Transcricothyroid injection of local anaesthesia: a serious complication

Abstract

Transcricothyroid membrane (CTM) injection of local anaesthesia is widely used during bronchoscopic procedures. It is an effective way of delivering topical anaesthesia, and has been shown to reduce patient discomfort, improve clinician satisfaction and reduce overall sedation requirements. Risks from this procedure are uncommon and usually minor. Localisation of the CTM is usually performed clinically by palpation of anatomical landmarks and can vary depending on clinician skillset and experience. Clinical identification may be less accurate compared with ultrasound guidance in identifying puncture site, however, ultrasound is not always readily available and seldom used for this purpose. This case describes a rare complication following attempted local anaesthetic infiltration into the cricothyroid space, after clinical identification of puncture site. An obstructive fluid-filled mass formed around the site of injection on the right vocal cord; resulting in airway compromise, abandonment of procedure and subsequent intubation.

Background

Cricothyroid membrane (CTM) injection of local anaesthetic is a commonly used form of anaesthetic delivery during bronchoscopy and there is good evidence surrounding its utility.¹ A randomised control trial showed a reduction in patient cough count, increased patient willingness to return and a lower cumulative lidocaine requirement in the cricothyroid group compared with spray-as-you-go method for topical anaesthesia. Complications described include minor bleeding and case reports of local surgical emphysema, with spontaneous recovery.^{2 3} Serious complications such as airway obstruction have not been reported.

Case presentation

A 73-year-old woman presented for elective bronchoscopy for investigation of a right middle lobe mass and mediastinal adenopathy. She had a hoarse voice for years, with some progression over the preceding months. She was a heavy active smoker.

Her initial observations prebronchoscopy showed saturations of 96% on room air, respiratory rate of 16/min. There was no stridor or respiratory distress. Her weight was 59.8 kg with a body mass index (BMI) of 23 kg/m². Her neck circumference was 34 cm.

Sedation used preprocedure was 4 mg midazolam intravenously and 75 μg fentanyl intravenously. She had 5 sprays of 5% cophenylcaine in each nostril and five sprays orally. The CTM was identified by inspection and palpation on neck extension by a first year respiratory advanced trainee. A 5 mL 2% lidocaine (20 mg/mL) was injected through her CTM via a 23-gauge butterfly-needle (19 mm length). There was no resistance on needle insertion and air was aspirated prior to injection with subsequent patient coughing as expected.

Bronchoscopy was performed via the perioral route. An obstructive mass was found on the right vocal cord, which appeared to be fluid filled. This was located immediately posterior to the needle puncture site. The mass was obstructing approximately 70% of the airway (figure 1) and the patient developed stridor without hypoxia, needing jaw support. No distal intratracheal puncture site was identified. Due to concerns of pending airway obstruction, the procedure was aborted. She had an uncomplicated intubation and was transferred to the intensive care unit for monitoring. No intervention including aspiration of the lesion was performed. Intravenous dexamethasone was administered for vocal cord oedema and the patient was monitored overnight. The following day, no specific intervention was documented prior to extubation. Routine pre-extubation assessments performed by the intensive care team were carried out. She was extubated without complication with no recurrent stridor or respiratory distress, however, voice hoarseness was ongoing.

Figure 1.

Initial bronchoscopy showing partially obstructive, fluid-filled mass arising from the right vocal cord.

A repeat awake bronchoscopy was performed the following week to inspect the larynx. There was some residual swelling of the right vocal cord with significant improvement and near resolution of the fluid-filled mass (figure 2).

Figure 2.

Relook bronchoscopy showing marked improvement of right vocal cord swelling, with some residual oedema.

The obstructive mass was thought most likely to represent an iatrogenic collection caused by misplaced lidocaine injection directly into the right vocal cord. This may have occurred as a result of cranial angling of the needle during insertion, rather than perpendicular to the CTM, and dislodgement of needle superiorly on coughing. While it is possible that there was a pre-existing lesion on the right vocal cord given the history of hoarse voice, the development of stridor post-CTM injection and the marked improvement of the lesion after 1 week makes this less likely.

Outcome and follow-up

The patient did not have any long-term sequelae from her initial complicated bronchoscopy to date. A repeat procedure with fine-needle aspiration of the mediastinal lymph nodes yielded a diagnosis of metastatic adenocarcimona of the lung. She was commenced on chemoradiotherapy and receives ongoing oncology follow-up.

Discussion

The CTM is usually identified clinically by visual inspection and palpation. Success rates have varied in the literature, depending on sex, patient positioning and body habitus. In a prospective study assessing correct identification of the CTM in 12 healthy subjects by 61 anaesthetic trainees (6 with BMI <30 kg/m²), 72% of non-obese men, 39% of obese men, 24% of non-obese women and 35% obese women had correct localisation by palpation as compared with subsequent ultrasound-guided identification.⁴ Another study assessed localisation of CTM of 2 overweight subjects by palpation and ultrasound guidance by 12 residents, with a repeat study 6 months later after renewal of skills. CTM was accurately identified in 46% by palpation and 100% on ultrasound. Six months later, localisation improved with ultrasound but not with palpation.⁵

A randomised controlled trial assigned 47 anaesthestic residents to digital palpation or ultrasound for identification of CTM puncture site in human cadavers. Ultrasound guidance significantly reduced the incidence of potential injuries to the upper airway and significantly increased the probability of correct CTM insertion. Only 9/23 residents allocated to the digital palpation group correctly identified the CTM compared with 15/24 in the ultrasound group.⁶

CTM injections are often performed prebronchoscopy with digital palpation of the space. Aspiration of air usually confirms puncture of the needle into the tracheal lumen, however, is not specific for correct localisation. This case describes a rare complication of misplaced local anaesthetic infiltration leading to potentially life-threatening airway obstruction and highlights the importance of careful injection site identification and infiltration technique. In this case, as air was initially aspirated, the most likely cause of the complication described was due to needle migration into the vocal cord during injection. Possible ways of mitigating this risk are to hold the needle in place and frequent aspiration of air to confirm needle tip position during injection.

CTM can be difficult to localise, especially in patients who are obese with poorly defined neck anatomy. Its correct identification has been shown to be suboptimal in the literature, with ultrasound-guidance being a much more reliable method. However, this may not be feasible preprocedure due to clinician expertise with ultrasound, ultrasound access and time restrains. Therefore, extra care needs to be taken with clinical identification prior to local anaesthetic infiltration, and CTM injection should not proceed in case of any doubt or concern on localisation via palpation or physician inexperience. Kristensen et al describe 42 anaesthetists receiving a 1-hour multimodality structured training programme in identification of CTM using ultrasound technique, either using the longitudinal or transverse approach on patients with poorly palpable neck anatomy. The mean time to identify the CTM was 24.0 s and 37.6 s, respectively.⁷ This suggests that a similar ultrasound training session could be considered for bronchoscopists, and its utility would be particularly valuable in patients with poor neck anatomy, without adding significant time burden to the procedure.

Learning points.

• Cricothyroid membrane (CTM) can be difficult to localise, especially in patients with poorly defined neck anatomy. Ultrasonography is a more reliable method.

• In cases where there is clinical uncertainty and limited proceduralist expertise, CTM injection should not proceed.

• Misplacement of local anaesthetic infiltration can lead to serious consequences, including potentially life-threatening airway obstruction. In this case, the most likely cause was needle migration into the cord during injection. Frequent aspiration of air throughout the injection process could mitigate this risk.

Ethics statements

Patient consent for publication

Obtained.