Intubation in spinal muscular atrophy (SMA) can be difficult or impossible,1 but the need for endotracheal intubation in SMA patients is increasing.2 In SMA type 1, respiratory failure can require frequent intubation in children ages three and below.3 As life expectancy in SMA continues to rise, medical treatments that require intubation could continue to rise accordingly.4 In addition to intubation for planned procedures, there is a growing need to intubate SMA patients for unplanned procedures. For instance, those with SMA type 1 and those with SMA type 2 are frequently admitted to the intensive care unit due to conditions like airway tract infections accompanied by difficulties in clearing secretions. In these cases, successful intubation can be critical.
The muscle weakness that occurs in SMA makes intubation technically challenging. One ability that is hindered by muscle weakness is the ability to open the mouth as widely as those with normal muscle strength, and the extent to which SMA patients can open their mouths is a factor that affects the ease of intubation. Though they are often unaware of it, between 50 and 100 percent of SMA patients experience limitations in the amount that they can open their mouths – or in their maximal mouth opening (MMO) because of the effects of SMA on brainstem motor nuclei.2 The complications of endotracheal intubation introduction by MMO limitations can be severe. 2,5,6 Research suggests that SMA patients with MMOs of 20 millimeters or less are at an increased risk for complications during intubation. This level of limitation frequently occurs in SMA patients who are under the age of 10.7 Experts suggest that MMO limitations in SMA patients should be regularly assessed and documented so that this complicating factor can be incorporated into decisions about intubation.2
Alternatives to Intubation
Given the technically difficulty of intubation in SMA patients and the risk of adverse consequences, researchers have explored alternatives for intubation and found that there are less invasive ways to ventilate this set of patients and that these alternatives may be appropriate in certain contexts. In children with neuromuscular disorders, it has been shown that noninvasive positive pressure ventilator support can be used in place of invasive intubation when managing surgeries associated with scoliosis.8 Case studies have also described successful alternatives employed specifically in SMA patients. For instance, a 50 year old woman with SMA type IV underwent synovectomy with an epidural technique so that tracheal intubation could be avoided.9 Retrograde intubation, which is a standard technique used in children with difficult airways, has also been used in SMA type 1, aided by the use of a feeding nasogastric catheter.10 One case study describes an 11 year old boy with SMA type 2 who underwent a spinal fusion procedure, and his doctors were able to avoid prolonged intubation by using a cough-assist device following the surgery.11
In cases where intubation is required, healthcare providers must consider when and how extubation will take place. Just as intubating SMA patients can be challenging, so too can extubating them, and tracheal extubation in children who have difficult airways may lead to adverse events.12 Extubation is therefore often avoided or delayed in an effort to reduce the risks for SMA patients.
Nonetheless, extubation is desirable for a variety of reasons. For instance, studies have shown that the number of days of ventilation is a major predictor of ability to swallow following extubation, with more days of intubation reducing SMA patients’ likelihood of recovering swallowing functions.13 While intubated patients who fail spontaneous breathing trials are considered high risk for extubation failure and often deemed “unweanable,”14,15 researchers have shown through multiple studies that there are safe ways to extubate even this set of patients. Specifically, combining noninvasive ventilation with assisted coughing once patients with neuromuscular disorders have been extubated can prevent the need for tracheostomy or reintubation in these patients previously deemed high risk for extubation failure.14,16
Other factors, like parental involvement can also affect the success of extubation in SMA patients.
Data show that extubation is more successful when the parents of SMA children are present and participate in the weaning procedure.3 According to this research, in cases where parents cannot be present, skilled nurses need to work with these patients on a one-on-one basis.
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