Department of Anaesthesia, Wythenshawe Hospital, Manchester, UK
Accepted for publication: May 17, 2000
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Abstract |
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Br J Anaesth 2000; 85: 547-9
Keywords: surgery, thyroplasty; anaethetic techniques
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Introduction |
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Several different anaesthetic techniques have been described for thyroplasty. These include local anaesthesia both alone3 and combined with midazolam sedation and flumazenil reversal.4 General anaesthesia has been used for part of the procedure.5 Such techniques all require the patient to be awake and able to phonate to allow the surgeon to judge optimal vocal cord medialization. However, it can be difficult to perform precision surgery on the larynx in the awake patient if manipulation of the larynx leads to reflex responses such as swallowing and coughing. The technique we describe uses continuous general anaesthesia, and provides a quiet operative field. This facilitates exact surgery and allows an accurate assessment of vocal cord medialization. A single case report, employing a similar technique was published, which showed a successful outcome.6
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Method |
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Temazepam 20 mg orally, was given as pre-medication. Anaesthetic monitoring consisted of ECG, non-invasive blood pressure, pulse oximetry and capnography. A total intravenous (i.v.) anaesthetic technique used a target controlled infusion of propofol (410 µg ml1). After induction of anaesthesia, a standard laryngeal mask airway (LMA) was inserted in the normal manner. A fibreoptic intubating endoscope was passed down the LMA to verify that the vocal cords were clearly visible through the distal aperture. Correct preoperative placement of the LMA is an essential requirement for thyroplasty using our technique. The breathing circuit was connected to the LMA using a catheter mount incorporating a rubber seal suction port. The patients breathed an oxygen enriched air mixture spontaneously. Small incremental i.v. doses of alfentanil were given as needed. Infiltration of the operation site with a mixture of lignocaine and epinephrine was carried out by the surgeon.
During the procedure a wide-bore flexible endoscope with an attached video camera was inserted through the suction port of the catheter mount and passed down the LMA. The resulting image of the vocal cords was displayed on a television screen. The surgeon used this image to carry out the thyroplasty and achieve optimal medialization of the paralysed vocal cord. Additional confirmation of a satisfactory airway was given by the presence of an adequate respiratory excursion of the breathing circuit reservoir bag and the display of a normal capnograph trace assessed both pre and postoperatively.
At the conclusion of surgery the propofol infusion was discontinued and the patient transferred to the recovery room. The LMA was removed upon emergence of the patient from anaesthesia. Requirement for analgesics after operation was minimal, and simple oral paracetamol based preparations were sufficient.
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Results |
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There were three anaesthetic complications. The first involved partial misplacement of the LMA and caused repeated short episodes of airway obstruction associated with surgical dissection of thyroid ala.
When the fibreoptic endoscope was passed down the LMA1 the epiglottis was seen folded under the LMA and was partially obstructing the laryngeal inlet. The LMA was removed, correctly re-positioned and the thyroplasty then proceeded uneventfully. As a result of this complication we now check LMA placement in the anaesthetic room with the fibre scope and have had no further intraoperative problems with LMA placement. The second complication involved the intraoperative displacement of the silastic block perforating through the inner perichondrium and mucosa into the larynx. A small haematoma occurred but this was not associated with any clinical or endoscopic signs of airway obstruction.
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Discussion |
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General anaesthesia for thyroplasty facilitates precision surgery with a quiet surgical field and suppression of reflex responses, which occur during laryngeal manipulation on an awake patient. By using an LMA the larynx remains uninstrumented and yet the airway is secure. The LMA also provides a conduit for fibreoptic endoscopic assessment of vocal cord medialization. A functional assessment of airway patency at the time of the thyroplasty can also be made as the patient is breathing spontaneously. If breathing becomes inadequate positive pressure ventilation can be given via the LMA. This technique gives more airway control than to sedation techniques.4 The assessment of optimal vocal cord medialization can occur under anaesthesia during the procedure, so that the patient does not have to wake until the end of the operation compared with previous general anaesthetic techniques.5 With an oxygen/air mixture endoscopy is tolerated without any decrease in oxygen saturation.
Thyroplasty can cause airway obstruction by haematoma or oedema. Intraoperative stridor due to laryngeal oedema occurred in one of the above cases and responded to nebulized epinephrine and i.v. steroid. However, surgery was abandoned. We keep a cylinder containing a mixture of helium and oxygen available for the stridulous patient, but so far it has not been used. Facilities for emergency tracheostomy are mandatory during this procedure.
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Acknowledgements |
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Footnotes |
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References |
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2 Sasaki CT, Leder SB, Petcu L, Friedman CD. Longitudinal voice quality changes following Isshiki thyroplasty type I: the Yale experience. 1990; 100: 84952
3 Koufman JA, Isaacson G. Laryngoplastic phonosurgery. Otolaryngol Clin N Am 1991; 24: 115164[ISI][Medline]
4 Donnelly M, Browne J, Fitzpatrick G. Anaesthesia for thyroplasty. Can J Anaesth 1995; 42: 8135[Abstract]
5 Griffin M, Russell J, Chambers F. General anaesthesia for thyroplasty. Anaesthesia 1998; 53: 1199208[ISI][Medline]
6 Grundler S, Stacey M. Thyroplasty under general anaesthesia using a laryngeal mask airway and fibreoptic bronchoscope. Can J Anaesth 1999; 46/5: 4603