Adaptation of Nerve Stimulation Technology to Aid Transtracheal Needle Insertion and Injection

Background and rationale

The trachea can be anesthetized by several different methods, one of which is transtracheal injection of a local anesthetic such as lidocaine. This technique is performed to prepare a patient for a variety of procedures, including awake fibreoptic intubation and cricothyroidotomy. Tracheal anesthesia is performed by first identifying the cricothyroid ligament; this structure is generally located by placing one finger on the thyroid cartilage and another on the cricoid cartilage. Approximately 4-6 mL of local anesthetic is delivered through a small needle or an intravenous catheter inserted in the neck midline. Anesthesia occurs quickly and permits the patient to be awake and aware during the procedures that follow.

Insertion of a needle into the trachea is not without risk to the patient. Several complicating factors affect the success rate of tracheal needle insertion, and in emergency situations where oxygen must be delivered through the insertion site, as in cricothyroidotomy, accurate needle insertion can mean the difference between life and death for the patient. One complicating factor in this procedure is that the thyroid cartilage and the cricoid cartilage can be difficult to identify, especially in obese people. Needle insertion is made more complicated due to the anatomy surrounding the cricothyroid membrane: the carotid artery and jugular vein lie laterally to the membrane, the cricothyroid artery is located superiorly and laterally, and the highly vascularized thyroid gland is located inferiorly. Intravascular injection of anesthetic can lead to a seizure, and inaccurate injection could lead to anesthesia of surrounding nerves. There is also a risk of puncturing through the posterior wall of the trachea, which may cause esophageal perforation.

Given these complications, a quick and easy method of ensuring accurate tracheal needle insertion, while avoiding damage to surrounding tissues, would greatly benefit clinicians and could potentially save lives in emergency situations. We wish to evaluate a simple technique to guide a needle tip into the trachea that mitigates the risks of conventional methods of needle insertion. We will use nerve stimulation equipment to aid in the guidance and placement of a needle tip into the tracheal lumen, which we predict will be faster and more accurate than current conventional methods. The nerve stimulation technology can alert the user to the exact moment the needle tip is suspended in the trachea and also alerts the user to when the needle tip is in contact with body tissue, avoiding accidental puncture of the lateral and posterior tracheal walls. We believe that this method of electrically-guided needle insertion will be a significant improvement over current methods of percutaneous needle insertion and transtracheal injection.

Study objective To assess the value of nerve stimulation equipment for guidance and placement of a needle-catheter assembly for transtracheal injection.