Comparison of modified anterior and traditional posterior accesses for ultrasound-guided superior laryngeal nerve block in awake endotracheal intubation: study protocol for a randomised non-inferiority clinical trial

Abstract

Introduction: Awake tracheal intubation (ATI) involves placing a tracheal tube in an awake, spontaneously breathing patient. Superior laryngeal nerve block (SLNB) can effectively abolish the glottic closure reflex, and blunt the sensation of the structures above the cords. A method that consists of SLNB along with translaryngeal injection (TLI) can provide satisfactory anaesthesia and intubating conditions. We present a novel modified access of SLNB, ultrasound (US)-guided anterior SLNB, to aid awake videolaryngoscopes-assisted endotracheal intubation in adult elective surgery patients, and we compare the effectiveness and safety to traditional US-guided posterior SLNB.

Methods and analysis: A total of 100 adult elective surgery patients requiring general endotracheal anaesthesia will be randomly assigned to the modified group (modified US-guided anterior SLNB) or the traditional group (traditional US-guided posterior SLNB). After SLNB, all participants will be performed with TLI. The primary outcome is the proportion of acceptable intubation conditions based on intubation scores. Secondary outcomes include: (a) the first-attempt intubation success rate, (b) haemodynamic changes during ATI, (c) time taken for airway anaesthesia and intubation, (d) recall of intubation, (e) participant perception of comfort during intubation, (f) perioperative complication rate. This report describes the study design of this randomised controlled trial.

Ethics and dissemination: The study protocol has been approved by an ethical committee of the West China Hospital (Sichuan University), and registered at the Chinese Clinical Trials Register (www.chictr.org.cn). Results will be published in a peer-reviewed journal.

Trial registration number: ChiCTR2200058086.

Keywords: adult anaesthesia; adult intensive & critical care; pain management; ultrasonography.

Figure 1

Probe placement and needle orientation in two methods of ultrasound (US)-guided superior laryngeal nerve block (SLNB). (A) Lateral view of US-guided anterior SLNB. (B) Vertical view of US-guided anterior SLNB. (C) Vertical view of US-guided posterior SLNB.

Figure 2

Transverse sonography of ultrasound (US)-guided anterior superior laryngeal nerve block (SLNB). (A) Transverse scan over the thyroid incisura notch before performing anterior SLNB. (B) After lidocaine injection, the drug pushes the TH-Mb and pre-epiglottis space away, and lidocaine rapidly diffuse to lateral spaces. (C) Left parasagittal scan through the TH-Mb immediately after injection of lidocaine. (D) Right parasagittal scan through the TH-Mb immediately after injection of lidocaine. Arrowheads: TH-Mb, asterisk: air-mucosa interface, white solid arrow: needle orientation, white dotted circled area: lidocaine. Epi, epiglottis; Hy, hyoid bone; PES, pre-epiglottic space; SM, strap muscles; TC, thyroid cartilage; TH-Mb, thyrohyoid membrane.

Figure 3

Parasagittal sonography of ultrasound-guided posterior superior laryngeal nerve block (SLNB). (A) Parasagittal sonography before performing posterior SLNB. (B) After injection, lidocaine pushes the TH-Mb and pre-epiglottis space away. Arrowheads: TH-Mb, white solid arrow: needle orientation, white dotted circled area: lidocaine. Hy, hyoid bone; PES, pre-epiglottic space; SLA, superior laryngeal artery; SM, strap muscles; TC, thyroid cartilage; TH-Mb, thyrohyoid membrane.

Figure 4

Transverse sonography for ultrasound (US)-guided transtracheal block. The sonogram shows the cricothyroid membrane (C-T Mb) and the comet tail artefacts (CTA). The white arrow shows the needle orientation of US-guided translaryngeal block.

Figure 5

Flow diagram of study conductance. SLNB, superior laryngeal nerve block; TLI, translaryngeal injection; US, ultrasound.