Continuous cervical epidural analgesia for Isshiki type - I thyroplasty.

Thyroplasty is an operation on the upper airway to improve voice quality in patients with unilateral vocal cord paralysis. It is a difficult anaesthetic procedure that requires sharing the airway with the surgeon. We describe a good anaesthetic technique, which provides a safe airway with excellent operating conditions, using continuous cervical epidural anaesthesia and postoperative analgesia in three patients. The use of a regional anaesthetic technique provides excellent anaesthesia and analgesia while allowing the patient to phonate at the request of the surgeon intraoperatively.

INTRODUCTION

Medialisation thyroplasty is a surgical procedure that decreases the incidence of dysphagia and dysphonia in patients with vocal cord paralysis and its subsequent complications like regurgitation and aspiration. This procedure is best performed in a patient who maintains the ability to phonate. It requires access to an uninstrumented larynx and a functional assessment of vocal cord medialisation. Unilateral vocal cord paralysis may occur as a result of intrathoracic disease i.e. tumours of the mediastinum and bronchi, an enlarged left atrium and aortic arch aneurysms, or dysfunction of the central nervous system i.e. neoplastic and infectious processes at meningeal level, neoplasm and vascular lesions within the medulla[1] or following surgery e.g. thyroidectomy. Unilateral vocal cord paralysis is idiopathic in 30-50% of cases. Unilateral vocal cord paralysis causes a hoarse, low pitched, rasping voice. The cause is often the involvement of the vagal nerve from its origin cranially, to its innervation of the muscles responsible for phonation. Complete interruption of the intracranial portion of the vagal nerve results in a paralysis characterised by the loss of the gag reflex on the affected side. The voice is hoarse, slightly nasal and the vocal cord lies immobile in the cadaveric position, i.e. midway between abduction and adduction.[1] The recurrent laryngeal nerves are most often damaged as a result of intrathoracic disease and are much more frequent causes of an isolated vocal cord palsy than are intracranial disorders.

Thyroplasty is a procedure during which a silastic wedge is inserted through a skin incision, at the level of the vocal cords, to move the paralysed vocal cord towards the midline. Assessment of the ideal position is done, by asking the patient to phonate at intervals, during the procedure. This requires the co-operation of the patient and has been achieved with local or regional anaesthesia and sedation. Thyroplasty type 1 is successful for both immediate restoration and long term maintenance of a more normal voice quality[2-5] and speaking pattern.[6] Thyroplasty also decreases aspiration,[2-5] in patients with unilateral vocal cord paralysis. Thyroplasty moves the paralysed anterior membranous vocal cord towards the midline by using a Silastic® implant for external compression of the paralysed vocal cord. A transverse incision is made in the neck at the level of the thyroid lamina. A window is cut into the thyroid cartilage and a preformed Silastic® implant is inserted, pushing the paralysed vocal cord medially.[7] After vocal cord adduction, breathlessness and hoarseness decrease. Closure of the glottic gap may decrease the incidence of pulmonary aspiration.[2-5] Thyroplasty has been performed with local anaesthesia alone or with sedation, using a combination of propofol and fentanyl or midazolam[89] Local anaesthesia, with or without sedation, allows the patient to phonate during surgery which enables the surgeon to assess the correct position of the Silastic wedge.[1011]

Several different anaesthetic techniques have been described for thyroplasty. These include local anaesthesia both alone[12] and combined with midazolam sedation and flumazenil reversal.[13] General anaesthesia has been used for part of the procedure.[14] Such techniques all require the patient to be awake and able to phonate to allow the surgeon to judge optimal vocal cord medialisation. However, it can be difficult to perform precision surgery on the larynx in an ‘awake patient’ if manipulation of the larynx leads to reflex responses such as swallowing and coughing. The technique we describe uses continuous cervical epidural anaesthesia and provides a bloodless operative field where patient can phonate as and when the surgeon requires. This facilitates exact surgery and allows an accurate assessment of vocal cord medialisation.

Written informed consent was taken in all the three cases before documentation of these cases.

CASE REPORTS

Case 1

A 70-year-old male patient weighing 70 kg presented with hoarseness of voice since two months and history of dysphonia along with dysphagia as well as history of recurrent aspiration and coughing. The patient had essential hypertension taking tab enalapril 5 mg twice daily and was controlled. Other systemic examinations were found to be normal. All routine biochemical investigations were within normal limits. Upper nasopharyngo laryngoscopic examination [Figure 1] as well as CT scan images revealed left vocal cord palsy.

Figure 1

Showing fiberoptic laryngoscopic view in case-1. Preoperative laryngoscope images. Left: maximally closed glottis. Right: open glottis on inhalation. Note that the left vocal cord (on the right side in the images) is paralysed

Case 2

A 58-year-old man with chronic obstructive pulmonary disease, bronchiectasis, and a history of treated pulmonary tuberculosis 30 years earlier, complained of hoarseness for three months. He described easy aspiration when swallowing, followed by difficulty coughing out the aspirated materials. There was no concomitant medical illness able to account for his symptoms. On laryngoscopic examination, the left vocal fold was paralysed and there was a persistent glottic gap and inadequate compensation of the contra lateral vocal fold. A thorough head and neck examination and transnasal upper endoscopic examination [Figure 2] were all normal except for the left vocal fold paralysis, confirmed by CT scan.

Figure 2

Fiberoptic laryngoscopic view of vocal cord showing left vocal cord palsy in case-2

Case 3

A 37-year-old woman complained of an 18-year history of hoarseness; a gradual onset at age 19, with deterioration of voice over a period of about one year. Since then, her dysphonia has been very stable. No other head and neck abnormality was noted with the exception of some tympanic membrane scarring, and an early childhood history of otitis. Upper nasopharyngo. laryngoscopy [Figure 3] and CT scan images was done for diagnosis, which revealed left vocal cord palsy.

Figure 3

Showing fiberoptic laryngoscopic view of vocal cord palsy in case-3

Anaesthesia technique

All the three patients were given ASA risk III of anaesthesia for surgery due to major surgery and compromised respiratory system, and written informed consent was taken according to hospital rules and regulations. All three patients were educated regarding postoperative pain assessment using VAS scale 0-10, where 0=no pain and 10=worst possible pain. Patients were premedicated with injection Glycopyrrolate 0.4 mg, injection Pentazocin 30mg and injection promethazine 25 mg I/M 40 minutes prior to operation. Preoperatively, nebulisation was done using ipratropium bromide, budesonide and salbutamol to improve respiratory conditions and prevent postoperative laryngeal oedema. A large bore intravenous cannula was inserted and dextrose normal saline fluid was started. An antiemetic prophylaxis was given in the form of injection ondensetron 4 mg intravenous and injection Dexamethasone 8 mg intravenous to prevent postoperative vocal cord oedema. All routine monitoring was done for ECG, noninvasive blood pressure, SPO2 and urine output measured intraoperatively.

Technique

The patient was made in sitting position, neck flexed and under all aseptic precautions, a continuous cervical epidural catheter was inserted at C6-C7 interspace; loss of resistance technique with 18G toughy epidural needle space was located at about 3-3.5 cm distance from skin and catheter inserted 3cm beyond the tip of the needle in cephalic direction 9. After confirming negative aspiration, 15 ml 0.25% bupivacaine along with clonidine 75 μgm was given as bolus dose followed by infusion of inj bupivacaine 0.25% at the rate of 7 ml/hour with infusion pump. Intravenous medazolam 2 mg given to all patients for intraoperative sedation, no additional other sedation was given in any form intraoperatively. Intraoperative surgeon's satisfaction and patient co-operation was optimum and good. Intraoperative period remained uneventful, Patients haemodynamic stability was maintained, and the patient remained sedated, but co-operative, to be aroused to follow verbal commands of surgeon as and when required for patient's phonation to assess the mobility of vocal cords as well as to know the functional quality outcome of voice at the time of placing implant which is very much important for better prognosis and successful surgical outcome postoperatively. No intraoperative or postoperative complications related to cervical epidural anaesthesia like hypotension, bradycardia, haematoma, infection, urinary retention nausea or vomiting were observed. Patient's preoperative voice and phonation ability were recorded, which was compared with intraoperative voice quality as well as postoperative voice. The postoperative ability to speak was far better in all the three points comparable to normal person's voice.

Postoperative analgesia was given through cervical epidural catheter in the form of injection bupivacaine 0.125% 10 ml along with 50 μgm clonidine every eight-hourly up to 24 hours Postoperative analgesia was assessed using VAS score which remained (no pain) in all three patients up to 24 hours, postoperatively, with patients satisfaction almost 100%. No side-effects or complications related to cervical epidural catheter or anaesthesia were observed in any of the three patients.

DISCUSSION

The surgical impetus for thyroplasty stems from the expectation that it produces better voice quality in unilateral vocal cord paralysis than the conventional para-vocal cord injection of teflon. Surgery on the shared airway is challenging for the anaesthetist. This technique provides a safe anaesthetic airway and optimal operating conditions for the surgeon. Anaesthesia, either local or general, for thyroplasty, presents a challenge for the anaesthesiologist as neither is considered ideal by the patient or surgeon. Several anaesthetic problems may arise during local anaesthesia with or without sedation. As the co-operation of the patient is needed at intervals during the procedure, a balance is required between provision of adequate sedation and anxiolysis, adequate airway control and the ability to reverse sedation rapidly when necessary. The procedure may last for two to three hours and patients may become uncomfortable and restless. Prolonged dissection, more than 30 minutes, and manipulation of the silastic implant may induce oedema, which may lead to overestimation of the degree of voice correction which has been obtained.[3]

Large amounts of sedation may lead to a loss of tone of the unsecured, shared upper airway, causing airway obstruction and respiratory compromise. The drugs available for sedation are limited to midazolam[7] or short-acting drugs such as propofol and fentanyl[9] Anaesthetic problems also arise during general anaesthesia.[15] The surgeon needs to see the larynx to assess the position of the vocal cords as a substitute to phonation. Direct access to the larynx may be difficult in patients with cervical spine problems or other anatomical airway abnormalities. If a tracheal tube is used to maintain the airway, there is a limited view of the vocal cords.

Our surgeons were confident that they could attain a good result with direct peroperative observation of the vocal cords; Continuous cervical epidural anaesthesia was selected to assess the movement of the vocal cords, as spontaneous breathing was required. The continuous cervical epidural anaesthesia enabled good control of the airway at all times along with excellent operative conditions. The surgeons could see the movement of the vocal cords constantly during the procedure.

CONCLUSION

Continuous cervical epidural anaesthesia with a bolus dose of injection bupivacaine 0.25% 15 ml + injection clonidine 75 μgm followed by infusion of bupivacaine 0.25% 7ml/hour, for thyroplasty, can be a very useful technique providing a safe and secure airway as well as free airway access to the surgeon to approach for surgical site. A conscious patient also cooperates for phonation to assess the voice quality intraoperativly as and when the surgeon demands. However, more randomised controlled trial studies can be done.