Comparing the Laryngoscopy View Using Miller and Macintosh Laryngoscopy Blades in Infants Under Two Years of Age

Overview

To compare the laryngoscopy view using two standard clinical devices, the Macintosh and Miller laryngoscopy blades, in infants between one day and two years of age. Miller blades (straight blades) are more commonly used than MacIntosh blades (curved) in pediatric clinical practice in some institutions especially in infants. The anatomy of infant airway has traditionally been considered to lend itself to advantages of the Miller blade. Some argue that the Miller blade offers a superior view of the laryngeal inlet because it lifts the epiglottis. However, others use the Miller blade to expose the larynx without lifting the epiglottis, supposedly to avoid traumatizing it. Despite the long-standing use of these blades, more than 50 years, no systematic study has ever compared the laryngoscopy views of the Miller and Macintosh blades in infants.

* After Institutional Review Board approval, the patients meeting inclusion criteria will be selected from the Operating room elective surgical list. * They will be randomized to one of the two groups: a #1 Miller or Macintosh blade. * After obtaining informed consent from the parent or the legal guardian, monitors (electrocardiogram, non-invasive blood pressure monitor and pulse oximeter) that are routine induction of anesthesia will be applied and anesthesia will be induced using an inhalation technique with sevoflurane, nitrous oxide and oxygen. An intravenous cannula will then be placed. The child will then receive a standard intubating dose of a muscle relaxant (rocuronium 0.5-1 mg/kg). The lungs will be mask ventilated using 100% oxygen in Sevoflurane for 3 minutes to allow appropriate time for the muscle relaxant to be fully effective. At that time, the randomized code for that child will be opened and laryngoscopy will be performed with either a Miller or MacIntosh blade as indicated by the code. * The best possible glottic view will be obtained by ensuring the following steps. The child's head will be positioned in the Magill position, muscle relaxant will be administered, firm forward traction will be applied to the laryngoscope handle, and if needed, external laryngeal manipulation will be applied. * During the same laryngoscopy, the best glottic visualization will be obtained with the blade lifting the epiglottis and not lifting the epiglottis, in random order (by flipping a coin). This difference is a matter of moving the position of the blade back without removing the blade from the larynx. * The two views will be recorded by a second doctor using a SONY camera at the mouth adjacent to the laryngoscope handle. * Photos of the glottic opening will be graded using the POGO scale (Ref1) by a third (blinded) anesthesiologist. * All of the intubations and image acquisition will be performed by Drs. Yuvesh Passi, Jerrold Lerman or Chris Heard. * The images obtained will not have patient identifiers included. They will be stored in a secure file once the study is completed that will be accessed only by investigators involved in the study. * No patient identifiers will be included on any documentation apart from the source documents. * The research data will be stored in a locked office of Dr. Lerman (Room 251) in Department of Anesthesia, Women and Children's Hospital of Buffalo during and after the study for security to protect subject privacy and confidentiality. * There will be no payments or compensation to the study subjects The primary hypothesis of this study is to compare the view of the larynx with Miller blade while lifting the epiglottis to the Macintosh blade lifting the tongue, in infants and children \<2 years of age. However, views will be obtained with the Miller and Macintosh blades both lifting and not lifting the epiglottis and comparisons between pairs of measurements will be performed. In order for to detect superiority of one technique over the other, we will need a difference in the POGO scores of 25 points with a standard deviation of 25 points, yielding a sample size of 15 children in each group. To account for photographic difficulties, unreadable photos as well as dropouts, we will enroll 25 children in each group. Therefore a total of 50 children will be enrolled.