A 59-yr-old male underwent laryngeal microsurgery with a carbon dioxide laser for extirpation of a polyp in the anterior commissure of the vocal cord and Reinke oedema in the right vocal cord. The patient had chronic bronchitis, arterial hypertension and obesity (body mass index 31.5 kg m−2); he had suffered periorbital emphysema following facial trauma some years before. On three occasions between 1987 and 1988, he had undergone resection for Reinke oedema. The electrocardiogram, non-invasive arterial pressure and pulse oximetry were monitored in the operating room. General anaesthesia was induced with propofol 2 mg kg−1, fentanyl 5 μkg−1 and rocuronium 0.6 mg kg−1. Laryngoscopy and intubation were carried out with a 7 mm orotracheal tube (Laser-Trach®; Kendall, Sheridan, Mansfield, USA) and the cuff was then filled with saline. The patient presented as grade II on the Cormack-Lehane scale and the trachea was intubated with no difficulty without the need for a rigid guide. The lungs were artificially ventilated conventionally with anaesthesia being maintained with sevoflurane 2% in oxygen and air (FiO2 = 0.4); end-tidal carbon dioxide concentration was measured, and muscular relaxation was monitored by accelerometry (Tof-Guard®; Organon Técnica, Boxtel, The Netherlands).
Correct placement of the suspension laryngoscopy was achieved on the fourth attempt by the surgeon. Moistened swabs were placed around the endotracheal tube cuff to shield it from the laser's energy and to protect the subglottic tissue. Excision of the anterior commissure polyp followed by elimination of the Reinke oedema in the right vocal cord was performed with a carbon dioxide laser. The procedure lasted 90 min. High pressures were not required during artificial ventilation and no untoward incidents were observed. On completion of surgery, the endotracheal tube was removed uneventfully and the patient recovered effective spontaneous ventilation. During the immediate postoperative period, the appearance of slight subcutaneous emphysema was observed in the anterior side of the neck progressing towards the eyelids. Respiration was normal, maintaining oxygen saturation of 97-98% with added oxygen via nasal spectacles at 21 breaths min−1. The emphysema progressively increased extending to all of the face, neck, thorax and extremities. Three hours after the endotracheal tube was removed, respiratory difficulty was reported, although oxygen saturation was maintained at 96% with a facemask. A chest radiograph showed large areas of subcutaneous emphysema, pneumomediastinum and a pneumothorax. The patient was sedated with propofol 2 mg kg−1 and a conventional laryngoscopy was performed before the administration of succinylcholine 1 mg kg−1 for endotracheal intubation with an 8 mm orotracheal tube. The intubation was without difficulty despite the cervical and facial emphysema. Bilateral pleural drains were inserted. After intubation, arterial blood-gas analysis showed a respiratory acidosis. After sedation, the patient developed a tendency to hypotension, which was controlled by a dopamine infusion 5 μg kg−1 min−1. The patient was transferred to the intensive care unit where artificial ventilation of the lungs was instituted. His airway was explored via a fibreoptic-bronchoscopy, which showed laceration towards the front of the trachea in the mucosa of the subglottic region at the level of the cricothyroid membrane. Artificial ventilation was discontinued and the tracheal tube was removed after 3 days; the generalized emphysema gradually reduced over the next few days; the pleural drains were removed 4 days after their insertion and the patient was discharged from hospital after 11 days.
The differential diagnosis of the subcutaneous emphysema included four possible causes: (a) alteration of the cutaneous barrier (in surgical procedures such as tracheostomy, dissection of the neck or external trauma), (b) alterations of the mucosal or cartilaginous barrier (intubation, endoscopic procedures, dental surgery, fracture of facial bones, thoracic drains, foreign bodies or neoplasms), (c) barotrauma (positive pressure ventilation, Valsalva manoeuvre, bronchial asthma, labour) or (d) bacterial infections with gas producing micro-organisms [1-7].
A possible aetiology of the emphysema in this case was the traumatic lesion of the mucosal barrier in some part of the upper airway. A suspicion of an alveolar lesion by barotrauma was discarded because artificial ventilation was uneventful during the intraoperative period.
Rupture of the mucosa may occur in the larynx, pharynx or oesophagus. We consider that in this case, the rupture was produced at the laryngeal level since laser surgery was performed at this site. Fibreoptic bronchoscopy showed an area of subglottic erosion, and during hospitalization in the intensive care unit no signs of mediastinitis (frequent in cases of perforation of pharyngeal or oesophageal mucosa [1-4]) were reported. The sequence of events points to a laryngeal lesion since emphysema was not observed until the patient was extubated, at which time the lesion behaved as a flap valve, so that air was gradually trapped in the subcutaneous tissue . Until then, the air leakage through the laryngeal lesion was not manifest since the airway above the cuff of the endotracheal tube was not pressurized. The origin of the laryngeal lesion may have occurred during intubation [1,7] or during surgery ; we believe it was most likely produced during surgery since endotracheal intubation was performed without difficulty. On the one hand, placement of the laryngoscope was not achieved until the fourth attempt; however, it is unlikely that a subglottic lesion would be caused by this manoeuvre. On the other hand, complications have been reported with the use of a laser in the air-way, including the appearance of subcutaneous emphysema and pneumothorax . These lesions may be avoided by protecting the subglottic tissue - in this case, moistened swabs were placed in the subglottic region around the cuff, but it may not have provided sufficient protection. In addition, if surgery is prolonged, as in this case, the swabs need to be checked regularly in case they dry out. Drying out not only increases the risk of airway fires, but also of soft tissue injury. These lesions include perforation of the cricothyroid membrane  or the cartilaginous laryngeal tissue with dissection of the tissue being produced by the turbulent airflow circulating through the upper airway and becoming manifest when the tracheal tube is removed. The picture is aggravated if the patient coughs or makes inspiratory efforts.
The appearance of subcutaneous emphysema during the postoperative period should be considered a severe complication, as the airway can be compromised [1-7]. As soon as this complication is detected, the patient requires surveillance (electrocardiogram, blood pressure, oximetry). The appearance of tension pneumomediastinum or pneumothorax requires emergency decompression by placement of pleural drains since, in addition to ventilatory compromise, haemodynamic failure may occur secondarily to the restriction in venous return . Intubation in these patients may add further difficulties because of the cervicofacial distortion produced by the emphysema . On stabilization of the patient, localization of the lesion by fibreoptic bronchoscopy or oesophagoscopy allows the aetiology to be established and surgical correction of the lesion to be performed. Early detection of an airway lesion caused during laser surgery is important; however, it seems unlikely that early detection before extubation will be possible in most cases unless fibreoptic bronchoscopy is performed routinely before extubation. Close observation for signs of subcutaneous emphysema is likely to be the only option in most cases. Endotracheal intubation should be maintained so that the upper airway 'rests' until scar formation of the lesion is initiated. This implies that the lesion needs regular assessment by fibreoptic endoscopy, and if the endotracheal tube is removed, close surveillance of the patient is vital.
F. J. Tercero
Hospital Clínic Universitari de Barcelona; Department of Anaesthesiology; Barcelona, Spain
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