Miller vs Macintosh size 0 and 1 blades for tracheal intubation of infants under 6 months: a randomized comparative study

Forty children undergoing elective surgery will be enrolled in the study. Infants will be randomized (using www.random.com) into two groups, the Miller and Macintosh blade groups, and whether the assigned blade is inserted above or below the epiglottis first, with allocation stored within sealed opaque envelopes until consent is obtained. The straight Miller laryngoscope blade is traditionally recommended for intubation in infants, due to the large size and flexibility of the infant and the Macintosh is the predominate model of the curved blade types. After standart anesthesia induction the assigned blade will be inserted into the mouth. All laryngoscopies will be performed by one of three paediatric anaesthetists. The Miller blade will be inserted into the mouth at the right commissure and the tongue swept gently to the left. The best laryngeal view will be achieved by optimizing the head position and applying external pressure to the larynx. As described by Passi et al., two laryngeal views will be obtained with the same blade in each patient: lifting the epiglottis or the tongue base. The order of the views (lifting the epiglottis or the tongue base) will be determined by randomization immediately before laryngoscopy. The laryngeal views will be photographed each time by an anaesthetist using a digital Olympus camera without using flash. The camera will be optimally positioned before laryngoscopy in order to capture the best possible views. The photos will be reviewed by a blinded anaesthetist using the percentage of glottic opening (POGO) score . This anaesthetist will be blinded to the study hypothesis as well as which blade was used and where it was placed. We will photo the child’s name and the randomization code—blade type and which view was taken before and after each photo of the larynx. Then the photos will be uploaded and the number of the photo will be recorded in the study record for the child so we will know which photo corresponds to which blade and position for each child. After all the photos are taken, they will be randomized and given to the blinded observer to measure the vocal cord span.