King Vision and Cervical Spines Movement
Condition: Need Tracheal Intubation
Study type: Interventional
Phase: Phase 2

Summary: 
      Extensive cervical spines movement during endotracheal intubation can result in serious
      neurological injury, especially in the patients with unrecognized cervical spines
      injury.[1-2] Moreover, direct laryngoscopy may be difficult if spine movement is limited
      because of arthritis, disc disease or a small gap between the occiput and the spinous process
      of the atlas.[3-4]

      Video laryngoscopes allow for intubation without alignment of the oral, pharyngeal, and
      tracheal axes which minimize the cervical movements, especially in the patients with
      restricted cervical movements. [5,6] Compared with the Macintosh laryngoscope, the use of
      AirWay Scope decreases median upper cervical-spine movement during intubation under in-line
      stabilization in patients with normal cervical-spine. [6] Unfortunately, the use video
      laryngoscopes are associated with longer times to tracheal intubation compared with the
      traditional techniques which may be attributed to the variable learning curves of the
      practitioners. [7-9]

      The King Vision video laryngoscope® (King Systems Company, a division of Consort Medical,
      Indianapolis, Indiana, USA) is an anatomically shaped, rigid laryngoscope that uses
      fiberoptic technology to view the larynx with micro camera offers a 160 degree of view
      potentially eliminating the need for neck flexion and head extension. [10]

      To the best of the authors' knowledge, there is no study has evaluated the King vision
      laryngoscope regarding the neck movement during routine tracheal intubation under general
      anesthesia.
    

Detailed description: 
      Hypothesis:

      The investigators hypothesize that the use of King Vision video laryngoscope may reduce the
      cervical spines movements during endotracheal intubation compared with the Macintosh
      laryngoscope.

      Aim of the study:

      The present clinical trial aims to compare the effects of the Macintosh and King Vision
      laryngoscopes, on cervical spines movement, time to intubation, laryngoscopic view, ease of
      intubation, number of intubation attempts, and number of optimization maneuvers during
      tracheal intubation, in the patients undergoing minor elective surgery under
      propofol-remifentanil-rocuronium anesthesia.

      Methods:

      Thirty two ASA I-II patients who need tracheal intubation will be included in this randomized
      cross-over controlled blind comparative study at the author's center after obtaining approval
      of the local Ethical Committee and an informed written consent from all participants.

      The Mallampati airway score, thyromental and sternomental distances, neck extension, and the
      degree of mouth opening will be evaluated preoperatively as factors predicting difficult
      intubation.

      Sample size calculation:

      A priori power analysis of the previous published data [9] showed that the investigators will
      need to study 14 pairs to detect a 10% difference in the cervical spine extension
      (occiput-C5) values (25.9 degrees) with a SD of 2.8 degrees, after intubation with of
      Macintosh laryngoscope, a type-I error of 0.05 and a power of 90%. The investigators will add
      10% more patients for a final sample size of 32 patients to account for patients dropping out
      during the study.

      Anesthesia:

      Patients will be placed on the operating room table with a rigid board from the shoulders to
      the occiput with the patient's head rested on a pillow in a position judged by the patient to
      be neutral. After verification that the patient will be properly centered, the fluoroscopy
      unit and operating room table will remain fixed for the rest of the study.

      Patients' monitoring includes pulse oximetry, noninvasive blood pressure electrocardiography,
      state and response Entropy (SE and RE) and train of four (TOF)stimulation of the ulnar nerve.

      Anesthetic technique will be standardized in all studied. After breathing 100% oxygen for 3
      min through a facemask in a neutral position, anesthesia will be induced with fentanyl
      2-3µg/kg/min and propofol 2-3 mg/kg to achieve a SE < 50 and the difference between RE and SE
      less than 10. Rocuronium 0.6 mg.kg will be administered for complete relaxation on the TOF
      (TOF-GE, Datex-Ohmeda Division, Instrumentarium Corporation, Helsinki, Finland). Anesthesia
      will be maintained using sevoflurane end-tidal concentrations of 2.5-3.5% in oxygen via a
      bag-mask for 3 min before endotracheal intubation.

      Standard precautions against radiation exposure will be taken, movement of the cervical
      spines during endotracheal intubation will be studied and recorded with portable X-ray
      machine. Laryngoscopy will be performed twice, once with the King Vision and once with the
      Macintosh laryngoscope in random order. For the first device, the patient's mouth will be
      opened and the tip of the tracheal tube will be introduced into the glottis. The second
      device will be studied in an identical manner, and intubation will be completed with the
      second device. The intubators who will participate in the study will receive a standard
      manikin based training which will be followed with 50 successful endotracheal intubations in
      the clinical practice with the use of Macintosh and King Vision® laryngoscopes.

      The studied data during intubation will be collected by an independent investigator. The
      intubator will attempt to minimize neck movement during both techniques through the
      acceptance of the first view [8] that will offer a reasonable opportunity to adequately
      position the tracheal tube at the glottis opening.

      Three lateral radiographs will be taken with a portable X-ray system provides fixed images
      from which hard copies are generated. Patient will be served as their own control with
      reference to the first image, which will be obtained after induction of anesthesia before
      laryngoscopy and intubation, with the patient in neutral position. A further two images, one
      with the Macintosh and one with King Vision laryngoscopes. These images will be taken at the
      time of laryngeal exposure, with the tip of the endotracheal tube passing between the vocal
      cords.

      On each image, lines will be drawn to mark the relative position of the occiput, atlas (C1),
      axis (C2) and the fifth cervical vertebra (C5). The angle between each of these lines will be
      measured to determine the degree of angulation of C1, C2 and C5 relative to the occiput and
      each other. [9] The radiographs will be reviewed by a radiology consultant who will be
      blinded to the order of intubation technique and unfamiliar with the laryngoscopes being
      used.

      Statistical Analysis

      Data will be tested for normality using the Kolmogorov-Smirnov test. Fisher exact test will
      be used for categorical data. Repeated two-way ANOVA and paired t-test will be used to study
      the changes in the primary and secondary endpoints during each intervention. The Wilcoxon 2
      rank sum test will be used for the non-parametric values. The investigators will avoid the
      carryover effect (persistence of the effect of the first intervention on the operative
      conditions into the second period) through the comparison of the effects of period (time
      effect) and the order of treatment using independent t-tests. Data will be expressed as mean
      ± SD, number (%), or median [range]. A value of P < 0.05 will be considered to be
      statistically significant.
    

Intervention name(s): Macintosh-King Vision; King Vision-Macintosh
Intervention type(s): Device; Device
Intervention description(s): laryngoscopy will be performed with the Macintosh followed by the King Vision laryngoscope; laryngoscopy will be performed with the King Vision followed by the Macintosh laryngoscope.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Investigator)
Primary purpose: Prevention
Keywords: Laryngoscope; Macintosh; King Vision; tracheal intubation; cervical spines