Anesthetic management in children with Hurler's syndrome undergoing emergency ventriculoperitoneal shunt surgery.

Mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorder characterized by progressive multiorgan accumulation of glycosaminoglycans. Patients with MPS I (Hurler's syndrome) present as one of the most difficult airway problems to be managed by anesthesiologists. Hydrocephalus with increased intracranial pressure is a frequent complication seen in these patients. The rarity of the syndrome accounts for the small number of case reports and anecdotal information on the intracranial manifestations of this syndrome. We describe the successful anesthetic management of 2 children with Hurler's syndrome who underwent ventriculoperitoneal shunt surgery for acute hydrocephalus.

INTRODUCTION

Mucopolysaccharidoses (MPSs) often present with difficulties in managing the airway.[12] Among the various subtypes, Hurler's (severe MPS I) and Hunter (MPS II) syndromes tend to be most challenging in this regard.[3] Hydrocephalus with increased intracranial pressure (ICP) is a frequent complication seen in patients with Hurler's phenotype.[24-7] These patients may require emergency ventriculoperitoneal (VP) shunt surgery to reduce an increased ICP. Here, we describe successful anesthetic management in 2 such children who underwent insertion of VP shunt for acute hydrocephalus and the literature in this context has been reviewed.

CASE REPORTS

Case 1

A 3-year-old boy, weighing 11 kg, was admitted with complaints of headache and vomiting for 2 days. He had a history of delayed developmental milestones and head banging. The child was diagnosed as a case of Hurler's syndrome and was on enzyme replacement therapy. A computed tomographic (CT) scan showed communicating hydrocephalus with dilatation of ventricles. The child had coarse facial features, large tongue, short neck, frontal bossing with a dolicocephalic head [Figure 1a], dorsolumbar kyphosis, and short stubby fingers with wide wrist [Figure 1b]. Hepatospleenomegaly was ascertained on abdominal examination. The head circumference was 49 cm. Airway examination revealed modified Mallampati class III. The child was premedicated with atropine 0.04 mg/kg orally 30 min prior to induction of anesthesia. Anesthesia was induced with fentanyl 2 μg/kg and propofol 2 mg/ kg maintaining spontaneous ventilation. After ensuring adequate mask ventilation, rocuronium 1 mg/ kg was given. A Cormack–Lehane (CL) grade IV was achieved in first laryngoscopy. The child was intubated in second attempt with the help of gum elastic bougie with an endotracheal tube (ETT) of 4.5 mm ID. Correct position of the ETT was confirmed. The intraoperative course was uneventful at the end of which trachea was extubated.

Figure 1

Child of Hurler syndrome with (a) frontal bossing (dolicocephalic) of head, and (b) short stubby fingers with wide wrist

Case 2

A 4-year-old girl, weighing 11 kg, a known case of Hurler's syndrome was admitted with complaints of vomiting and decreased appetite for 5 days. A CT scan of head revealed communicating hydrocephalus with periventricular ooze. The child was posted for an emergency VP shunt insertion. The child had a history of delayed developmental milestones and was on enzyme replacement therapy for 2 years. She had coarse facies, dolicocephalic head, large tongue, flat nasal bridge with wide intercanthal distance, and multiple skeletal deformities. Systemic examination revealed hepatospleenomegaly and neck rigidity. Routine echocardiography showed thick mitral and aortic valve, and trivial mitral regurgitation.

The child was premedicated with glycopyrrolate 0.1 mg with existing intravenous (IV) access. In the operating room, anesthesia was induced with fentanyl 2 μg/kg and propofol 2 mg/kg; spontaneous ventilation was maintained along with cricoid pressure. Mask ventilation with oxygen and sevoflurane was attempted but was difficult; it was achieved subsequently with an inverted mask technique. Rocuronium 1.0 mg/kg was given for neuromuscular blockade. Tracheal intubation was attempted using Macintosh laryngoscope blade size # 2 and a laryngoscopic view of CL grade IV was achieved. A second attempt was made with the help of an assistant who provided jaw lift. A CL grade III was achieved with optimal external laryngeal manipulation and an uncuffed ETT of 4.5 mm ID was passed blindly beneath the epiglottis. Correct position of the ETT was confirmed by bilateral chest auscultation and capnography. The intraoperative course was uneventful at the end of which the child was extubated after reversal of residual neuromuscular blockade.

DISCUSSION

MPS I (Hurler's syndrome ~ 1 case per 100,000 live births), is caused by a deficiency of the lysosomal enzyme α-l-iduronidase leading to multiorgan accumulation of glycosaminoglycans. These children usually die within the first decade of life, as a result of cardiorespiratory failure and progressive neurologic disease.[7] In the severely affected patient the clinical course is dominated by airway problems with frequent upper respiratory tract infections. Specific airway involvement can manifest as a narrowed nasal passages, large tongue, adenotonsillar hypertrophy, short and immobile neck, high epiglottis, hypoplastic mandible with short ramus, and thickened glottis/supraglottis. The head is enlarged with characteristic coarse facial features, hypertelorism, flattened nasal dorsum and peg-like teeth. Cervical spine instability may occasionally be seen in Hurler's syndrome. These abnormalities, along with excessive secretions, stiff temporo-mandibular joints and anteriorly placed larynx may cause mask ventilation and endotracheal intubation extremely difficult.[1-378] The incidences of difficult and failed intubation in patients with Hurler's syndrome are 54 and 23%, respectively.[1] These patients are at risk of severe respiratory insufficiency as a result of restrictive lung disease, obstructive sleep apnea, and/or asthma. The cause of the restriction is predominantly extrinsic to the lung and involves a combination of skeletal abnormalities of the chest and spine and hepatosplenomegaly, limiting diaphragmatic excursion. Cardiac manifestations such as valvular disease, arrhythmia, cardiomyopathy, congestive heart failure, coronary artery disease, pulmonary and systemic hypertension, and corpulmonale are common, and may worsen with age. These children may have progressive neurodegenerative disease. Evidences suggests that brain atrophy, white matter lesions and communicating hydrocephalus are more prominent in Hurler's phenotypes.[5] Theories behind development of hydrocephalus include engorgement of the arachnoid granulations by stored material and obliteration of the subarachnoid space by infiltration of the accumulated material in the leptomeninges, both of which impede cerebrospinal fluid resorption.[4-6] Venous hypertension has been proposed as one of the possible causes responsible for ventricular and sulci enlargement in these patients.[5]

Anesthetic induction and airway management in children with Hurler's syndrome undergoing emergency VP shunt surgery for acute hydrocephalus is quite challenging. No problem was encountered while managing these 2 children possibly due to adequate preoperative planning. The preoperative preparation should include flexion and extension radiographic views of the neck, for evaluation of cervical spine stability. Even in young children, an electrocardiogram is important and a 2-D echocardiography should be done if a murmur is detected. Securing an IV access may be difficult in presence of tissue deposits, contractures, and bony defects. A difficult intubation trolley should always be ready in the operating theater before the administration of anesthesia. Sedative premedication should be avoided. Awake fiberoptic intubation or intubation after deep inhalation induction is preferred in older patients, thereby ensuring spontaneous ventilation until the airway has been secured.[38] IV induction, however, may be preferable in mentally retarded, unco-operative children and those with lesser degrees of craniofacial involvement.[8] Nevertheless, the cornerstone of management includes avoidance of a “can’t ventilate, can’t intubate” situation.

Intracranial hypertension manifesting as vomiting predispose the children at risk for pulmonary aspiration. In such cases, rapid sequence induction with cricoid pressure should be performed.[9] Instability of cervical spine should be presumed in the absence of flexion–extension cervical spine films and cervical spine must be immobilized during tracheal intubation. Neither awake fiberoptic intubation nor deep inhalational induction without muscle relaxants are ideal techniques of airway management in children with acute hydrocephalus. Awake fiberoptic intubation is more difficult in these children who are also mentally retarded. Excessive secretions can further complicate the scenario. Hence, a carefully titrated dose of opioids and propofol preserving spontaneous ventilation and then ensuring adequate face mask ventilation along with cricoid pressure during induction maneuver is ideal. This technique was followed in both of our children. Adequate seal is achieved with the pediatric face mask applied upside down.[8] In the absence of an IV access, inhalational induction with sevoflurane and gentle cricoid pressure may be the alternative. Once an IV access is secured and mask ventilation is established, an intubating dose of rocuronium may be administered to facilitate rapid sequence induction.[9] However, administration of muscle relaxant causes loss of muscle tone; the presence of thickened supraglottic tissue and large tongue may lead to upper airway obstruction during manual ventilation. An oropharyngeal airway may exacerbate the obstruction by displacing the epiglottis downward. Nasal airways have proven to be more effective but advancement may be difficult because of narrowed nasal passages. Laryngeal mask airway may be a better option; however, repeated attempts may be required for correct placement.[23] Fiberoptic intubation under general anesthesia is the ideal method. Indirect laryngoscopy with videolaryngoscopes may be useful for airway management, but there are no published data showing the usefulness of these devices in children with mucopolysaccharidosis.[3]

Recovery after general anesthesia in patients with MPS is often slow and accompanied by periods of breath holding, apnea, bronchospasm, negative pressure pulmonary edema, and respiratory arrest. The child should be awake with adequate airway reflexes for an extubation trial. Both of our patients had an uncomplicated recovery and were successfully extubated at the end of surgery.

To conclude, airway management in children with Hurler's syndrome presenting with acute hydrocephalus is challenging and requires a fine balance between neuroanesthetic principles and difficult airway management techniques. The availability a plethora of videolaryngoscopes may prove airway management in such “most difficult” cases much safer in times to come.