Bilateral vocal cord edema following anterior cervical discectomy-usefulness of bonfils retromolar fiberscope.

We present a case of a 40-year-old male patient who presented to us with radicular pain in arm for anterior cervical discectomy with fusion. The preanesthetic checkup including indirect laryngoscopy was normal with routine investigations within normal limits. The patient was induced and intubated with the established routine technique without any obvious airway problems. Prophylactic dexamethasone was administered, and the intraoperative course was uneventful. Immediately after extubation, it was noticed that the patient had inspiratory stridor and whispered voice on the operation theater table itself. Assessment by Bonfils retromolar fiberscope under fentanyl sedation revealed bilateral vocal cord edema. The patient was re intubated and put on T piece with humidified O2. After 72-h, patient was extubated after confirming normal vocal cord movement under flexible fiberscope guidance. This case is presented to alert anesthesiologist about the possibility of vocal cord edema even though other potential airway complications are possible. We would also highlight the importance of Bonfils retromolar fiberscope in awake vocal cord examination and flexible fiberscope use in managing patients presenting with airway problems during extubation.

INTRODUCTION

Potential complications of anterior cervical discectomy are transient sore throat, dysphagia, hoarseness, dysphonia, esophageal perforation, and respiratory insufficiency due to upper airway obstruction. Airway obstruction could occur due to vocal cord palsy, pharyngeal edema, hematoma, cerebrospinal fluid leak, angioedema, and graft or plate dislodgement.[1] Though vocal cord palsy due to recurrent laryngeal nerve (RLN) paralysis had been reported, there are no confirmed reports of vocal cord edema in the literature. Retro molar scopy had been successfully used to aid intubation in awake patients without anesthesia.[2] Flexible fiberscope had been useful during extubation of complicated airway. This case report should alert us to anticipate airway complications after anterior cervical discectomy particularly the possibility of vocal cord edema. If available retro molar scope is very much useful in such situations to make a diagnosis.

CASE REPORT

A 40-year-old male with a history of smoking and no comorbidities who presented with the diagnosis of C5-C6 disc prolapse with left sided radiculopathy was posted for C5-C6 discectomy and anterior fusion. The preanesthetic checkup including indirect laryngoscopy was normal with routine investigations within normal limits. After premedication with midazolam 2 mg and injection morphine 4.5 mg, the patient was induced with injection thiopentone 250 mg and intubated using injection vecuronium 4 mg after connecting standard monitors. Vocal cords were found to be normal during intubation. Atraumatic endotracheal intubation was accomplished with size 8 tube inserted to a depth of 23 cm and secured properly. Then prophylactic dexamethasone 8 mg was administered intravenously anesthesia was maintained with O2+ N2O+ isoflurane. The surgery was performed on the left side of the neck after exposing C4, C5, and C6 vertebra. After 5-h of uneventful intraoperative course, extubation was attempted when patient was fully awake. Immediately, patient developed stridor, whispering voice and oxygen saturation started dropping. Suspecting airway edema adrenaline nebulization was given which helped in maintaining oxygen saturation but stridor was not relieved. To rule out vocal cord paralysis, retromolar scopy was done after administering 100 mcg of fentanyl. Diffuse edema of the vocal cords and the surrounding tissue was observed [Figure 1]. As vocal cord movement was sluggish bilaterally, patient was re intubated, initiated mechanical ventilation, switched over to T piece with humidified O2 after 1-h. Patient received intravenous dexamethasone 8th hourly to relieve edema.

Figure 1

Vocal cord edema

After 72-h, patient was shifted to the operation theatre again and was sedated with fentanyl 100 mcg and midazolam 2 mg. As adequate time was present, after proper preparation, extubation was attempted over flexible fiberscope. After tube had been withdrawn over fiberscope, the tip of the fiberscope was slowly withdrawn just out of vocal cords to examine them. It was decided to re intubate with the same tube if the diffuse vocal cord edema persisted. Vocal cord edema had come down to a significant extent except for the big gap formed at the posterior part of vocal cords because of the pressure created by endotracheal tube [Figure 2]. As patient did not develop stridor, extubation was performed. Further postoperative course was uneventful.

Figure 2

Vocal cord after 72-h

DISCUSSION

Serious complication of anterior cervical discectomy is vocal cord palsy which occurs due to RLN involvement. It can present as hoarseness, dysphagia, aspiration, and airway compromise if bilateral. There are two main reasons for vocal cord palsy. Emery et al.[3] proved that operation time exceeding 5-h was associated with re intubation and Sagi et al.[1] showed that multilevel exposure of cervical vertebra and higher level greater than C4 are exposed higher the incidence of airway complications. Symptomatic RLN palsy was 8.3%, and asymptomatic RLN palsy was 15.9% with the overall incidence of 24.2%. Unilateral RLN palsy is more common than bilateral in the anterior approach. The reasons implicated in vocal cord palsy are indirect intraoperative injury to the nerve, entrapment of the nerve between instrumentation and endotracheal tube, or traction injury of the nerve. In many cases, endotracheal tube alone is responsible for RLN palsy (7.5-11.2% of vocal cord paralyses).[4]

A traumatic injury to the nerve most likely occurs during a right-sided approach in cervical spine surgery as the right-sided nerve is shorter and has a more oblique course than the left RLN.[5] Traction of varying degree interrupts perineural blood flow and traumatizes the nerve.[6] Possible influence of endotracheal tube cuff pressure on RLN injury had been demonstrated. The increase of the retractor-induced cuff pressure reduces mucosal blood flow unilaterally and may trap the nerve itself contra laterally. Significant increase in cuff pressure (168% of baseline values) and airway pressure of tracheal tube during cervical retraction in anterior cervical discectomy was observed by Garg et al.[7]

Deflation and reinflation of the endotracheal tube cuff is known to reduce the iatrogenic trauma to the RLN, as was demonstrated by Apfelbaum et al.[8] Preoperative laryngoscopy is mandatory to know the state of vocal cords, in patients with a higher risk of RLN damage, such as those undergoing cervical repeated operation, those with an enlarged thyroid, or those who have undergone thyroid surgery.[3] Voice exam with specific questions about voice fatigue to identify patients at risk has been recommended by Hachwa and Halim-Armanios.[9]

In an emergency situation to rule out vocal cord palsy, retromolar scope is very useful to examine the vocal cords. Without much equipment or patient preparation, examination of vocal cords was successful, while the patient was recovering from anesthesia after extubation. Retro molar scope is a reliable and atraumatic device for difficult airway management.[2] It is very useful in the patients with limited neck mobility, limited mouth opening, to navigate through a large tongue or to lift a floppy epiglottis Abramson et al.[2] showed in their case report series on awake insertion of the Bonfils retromolar intubation fiberscope, this device may be more beneficial than the flexible fiberoptic laryngoscope. As this intubation aid is more affordable, durable, does not get easily damaged and easier to clean it should be a part of anesthesiologist's armamentarium.