Comparison between ultrasound-guided and anatomical landmark-guided block of internal branch of the superior laryngeal nerve for awake fiber-optic intubation in suspected difficult intubation: a randomized controlled study

Abstract

Background Airway anesthesia is pivotal for successful awake intubation provided either topically or by nerve blocks. The widespread use of ultrasonography allows anesthesiologists to evaluate complex and varied anatomy before needle insertion. This study aims to evaluate the effect of ultrasound-guided technique for the block of the internal branch of the superior laryngeal nerve in difficult airway patients in comparison to blind anatomical technique. Sixty patients aged 18–60 years, of either sex, with the American Society of Anesthesiologists’ physical status (ASA) I–II were divided into two groups 30 patients of each. Group (L): using anatomical landmark technique to bilateral block internal branch of the superior laryngeal nerve (ibSLN) with 1 mL 2% Lidocaine and group (U): using ultrasound technique to bilateral block the ibSLN with 1 mL 2% Lidocaine. Assessment of the excellence of airway anesthesia during intubation by using the 5 points grading scale, time for intubation, effects on hemodynamic variables, and evaluation of patient awareness of pain and discomfort during fiber-optic intubation using numerical rating scale were compared. Results The duration of tracheal intubation was shorter in the ultrasound group as compared to the anatomical group; also, patient comfort was significantly better in the ultrasound group besides the effect of tracheal intubation on hemodynamics which was significant with a higher peak value during intubation and post-intubation in the anatomical group compared to the ultrasound group. Conclusions This study concludes that an ultrasound-guided block of ibSLN used as a part of the preparation of the airway for awake fiber-optic intubation enhances the quality of airway anesthesia and patient tolerance during the procedure.

Comparative review of airway anesthesia and sedation methods for awake intubation

“…Additionally, two studies assessed the effect of ultrasound guidance compared with landmark-based techniques of the superior laryngeal nerve block [11,12 ▪▪ ]. Both studies revealed the benefit of ultrasound guidance in achieving higher quality airway anesthesia, shorter time to intubation, and increased patient comfort [11,12 ▪▪ ]. Though not described specifically in these studies, we posit that the use of ultrasound guidance for the superior laryngeal nerve block may be particularly beneficial in patients for whom landmark techniques may be more difficult, due to body habitus, aberrant anatomy, and/or distortion of normal airway landmarks.…”

“…Additionally, both nebulization and topicalization may take more time to perform to achieve adequate anesthesia, are dependent on delivery systems or devices, and may provide less dense coverage compared with targeted nerve blocks. This is supported by multiple studies revealing that nerve blocks led to higher quality of airway anesthesia (usually assessed by either the performer of the awake intubation or an independent observer), as well as a higher degree of patient comfort and postoperative patient satisfaction [11,12 ▪▪ ,13–23]. Whereas most studies compared the efficacy of the addition of nerve blocks to nebulization, an interesting study by Khandelwal et al [16] assessed the addition of nebulization to nerve blocks.…”

“…Additionally, two studies assessed the effect of ultrasound guidance compared with landmark-based techniques of the superior laryngeal nerve block [11,12 ▪▪ ]. Both studies revealed the benefit of ultrasound guidance in achieving higher quality airway anesthesia, shorter time to intubation, and increased patient comfort [11,12 ▪▪ ].…”

“…The block is performed with the patient in similar position to the landmark approach, and a high-frequency ultrasound probe is placed parasagitally on the side that the block is to be performed. After identification of the hyperechoic greater horn of the hyoid bone and thyrohyoid membrane, a needle is inserted out-of-plane immediately under the thyrohyoid membrane, and 1–2 ml of local anesthetic is injected following negative aspiration of blood [12 ▪▪ ]. Bilateral injections are performed regardless of approach.…”

“…In order to perform an awake intubation safely and to optimize the comfort of the patient, adequate anesthesia of upper and lower airways is crucial. Table 1 describes recent evidence for techniques of topicalization of the airways, which often compare the use of nerve blocks and nebulization [11,12 ▪▪ ,13–23]. Numerous studies have demonstrated the likely benefit of performing nerve blocks, including both superior laryngeal and transtracheal nerve blocks, over nebulization [13–18].…”