Comparison of Storz C-MAC and D-MAC Orotracheal Intubation Systems in Morbidly Obese Patients
Condition: Obesity
Study type: Interventional
Phase: Phase 4

Summary: 
      The investigators hypothesize that the D-MAC (Dblade with C-MAC system) may be a suitable
      alternative device for difficult laryngoscopy and tracheal intubation in morbidly obese
      patients. The D-MAC will enable superior view of the glottic structures as well as easier
      endotracheal intubations than the C-MAC blade. This is the first study to investigate the
      individual and comparative performances of C-MAC and D-MAC in this patient cohort.
    

Detailed description: 
      Since the introduction of laryngoscopy, blades have undergone design innovations with the
      goal of improving laryngeal visualization and successful tracheal intubation because
      difficult intubation may be encountered even in patients with favorable anatomy.

      Failed intubation shows occurrence in 0.05% of surgical patients and in 0.13% to 0.35% of
      obstetric and obese patients and the incidence of unsuspected difficult intubation is
      estimated to be higher at approximately 3%, with poor airway visualization being a major
      contributing factor.

      Moreover airway management in the obese patient population requires special consideration. An
      increased BMI is associated with reduced posterior airway space and improper mask
      ventilation, both of which may lead to rapid development of hypoxemia and possible
      desaturation immediately after anesthetic induction.

      As the prevalence of obesity has increased from 23% in 1992 to 33.8% in 2008 and an estimated
      140,000 surgical bariatric cases are performed in the U.S., anesthesiologists face challenges
      of airway management in this population.

      The main advantage of video intubation is provision of superior views compared to traditional
      laryngoscopy.

      This study is designed to determine preliminarily the efficacy of the the D-BLADE [D-MAC]
      intubation systems compared to C-MAC in the bariatric population. The hypothesis is that
      D-MAC will enable superior view of the glottic structures as well as easier endotracheal
      intubations than the C-MAC blade.

      A. General Study Design- The study will include a total of 50 morbidly obese patients (BMI ≥
      40kg/m2) scheduled for elective surgery (bariatric, gynecological, urological, general
      abdominal and otorhinolaryngology) at Memorial Hermann Hospital.

      All patients will be intubated using conventional endotracheal tubes and preferably without
      any alternative aid to intubation. Patient will be followed for the time they will spend in
      the operating block (from the airway assessment time to the time of PACU discharge).

      In the operating room, ASA standard monitoring devices will be applied: a pulse oximeter, a 3
      lead ECG, and a blood pressure cuff (or invasive blood pressure depending on the patients'
      conditions). Pre-induction baseline measurements of blood pressure, heart rate, percent
      oxygen saturation and end tidal CO2 will be made. Patients will be positioned in a head
      elevated position (RAMP or TROOP pillow) and pre-oxygenated for 5 minutes. One set of
      pre-insertion vital signs (after induction) will be obtained. From the time anesthetic
      induction is begun until five minutes after the patient has been successfully intubated, five
      sets of vital signs will be recorded at one minute intervals. General anesthesia will be
      induced by bolus administration of propofol (2-3 mg/kg), fentanyl (2 mcg/kg), and
      succinylcholine (1mg/kg) per ideal body weight (assuming an ideal BMI of 32 kg/m2 up to a BMI
      of 50 kg/m2 and an ideal BMI 35 kg/m2 over 50 kg/m2. A rapid sequence induction (RSI) will be
      performed. RSI will be achieved with suxamethonium.The lungs will be mechanically ventilated
      with a semi-closed circle system to maintain an end-tidal CO2 near 35 mmHg. Patients' lungs
      will be ventilated via face-mask for 3 minutes with 100% oxygen until the patient is
      completely relaxed.

      A ll investigators (residents and attending) will be trained based on manufacturer
      recommendations, and each resident will perform at least 3 intubations with the C-MAC and
      D-MAC video laryngoscope prior to enlisting any patients for the study. Intubations will be
      performed by 2nd and 3rd year (CA-2 and CA-3) residents. Size 3 blades of CMAC will be
      utilized in all cases (a size 4 will be available if necessary).

      A computer-generated list will randomize the order of C-MAC and D-MAC to prevent bias. The
      resident will use either the C-MAC first followed by the D-MAC, or viceversa, and will
      declare the Cormack-Lehane Scale score for each method. Intubation will be attempted after
      the second laryngoscopy technique being used. External neck pressure may be applied by an
      assistant to improve laryngeal exposure. Any external manipulation will be recorded, and the
      optimal view obtained and the time required to obtain it for each method will be recorded.

      The resident will have only one attempt each for C-MAC and D-MAC laryngoscopy. If the first
      attempt is unsuccessful, the attending anesthesiologist will take one more attempt for that
      particular method, C-MAC or D-MAC. The number of attempts (maximum 4 total as defined by
      reinsertion of either the blade or endotracheal tube), time required to obtain optimum view,
      CL score of view, and time required to intubate will all be recorded. Intubation time is
      defined by time from which the anesthesiologist has ETT in hand to when the ETT cuff passes
      distally through vocal cords. If unsuccessful, the direct laryngoscopy/flexible fiberoptic
      laryngoscopy will be performed to intubate the trachea. If more than 4 attempts are needed,
      or if the anesthesiologist discontinues use of the video laryngoscope, the case will be
      considered a failure. The resident's subjective opinion on laryngoscopy and intubation
      difficulty level (from 1 = Extremely Easy, to 5 = Extremely Difficult) will also be recorded.

      In order to maintain patient safety all intubation attempts will be performed within the
      safety apnea time or time for oxygen blood saturation to drop to 92%.

      B. Measurements Pre-operatively, morphometric characteristics of all patients will be
      recorded: Mallampati score, adequacy of neck mobility, neck circumference, thyromental
      distance, sternomental distance, and interincisor gap distance.

      Degree of irritation: Following intubation in either group, the appearance of oropharynx,
      pharynx, epiglottis, and arytenoids will be checked. The presence of abrasions, bleeding,
      redness, perforation or other signs of tissue or dental injury will be recorded. Also, the
      patient's subjective report of soreness, hoarseness, or dysphagia post-operatively will be
      recorded as well.

      DATA ANALYSIS:

      This investigation will serve as preliminary study to determine if there is an improved rate
      of airway view during C-MAC or D-MAC video laryngoscopy. The study will have a time frame of
      12 months. Data will be summarized using mean ± SD, median and interquantile, and frequency
      (%) for discrete variables by each group. Appropriate tests like t-test, ANOVA, chi-squared,
      and Fischer tests will be used to compare the mean primary outcome variable, duration of
      desaturation, between two groups after adjusting the effects of risk factors.

      For the secondary outcome variables, appropriate tests like t-test, ANOVA, or the chi-squared
      tests will be performed to compare the continuous variables between two groups to compare the
      percentage of discrete outcome variables between two groups.

      Statistical analyses will be conducted using STATA 10.0 College Station, TX and a p-value <
      0.05 will be considered as statistical significant.
    

Intervention name(s): DMAC; CMAC
Intervention type(s): Device; Device
Intervention description(s): The D blade will constitute the experimental treatment and in a cross over fashion will be tested against CMAC blade; The CMAC Blade will constitute the active comparator treatment and in a cross over fashion will be tested against D-blade
Other intervention name(s): D-Blade CMAC system; CMAC blade
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Laryngoscopy; Airway Management; Intubation