Your aeromedical EMS crew is dispatched directly to a preschool for a patient with a possible head injury. The patient is a 4-year-old, 20-kg boy with known Hurler’s syndrome who was struck in the head during a fall from a standing position. The school nurse arrived to find him unconscious, apneic and without a palpable pulse. She initiated CPR, which resulted in a palpable pulse, and continued ventilations via mouth-to-mouth until an ambulance arrived.
On arrival of ground EMS, ventilations were continued via a bag-valve mask (BVM) and supplemental oxygen while C-spine precautions where maintained. Endotracheal (ET) intubation was attempted but the laryngoscope blade wasn’t able to be placed into the patient’s mouth. BVM ventilations were continued while the patient was placed on a long spine board and secured for transport.
On arrival of your aeromedical crew, a quick assessment determines the patient needs to have his airway secured prior to the 45-minute air transport, but the patient’s airway is predicted to be a difficult intubation. The boy has a large tongue with very limited mouth opening. Due to his anatomy and history, you anticipate difficulty with airway control, ventilation and oxygenation. BVM ventilation with high-flow oxygen is continued while a laryngeal mask airway (LMA Unique #2) as a rescue airway is readied. The surgical airway kit is also opened and made immediately ready.
The patient receives atropine 0.02 mg/kg, etomidate 0.3 mg/kg, and rocuronium 1 mg/kg. Once paralyzed, an attempt at intubation is made with a size 2 Miller blade, but his tongue can’t be controlled due to its abnormally large size. The intubation attempt is discontinued and BVM ventilation resumed. A second attempt with a size 1 Macintosh blade is made, but despite better tongue control, you’re unable to visualize airway structure. The second attempt is discontinued and the LMA is inserted.
Capnography reveals a normal-looking capnogram, but the end tidal carbon dioxide is running in the low-70s despite trying to increase his minute volume. The pulse oximeter shows an oxygen saturation (SpO2) in the mid- to upper-90s. The patient is given midazolam 0.1 mg/kg to keep him sedated and he’s loaded into the helicopter for transport to the Level 1 trauma center.
In flight, the patient’s pulse oximetry starts falling and drops to approximately 60% with 35 minutes remaining in transport. The LMA is removed and BVM ventilation resumed with improvement of SpO2 back to the mid-90s. An oropharyngeal airway is inserted but seems to cause airway obstruction despite correct sizing and manipulation of position and is removed. Because of the ongoing airway issues and the distance to the trauma center it’s decided to divert to a nearby community hospital for assistance with the airway.
A child with mucopolysaccharidoses, characterized by a large tongue and short neck, is difficult to intubate. Photo courtesy Pinto et al.6
Hospital Care
Upon arrival at the community facility the anesthetists attempts to intubate the patient twice, once using direct laryngoscopy and a second attempt using a pediatric Glidescope. The best view obtained is only the tip of the epiglottis-the patient can’t be intubated. Because of the patient’s age and tracheal malformations, a surgical cricothyrotomy isn’t attempted. Instead, a retrograde intubation is performed by the flight crew and hospital staff using a guide wire obtained from a 30 cm triple lumen central line kit and size 4.5 uncuffed ET tube.
You elect to use an ET tube that’s 0.5 mm smaller than predicted due to his reported narrow trachea. After making a few positioning changes to get the ET tube to thread and passing an introducer over the guide wire though the glottic opening to stiffen the wire, the patient is successfully intubated. Transport is resumed and the remaining flight is uneventful. The patient is delivered stable with a secured airway on arrival to the receiving hospital.
Discussion
Hurler’s syndrome is one of several conditions classified under the category of mucopolysaccharidoses. It has an incidence of 1 in 100,000 live births. This syndrome is caused by a deficiency of the enzyme alpha-L-iduronidase. What makes this condition challenging to emergency medical providers is the associated airway and respiratory issues. Hurler’s syndrome may present with enlarged tongue, short neck, copious bronchial secretions, reduced chest wall compliance, and many airway malformations such as large tonsils, adenoids, tracheal narrowing, and joint immobility affecting the temporomandibular and atlanto-occipital joints.
When faced with these patients, the challenge of intubating and difficulty with BVM ventilation become apparent. High airway pressures are needed to overcome the decreased chest wall compliance during ventilation. To add to the compliance issue, these patients may also have short trunks, kyphoscolaosis (i.e., abnormally shaped spine), hepatomegaly (i.e., enlarged liver) and an exaggerated lumbar lordosis, making ventilation even more challenging. Their airway issues are so problematic that they have a perioperative mortality in the controlled environment of the operating room of 20%, with the majority of deaths being caused by failure to control the airway.1
Teaching Points
Prior to performing a rapid sequence intubation, it’s important to carefully assess the airway. LEMON (look, evaluate, Mallampati, obstruction, neck) is a mnemonic that can be used to identify potentially difficult intubation.
It’s equally important to assess for difficult BVM ventilation.2 It was clear by physical exam that this patient was going to be difficult to intubate because of his large tongue, short neck and decreased mouth opening. Additionally, intubation was required due to the long transport time and potential for increased difficulty in BVM ventilation in the confined spaces of the prehospital environment. The decision to utilize paralytics needs to be weighed very carefully against the risk of death in these patients because the incidence of airway failure and failure to ventilate is high. In this case the crew knew they were able to ventilate successfully prior to intubation, which supported the decision to utilize a paralytic.
In considering other options for airway management, surgical cricothyrotomy was unlikely to be successful. This patient was very young and had trachea malformations and subglottic narrowing. Pediatric cricothyrotomy in general isn’t supported in the literature, as there are significant failure rates with poor outcomes.2 Transtracheal jet insufflation (TTJI) is often discussed as an option in pediatrics. In this case it was also likely not to work due to the decreased compliance and secretions. TTJI is a potential temporary solution for failure to oxygenate. It’s important to understand that when using this procedure, little CO2 is exchanged and the patient will become hypercapneic.
Due to the ability to oxygenate this patient and ventilate with a BVM, TTJI wouldn’t have offered any advantage. In this case, the LMA was likely unsuccessful due to the high airway pressures required to overcome chest and lung compliance, though it’s possible a different sized LMA may have proven more effective. Other surpraglottic airways that can maintain seal with higher airway pressures, such as the LMA Pro-Seal and King LT, might have a role in such cases.3 Oralpharyngeal airways are known to cause airway obstructions in Hurler’s by displacing the epiglottis downward.4
With all the challenges that the Hurler’s patient can present, retrograde intubation may offer a viable method for controlling the airway. Retrograde intubation unfortunately isn’t a fast procedure, and the provider must be able to oxygenate the patient during the procedure,5 but the main advantage is that it doesn’t require a view of the glottic opening. A problem we encountered with the central line guide wire is that it was too flexible, allowing the ET tube to curve downward. By placing a standard dilator over the guide wire, we were able to get the ET tube to follow the wire into the glottic opening.
Conclusion
Although Hurler’s syndrome is relatively rare, other congenital conditions exist that can make airway management challenging even in the most controlled environments. When performing an airway assessment on these patients, it’s important to appreciate the potential for difficult airway management and consider other options to maintain oxygenation and ventilation.
References
1. Wilder RT, Belani KG. Fiberoptic intubation complicated by pulmonary edema in a 12 year old child with Hurlers syndrome. Anaesthesiology 1990;72(1);205-207.
2. Walls RM, Murphy MF, editors: Manual of emergency airway management, 4th edition. Lippincott Williams & Wilkins: Philadelphia, 2012.
3. Keller C, Brimacombe J. Mucosal and oropharyngeal leak pressure with the ProSeal versus laryngeal mask airway in anesthetized paralyzed patients. Br J Anaesth. 2000;85(2):262-266.
4. Baum C, O’Flaherty JE, editors: Anaesthesia for genetic, metabolic and dysmorphic syndromes of childhood. Lippincott Williams & Wilkins: Philadelphia, pp. 145-146, 1999.
5. Lin Y. Cervical spine disease and Down syndrome in pediatric anesthesia. Anaesthesiol Clin. 1998;16(4):911-923.
6. Pinto LLC, Vieira TA, Giugliani R. Expression of the disease on female carriers of X-linked lysosomal disorders: A brief review. Orphanet J Rare Dis. 2010;5:14.
