Comparison of McGrath Videolaryngoscopy and Direct Laryngoscopy for Intubation in Patients With Morbid Obesity in Non-cardiac Surgery

In the preoperative period, patient's airway data will be recorded by a research coordinator or anesthesia provider (Table 1). Patients will be positioned supine and in a standardized ramped position on the OR table. Patients will be pre-medicated with midazolam 0-2 mg IV, as clinically appropriate. All patients will be pre-oxygenated until the fraction of expired oxygen exceeds 80%. General anesthesia will be induced as preferred by the attending anesthesiologist, usually with a combination of lidocaine 1 mg/kg, propofol 2-5 mg/kg, fentanyl 1-3 µg/kg, and rocuronium 0.6-1.2 mg/kg or succinylcholine 1.5 mg/kg.

Manual bag-mask ventilation will be initiated, with no restriction on the use of oral airways, nasal airways, laryngeal masks. Complete muscle relaxation will be confirmed by absence of palpable twitches in response to supra-maximal train-of-four stimulation of the ulnar nerve at the wrist. After confirming adequate bag mask manual ventilation, patients will be randomized 1:1, stratified for BMI >50 kg/m2, to:

• Direct laryngoscopy using an appropriately sized Macintosh blade (usually size 3 or 4);
• McGrath videolaryngoscopy in an appropriate size (usually blade size 3 or 4). Randomization will be based on computer-generated codes accessed from the Redcap system shortly before anesthetic induction. Allocation will thus be concealed until the last possible minute.

Intubations will be performed with a regular endotracheal tube of adequate diameter, usually 7.5 mm or 8.0 mm. Endotracheal tubes will be equipped with a hockey-stick-shaped stylette, which will be prepared by the anesthesiologist in advance.

The McGrath or the Macintosh blade will be introduced into oral cavity according to manufacturer recommendations and clinical practice. Minor airway manipulation procedures including BURP or Sellick maneuvers will be allowed to improve visualization of the vocal cords.