Point of care neck ultrasonography may be useful during anesthesia for carotid body tumor excision.

Sir,

Carotid body tumor (CBT) or chemodectomas are nonchromaffin paragangliomas arising from chemoreceptor cells present at the bifurcation of carotid artery. Surgical excision is performed due to their tendency for developing malignancy.

Diagnosis of CBT is based on clinical history and radiological examination. The patient may present with symptoms of dysphagia, choking, or hoarseness depending upon the cranial nerve involved, as there is a close anatomical relationship with cranial nerves.[1]

Excision of tumor poses several anesthetic challenges and is associated with various perioperative complications. Intraoperative issues are related to hemorrhage, cerebral perfusion, arrhythmia, and hypothermia. Postoperative complications include stroke, cranial nerve injury, profound hypotension, Horner's syndrome, and respiratory depression.

Ultrasonography (USG) has been used in the diagnosis of CBT.[2] We present the use of USG for evaluation of postoperative cranial nerve involvement in CBT.

A 25-year-old female weighing 52 kg was posted for right-sided CBT under general anesthesia. She had a swelling of right side of neck for 5 years that was painless and nonpulsatile. There were no other associated clinical findings. A computed tomography (CT) angiography [Figure 1c] and magnetic resonance (MR) scan established the diagnosis of Shamblin Type II CBT of size 4.8 × 3.5 cm between internal and external carotid arteries displacing common carotid laterally and encasing internal carotid artery (>180°).

Figure 1

USG showing (a) the vocal cords (VC) and arytenoids cartilage (ArC); (b) esophagus (OES); common carotid artery (CCA); left lobe of thyroid (Lt Thy); thyroid isthmus (ISTH); trachea (TR); (c) Angiogram of CBT; (d) CBT being excised

Her routine preoperative haematological investigations, chest X-ray, and echocardiography were within normal limits. Indirect laryngoscopy revealed normal vocal cord movements with no tumor extension in hypopharynx.

General anesthesia was administered after institution of electrocardiography, invasive blood pressure, central venous pressure, pulse oximetry, capnography, urine output, and temperature monitoring. For controlled hypotension, dexmedetomidine 0.5 μg/kg/h was used with a target MAP of 60–70 mmHg. The operation room temperature was set at 21°C, and the patient's core temperature was allowed to drift up to 32–33°C. The tumor was excised [Figure 1d] and blood loss of 1.5 l was adequately replaced. Ipsilateral deviation of tongue was observed postoperatively.

USG examination was performed using the high-frequency linear ultrasound probe (M-Turbo, Fujifilm SonoSite, Inc, Bothell, WA, USA) before induction of anesthesia and after tracheal extubation at the end of the procedure. USG transducer was used in the transverse plane over thyroid cartilage and the structures in the neck were identified. The patient was asked to make the sound of “ee-ee” to help visualize the location of the vocal cords [Figure 1a]. Thereafter, the patient was asked to swallow, resulting in visible peristaltic movement of the esophageal lumen posterolateral to the trachea [Figure 1b]. Skin over both structures was marked to work as a guide and facilitate later sonography.[3] Her vocal cord movements were normal with a good deglutition reflex both pre and postoperatively. Patient was discharged on 10th postoperative day without additional neurological deficit though her tongue weakness persisted.

USG of the neck has been used to evaluate the extent of CBT lesion, its vascularity, and involvement of surrounding vascular structures. USG has been introduced in airway management being safe, portable, and widely available equipment. In a patient with CBT, airway obstruction or aspiration may occur due to intraoperative IX and X nerve injury or postoperative edema. The dynamic nature of edema around cranial nerves mandates frequent observation for stridor and wheezing after extubation.[4] USG is well established in airway management and can be used in cases of CBT for detection of possible cranial nerve IX, X injury.

An awake cooperative patient can help identify the vocal cord by making the sound of “ee” and the esophagus by swallowing action. Marking these structure preoperatively helps in identifying them in the postoperative period particularly in cases of left-sided CBT or in patients who have undergone extensive dissection. With this technique, a fully awake patient is also not required for evaluation of IX and X nerves. However, full aseptic precautions have to be undertaken for performing the USG as it has to be done before applying dressing to the surgical wound after tracheal extubation.

Following CBT surgery, postoperative monitoring for cranial nerve involvement is required to ensure safe outcome. Point of care USG may play a role being both a subjective and an objective tool for evaluation of IX and X cranial nerve function. We suggest using this technique to evaluate the cranial nerve status before and following CBT excision subject to availability.

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Nil.

Conflicts of interest

There are no conflicts of interest.