Acute management of AFM

Immunomodulatory therapies or antiviral therapies

There is a lack of evidence regarding the potential benefit or harm of therapies in humans. No standardized pharmacological treatment can be universally recommended.

• A common approach is to provide intravenous immunoglobulin during the acute phase, which may provide anti-enteroviral neutralizing antibodies, with minimal potential harm.

Respiratory Status

• Patients with AFM are at high risk for respiratory failure

The cause for respiratory failure in most cases is hypoventilation secondary to respiratory muscle weakness.

Patients may also have bulbar weakness and thus be at risk for aspiration due to the inability to protect the airway

1. Monitoring for respiratory insufficiency and/or failure

• Keep an eye for signs that suggest the risk of respiratory failure, such as poor head control, drooling, inability to raise arms above the head, neck weakness, or altered voice quality.
• Settings without intensive care facilities should consider the transfer of patients with the risk of evolving respiratory failure to a higher level of care institutions.
• Respiratory function should be assessed every 4 hours until clinical stabilization.
  Patients >/= 6 years old monitorization may include testing of negative inspiratory force (NIF), vital capacity (VC), oxygen saturation levels, and blood gas analysis (to detect evolving hypercarbia).
  Patients

2. Supportive measures to minimize the risk for respiratory failure

1. Early mobilization
2. Chest Phyisical Therapy
3. Cough assist
4. Aggressive screening for concomitant respiratory tract infection and treatment where appropriate
5. Minimize sedation (see below for expanded discussion)
6. Avoidance of medications that may make exacerbate weakness (e.g. magnesium, paralytics, steroids, opioids, etc)
7. Promotion of sleep and maintenance of day-night cycles
8. Formal swallowing evaluation recommended prior to initiation of oral diet to assess for aspiration risk

3. Sedation

• Procedures should be modified where appropriate to minimize the exposure to sedation.

1. Environmental modifications can be optimized to reduce the need for sedation (e.g. Child Life involvement, allowing parents to be present in the MRI suite, explaining procedures to the child prior to initiation).

• If sedation is needed for procedures (e.g. MRI), understand that it carries a risk of respiratory decompensation; patients should be closely monitored and short-acting agents used where possible.

1. Short-acting agents preferred when opioids and benzodiazepines must be provided: fentanyl > hydromorphone and midazolam > diazepam.

• The sedating team (critical care or anesthesia) should be alerted to risk for respiratory failure so they can plan to provide medications with low risk for respiratory suppression (e.g. dexmedetomidine, ketamine, propofol).

4. Criteria for respiratory failure

• Generally speaking, have a low threshold for non-invasive ventilation or intubation in patients with neuromuscular weakness or bulbar weakness
• Where intubation is required, medications with the least effect on respiration should be used e.g. dexmedetomidine.

1. The threshold for intubation should be similar to parameters for other acute neuromuscular disorders (such as Guillan-Barre Syndrome and Myasthenia Gravis)
   1. Vital capacity ≤20 mL/kg
   2. NIF less than -30 cmH2O
   3. PaCO2 to ≥50 mmHg
   4. Desaturation and/or O2 requirement
   5. Sweating about the head and neck, wide pulse pressure, tachypnea, tachycardia; may reflect CO2 retention
2. Patients with the inability to swallow or manage secretions may also benefit from intubation.
3. Consider nasal intubation for younger patients (less noxious and tolerated with less sedation).
4. Non-invasive ventilation may be considered where appropriate (e.g. BiPAP while asleep).
5. Consider mandatory minute ventilation (MMV) to trend the patient’s ability to generate the target volume.

5. Criteria for extubation

1. Optimal conditions: patient completes an extubation readiness trial, tidal volumes > 5 mL/kg, gag, and cough are intact.
2. Consider a prolonged extubation readiness trial or trial with minimal ventilator support (PS and PEEP only) to evaluate for fatigability.
3. Patients with poor handling of secretions are at high risk for re-intubation.
4. Consider transitioning to non-invasive mechanical support after extubation (e.g. BiPAP).

6. Criteria for tracheostomy

1. Patients requiring prolonged intubation, as it is associated with an increased risk for infection.
2. Patients with extensive bulbar weakness, profound weakness involving the upper extremities and neck, and/or diaphragmatic dysfunction may be at increased risk for prolonged respiratory failure and thus benefit from tracheostomy.

Bowel and Bladder Dysfunction

Patients with AFM are at increased risk for gut dysmotility, bladder dysfunction/atonia.

1. Patients may benefit from the early introduction of a bowel regimen as constipation is common.
2. Bladder distention and prolonged periods between urination may be a sign of a neurogenic bladder. Consider evaluation with a bladder scanner, post-void residual, and/or scheduled in and out catheterization (preferred over indwelling Foley).

Pain Issues

Patients with AFM are at high risk for pain/allodynia. In sedated patients or young children, pain may be recognized by irritability, tachycardia, and refusal to move or participate in therapy.

1. Recognition of and treatment for pain/allodynia may allow for reduced exposure to sedating medications and improved cooperation with therapy/early mobilization. Anecdotally, gabapentin has been effective in reducing pain in AFM patients. Consider starting pain medications early and titrating to effect.
2. Dysautonomia/dysrythmias can occur. Monitoring is recommended.
3. Anxiety may accompany pain and exacerbate the pain symptoms. Low dose benzodiazepines may be a useful adjunct to pain medications in some patients.
4. For patients with incomplete eye closure, order scheduled lacrilube to prevent corneal abrasions. Corneal abrasions are also a source of pain.
5. Early mobilization/therapy may help minimize pain and secondary injuries associated with immobilization and weakness.

Early rehabilitation

• Consult PT/OT and PM&R at the time of diagnosis for assessment
• Physical, occupational, and speech therapy should be commenced as early as possible.
• Consider early initiation of electrical stimulation therapy to minimize disuse muscle atrophy.
• Psychology and/or Child Life consult early on should be provided to assist the child and family with coping and adjustment.