A 47-year-old woman presents to the Emergency Department with progressive bilateral ptosis, diplopia, dysarthria, dysphagia and descending limb weakness 4 days after receiving cosmetic botulinum toxin injections. She is alert, has preserved sensation and diminished tendon reflexes. Her respiratory rate is 18 breaths/minute, oxygen saturation is 97% on room air, and there are no signs of respiratory fatigue or upper airway compromise. 

Following urgent discussion with Infectious Diseases or Microbiology, what is the most appropriate next step in management?