Mucopolysaccharidosis VI is a rare autosomal recessive inherited lysosomal storage disorder associated with a variable anesthetic risk. To our knowledge, there are only 3 case reports and several very small case series in the literature describing anesthesia for patients with this condition, and all describe children.1–4 Clinical features worsen with advancing age.4 We present the anesthetic management of a 31-year-old woman undergoing C2-3 cervical spine decompression laminectomy.
The patient has given her consent for this report to be published.
A 31-year-old woman with a history of mucopolysaccharidosis type VI (diagnosed in early childhood) was scheduled for elective C2-3 decompression laminectomy. She presented with a progressive history of lower limb pain, stiffness, and sensory disturbance with limited mobility, requiring a cane to walk. Magnetic resonance imaging revealed not only lumbar spondylolisthesis at L5-S1 and bilateral L5 foraminal narrowing thought to be responsible for her pain but also an asymptomatic tight spinal canal stenosis at C2-3.
The patient also had a history of mild mitral and aortic valvular disease, mild restrictive lung disease, and possible early sleep apnea (although a sleep study performed several years ago was within normal limits). She had not received general anesthesia since a hernia repair as a child, and the anesthetic record was not currently available. She was in moderately good physical and mental health such that she was able to work part-time as an office assistant in the family business.
On examination, she was 153 cm tall and weighed 63 kg (body mass index = 27 kg/m2). She had coarse facial features: a short neck and a Mallampati score of 3. Her only medication was galsulfase, a specific enzyme replacement therapy. Musculoskeletal abnormalities were confined to mild flexion deformities in both wrists and generalized weakness in both legs.
Because adequate visualization with direct laryngoscopy was considered unlikely, and neck extension was contraindicated due to the unstable cervical spine, after insertion of IV and arterial catheters, we performed elective awake fiberoptic tracheal intubation. The airway was prepared with topically administered 4% lidocaine, and a computer-controlled infusion of remifentanil was commenced, targeting a predicted effect-site concentration of 1.0 to 1.5 ng/mL. The fiberoptic scope was passed orally through the cords, and both the supraglottic and subglottic tissues were noted to be enlarged. It was also noted that the upper trachea was abnormal in appearance with a lack of obvious cartilaginous rings until just above the carina, making it difficult to differentiate between trachea and esophagus. A size 7.0 reinforced endotracheal tube was passed easily and the position confirmed.
Anesthesia was induced with propofol (200 mg), and muscle relaxation was provided with rocuronium (50 mg). The patient was then positioned prone, and anesthesia was maintained with remifentanil and desflurane, with morphine administered at the end of the case (10 mg total). The intraoperative course was uneventful with hemodynamic stability throughout. Despite significant facial swelling at the end of the operation, the trachea was extubated without incident after positioning her head up and attempting a cuff deflation once a regular breathing pattern, movement of all limbs, eye-opening, and adequate cough were established. The patient made an excellent postoperative recovery, and she was discharged home on the fourth postoperative day.
The lysosomal storage disorders are one of the groups of conditions referred to as inborn errors of metabolism. They are due to a variety of mutations of lysosomal enzymes in macrophages so that their normal function of scavenging cellular debris is impaired. Thus, retained products, such as mucopolysaccharides, lipids, and other substances, accumulate in organs and tissues throughout the body.
Mucopolysaccharidosis VI, or Maroteaux-Lamy Syndrome (Fig. 1), is an autosomal recessive disorder resulting from a deficiency of lysosomal enzyme N-acetylgalactosamine 4-sulfatase (arylsulfatase B), causing an accumulation of dermatan sulfate.5,6 Specific enzyme replacement therapy with recombinant galsulfase6 via infusion has recently become available. There have been promising results with respect to mobility but importantly, the therapy has not been shown to alter other existing disease manifestations such as facial and airway features.7 Furthermore, the efficacy and safety of this treatment have not been established in babies and infants. The incidence of mucopolysaccharidosis VI is reported to be about 1 in 320,000 births.8,9 The deficient lysosomal enzyme causes defective glycosaminoglycan catabolism, which results in accumulation of partially degraded or nondegraded glycosaminoglycans (a major component of connective tissue). There is thus widespread connective tissue disease, predominantly affecting the skeleton, heart valves, and other areas with connective tissue stroma.5,6 It typically results in coarse facies, growth retardation, skeletal disorders, joint stiffness, myelopathy, and valvular disease.10 Unlike some of the other mucopolysaccharidoses, this variant does not tend to be associated with mental retardation. Understandably, the characteristic features of macroglossia, enlarged tissues of the nasopharynx, excessive secretions, short neck, floppy or malformed tracheal cartilage, cervical spine stenosis, sleep apnea, restrictive lung disease, and valvular insufficiency all pose potential challenges to the anesthetist.1,4,10 In fact, the most common variant of the mucopolysaccharidoses (type I, Hurler syndrome) has been referred to as “the worst airway problem in pediatric anesthesia.”11
Many anatomical factors predispose the patients to airway obstruction and difficult tracheal intubation. In 1 hospital’s review, it was reported that difficulty was encountered in 75% of 16 attempted intubations in 5 affected children over 10 years.4 Patients often have thick nasal and oral secretions,11 hypertrophied turbinates, and a narrowed nasopharynx, making nasal intubation difficult. It is important to note that some authors report that the use of an oral airway may fail to relieve or even worsen airway obstruction due to the high, elongated position of the epiglottis.12 A short neck with limited mobility, adenotonsillar hypertrophy, an anterior larynx, and an elongated epiglottis can make direct laryngoscopy difficult, and a narrow trachea may necessitate a smaller endotracheal tube.2,9,12 Cervical spine stenosis due to odontoid hypoplasia and dural thickening2 may limit the safety of neck manipulation.
During our fiberoptic bronchoscopy, we observed the described phenomenon of abnormal tracheal anatomy that has a similar appearance to the esophagus. This can make confirmation of the position of the endotracheal tube misleading.4 Restrictive lung disease (plus or minus pectus excavatum) is often present so that ventilation may also be a problem in these patients. Postoperatively, there is a risk of upper airway obstruction, and there have been reports of postoperative pulmonary edema in children2 thought to be due to forced expiration against a narrowed and thickened glottis, which may have been exacerbated by instrumentation of the airway. These authors2 thus routinely administer dexamethasone to these patients before extubation and further note that in the event an emergency surgical airway is required, the short stiff necks typical in these patients can make access and identification of anatomical landmarks extremely difficult. Finally, limited extension of the wrists can make radial artery cannulation problematic, and claw deformities can make IV access difficult.
An intriguing additional issue in such cases relates to the fact that dermatan sulphate, a glycosaminoglycan (mucopolysaccharide) structurally related to heparin, has well-documented antithrombotic properties, and indeed, it is a major ingredient in the therapeutic heparinoid, danaparoid. Although the excess dermatan sulphate in mucopolysaccharidosis VI accumulates primarily in those connective tissues where it is normally a structural molecule6 (e.g., in collagen), some can be demonstrated to spill into the circulation where it binds to heparin cofactor II. In this regard, it is relevant to note that increased serum levels of heparin cofactor II-thrombin complex are considered a useful marker of the activity of several of the mucopolysaccharidoses, including type VI.13 Increased bleeding tendency has been reported in some of these patients,2 although no abnormal bleeding tendency was noted in the present case. Perhaps the question of abnormal coagulation, in particular antithrombotic tendencies, remains to be investigated in patients with mucopolysaccharidosis and other lysosomal enzyme disorders.
In conclusion, we present the anesthetic management of a patient with a rare genetic condition with major structural abnormalities of the upper airway in whom awake fiberoptic tracheal intubation was performed due to the high risk of difficult intubation and ventilation. We encountered no major problems and emphasize that careful advance planning and experienced support for difficult airway management are important when anesthetizing such a patient.
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