This study was approved by the Hanyang University Guri Hospital Institutional Review Board on Human Subjects Research and Ethics Committees (GURI 2014-16). All patients provided written informed consent prior to enrolment. Sixty patients (aged 18–65 years) scheduled for elective surgery and classified as American Society of Anesthesiologists physical status I or II were included in the study. Exclusion criteria were patients with a history of difficult intubation, larynx surgery, or larynx radiotherapy; anticipated esophago-tracheal reflux; Mallampati view 3 or 4; frequent episodes of epistaxis; or bleeding tendency. On preoperative visits, residents evaluated the patients for the presence of nasal injury, dyspnea, sinusitis, allergic rhinitis, and a history of smoking.
Upon the patient’s arrival at the operating room, a nurse, who was blinded to the study, opened an envelope containing the randomization numbers and group information—i.e., Magill forceps (M) or vascular forceps (V). The following patient characteristics were measured and recorded: age, sex, weight, height, body mass index, Mallampati view, thyromental distance, maximal mouth opening, and neck circumference. Elective monitoring was performed. A bispectral index (BIS) monitor (A-2000TM, version 3.3; Aspect Medical System Inc., Newton, MA, USA) was used to monitor the depth of anesthesia.
Before induction of anesthesia, one side of the patient’s nostril was blocked. The patient was then instructed to sneeze through the opposite nostril to confirm that the nostril was blocked, and the selected nostril was packed with gauze containing epinephrine. Denitrogenation was performed by having the patients breathe 100% oxygen for three minutes to remove all nitrogen gas from their airway. After acquiring intravenous access and completing denitrogenation, remifentanil and 2% propofol were administered by an Orchestra® Base Primea infusion device (Fresenius Kabi, France). Rocuronium 0.6 mg kg−1
iv was administered when the BIS value was < 60 and verbal response was absent. An Innervator nerve stimulator (Fisher & Paykel Healthcare, Auckland, New Zealand) was placed along the ulnar nerve to monitor the train-of-four reactions, and nasotracheal intubation was initiated once the train-of-four reaction was zero.
Nasotracheal tubes (NTTs) (Mallinckrodt Medical, Covidien, Ireland) with an internal diameter of 7.0 and 6.5 mm were used for males and females, respectively. The tubes were placed into sterile saline maintained at 45°C and then lubricated with water-soluble gel. In group M, the NTT was oriented with the concavity facing caudally, and the tube was advanced along the nasal floor to the posterior nasopharyngeal wall. The GlideScope blade was then placed into the patient’s mouth, and the tip of the NTT was inserted into the trachea using Magill forceps via the GVL monitor (Fig. 1). In group V, a lubricated Sheridan T.T.X.™ endotracheal tube exchanger (Teleflex Medical, Durham, NC, USA) was inserted into the NTT with the tip of the tube exchanger protruding approximately 15 cm from the distal end of the NTT (Fig. 2). A tube exchanger lubricated with water-soluble gel was inserted into the nasal cavity, and the GlideScope blade was then placed into the patient’s mouth. Using vascular forceps, the tube exchanger was advanced along the lower pathway of the nasal airway and passed through the glottis. The NTT was then advanced along the tube exchanger via the GVL monitor. Three anesthesiologists (M.K.O., W.J.J., and S.Y.C.) performed the nasotracheal intubations.
Total intubation time was defined as the time from when the anesthesiologist picked up the device to when three successive end-tidal CO2 waves were obtained following intubation. Immediately after extubation, the patient’s airway was assessed for blood in the intubation tube, the presence of damaged oral tissue, damage to the teeth, and other complications. A blinded observer assessed the patients for sore throat at one and 24 hr postoperatively.
To calculate the sample size, we used the average (standard deviation [SD]) intubation time obtained from a pilot study—i.e., 66.1 (15.5) sec. We needed 28.8 patients to detect a 20% difference between the groups. Assuming a 2% dropout rate, this study required 60 patients. We used IBM® SPSS® Statistics 21.0 for Windows for statistical analyses (SPSS Inc., Chicago, IL, USA). Unpaired Student’s t tests were used to compare the numerical data of the two groups. The mean difference and the 95% confidence interval (CI) of the mean difference were calculated. Categorical data (ratio of sore throat, epistaxis) were analyzed using Fisher’s exact test. The relative risks of the proportion of categorical data and 95% CI were calculated.