A method for ultrasonographic visualization and injection of the superior laryngeal nerve: volunteer study and cadaver simulation

Ultrasound-guided superior laryngeal nerve block: a randomized comparison between parasagittal and transverse approach

BACKGROUND

Different approach ultrasound-guided superior laryngeal nerve block was used to aid awake intubation, but little is known which approach was superior. We aimed to compare the parasagittal and transverse approaches for ultrasound-guided superior laryngeal nerve block in adult patients undergoing awake intubation.

METHODS

Fifty patients with awake orotracheal intubation were randomized to receive either a parasagittal or transverse ultrasound-guided superior laryngeal nerve block. The primary outcome was patient's quality of airway anesthesia grade during insertion of the tube into the trachea. The patients' tube tolerance score after intubation, total procedure time, mean arterial pressure, heart rate, Ramsay sedation score at each time point, incidence of sore throat both 1 h and 24 h after extubation, and hoarseness before intubation, 1 h and 24 h after extubation were documented.

RESULTS

Patients' quality of airway anesthesia was significantly better in the parasagittal group than in the transverse group (median grade[IQR], 0 [0-1] vs. 1 [0-1], P = 0.036). Patients in the parasagittal approach group had better tube tolerance scores (median score [IQR],1[1-1] vs. 1 [1-1.5], P = 0.042) and shorter total procedure time (median time [IQR], 113 s [98.5-125.5] vs. 188 s [149.5-260], P < 0.001) than those in the transverse approach group. The incidence of sore throat 24 h after extubation was lower in the parasagittal group (8% vs. 36%, P = 0.041). Hoarseness occurred in more than half of the patients in parasagittal group before intubation (72% vs. 40%, P = 0.023).

CONCLUSIONS

Compared to the transverse approach, the ultrasound-guided parasagittal approach showed improved efficacy in terms of the quality of airway topical anesthesia and shorter total procedure time for superior laryngeal nerve block.

TRIAL REGISTRATION

This prospective, randomized controlled trial was approved by the Ethics Committee of Nanjing First Hospital (KY20220425-014) and registered in the Chinese Clinical Trial Registry (19/6/2022, ChiCTR2200061287) prior to patient enrollment. Written informed consent was obtained from all participants in this trial.

Regional anesthesia and POCUS in the intensive care unit

This chapter focuses on resident recruitment and recent US National Resident Matching Program changes and the impact in the evaluation and ranking of applicants within the specialty of anesthesiology. Recruitment challenges are examined as well as program strategies and potential future directions. Also discussed are DEI initiatives within the recruitment process.

Preoperative Ultrasound-Guided Internal Branch Block of Superior Laryngeal Nerve Reduces Postoperative Sore Throat Caused by Double Lumen Endotracheal Intubation: A Randomized Trial

BACKGROUND

Postoperative sore throat (POST) is one of the more common side effects of tracheal intubation patients under general anesthesia (GA) after extubation using double-lumen endobronchial tubes (DLTs). The internal branches of the superior laryngeal nerve (SLN) block (iSLNB) have been reported to anesthetize the larynx for airway manipulation (such as awake tracheal intubation) and pain treatment efficiently. We hypothesized that ultrasound-guided iSLNB (US-guided iSLNB) combined with GA would ameliorate the incidence and severity of POST and hoarseness.

METHODS

Patients (n = 82) undergoing thoracoscopic resection of pulmonary nodules/lobes/segments with one-lung ventilation (OLV) under GA were randomized into 2 groups depending on whether performed with iSLNB (S group, n = 41) or not (C group, n = 41) under GA. Patients in the S group received US-guided iSLNB bilaterally before surgery. POST and hoarseness were assessed at 2, 6, and 24 hours after surgery. The primary outcome of this study was the incidence of POST at 6 hours after surgery between groups.

RESULTS

The overall accumulated incidence of POST was lower in the S goup than in the C group (9/41 vs 20/41; 95% CI, 0.30 [0.11-0.77]; P = .011). The incidence and severity of POST was lower in the S group than in the C group at 2 hours (9/41 vs 20/41; 95% CI, 0.30 [0.11-0.77]; P = .008 and P = .004) and 6 hours after (7/41 vs 17/41; 95% CI, 0.29 [0.10-0.81]; P = .012 and P = .015) surgery. The incidence and severity of POST at 24 hours after surgery was nonsignificant. However, the incidence and severity of hoarseness was comparable between the 2 groups at 2, 6, and 24 hours after surgery.

CONCLUSIONS

Preoperative US-guided iSLNB could significantly ameliorate the incidence and severity of POST induced by double-lumen bronchial catheter intubation.

Anesthetic management of airway stent placement by rigid bronchoscopy with superior laryngeal nerve block while preserving spontaneous breathing: A case report

Key Clinical Message

The combination of superior laryngeal nerve block can reduce the respiratory depression that occurs during management under total intravenous anesthesia.

Abstract

Anesthetic management of endobronchial stent placement by rigid bronchoscopy requires the maintenance of spontaneous breathing while suppressing upper airway reflexes. The combination of superior laryngeal nerve block (SLNB) can reduce the respiratory depression that occurs during management under total intravenous anesthesia. The patient was diagnosed as having lung cancer with invasion into the right middle bronchus and stenosis of the right main bronchus on chest computed tomography, and emergency airway stent placement was performed. Sedation was initiated with propofol and dexmedetomidine, and ultrasound-guided SLNB was performed after local anesthetic spraying into the oral cavity and trachea. Bucking was minimally controlled during insertion of the rigid bronchoscope. The patient's intraoperative hemodynamics remained stable, and there were no hypoxic events. SLNB can provide the suppression of the upper airway reflex while minimizing effects on spontaneous breathing, and may be useful for achieving balanced anesthesia during rigid bronchoscopy.

Modified anterior approach versus traditional posterior approach for ultrasound-guided superior laryngeal nerve block in awake endotracheal intubation: a randomized non-inferiority clinical trial

STUDY OBJECTIVE

This study was undertaken to compare the effect of the modified ultrasound-guided anterior superior laryngeal nerve block (SLNB) with the traditional ultrasound-guided posterior SLNB in providing intubation conditions during awake tracheal intubation (ATI) in patients without difficult airway.

DESIGN

Randomized, assessor-blind. Registration number: ChiCTR2200058086.

SETTING

West China Hospital of Sichuan University, Chengdu, China.

PATIENTS

104 patients aged 18-65 years, of American Society of Anesthesiologists status I-III, posted for elective general surgery with general endotracheal anesthesia.

INTERVENTIONS

The patients were randomized into two groups (modified group, n = 52; traditional group, n = 52). Modified anterior SLNB or traditional posterior SLNB was performed under ultrasound guidance.

MEASUREMENTS

The primary outcome was the proportion of acceptable intubation condition (AIC), which was analyzed in both per-protocol (PP) and intention-to-treat (ITT) populations. The prespecified non-inferiority margin was -4.8%. Secondary outcomes included intubation success rate on the first attempt, hemodynamic parameters during ATI, time taken for airway anesthesia and intubation, recall of intubation, patient perception of comfort, and incidence and severity of postoperative complications.

MAIN RESULTS

In the PP population, the proportion of AIC in the modified group was 49/49 (100%) and that in the traditional group was 49/49 (100%), absolute difference 0, lower limit of 1-sided 95% CI, -0.3%. In the ITT population, the primary outcomes in the modified and traditional group were 52/52 (100%) and 51/52 (98.1%), respectively, with an absolute difference of 1.9% and a lower limit of 1-sided 95% CI of -1.2%. The non-inferiority of modified ultrasound-guided anterior SLNB was confirmed in both populations.

CONCLUSIONS

Among adults without difficult airways during videolaryngoscope-assisted ATI, the modified ultrasound-guided anterior SLNB, compared to the traditional posterior approach, showed a statistically non-inferior effect in terms of providing AIC.

Airway nerve blocks for awake tracheal intubation: A meta-analysis of randomized control trials and trial sequential analysis

STUDY OBJECTIVE

This systematic review and meta-analysis aimed to assess the superiority of airway nerve blocks versus airway anesthesia without nerve blocks for awake tracheal intubation (ATI).

DESIGN

Systematic review and meta-analysis of randomized controlled trials (RCTs).

SETTING

All studies that assessed the superiority of airway anesthesia technique for awake tracheal intubation were searched in PubMed, Web of Science, Cochrane Library, Ovid Medline, Embase and Chinese databases (including China National Knowledge Infrastructure, Wanfang database, and VIP databases) and trial registry databases from their inception to December 2022.

PATIENTS

Adult patients included in randomized controlled trials comparing airway anesthesia with or without airway nerve blocks for ATI.

INTERVENTIONS

Airway nerve (including superior laryngeal nerve, glossopharyngeal nerve, or recurrent laryngeal nerve) blocks for ATI.

MEASUREMENTS

The primary outcome was the intubation time. Secondary outcomes were quality of intubating conditions (including patient reaction to placement of the flexible scope and tracheal tube, coughing and gagging, and patient satisfaction) and overall complications during ATI.

MAIN RESULTS

Fourteen articles with 658 patients were identified for analysis. When compared with airway anesthesia without nerve blocks, airway nerve blocks significantly reduced intubation time (standardized mean difference [SMD] -2.57, 95% CI -3.59- -1.56, p < 0.00001), improved anesthesia quality of ATI with higher no reaction to placement of the flexible scope and tracheal tube (relative risk [RR] 9.87; 95% CI 4.10-23.75, p < 0.00001), lower cough or gag reflex during intubation (RR 0.35, 95% CI 0.27-0.46, p < 0.00001), higher excellent patient satisfaction rate (RR 1.88, 95% CI 1.05-3.34, p = 0.03), and lower overall complications (RR 0.29, 95% CI 0.19-0.45, p < 0.00001). The overall quality of evidence was moderate.

CONCLUSIONS

Based on current published evidence, airway nerve blocks provide better airway anesthesia quality for ATI with a shorter intubation time, better intubation conditions including higher no reaction to placement of the flexible scope and tracheal tube, lower cough or gag reflex during intubation, higher excellent patient satisfaction, and lower overall complications.

Comparison of landmark-guided and ultrasound-guided technique for superior laryngeal nerve block to aid fibreoptic intubation - An observational study

Background and Aims

Awake fibreoptic intubation (AFOI) is the gold standard in the management of the difficult airway. Several methods to achieve airway anesthesia to aid AFOI include superior laryngeal nerve block (SLNB). This study aimed to compare land-mark-guided and ultrasound-guided techniques for SLNB to aid AFOI.

Material and Methods

This was a prospective, observational study. Patients in both groups received 1 mg Midazolam and 50 μg of fentanyl for mild sedation before intubation, nasal passages were anaesthetized using lignocaine-coated nasopharyngeal airways, nebulization of 3 ml of 2% lignocaine, and intratracheal injection of 2 ml of 2% lignocaine given through cricothyroid membrane. Patients in Group L received SNLB, at the lateral end of the thyrohyoid membrane (2 ml of 1.5% lignocaine). Patients in Group U had their thyrohyoid membrane visualized using linear ultrasound probe (8 - 13 Hz) and the injection was placed just superficial to the membrane using out of plane method. The groups were compared with respect to quality of anesthesia (assessed on a 5-point scale), patient comfort during AFOI, time taken to intubation and Haemodynamics.

Results

A total of 25 patients were enrolled: 13 in Group L and 12 patients in Group U. The demographics were comparable. Quality of airway anesthesia, time taken to intubation, haemodynamics and patient comfort were comparable. All were intubated successfully and there were no complications.

Conclusion

USG-guided SLNB was comparable to landmark-based method with respect to quality of airway anesthesia and patient comfort. USG-guided block did not add any advantage over the landmark-based method.

Ultrasonography for airway management

Ultrasonography (USG) allows a new approach to the airway in anaesthesia and intensive care. USG visualises the airway from the mouth to the lungs. By exploring the entire airway, USG proposes new criteria (1) to assess the risk of difficult laryngoscopy, (2) to anticipate the management of a difficult airway, (3) to confirm the position of the endotracheal tube (ETT), and (4) to confirm that the lungs are effectively ventilated. Intraoperatively, USG may also help to resolve acute ventilatory problems such as pneumothorax, delayed selective bronchial intubation after patient positioning (Trendelenburg, prone or lateral position) or acute pulmonary oedema.

Awake fiberoptic orotracheal intubation: a protocol feasibility study

Objective

To assess the feasibility of an awake fiberoptic intubation (AFOI) protocol.

Methods

We enrolled 40 patients with simulated difficult intubation. The protocol consisted of conscious sedation (midazolam, 0.03 mg/kg and sufentanil, 0.1 µg/kg), regional anesthesia, and intubation. The time, first-attempt intubation success rate, hemodynamic parameters, blood oxygen saturation (SpO₂), intubation amnesia rate, patient satisfaction, and relative complications were recorded.

Results

AFOI was completed in all patients. The average total AFOI time was 14.17 ± 1.47 minutes, and the time to placing the landmark-guided bilateral superior laryngeal nerve block was 1.24 ± 0.42 minutes. The first-attempt intubation success rate was 97.5%, and patient satisfaction was 90%. Blood pressure changed (<20%) briefly after administering conscious sedation. Heart rates did not change significantly, and SpO₂ remained stable and ≥95%. Three patients had a sore throat, which resolved on postoperative day 1 without other complications. On postoperative day 1, 82.5% (33/40) of the patients had no recall of AFOI, and 17.5% (7/40) had only an indistinct memory.

Conclusions

The protocol was feasible with a high first-attempt intubation success rate and low complications rate. Hemodynamic parameters and respiration remained stable, with high patient satisfaction and effective amnesia.

Ultrasound-guided internal branch of superior laryngeal nerve block on postoperative sore throat: A randomized controlled trial

Introduction

Ultrasound-guided internal branch of the upper laryngeal nerve block (USG-guided iSLN block) have been used to decrease the perioperative stress response of intubation. It is more likely to be successful than blindly administered superior laryngeal nerve blocks with fewer complications. Here, we evaluated the efficacy of USG-guided iSLN block to treat postoperative sore throat (postoperative sore throat, POST) after extubation.

Methods

100 patients, aged from 18 to 60 years old, ASA I~II who underwent general anesthesia and suffered from the moderate to severe postoperative sore throat after extubation were randomized into two groups(50 cases per group). Patients in group S received USG-guided iSLN block bilaterally (60mg of 2% lidocaine, 1.5ml each side), whereas those in group I received inhalation with 100 mg of 2% lidocaine and 1mg of budesonide suspension diluted with normal saline (oxygen flow 8 L /min, inhalation for 15 minutes). The primary outcome were VAS scores in both groups before treatment (T0), 10 min (T1), 30 min(T2), 1h(T3), 2 h(T4), 4h(T5), 8h(T6), 24h(T7), and 48h(T8) after treatment. The secondary outcome were satisfaction scores after treatment, MAP, HR, and SPO2 fromT0 to T8. The adverse reactions such as postoperative chocking or aspiration, cough, hoarseness, dyspnea were also observed in both groups.

Results

Patients in group S had significantly lower VAS score than that in group I at points of T₁ ~ T₆ (P < 0.01). HR of group S was lower than that of group I at points of T₁ ~ T₂and T4 (P < 0.05), and MAP was lower than that of group I at points of T₁ ~ T₃ (P < 0.05). Satisfaction scores of group S were higher than that of group I (P <0.05), In group S, 2 case (4%) needed to intravenous Flurbiprofen Injection 50 mg to relieve pain; in group I, 13 cases (26%) received Flurbiprofen Injection. 2 case of group S appeared throat numbness after treatment for 3 hours; 2 patients have difficult in expectoration after treatment recovered after 3hour. No serious adverse events were observed in both groups.

Conclusion

Compared with inhalation, USG-guided iSLN block may effectively relieve the postoperative sore throat after extubation under general anesthesia and provided an ideal treatment for POST in clinical work.

High frequency jet ventilation at the distal end of tracheostenosis during flexible bronchoscopic resection of large intratracheal tumor: Case series

INTRODUCTION

Resection of a large intratracheal tumor with severe obstruction via flexible bronchoscope remains a formidable challenge to anesthesiologists. Many artificial airways positioned proximal to tracheal obstruction can not ensure adequate oxygen supply. How to ensure effective gas exchange is crucial to the anesthetic management.

PATIENT CONCERNS

Five patients of intratracheal tumor occupying 70% to 85% of the tracheal lumen were scheduled for tumor resection via flexible bronchoscope.

DIAGNOSIS

The patients were diagnosed with intratracheal tumor based on their symptoms, radiographic findings and tracheoscopy.

INTERVENTIONS

We describe a technique of high frequency jet ventilation (HFJV) using an endobronchial suction catheter distal to tracheostenosis during the surgery, which ensured the good supply of oxygen. We applied general anesthesia with preserved spontaneous breathing. A comprehensive anesthesia protocol that emphasizes bilateral superior laryngeal nerve (SLN) block and sufficient topical anesthesia. An endobronchial suction catheter was introduced transnasally into the trachea and then advanced through the tracheostenosis with the tip proximal to the carina under direct vision with the aid of fiber bronchoscope. HFJV was then performed through the suction catheter.

OUTCOMES

The SPO2 maintained above 97% during the surgery. Carbon dioxide retention was alleviated obviously when adequate patency of the trachea lumen achieved about 30 min after the beginning of surgery. HFJV was ceased and all patients had satisfactory spontaneous breathing at the end of the procedure.

CONCLUSION

HFJV at the distal end of tracheostenosis is a suitable ventilation strategy during flexible bronchoscopic resection of a large intratracheal tumor.

Ultrasound appearance of peripheral nerves in the neck: vagus, hypoglossal and greater auricular

Background and aim

Information in ultrasonography about reference values of nerves, particularly of those located in the neck is limited. The aim of the study is to demonstrate the feasibility of direct visualization of the vagus, hypoglossal and greater auricular nerves, testing the method on healthy volunteers and estimate the reference values for two perpendicular diameters and cross-sectional area (CSA).

Methods

A prospective study was carried out on 21 healthy volunteers (12 women and 9 men), recording their demographic characteristics. A 13 MHz transducer was used on a Hitachi EUB-8500 machine. The vagus nerve was measured at the bifurcation of common carotid artery (CCA) and at the intersection of the internal jugular vein with omohyoid muscle. The hypoglossal nerve was identified as it crosses the posterolateral border of the mylohyoid muscle in the submandibular space. The auricular nerve was identified on the superficial surface of the sternocleidomastoid muscle at 1 cm from its posterior margin. The mean CSA on axial scans, nerve width and thickness were determined. The side-to-side and gender differences of the estimated reference values and their correlations with the weight, height, and body mass index (BMI) were evaluated.

Results

The mean ultrasound-estimated CSA was measured for the vagus nerve at CCA bifurcation (2.14 ± 0.79 on the left 2.86 ± 1.27 on the right), vagus nerve at the level of omohyoid muscle (2.10 ± 0.06 on the left and 2.43 ± 0.08 on the right), hypoglossal nerve (1.71 ± 0.08 on the left, 1.24 ± 0.06 on the right) and greater auricular nerve (0.90 ± 0.53 on the left and 0.79 ± 0.71 on the right). The vagus nerve was significantly larger on the right side compared to the left side. Larger hypoglossal nerve was observed in men compared to women. Significant correlations were observed between weight and CSA of the greater auricular nerve.

Conclusion

Direct visualization of the vagus, greater auricular nerve and hypoglossal nerves is feasible. Reference values for the size of the studied nerves at specific anatomic landmarks were established. Side, gender and body weight differences of the nerves CSA were noted.

Ultrasound measurement of anatomical parameters of the upper airway in adults

BACKGROUND

Most of the works on ultrasound airway anatomy are limited to a morphological description. A study was conducted in order to provide an objective normal range of measurements.

MATERIALS AND METHODS

Observational study to describe the ultrasound characteristics of the upper airway in adults without clinical difficult airway criteria, compared to cadaver dissection anatomical models.

RESULTS

The study included 45 volunteers (27 men and 18 women), and 3fresh cadavers. The quality of the examination was very good/good in 93% of the cases.

MEASUREMENTS

tracheal diameter (1.3±0.3cm), vocal cord (1.6±0.5cm), cricothyroid membrane (0.94±0.32cm), cricotracheal membrane (0.3±0.09cm), thickness of the muscles in the floor of the mouth (MFM) (1.5±0.26cm), sub-mandibular subcutaneous fat plus MFM (2.11±0.34cm), hyoid-mandible distance (5.35±0.69cm), palate-floor of the mouth distance (4.92±0.5cm), palate-anterior border of the mandible (5.51±0.7cm), and palate-pharynx angle (114±14). Observed differences: Males had a larger tracheal diameter than females (M: 1.4±0.3 vs. F: 1.2±0.2cm, p=0.014). Subject height showed a significant correlation with the tracheal diameter (R: 0.501, p<0.001), as well as the length of the vocal cord (R: 0.363, p=0.016), the thickness of MFM (R=0.299, p=0.046) as well as the hyoid-mandible (R: 0.556; p<0.001) and palate-mandible distances (R: 0.362; p=0.015).

CONCLUSIONS

Ultrasound allows the anatomy of upper airway to be evaluated, as well as to calculate distances between the anatomical structures. The study defines these distances in adult volunteers without clinical difficult airway criteria.

Ultrasound-Guided Glossopharyngeal Nerve Block: A Cadaver and a Volunteer Sonoanatomy Study

BACKGROUND AND OBJECTIVES

Glossopharyngeal nerve (GPN) blocks are usually performed by topical, intraoral, or peristyloid approaches, which carry significant complication risks due to the proximity of important neurovascular structures. This study presents a proof of concept for a new ultrasound (US)-guided technique, which would block the GPN distally, in the parapharyngeal space, away from the immediate vicinity of high-risk collateral structures.

METHODS

Five cadaver heads were dissected, and the location of the GPN was explored bilaterally. In 40 healthy volunteers (20 men and 20 women; median age, 35.5 years [range, 24-69 years]) parapharyngeal sonograms were obtained, saved, and analyzed. To assess the technical feasibility of a distal GPN block in the parapharyngeal space, unilateral US-guided dye injections were performed in 3 fresh cadavers, followed by dissections.

RESULTS

The GPN was consistently identified between the stylopharyngeal and middle pharyngeal constrictor muscles in all cadaver specimens. The median distance between the GPN and the ipsilateral greater horn of the hyoid bone was 2.4 cm (range, 2.3-2.7 cm) on the right and 2.6 cm (range, 2.3-2.9 cm) on the left. The mean skin-to pharyngeal wall distances in the volunteers were 2.03 (SD, 0.41) cm on the right and 2.02 (SD, 0.45) cm on the left. The mean hyoid bone-to-pharyngeal wall distances were 2.04 (SD, 0.35) cm (right) and 2.07 (SD, 0.35) cm (left). The fresh cadaver dissections demonstrated dye deposition adjacent to the GPN in the parapharyngeal space in all specimens.

CONCLUSIONS

Based on our anatomical results in cadavers and healthy volunteers, we submit that successful and safe blockade of the distal GPN at the pharyngeal wall level is technically feasible under US guidance.

Comparison of ultrasound and anatomical landmark-guided technique for superior laryngeal nerve block to aid awake fibre-optic intubation: A prospective randomised clinical study

Background and Aims:

Ultrasonography has emerged as a novel, portable, non-invasive tool encouraging airway assessment and procedural interventions. This study assesses the feasibility of ultrasound for block of internal branch of superior laryngeal nerve (ibSLN) block during upper airway anaesthesia to aid awake fibre-optic intubation.

Methods:

Forty American Society of Anesthesiologists’ physical status I–II patients, aged 18–60 years, deemed to have a difficult airway (modified Mallampati class III–IV or inter-incisor distance <2.5 cm) and planned for awake fibre-optic intubation were randomised to either landmark group (L, n = 20) or ultrasound group (U, n = 20). All patients received nebulised 4% lignocaine (3 mL) and transtracheal injection 3 mL 2% lignocaine. Group L received landmark-guided bilateral ibSLN block with 1 mL 2% lignocaine. Group U received bilateral ibSLN block with 1 mL 2% lignocaine using a high-frequency ultrasound transducer to define the SLN space. The primary objective was assessment of quality of airway anaesthesia. Secondary objectives were time for intubation, haemodynamic parameters and patient perception of discomfort during procedure.

Results:

The quality of anaesthesia was significantly better in Group U than in Group L (P < 0.001). The mean time for intubation was shorter in Group U (71.05 ± 9.57 s) compared to Group L (109.05 ± 30.09 s, P < 0.001). Heart rate, mean arterial pressure and patient perception of discomfort were significantly increased in Group L.

Conclusion:

Ultrasound for ibSLN block as a part of preparation for awake fibre-optic intubation improves quality of airway anaesthesia and patient tolerance.

Ultrasound: A promising tool for contemporary airway management

Airway evaluation and its management remains an ever emerging clinical science. Present airway management tools are static and do not provide dynamic airway management option. Visualized procedures like ultrasound (US) provide point of care real time dynamic views of the airway in perioperative, emergency and critical care settings. US can provide dynamic anatomical assessment which is not possible by clinical examination alone. US aids in detecting gastric contents and the nature of gastric contents (clear fluid, thick turbid or solid) as well. US can help in predicting endotracheal tube size by measuring subglottic diameter and diameter of left main stem bronchus. US was found to be a sensitive in detecting rotational malposition of LMA in children. Also, US is the fastest and highly sensitive tool to rule out a suspected intraoperative pneumothorax. In intensive care units, US helps torule out causes of inadequate ventilation, determine the tracheal width and distance from the skin to predict tracheotomy tube size and shape and assist with percutaneous dilatational tracheostomy. US can help in confirming the correct tracheal tube placement by dynamic visualisation of the endotracheal tube insertion, widening of vocal cords (children), and bilateral lung-sliding and diaphragmatic movement. Thus, ultrasonography has brought a paradigm shift in the practise of airway management. With increasing awareness, portability, accessibility and further sophistication in technology, it is likely to find a place in routine airway management. We are not far from the time when all of us will be carrying a pocket US machine like stethoscopes to corroborate our clinical findings at point of care.

Sonographically guided superior laryngeal nerve block during awake fiberoptic intubation

We report 5 patients who underwent ultrasound-guided superior laryngeal nerve block before awake intubation and general anesthesia. We used a 8- to 15-MHz hockey stick-shaped ultrasound transducer (HST15-8/20 linear probe, Ultrasonix) to visualize the superior laryngeal nerve. A 3.8-cm 25-G needle was inserted in real time and directed toward the superior laryngeal nerve followed by circumferential placement of local anesthetic. All 5 patients tolerated subsequent awake fiberoptic intubation with either minimal or no sedation. Sonographically guided superior laryngeal nerve block may be useful in patients where identification of landmarks in the neck is difficult as a result of patient anatomy.

The thyrohyoid membrane as a target for ultrasonography-guided block of the internal branch of the superior laryngeal nerve

STUDY OBJECTIVE

The objective was to present a proof of concept for a simple and consistently successful ultrasonograpy (US)-guided technique to block the internal branch of the superior laryngeal nerve (iSLN).

DESIGN

This was a volunteer and cadaver anatomy study.

SETTING

The setting was an anesthesiology department and an anatomy laboratory at a medical school

MEASUREMENTS

H13-6 MHz US scans were performed in 40 healthy volunteers positioned supine and with extended necks. The goals were to identify the thyrohyoid membrane, measure its depth (in centimeters) using the shortest vertical distance from the skin, and record the scanning time (in seconds) needed to obtain the optimal image. Anatomical dissection was performed with an operating microscope bilaterally on 5 adult cadaver heads, fixed in formalin, to expose the point of iSLN penetration through the thyrohyoid membrane. The distance between the greater horn of the hyoid bone and the nerve entry point into the thyrohyoid membrane was measured. Ultrasonography-guided in-plane injections were performed unilaterally with 22-gauge 50-mm nerve block needles in 3 fresh cadavers with 2-mL lidocaine/methylene blue mixture deposited under direct vision just superficial to the thyrohyoid membrane to evaluate technical feasibility and injectate spread.

MAIN RESULTS

Anatomically, the iSLN was identified in all formalin-preserved cadavers, with hyoid bone greater horn to nerve-membrane interface distances measuring 1.0-2.4 cm (mean, 2.0 cm; SD, 0.5). Sonographically, the iSLN was not visualized, whereas the hyoid bone and the thyrohyoid membrane were visualized in all volunteers. The mean distance from skin to thyrohyoid membrane was 1.69 cm (SD, 0.38). The mean time needed to scan was 15 seconds (SD, 2.3). After US-guided injection, the dye deposition was observed around the iSLN in all cadaver specimens.

CONCLUSIONS

A simpler and consistently reproducible US-guided iSLN block is feasible using the thyrohyoid membrane as target plane for local anesthetic injection. Clinical trials are needed to determine its effectiveness and safety, needle entry point, trajectory, and local anesthetic volume.

Ultrasonography for clinical decision-making and intervention in airway management: from the mouth to the lungs and pleurae

OBJECTIVES

To create a state-of-the-art overview of the new and expanding role of ultrasonography in clinical decision-making, intervention and management of the upper and lower airways, that is clinically relevant, up-to-date and practically useful for clinicians.

METHODS

This is a narrative review combined with a structured Medline literature search.

RESULTS

Ultrasonography can be utilised to predict airway difficulty during induction of anaesthesia, evaluate if the stomach is empty or possesses gastric content that poses an aspiration risk, localise the essential cricothyroid membrane prior to difficult airway management, perform nerve blocks for awake intubation, confirm tracheal or oesophageal intubation and facilitate localisation of tracheal rings for tracheostomy. Ultrasonography is an excellent diagnostic tool in intraoperative and emergency diagnosis of pneumothorax. It also enables diagnosis and treatment of interstitial syndrome, lung consolidation, atelectasis, pleural effusion and differentiates causes of acute breathlessness during pregnancy. Patient safety can be enhanced by performing procedures under ultrasound guidance, e.g. thoracocentesis, vascular line access and help guide timing of removal of chest tubes by quantification of residual pneumothorax size.

CONCLUSIONS

Ultrasonography used in conjunction with hands-on management of the upper and lower airways has multiple advantages. There is a rapidly growing body of evidence showing its benefits.

TEACHING POINTS

• Ultrasonography is becoming essential in management of the upper and lower airways. • The tracheal structures can be identified by ultrasonography, even when unidentifiable by palpation. • Ultrasonography is the primary diagnostic approach in suspicion of intraoperative pneumothorax. • Point-of-care ultrasonography of the airways has a steep learning curve. • Lung ultrasonography allows treatment of interstitial syndrome, consolidation, atelectasis and effusion.

Ultrasound for the anesthesiologists: present and future

Ultrasound is a safe, portable, relatively inexpensive, and easily accessible imaging modality, making it a useful diagnostic and monitoring tool in medicine. Anesthesiologists encounter a variety of emergent situations and may benefit from the application of such a rapid and accurate diagnostic tool in their routine practice. This paper reviews current and potential applications of ultrasound in anesthesiology in order to encourage anesthesiologists to learn and use this useful tool as an adjunct to physical examination. Ultrasound-guided peripheral nerve blockade and vascular access represent the most popular ultrasound applications in anesthesiology. Ultrasound has recently started to substitute for CT scans and fluoroscopy in many pain treatment procedures. Although the application of airway ultrasound is still limited, it has a promising future. Lung ultrasound is a well-established field in point-of-care medicine, and it could have a great impact if utilized in our ORs, as it may help in rapid and accurate diagnosis in many emergent situations. Optic nerve sheath diameter (ONSD) measurement and transcranial color coded duplex (TCCD) are relatively new neuroimaging modalities, which assess intracranial pressure and cerebral blood flow. Gastric ultrasound can be used for assessment of gastric content and diagnosis of full stomach. Focused transthoracic (TTE) and transesophageal (TEE) echocardiography facilitate the assessment of left and right ventricular function, cardiac valve abnormalities, and volume status as well as guiding cardiac resuscitation. Thus, there are multiple potential areas where ultrasound can play a significant role in guiding otherwise blind and invasive interventions, diagnosing critical conditions, and assessing for possible anatomic variations that may lead to plan modification. We suggest that ultrasound training should be part of any anesthesiology training program curriculum.