Abstract
Background:
Nasotracheal intubation is challenging for anaesthesiologists in faciomaxillary injuries due to the anticipated difficult airways. The effectiveness of a non-channelled McGrath video laryngoscope was compared with a conventional Macintosh laryngoscope during nasotracheal intubation.
Methods:
Sixty American Society of Anaesthesiologists I–II patients aged between 18 and 60 years of both sexes undergoing elective faciomaxillary surgeries from September 2019 to February 2020 were prospectively randomised into two groups (Macintosh laryngoscope Group, McGrath video laryngoscope Group) of 30. The primary outcome was ease of intubation (Modified Intubation Difficulty Scale) and Nasotracheal intubation time (T1 time: from nostril to nasopharynx, T2 time: from nasopharynx until the first ETCO2, total time: T1 + T2). The secondary outcomes were Cormac Lehane grade, additional manoeuvres requirement, intubation failure, tracheostomy incidence and associated complications.
Results:
T1, T2 and total (T1 + T2) time (mean ± SD) were statistically prolonged in the McGrath video laryngoscope than Macintosh laryngoscope group, with p = 0.044, p = 0.000 and p = 0.000, respectively. The McGrath video laryngoscope facilitated a better laryngoscopic view (p = 0.002), favourable intubation difficulty scale scores, less lifting force (p = 0.002), reduced lip trauma (p = 0.002) and decreased Magill’s forceps use (p = 0.002) than the Macintosh laryngoscope group.
Conclusion:
Despite longer intubation time, the non-channelled McGrath video laryngoscope offered favourable intubating conditions with superior glottis view, less lifting force and reduced Magill’s forceps requirement, causing decreased airway trauma, lower intubation difficulty scale scores than Macintosh laryngoscope for nasotracheal intubation.
Introduction
Macintosh laryngoscope
McGrath video laryngoscope
Patients and methods
This randomised, prospective, comparative study was performed in a tertiary unit centre after obtaining institutional ethics committee approval (EC/NIMS/2395/2019 40TH ESGS NO.869/2019) and registered with the Clinical Trial Registry of India (CTRI/2020/02/023135). Individuals aged 18–60 years of both genders with American Society of Anaesthesiologists (ASA) Grade I–II, mallampati grade 1–3 undergoing elective faciomaxillary surgeries under general anaesthesia requiring NTI from September 2019 to February 2020 were included. Patients were excluded if they had rhinostenosis, pregnancy, ASA grade 3 and 4, bleeding tendencies, or poor pulmonary reserve. Following written informed consent, 60 patients were assigned into two groups (Group McG and Group ML) of 30 each by block randomisation method. The consort flow diagram illustrates the patients’ details of randomisation, allocation and follow-up (Figure 3).
Consort flow diagram
The Group McG was intubated using McG VL while the ML group was intubated by ML. Patient’s clinical history, age, sex, height, weight, body mass index (BMI) and airway parameters (neck circumference [NC], mouth opening [MO], thyromental distance [TMD], sternomental distance [SMD] and Mallampati grade, MPG) were noted. The tablets alprazolam 0.25 mg and ranitidine 150 mg were used for premedication of the patients before and on the morning of surgery. (The drug ranitidine is not currently licenced in the United Kingdom, but is part of our institutional protocol. Hence, we used this drug for premedication). In the operating theatre, standard ASA monitors; electrocardiogram (ECG), pulse oximetry (SPO2), end-tidal carbon dioxide (ETCO2) and non-invasive blood pressure (NIBP) were connected. Intravenous (IV) access was secured, and the Ringer’s lactate fluid was started. Both nostrils were decongested with 0.1% xylometazoline drops. The patients were preoxygenated with 100% oxygen for 3 minutes, premedicated with injection (inj) IV fentanyl 2 µg/kg and glycopyrrolate 0.1 mg, and induced with inj thiopentone sodium 5 mg/kg body weight. After confirming manual ventilation, neuromuscular blocking agent Inj. Atracurium 0.5 mg/kg was administered, and 3 minutes later, laryngoscopy was attempted by an experienced anaesthesiologist (who performed at least 20 successful NTIs) with ML or McG VL as per randomisation. The patient’s nose was lubricated with 2% lignocaine jelly, and the appropriate size NTT was negotiated from the patient’s nose (patient’s right or left nostril) to the nasopharynx. After obtaining the best glottic view, the NTT was advanced through the vocal cords, and successful tracheal intubation was confirmed by auscultation and capnography.
Intubation time: T1 time: the distal tip of the NTT tube entering the nasopharynx from the nostril.
Time T2: the distal tip of NTT passing from the nasopharynx to the trachea between the vocal cords and the first ETCO2 trace appearance.
Total time: T1 + T2 were noted.
The ease of intubation using a modified Intubation Difficulty Scale (IDS) was also documented. IDS Difficulty level was graded as easy (grade 0), mild difficult (grade 1 to 4), or difficult IDS (grade > /5) (Ono et al 2014).
The lifting force for laryngoscopy, additional manoeuvres like bougie, Magill’s forceps and optimal external laryngeal manipulation (OELM) requirements to aid in intubation were also noted. The incidence of failed intubation (when the patient could not be intubated after three attempts), tracheostomy and desaturation episodes were recorded. Airway complications like oral and nasal mucosal bleeding and trauma to the lips, tongue, pharynx and larynx were also noted, and the study ended here. The patients were connected to mechanical ventilation, and anaesthesia was maintained on air: oxygen (ratio 50:50), isoflurane inhalational agent, and atracurium-fentanyl infusion tailored to the patient’s needs. All the patients received IV Paracetamol 20 mg/kg infusion intraoperatively. At the end of the surgery, the residual neuromuscular blockade was reversed with 0.05 mg/kg neostigmine and 0.4 mg glycopyrrolate, and the patients were extubated following good recovery and moved to the postoperative period.
Results
The demographic data (age, sex, weight, height and ASA grade) and airway parameters (MO, MPG, TMD, SMD and NC) were statistically comparable in both groups (Table 1).
Demographic profile and Airway assessment parameters
n: number of patients; MO: mouth opening; TMD: thyromental distance; SMD: sternomental distance; NC: neck circumference; fb: finger breadth; n: number of patients.
Regarding NTI time, the ML group experienced statistically lower T1 intubation time ((p = 0.044), lower T2 time (p = 0.000) and lower total intubation time (T1 + T2) than the McG group (p = 0.000; Table 2; Figure 4).
Time taken for intubation
Time taken for intubation
The McG group had a significantly better glottic view (CL grade 1) (17) than the ML group (9) (p = 0.002). Easy IDS score was also rated in many McG group patients (12) than ML group (5) (p = 0.012). All McG group patients were intubated in the first attempt, while two patients needed more than one attempt in the ML group. The lifting force and the frequency of Magill’s forceps use were significantly lower in the McG than ML group (p = 0.002). The use of other manoeuvres, OELM and bougie, were lower in the McG group than ML group but did not gain statistical significance. There were no desaturation or intubation failure episodes, thus avoiding tracheostomy in both groups (Table 3).
Intubation parameters
n: number of patients; IDS: Intubation Difficulty Scale; OELM: optimal external laryngeal manipulation; IOD: incidence of desaturation; IF: intubation failure; IOT: incidence of tracheostomy.
Regarding airway injury, there was a statistically lower incidence of trauma to the lips in the McG group than in the ML group (0) (p = 0.002). Trauma to the rest of the airway gained no statistical significance between both groups (Table 4).
Airway injury
n: number of patients; NA: not applicable.
Discussion
Nasal intubation indicated in intraoral surgery is more complex than OTI due to the malalignment between the tip of NTT and the glottic inlet (Holzapfel, 2003). To ease the intubation process, VLs have been designed with developing medical technology (O’Leary et al 2008). There are many clinical trials comparing McG VL with ML on OTI in difficult airway management, but only a few studies have looked at their efficacy on NTI. So, this study compared the clinical performance between these two scopes for NTI.
Regarding intubation time, T1 time was longer for manipulating McG VL in attaining an optimal laryngeal view. The McG group also experienced prolonged T2 time and total time (T1 + T2), which may be attributed to the hand-eye coordination in redirecting the NTT tip from the posterior pharyngeal wall anteriorly into the glottis and trachea. Our results corroborate with Srinivasan et al (2021) and Sun et al (2014) meta-analysis trials with a longer intubation time with VL than ML.
Many patients exhibited CL grade I in the McG group than the ML group (p = 0.002) with improved IDS due to the clear magnified image of vocal cords offered by the camera similar to Malik et al’s (2008) study.
The lighter weight of the McG blade contributed to less Upwards Lifting Force (ULF) for laryngoscopy, facilitating better NTT alignment to the glottis and easy NTII. This is supported by Hindman et al (2014), who observed a lesser lifting force with Airtraq than ML and Kim et al (2014) study.
First-pass intubation was successful in all 30 McG group patients but only in 28 ML group patients, consistent with the Aziz et al (2012) trial.
The larynx and glottis are lifted upwards by ML laryngoscopy manoeuvre. This increases the distance between the glottic orifice and the posterior pharyngeal wall, causing upwards and downwards sliding of the nasally introduced tube. This necessitated the higher Magill forceps employment for NTT negotiation than the McG group in agreement with the Kwak et al (2016) trial.
Higher OELM was required with ML (6 patients) as the epiglottis is elevated and anterior tilt of the larynx is reduced, while none with McG, consistent with Kim et al (2018), who reported higher use of OELM in the ML group than in the McG group.
Several studies have demonstrated the importance of a gum elastic bougie in guiding the tip of NTT from the posterior towards the glottis. Both McG and ML groups required bougie but with statistical similarity, identical to Mallik et al (2008) study.
The heavy weight of the ML blade and the employment of additional manoeuvres contributed to a higher incidence of lip trauma than the lighter McG blade. Other airway complications were low and statistically indifferent in both groups. Sargin and Ulcer (2016) reported more incidence of airway complications with ML than McG, whereas Taylor et al (2013) observed no differences in complications between the groups.
Limitations
The investigators could not be blinded to the type of laryngoscope used for NTI. This trial was done in a single centre using a small sample size and hence cannot be extrapolated to the general population.
Conclusion
Although intubation time was prolonged, McG was superior to ML in terms of glottic view, IDS score employing fewer Magill’s forceps use and lifting force resulting in reduced airway trauma. McG should be considered a safe and effective replacement for direct laryngoscopy for airway management in faciomaxillary surgery employing NTI.
Footnotes
Authors contribution
All the authors have read and approved the final version of the manuscript to be published. The requirements for authorship, as stated earlier in this document, have been met, and each author believes that the manuscript represents honest work.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
