Ultrasound-Guided Thyroid Cartilage Plane Block vs Ultrasound-Guided Traditional Superior Laryngeal Nerve Block for Awake Fiberoptic Intubation in Patients With Limited Neck Mobility Undergoing Cervical Spine Fixation

The aim of the work to compare between the effectiveness and safety of ultrasound-guided superior laryngeal nerve block through surface injection of local anesthetic solution on the thyroid cartilage and ultrasound-guided traditional superior laryngeal nerve block on quality of airway anesthesia for awake fiberoptic intubation in patients with limited neck mobility undergoing cervical spine fixation.

The difficult airway is a challenge for the anesthesiologist. When a patient presents with anticipated difficult airway, the strategies can be varied, depending on the clinical context, the available resources, and the level of training of human resources. However, most clinical practice guidelines agree that difficult airway management shall be approached with the patient awake. Intubating the patient awake improves the perioperative safety, since it allows for spontaneous breathing, maintaining the patency of the airway, and cooperation with the operator.

Awake fibreoptic intubation (AFOI) is the gold standard in the management of the difficult airway.

Several ways to administer local anaesthetic to the upper airway to aid AFOI have been described including nebulisation, spray-as-you-go techniques and airway nerve blocks, each with its own potential advantages and disadvantages.

The objective of the ideal technique is the use of the lowest possible dose of the local anesthetic agent, to achieve a successful block that facilitates the intubation conditions, and increases the safety and tolerability of the patient.

Airway topicalization is commonly used to facilitate awake tracheal intubation and can be implemented in various ways. There are reservations about performing topical anesthesia of the airway because of some unsolved drawbacks, including poor airway anesthesia quality due to unreliable effects and the increased risk of exceeding the maximum dose of local anesthesia, leading to local anesthetic systemic toxicity (LAST).

Airway nerve blocks provide better anesthesia quality for awake tracheal intubation and lower overall complications than topical anesthesia.

Ultrasound-guided superior laryngeal nerve block is a viable alternative for topical anesthesia during awake tracheal intubation. However, direct recognition of the superior laryngeal nerve under ultrasonography can be challenging due to its small dimensions and large probe size. Several methods have been reported to block the superior laryngeal nerve, utilizing the thyroid hyoid membrane and superior laryngeal artery as anchors to locate the superior laryngeal nerve.

Thyroid cartilage plane block is a new approach for local anesthetic injection targeting an interfascial plane between the thyroid cartilage laminae and the muscle groups above. This approach, distant from any nerves or vascular structures, may offer enhanced safety compared to the superior laryngeal nerve space block.

Eligibility Criteria:
Inclusion Criteria:

* patients aged between 18-65 years
* either gender
* ASA I-II
* limited neck mobility

Exclusion Criteria:

* patients who refuse to give consent
* non-cooperative patients
* have asthma or ischemic heart disease
* preoperative hoarseness, sore throat
* mental or neurological disorders
* contraindications for regional block (coagulopathy , infection at the needle insertion site and allergy to local anesthetics)
* body mass index (BMI) \>26 kg/m2.