were collected for light (LM) and scanning electron microscopic (SEM) examination by a blinded observer.R Re es su ul lt ts s: : LMA intracuff pressure decreased with time in G1 (P <0.001) and increased in G2 (P <0.001). There was a significant difference between the groups (P <0.001). In both groups, the LM study showed a normal epithelium covering the pharyngeal mucosa and mild congestion in the subepithelial layer. There were no differences between the groups (P >0.10) or among the areas sampled (P >0.05). In both groups, the SEM study showed a normal pharyngeal mucosa with mild superficial desquamation. Few specimens in G1 and G2 showed more intense epithelial desquamation.C Co on nc cl lu us si io on n: : High LMA intracuff pressures produced by N 2 O do not increase pharyngeal mucosal injury in dogs.Objectif : Pendant l anesthésie générale, le protoxyde d azote (N 2 O) diffuse rapidement dans le ballonnet gonflable du masque laryngé (ML), ce qui augmente la pression intraballonnet. Il n existe pas de corrélation évidente entre cette pression et la pression sur le pharynx. Nous avons étudié les effets de pressions élevées à l intérieur du ballonnet du ML, secondaires au N 2 O, sur la muqueuse pharyngée de chiens. Résultats : La pression intraballonnet du ML a diminué avec le temps dans le G1 (P < 0,001) et augmenté dans le G2 (P < 0,001). Il n y a pas eu de différence intergroupe significative ( P < 0,001). Dans les deux groupes, l examen MC a montré qu un épithélium normal recouvrait la muqueuse pharyngée et qu une congestion mineure existait dans la couche sous-épithéliale. Encore ici, il n y a pas eu de différence intergroupe (P > 0,10) ou de différence entre les zones échantillon-nées (P > 0,05). Dans les deux groupes, l examen MEB a montré une muqueuse pharyngée normale et une desquamation superficielle légère. Peu de spécimens du G1 et du G2 ont affiché une desquamation épithéliale plus importante.

“Comparison of Cuff Pressure Changes Between Air with Oxygen or Nitrous Oxide with Oxygen During General Anaesthesia Using Proseal LMA for Laproscopic Surgery”

“…[20,18] Study with the PLMA suggested that directly measured mucosal perfusion pressure rarely exceeded 25 mmHg [7] and therefore, did not increase pharyngeal mucosal injury, while others recommend reducing the cuff volume until it just seals the leak . [21,22] The cuffs of PLMA inflated with maximum recommended cuff volumes, exerted lower pressures predominantly below 15 mmHg on the pharyngeal and hypopharyngeal mucosa. It was also reported that PLMA along with nasogastric tube, induce significantly higher pharyngeal pressures in posterior location when compared to other devices.…”

ProSeal TM laryngeal mask airway cuff pressure changes with and without use of nitrous oxide during laparoscopic surgery

“…[22] However, another study with the PLMA suggested that directly measured mucosal perfusion pressure rarely exceeded 25 mmHg[19] and therefore, did not increase pharyngeal mucosal injury, while others recommend reducing the cuff volume until it just seals the leak. [2324]…”

A heated humidifier does not reduce laryngopharyngeal complaints after brief laryngeal mask anesthesia

“…Ciliated pseudostratified respiratory epithelium and the stratified squamous epithelium which cover the laryngo-pharyngeal mucosa are relatively resistant to minor injury. 13 Williams et al 14 suggested that at constant suboptimal humidity, an increasing exposure time increases mucosal dysfunction. Asmundsson et al 15 also suggested that irreversible cessation of ciliary activity leading to inflammation and sloughing of the upper airway mucosa requires an exposure time to dry gases of more than three hours.…”