Morquio’s syndrome
Morquio’s syndrome is one of the mucopolysaccharidoses (MPS), which is a group of inherited multisystem storage disorders. Specific enzyme deficiencies cause an incomplete degradation of complex glycosaminoglycans and the storage of acid mucopolysaccharides. Clinical manifestations reflect the accumulation of specific MPS derivatives in various organs. It is subdivided into types:
◆ Type I: Hurler, Scheie, and Hurler–Scheie syndromes
◆ Type II: Hunter’s syndrome
◆ Type III: Sanfilippo syndromes A, B, C, and D
◆ Type IV: Morquio’s syndrome, types A and B
◆ Type VI: Maroteaux–Lamy syndrome
◆ Type VII: Sly syndrome.
1 Acknowledge the difficulties in an adult with a congenital syndrome affecting the airway
2 Discuss the difficulties in managing paediatric-sized patients in the adult setting.
1C01; 2A01
A 40-year-old female presents with left pelvi-ureteric junction obstruction with marked hydronephrosis. She has a nephrostomy in situ and requires a ureteroscopy and endopyelotomy. She has Morquio’s syndrome. She has had multiple orthopaedic procedures as a child. Her most recent anaesthetic was 10 years ago, and her notes are not available. She has no other past medical history. She is active and has no overt cardiorespiratory symptoms.
All of the MPS are primarily characterized by the following clinical features:
◆ Physical deformities
◆ Skeletal abnormalities
◆ Cardiac defects
◆ Ocular defects
◆ Neurological/mental disabilities
◆ Reticuloendothelial abnormalities.
Morquio’s syndrome has an incidence of <1 in 250 000. It is autosomal recessive, therefore affecting males and females equally. There is an accumulation of keratan sulphate. The diagnosis is made by the characteristic clinical features, keratan sulphaturia, and specific enzymatic assays. The main features are skeletal abnormalities.
◆ Short stature
◆ Pectus carinatum (pigeon chest)
◆ Lower rib flaring
◆ Genu valgus
◆ Valgus deformity of the elbow
◆ Ulnar deviation of the wrist
◆ Metacarpal deformities
◆ Ligamentous laxity and hypermobile joints (but not hips, knees, elbows)
◆ Flat feet
◆ Waddling gait.
◆ Short trunk and neck
◆ Platyspondyly universalis (flattened vertebrae)
◆ Wide intervertebral disc spaces
◆ Progressive spinal deformity: lumbar lordosis, dorsal kyphosis, and barrel-shaped chest
◆ Odontoid hypoplasia and subluxation of C1 on C2, leading to spinal cord compression.
◆ Restrictive lung defect secondary to thoracic spine problems
◆ Aortic and mitral regurgitation
◆ Corneal clouding
◆ Conductive hearing loss
◆ Hepatosplenomegaly
◆ Mid-face hypoplasia and a depressed nasal bridge, resulting in a broad, flat face
◆ Enamel dysplasia
◆ Death from spinal cord problems or cor pulmonale in 3rd to 4th decade.
On examination, this patient has the typical stature of Morquio’s syndrome. She is 100 cm tall and weighs 25 kg. Her heart sounds are normal, and her chest is clear. Her airway examination reveals moderate mouth opening (Mallampati class 2), moderate jaw protrusion, and a full set of teeth. She has a very short neck, with no cervical extension and minimal flexion.
Her investigations show the following:
◆ Normal blood biochemistry and haematology
◆ ECG: sinus tachycardia; rate of 120
◆ Pulmonary function tests: FEV1 0.5 L, FVC 0.75 L, ratio 66.7%
◆ Echocardiogram: normal valves, good LV function.
Her C-spine X-rays show the following:
◆ Very limited movement
◆ Abnormal, reduced height vertebrae
◆ The anterior arch of the atlas and C2 fused inferiorly
◆ Central subluxation, appears stable
◆ Bony protruberance into the hypopharynx by the anterior arch of the atlas.
This lady is a paediatric-sized patient; her height is equivalent to that of a 4-year-old and her weight to that of an 8-year-old child.
◆ Positioning for surgery will require the Lloyd–Davies set-up
◆ Paediatric-sized equipment
◆ Temperature control
◆ Fluid balance
◆ Difficult, prolonged surgery
◆ Drug dosing.
She is going to be difficult to both maintain an airway and to intubate. Conventional direct laryngoscopy will not be possible, due to:
◆ Facial abnormalities
◆ Excess pharyngeal mucosa
◆ Atlas protruberance into the hypopharynx
◆ Lack of C-spine mobility
◆ Atlanto-axial subluxation.
Since this lady is an adult with normal intelligence, her management will be different to that seen in paediatric practice. The safest way is to secure the airway awake. However, there are some specific issues to be considered in this case.
Regarding the size of the ETT, a 4-year-old child would normally take a 5.5, and an 8-year-old a 6.5 internal diameter ETT. Although this lady has a relatively large head, in comparison to her body, a small ETT is preferable for fibreoptic intubation to minimize the difficulty in railroading the tube. Appropriately sized rescue equipment also needs to be sourced and be immediately available for the duration of the perioperative period.
A spray-as-you-go technique is the safest approach, using whatever method of topicalization with which the operator is most familiar. The maximum dose needs to be carefully calculated, since she is only 25 kg: 9 mg/kg = 225 mg = 5.5 mL of 4%, or 11 mL of 2%, lidocaine.
This should be cautious. The aim is to achieve a cooperative and relaxed patient and maintain verbal contact. Drugs should be titrated very carefully, as doses (particularly of anxiolytics) cannot be directly extrapolated from paediatric dose calculations. The agent used will depend on individual preference and experience, e.g. midazolam or TCI propofol or remifentanil.
The patient will also require a preoperative anticholinergic (such as glycopyrrolate 150 micrograms) and supplemental oxygen. The cervical spine should be protected by keeping the neck in a neutral position.
This patient had an AFOI under sedation which was technically very difficult. After topicalization of the airway, the oral route was attempted. However, there was very little air space, due to a large epiglottis, excess pharyngeal mucosa, and the protrusion of an osteophyte into the hypopharynx. The vocal cords were visualized, but the fibrescope was unable to pass through, due to the very acute angle. The level of sedation had to be reduced, as the patient’s airway tended to obstruct very easily. The nasal route was then attempted after further topicalization. (A total of 200 mg of lidocaine was administered.) This approach was much easier, due to the less acute angle of the airway. A size 6.0 ETT was railroaded with ease.
Muscle relaxation should be reversed, and any residual drugs in the IV line must be adequately flushed through. This lady had a brief apnoea after her cannula was flushed, probably due to residual remifentanil. Dexamethasone 4 mg was given intraoperatively to reduce any airway swelling, in view of the prolonged airway instrumentation in the presence of a pre-existing narrow airway. The cuff was deflated to check for a leak around the tube prior to extubation. The patient was extubated awake in the sitting position. Due to the local anaesthesia, the nasal ETT is usually well tolerated.
The patient should have supplemental oxygen and regular observations. Ideally, she should be nursed in a high dependency area. Non-opioid analgesia should be maximized, with judicious parenteral opioid, if necessary. Transcutaneous carbon dioxide monitoring may be useful. The doses of all drugs and fluids will need to be carefully calculated.
Abandon the procedure. This is non-lifesaving surgery. Any further attempts will cause trauma and oedema to an already narrow airway. This patient would need very careful planning for a future date and may need the assistance of experts from a specialized unit.
In retrospect, the nasal route should have been the initial plan. It is easier to anaesthetize with a smaller dose of local anaesthetic, and it provides a straighter approach to the larynx. The osteophyte had also been noted on the C-spine X-ray, but its relevance not appreciated until during the procedure.
Summary
This case highlights some of the problems in dealing with a congenital syndrome within an adult hospital setting. It also reminds us that, on occasion, we may need to abandon the procedure and do no further harm.