Ultrasound description of a superior laryngeal nerve space as an anatomical basis for echoguided regional anaesthesia

Abstract

I.V. access was obtained and ECG, pulse oximetry, and continuous invasive arterial pressure monitoring were established. The patient was placed in the right lateral position and commenced on NIV. The insertion of the intrathecal catheter was technically difficult, and the epidural space was located with a 16 G Tuohy and the use of the image intensifier and contrast. A dural tap was achieved at 7 cm and an intrathecal catheter inserted to 11 cm. After incremental titration with 5 ml of levobupivacaine 0.25%, a block to T12 provided conditions suitable for surgery, which was completed without incident.After operation, NIV was continued. An infusion of bupivacaine 0.1% was commenced intrathecally at 1-1.5 ml h 21 , providing excellent analgesia and was continued for the following 4 days. The infusion was titrated to block height of T10-11 which provided good analgesia with no respiratory problems or motor block. The catheter was removed on day 5, following which the patient's analgesia requirement were met with paracetamol and nefopam. The patient was discharged home on day 11.The heterogeneity of ventilator-dependent patients and small number of studies of perioperative care makes the prediction of risk difficult. Patients now focus on psychosocial factors, rather than survival, leading to the concept of prolonged survival and acceptable exposure to risk. In this patient cohort, preoperative assessment and risk stratification is complex. Symptoms such as dyspnoea and orthopnoea are often late findings and physical evaluation is essential to detect accessory muscle recruitment, supine abdominal paradox, and encumbrance of upper or lower airways. 1 A substantial loss of respiratory muscle strength is typically accompanied by little or no change in spirometry or arterial blood gases. 2 Lung function tests can reveal a characteristically low vital capacity, reduced total lung capacity, and preserved residual volume. Transfer factor is normal when adjusted for lung volume.Evaluation of respiratory muscle strength is extremely useful, and has been shown to be sensitive and prognostic. 3 Peak expiratory flow during cough gives an overall evaluation of cough efficiency, values below 160-270 litre min 21 suggesting poor airway clearance. Evaluation of respiratory muscle strength is achieved by measuring maximal inspiratory pressure (PImax) and sniff nasal inspiratory pressure. A maximal expiratory pressure (PEmax) below 45 cm H 2 O may indicate compromised cough efficiency.There are few reports of the use of Bipap in the operating theatre. 4 -7 Our case highlights that using intraoperative NIV can be useful, and avoid the need for general anaesthesia and invasive ventilation.

Sonographically Guided Superior Laryngeal Nerve Block During Awake Fiberoptic Intubation

“…[7][8][9] In cadavers, it is possible to simulate ultrasound-guided superior laryngeal nerve blockade and demonstrate dye placement around the nerve by placing the injectate either near the hyoid bone or directly onto the nerve. [8][9][10] Consistent sonographic visualization of the superior laryngeal nerve in patients however continues to be a challenge. 11 This case series demonstrated that effective ultrasoundguided superior laryngeal nerve block can be achieved in patients who require awake fiberoptic intubation.…”

“…Until recently, ultrasonographic visualization of the superior laryngeal nerve has not been possible due to its small size (1 mm diameter in most cases) and the limited resolution capabilities of most ultrasound imaging systems. [10][11][12] Relatively new improvements in ultrasound imaging technology have resulted in commercially available ultrasound probes that offer higher resolution.…”

“…Barberet et al 10 used a 12-MHz probe to demonstrate that it was possible to scan the superior laryngeal nerve space but not the superior laryngeal nerve in cadavers and 100 patients. They were able to visualize the thyroid cartilage and hyoid bone with the probe in a parasagittal plane.…”

Upper Airway Blocks for Awake Difficult Airway Management

“…Ultrasonography (US) has already been applied in assisting the performance of iSLN block, however, yielding conflicting results. Barberet et al, for instance, describe a 'SLN space' as an anatomical basis for echo-guided SLN block after being unable to identify the SLN in 100 volunteers using a 12 MHz linear probe 18 . They could not exclude the nerve being present in the SLN space, defined by them to be located between the hyoid bone superiorly, thyroid cartilage inferiorly, thyrohyoid muscle anteriorly and thyrohyoid membrane posteriorly -the structures optimally visualized in 81% of their scans.…”

Transverse approach for ultrasound-guided superior laryngeal nerve block for awake fiberoptic intubation

“…Initially, authors had suggested depositing the drug in superior laryngeal space. [2] Lately in a case series by Sawka et al ., they successfully visualized the SLN and accurately placed local anesthetic around it followed by AFOI. [3]…”