Ankylosing spondylitis is a predominantly axial arthritis usually beginning in the sacroiliac joints and slowly progressing to spinal fusion . The overall incidence rate is about 1.6% of the population . The primary sites are the sacroiliac joint and the spinal column. The thoracic spine may assume an accentuated kyphosis and fusion of costovertebral joints results in diminished chest expansion . If the duration of the disease is ≥ 16 yr, 75% of the patients develop cervical ankylosis and have a higher risk of cervical fracture . Cervical motion may become severely restricted with eventual head fixation in a flexed position. The tracheal intubation of the patient with fixed kyphosis of the cervical spine is known to be difficult, especially if there is involvement of the temporomandibular joint. In this circumstance, it is important to use an intubating technique, which involves minimal neck movement .
Various intubating techniques have been tried in patients with cervical spine pathology, including injuries. These include awake tracheal intubation, transnasal fibreoptic intubation and retrograde intubation . The laryngeal mask airway is a well-established device used in the management of failed intubation. However, insertion is more difficult when the patient's occipito-atlantoaxial complex is flexed. It also has certain limitations in its use for intubation.
The intubating laryngeal mask airway is a modification of the standard laryngeal mask airway, which is claimed to be best inserted when the patient's head is supported by a pillow, without placing the head and neck in the Magill position . We report a case of successful insertion of the intubating laryngeal mask and subsequent intubation through it in a patient with ankylosing spondylitis with cervical involvement resulting in a fixed flexion deformity who underwent coronary artery bypass grafting.
The patient, a 58-yr-old ex-smoker, was diagnosed as suffering from coronary artery disease with hypertension and ankylosing spondylitis. Coronary angiography revealed that the left anterior descending artery had a 90% stenosis in the proximal segment, the left circumflex had a 40% stenosis and the right coronary artery, which was the dominant one, had a 90% stenosis. The patient was advised to undergo coronary artery bypass graft surgery.
Besides this, the patient had been suffering from ankylosing spondylitis since 1956, with cervical involvement since 1982. His neck movements were severely restricted and the case was brought to the attention of the anaesthesiologists as a potential difficult intubation. On preoperative examination, the patient had no neck extension (Fig. 1). There was a minimal degree of flexion and lateral movement. Consequently, he could not lie down supine and had to be propped up on a couple of thick pillows to support his flexed neck comfortably (Fig. 2). However, his mouth opening was more than four fingers' breadth. According to the Mallampatti classification, the patient was in Class 1. The thyromental distance was within normal limits. There was no evidence of temporomandibular joint involvement. No other orofacial or neck abnormality was found. Radiography of the neck (Fig. 3a,b) showed a loss of normal cervical lordosis and evidence of ossification of the anterior and posterior longitudinal ligaments with ankylosis of the facet joints from the second to the seventh cervical vertebrae. With the aids available, we found the intubating laryngeal mask airway to be the most suited for intubation in this patient, especially since it does not require head or neck manipulation for placement and can be inserted from any position. The biggest advantage lay in the fact that if intubation was not possible, it would be possible to ventilate the patient's lungs. We kept the fibreoptic bronchoscope on standby for tracheal intubation. If the intubating laryngeal mask airway could not be passed, we intended to awaken the patient and proceed with fibreoptic intubation. If the intubating laryngeal mask airway could be passed and the patient's trachea could not be intubated, we planned to use the fibreoptic bronchoscope through the intubating laryngeal mask airway for intubation. If neither of the above was successful, we planned to do a retrograde intubation.
The patient's routine blood investigations were all within normal limits. His electrocardiogram showed evidence of inferior wall myocardial ischaemia. When the patient arrived in the operation theatre, the Hewlett-Packard electrocardiograph monitor and Datex pulse oximeter were attached and the peripheral venous and radial arterial lines were placed under local anaesthesia (Hewlett-Packard, Andover, MA, USA).
The patient was propped up on two pillows at 45°. He was sedated with midazolam 1 mg and fentanyl 150 μg intravenously (i.v.). General anaesthesia was administered with a 50% mixture of nitrous oxide in oxygen and 7% sevoflurane. After confirming that bag-and-mask ventilation was possible, 70 mg propofol was administered i.v. Once the patient was judged to be in a sufficiently deep plane of anaesthesia, direct laryngoscopy was performed that revealed a Cormack and Lehane Grade 4. An intubating laryngeal mask airway Size 4 was then easily inserted with the anaesthesiologist facing the patient. The cuff was inflated with 40 mL air and the correct positioning of the intubating laryngeal mask airway was ascertained by checking for bilaterally equal air entry on auscultation of the chest and was confirmed by capnography. Adequate muscular relaxation was provided with succinylcholine 100 mg. A Size 8 cuffed silicone endotracheal tube was lubricated with water-based lubricating jelly and inserted through the intubating laryngeal mask. The cuff of the endotracheal tube was inflated and correct placement now confirmed by ventilating the lungs through the tube. The intubating laryngeal mask airway was removed using a 6 mm red rubber tracheal tube as a 'pusher' to prevent accidental extubation while the device was being withdrawn. The oxygen saturation and haemodynamics were maintained within normal limits at all times during the process of tracheal intubation.
Although the approach to the internal jugular vein was difficult because of the absence of mobility of the head and the presence of pillows, cannulation was uneventful. The intraoperative period was uneventful. The patient underwent two bypass grafts (the left internal mammary artery was grafted to the left anterior descending artery, and the radial artery was grafted to the distal right coronary artery).
Postoperatively, the patient was taken to the intensive care unit and received automatic ventilation of the lungs for 13 h. The trachea was extubated with the help of a Patil Two-Part intubation catheter (Cook® Critical Care, Bloomington, IN, USA) when respiratory mechanics returned to normal. The intubation catheter was inserted, the endotracheal tube removed and then the intubation catheter was attached to a source of oxygen via a T-piece. Two hours later, the intubation catheter was removed as the patient could maintain SPO2 and PCO2 satisfactorily. Postoperative recovery was uneventful and the patient was discharged on the 10th postoperative day.
The 'difficult airway' is an anaesthesiologist's nightmare in spite of rapid progress made in the field. A plethora of aids have been designed to overcome this difficulty. Horton and colleagues  demonstrated the movements of the cervical vertebrae during laryngoscopy. In their study, with the patient in the standard intubating position, the lower neck was relatively straight and increasing curvature occurred from the mid-cervical spine upwards. Extension at the atlantoaxial joint was probably near maximum. Jackson emphasized that full craniocervical extension was required to establish a line of vision at direct laryngoscopy . Our patient had cervical spondylitis with a fixed kyphotic deformity that prevented adequate extension of the neck at the upper cervical vertebrae. Hence, though laryngoscopy was thought to be possible as there was adequate mouth opening, visualization of the vocal cords was not expected and indeed was confirmed during direct laryngoscopy in our patient.
Studies have shown that patients with ankylosing spondylitis are more prone to spinal fractures. Fractures in these patients may be the result of minor trauma and may lead to severe neurological deficits [6-9]. Endotracheal intubation in the presence of cervical spine disease may be associated with a risk of neurological injury [10,11]. This necessitates care to be exercised especially during positioning for laryngoscopy and intubation.
Techniques already proposed for intubating the trachea of patients with cervical spine injuries include awake tracheal intubation, transnasal fibreoptic intubation, retrograde intubation and direct laryngoscopy with head and neck stabilization. However, most of these methods require extension of the cervical spine especially from the occiput to the third cervical vertebra, which was to be avoided in our patient. Other methods require a co-operative patient and the airway to be free of secretions .
Fibreoptic intubation was a very good option for this patient. However, optimal positioning of the patient for oral intubation is better achieved with slight extension of the neck rather than with flexion [13,14]. Recently the laryngeal mask has been used successfully in patients in whom tracheal intubation, lung ventilation via a facemask, or both, have failed and has emerged as an important aid in cases of difficult airway . The advantage lies in the fact that effective lung ventilation can usually be carried out even if tracheal intubation is not possible. Insertion of the laryngeal mask is best achieved when the patient's neck is flexed and the head is extended . The laryngeal mask airway is difficult to insert when the occipito-atlantoaxial joints are flexed. Tracheal intubation has been attempted through the laryngeal mask but found to be difficult. In addition, the bars at the aperture of the mask may obstruct passage of the tracheal tube .
The intubating laryngeal mask airway is an airway device designed in an attempt to overcome the limitations in the use of the laryngeal mask airway for intubation . It offers several advantages for difficult airway management. We used the intubating laryngeal mask airway in our case for these very reasons. The difficulty in viewing the larynx that often underlies failed laryngoscopic intubation is irrelevant to the placement of an intubating laryngeal mask. This mask allows both subsequent tracheal intubation and ventilation of the lungs to be continued during intubating attempts, thus minimizing the risk of hypoxaemia and allowing an unhurried approach to securing the airway .
When the intubating laryngeal mask airway is used, no movement of the cervical spine is required and this is particularly important in patients with cervical spine pathology . Our patient had severely decreased cervical spine mobility and hence it was essential to avoid extreme neck movements during positioning for laryngoscopy. Patients with ankylosing spondylitis are at risk of an occult cervical fracture. Minor trauma is sufficient to fracture an ankylosed spine and an undislocated fracture is very difficult to recognize on a radiograph, especially in the lower cervical region [2,10]. Schuschnig and colleagues described rapid sequence induction in patients with cervical spine injury using an intubating laryngeal mask airway and found no variation in the degrees of flexion or extension of the cervical spine .
The ease of placement of the intubating laryngeal mask airway - without head and neck manipulation and without the need for the anaesthesiologist to be positioned behind the head or to insert fingers in the mouth - makes it possible to insert it in any position . Therefore, insertion of the intubating laryngeal mask airway may be less difficult than the conventional laryngeal mask airway in a patient with a flexed neck.
The placement of the intubating laryngeal mask airway and subsequent intubation are blind techniques and thus accessory equipment is not required and placement is unaffected by heavy secretions and blood which might impair fibreoptic techniques. Furthermore, it is easy to learn the technique . This is a major advantage in developing countries where other equipment or the expertise for their use may not always be available on hand.
Shung and colleagues  found that changes in arterial pressure and heart rate were within acceptable clinical limits even when the intubating laryngeal mask airway was inserted with the aid of local anaesthesia, the patient being awake but sedated. Our patient also stayed haemodynamically stable throughout the induction, placement of the mask and subsequent tracheal intubation. This was an added advantage as he was suffering from coronary artery disease and could have become ischaemic with gross changes of heart rate and arterial pressure.
We used sevoflurane for induction as it is an inhalational anaesthetic which is also pleasant smelling, non-irritant to the airways and has a blood-gas partition coefficient similar to nitrous oxide or desflurane . Induction of anaesthesia with sevoflurane is rapid, emergence is quick and thus it plays an important role in the management of the difficult airway. In addition, it potentiates muscle relaxation and may prevent movement in response to laryngoscopy and tracheal intubation. Katoh and colleagues showed that sevoflurane prevented gross purposeful movements in response to tracheal intubation at a concentration of 3.55%, which can be reduced by the addition of fentanyl . Thwaites and colleagues showed in children that tracheal intubating conditions during sevoflurane anaesthesia were clinically comparable with those achieved with anaesthesia using propofol and succinylcholine. However, the timing of tracheal intubation with inhalational agents is complicated by the lack of reliable end-points. The ED50 and ED95 end-tidal sevoflurane concentrations for tracheal intubation vary widely. In addition, deep anaesthesia is difficult to assess clinically . Our patient was tested for effective ventilation via the intubating laryngeal mask airway, which was possible despite the porentially difficult airway. Hence, we decided to give succinylcholine to assist the intubation.
In conclusion, we anticipated and found the intubating laryngeal mask to be well suited for our patient who had a fixed cervical flexion deformity because of ankylosing spondylitis. Every patient with long-standing ankylosing spondylitis has an increased risk of cervical fracture and intubation is best achieved by techniques that minimize movement. The intubating laryngeal mask airway can be inserted with minimal neck movement and may prove to be a safe additional tool in the management of such patients. Even though fibreoptic bronchoscopy is the usual choice in such patients, the non-availability of the technique and the need for training make the intubating laryngeal mask airway an alternative worth considering.
The authors thank Drs Joseph Monteiro and Uday Gandhe, Consultant Anaesthesiologists, P. D. Hinduja National Hospital, for their constructive critical review of drafts of this paper. We also thank Dr Prashant Shetty, Consultant Radiologist, for his expert advice on the radiographs.
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