The use of videolarygoscopy (VL) as first choice for tracheal intubation versus direct laryngoscopy (DL) is a matter of debate. These two methods were compared in several studies. First attempt intubation success and glottic visualization with VL versus DL by pediatric emergency medicine providers in simulated patients were evaluated and it was concluded that VL was associated with greater first-attempt success during intubation by pediatric emergency physicians on an adult simulator. The ease of viewing the glottis under direct vision during conventional laryngoscopy with the quality of indirectly viewing on a monitor during laryngoscopy with a Macintosh videolaryngoscope was compared in a multicenter study. The results were that VL can lead to better viewing conditions but in rare cases it may result in worse viewing conditions. The study evaluating the efficacy and safety of VL compared to DL in decreasing the time and attempts required and increasing the success rate for endotracheal intubation in neonates concluded that there was insufficient evidence to recommend or refute the use of VL for endotracheal intubation in neonates. Diverse videolaryngoscopes where also compared in patients undergoing tracheal intubation for elective surgery: the GlideScope Ranger (GlideScope, Bothell, WA), the V-MAC Storz Berci DCI (Karl Storz, Tuttlingen, Germany), and the McGrath (McGrath series 5, Aircraft medical, Edinburgh, UK) and tested whether it is feasible to intubate the trachea of patients with indirect videolaryngoscopy without using a stylet. The authors concluded that the trachea of a large proportion of patients with normal airways can be intubated successfully with certain VL blades without using a stylet, although the three studied VL's clearly differ in outcome. The Storz VL displaces soft tissues in the fashion of a classic Macintosh scope, affording room for tracheal tube insertion and limiting the need for stylet use compared with the other two scopes. Although VL's offer several advantages, including better visualization of the glottic entrance and intubation conditions, a good laryngeal view does not guarantee easy or successful tracheal tube insertion. Three different videolarygoscope devices were compared to direct laringoscopy in obese patients undergoing bariatric surgery: Video Mac and GlideScope required fewer intubation attempts that DL and Video Mac provide shorter intubation times and improved glottis view compared to DL. A recent metanalysis stated that videolaryngoscopes may reduce the number of failed intubations, particularly among patients presenting with a difficult airway. They improve the glottic view and may reduce laryngeal/airway trauma. However currently, no evidence indicates that use of a VLS reduces the number of intubation attempts or the incidence of hypoxia or respiratory complications, and no evidence indicates that use of a VL's affects time required for intubation. DM is accepted as a risk factor for difficult intubation.

The aim of this study is to compare VL to DL in adult diabetic patients requiring tracheal intubation for anesthesia, in terms of intubation time, intubation success, glottic view quality, intubation failure, conversion to another laringoscopy method and adverse outcomes related to tracheal intubation.

METHODS After obtaining ethical approval and written informed patient consent, consecutive patients having diabetes mellitus (DM) and requiring elective intubation for anesthesia will be randomly allocated to either the videolaryngoscopy (Group VL) or the direct larngoscopy (Macintosh laryngoscope) (Group DL). Age, gender, body mass index, American Society of Anesthesiologists (ASA) physiologic classification, the duration of DM will be recorded. The patients will be evaluated for difficult airway predictors and the following parameters will be recorded: Malampati class, thyromental distance, sternomental distance, mandibulohyoid distance, interincisor distance, neck circumference, the ability of upper lip overbite and lower lip overbite, the presence of limited neck extension. Fentanyl-propofol-rocuronium will be used for anesthesia induction. After subsequent positive-pressure ventilation using a face mask and an oxygen-air-sevoflurane mixture for 3 min, the trachea will be intubated according to group allocation using either DL (Macintosh laryngoscope) or VL (CMAC). During intubation, the following data will be documented: intubation time, number of intubation attempts, use of extra tools to facilitate intubation, conversion to another laryngoscopy method,intubation difficulty and the quality of the view of the glottis will be assessed according to the Cormack and Lehane scoring system and the percentage of glottic opening. Adverse events related to tracheal intubation will be also evaluated: desaturation (SPO2\<94), hypercabia (ETCO2\>35), hypertension (mean arterial pressure \>20% above baseline values), tachycardia (heart rate \>20% above baseline values), new onset arrhythmia, laryngospasm, bronchospasm, airway trauma and sore throat in PACU). The primary outcome measure is the time to intubation; first-attempt intubation success and ease of intubation, secondary outcome measures are the glottic view guality, conversion to another laryngoscopy method and adverse outcomes related to tracheal intubation.