Nasotracheal intubation carries the risk of substantial airway morbidity. Approximately 50% of patients develop epistaxis (1–3) and more serious complications have been reported, including turbinectomy (4), adenoidectomy (3), nasal polypectomy (5), pharyngo-esophageal perforation (6,7), septal perforation (8), nasoseptal/parapharyngeal abscess (9), and nasal necrosis (10). Pharmacological techniques for minimizing morbidity are frequently used that anesthetize, lubricate, or shrink the nasal mucosa; however, mechanical techniques have also been described, including thermosoftening the tracheal tube in hot water (11,12), using an introducer with an inflatable balloon tip (13), and dilating incrementally with nasopharyngeal tubes (14). One study showed that a silicone-based, straight wire-reinforced tracheal tube with a soft hemispherical bevel and a cuff that was flush with the tube wall when deflated (silicone tracheal tube; Euromedical Industries, Kedah, Malaysia) had more frequent success than two conventional polyvinyl chloride (PVC)-based nasotracheal tubes with diagonal bevels for fiberoptic-guided nasotracheal intubation (15). We tested the hypothesis that a silicone-based wire-reinforced tube with a hemispherical bevel (silicone tracheal tube) is superior to a PVC-based precurved tube with a conventional diagonal bevel (PVC tracheal tube) for nasotracheal intubation (Fig. 1).
With ethical committee approval and written, informed consent, 80 ASA physical status I or II patients requiring nasotracheal intubation for tonsillectomy participated in the study. Patients were excluded if they were <18 yr old; had cardiorespiratory or cerebrovascular disease; were at risk of aspiration; had a history of nasal surgery, nasal pathology, spontaneous nosebleeds, or a bleeding diathesis; or were taking anticoagulant drugs. Patients were randomly assigned (by opening an opaque, sealed envelope) to airway management with the silicone tracheal tube (7.0-mm inner diameter [ID] for men and women; outer diameter [OD], 10.6 mm) or a PVC tracheal tube (RAE™; Mallinckrodt, Glens Falls, NY; men: ID, 7.0-mm; OD, 9.5 mm; women: ID, 6.5-mm; OD, 9.0 mm). All intubations were performed by a single anesthesiologist who had considerable experience with both tubes (>50 nasal uses each).
Coagulation studies were performed in each patient before surgery. Patients were premedicated orally with diazepam 5 mg and roxatidine 75 mg 1.5 h before induction. Routine monitoring was applied before induction and included an electrocardiograph, pulse oximeter, capnograph, noninvasive blood pressure monitor, and peripheral nerve stimulator. The patient was placed in the supine position with the head and neck on a standard pillow 7 cm high. Immediately before induction, patients were questioned as to which side of the nose was easier to breathe through. Oxygen was administered via a face mask for 5 min. Lidocaine 0.5 mg/kg was given IV with the tourniquet inflated for 30 s to prevent propofol pain. Anesthesia was induced with fentanyl 2 μg/kg and propofol 2.5 mg/kg and was maintained with sevoflurane 2% in 100% oxygen until the intubation was complete. Muscle relaxation was obtained with vecuronium 0.1 mg/kg. Patients were ventilated via a face mask until the train-of-four count was 0. No vasoconstrictors or disinfectants were applied to the nasal mucosa.
Intubation was subdivided into three phases: 1) passage through the nose into the pharynx, 2) laryngoscope-guided passage into the glottic inlet, and 3) laryngoscope-guided passage into the trachea. The tracheal tube, lubricated with a water-based gel, was inserted into the nostril that was easiest to breathe through. If no resistance was felt, the tube was advanced until its tip was in the pharynx. If resistance was felt, the tube was withdrawn, and the following manipulations were applied in sequence: 1) reinsertion into the same nostril with rotation of the tube, 2) reinsertion into the other nostril, and 3) reinsertion into the other nostril with rotation of the tube. If the tracheal tube was in the pharynx, a Macintosh No. 3 blade was applied, and the tube was advanced into the glottic inlet so that the distal tip was 0.5 cm through the vocal cords. If the tracheal tube could not be advanced into the glottic inlet, Magill’s forceps were used for the second attempt. If the tube was in the glottic inlet, it was advanced into the trachea by using Magill’s forceps. If resistance was felt, the tube was withdrawn, and the following manipulations were applied in sequence: 1) counterclockwise rotation of the tube and 2) external laryngeal pressure. If the tracheal tube failed to enter the pharynx, glottic inlet, or trachea, insertion was considered a failure, and an oral technique was used.
The following data were collected by an unblinded observer: number of insertion attempts (into the pharynx, glottis, and trachea), Cormack and Lehane grade (16), and intubation time (from insertion of the tracheal tube into the nostril to confirmation of tracheal intubation by capnography). The severity of epistaxis was estimated 5 min after the intubation by a blinded observer who aspirated the pharynx by using a 12F suction catheter that was 50 cm long. The suction tubing had an internal diameter of 7 mm and was 2.5 m long. Blinding was accomplished by covering the patient’s face and nasotracheal tube with a green towel. The intubator used the laryngoscope to elevate the tongue sufficiently for the blinded observer to place the catheter into the pharynx without exposing the tracheal tube. The severity of epistaxis was graded according to the distance blood traveled up the suction catheter and tubing (11,14): 0 (none), no blood aspirated; 1 (slight), blood aspirated by <50 cm; 2 (moderate), blood aspirated from 50 to 300 cm; and 3 (severe), blood aspirated by >300 cm and reaches the canister of the suction system. Any kinking of the tubes or other adverse events were noted. A further blinded observer interviewed the patients about postoperative nasal complications (pain, bleeding, nasal occlusion, and secretions) 18–24 h after surgery.
Sample size was selected to detect a projected difference of 20% between the groups for a Type I error of 0.05 and a power of 0.8 with respect to epistaxis (on the basis of a 50% incidence of epistaxis). Descriptive data were tested by using a two-tailed independent Student’s t-test. Categorical data were tested by χ2 test. The Kruskal-Wallis test was used to test scored data. Unless otherwise noted, data are presented as mean ± sd. Significance was taken as P < 0.05.
Patient characteristics (Table 1) and coagulation data were similar between the groups. All coagulation data were within the normal range. There were no intubation failures. The number of attempts at pharyngeal (47 versus 56; P = 0.04) and tracheal (43 versus 55; P = 0.005) placement was less for the silicone tracheal tube than for the PVC tracheal tube, but the number of attempts at glottic placement was more (72 versus 49; P < 0.0001) (Table 2). Intubation time was similar between groups. The frequency (32.5% versus 80%; P < 0.0001) and severity of epistaxis were less for the silicone tracheal tube (Table 3). There was no kinking of the tube, and there were no other adverse events. The total number of patients with postoperative nasal symptoms was less for the silicone tracheal tube than for the PVC tracheal tube (10 versus 21; P < 0.05) (Table 3).
We found that pharyngeal and tracheal placement were easier but that glottic placement was more difficult with the silicone tracheal tube than with the PVC tracheal tube. This is probably because the silicone tube’s soft, hemispherical tip reduces the risk of impaction with the nasal and subglottic mucosa, but the floppy tube is more likely to fall back against the posterior pharyngeal wall rather than be directed superiorly toward the glottic inlet. Hence, Magill’s forceps were required more often. We found that epistaxis and postoperative nasal complications were less common with the silicone tracheal tube. This is related to easier passage of the silicone tracheal tube through the nose despite the tube’s larger outer diameter. Reduced frictional forces between silicone and mucosa may also have contributed to easier insertion and reduced complications. The intubation success and complication rates for the PVC tracheal tube were similar to those in other studies (11,12). Our findings are consistent with those of Barker et al. (15), who showed that the silicone tracheal tube was superior to the Mallinckrodt reinforced tube or the Portex (Keene, NH) Blue Line tube for fiberoptic-guided nasotracheal intubation. The silicone tracheal tube with a hemispherical bevel has also been shown to be superior to a similar silicone tracheal tube with a diagonal bevel when used for oral intubation via the intubating laryngeal mask airway (17).
Chemicals such as cocaine, lidocaine/phenylephrine, oxymetazoline, xylometazoline, saline, and water-soluble gel have been used to reduce the incidence of morbidity during nasotracheal intubation, but their efficacy is controversial (2,18–21). Four mechanical techniques have also been described. Lu et al. (11) and Kim et al. (12) reported that thermosoftening of a PVC-based tracheal tube in hot water reduces the incidence of epistaxis. Watanabe et al. (13) reported that the incidence of epistaxis and subglottic impaction was reduced by using the Airguide™ nasotracheal intubation system. This consisted of a curved PVC-based tracheal tube with a flat distal tip and an introducer with a balloon that was inflated at the distal tip. Adamson et al. (14) found that incrementally dilating the nasal passage before nasotracheal intubation increased the incidence of epistaxis. Elwood et al. (22) reported that the incidence of epistaxis was reduced by using a red rubber catheter-guided nasotracheal intubation technique in children.
The silicone tracheal tube has advantages over other mechanical techniques in that there is no risk of thermal injury, no special preparations or extra equipment is required, there is no risk of foreign-body aspiration, and it is simple. The disadvantages are that only 6–8 mm-ID sizes are available, in some patients the tube may be too short to ensure that the cuff has fully penetrated the glottis, and the wire reinforcing does not extend to the proximal connector and so kinking may occur (although the last two events did not occur in our study). Interestingly, the silicone tracheal tube can be modified for tracheal resection by removing the tip distal to the cuff. This allows the cuff to be closer to the area of surgery (23).
Our study has two limitations. First, all nasal intubations were performed by a single experienced user. Second, all nasal intubations were in healthy, anesthetized paralyzed patients. Our results may not be applicable to inexperienced users or to other patient populations.
We conclude that the pharyngeal and tracheal placement phases of nasotracheal intubation require fewer attempts with the silicone tracheal tube than the PVC tracheal tube but that the glottic placement phase requires more attempts. Nasal morbidity is less common with the silicone tracheal tube.
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