Management of Myasthenia Gravis Patients on Mechanical Ventilation

Introduction to Pyridostigmine Discontinuation

In myasthenia gravis patients who are intubated and mechanically ventilated, pyridostigmine should typically be discontinued because the ventilator is providing respiratory support, eliminating the primary therapeutic target of the medication, while continuing it increases the risk of cholinergic crisis and complicates management 1, 2

Pyridostigmine is an acetylcholinesterase inhibitor that increases acetylcholine concentration at the neuromuscular junction by preventing its breakdown, thereby improving muscle strength in myasthenia gravis patients 3
Once a patient requires intubation and mechanical ventilation, the ventilator is performing the work of breathing, making the respiratory muscle-strengthening effects of pyridostigmine unnecessary and potentially problematic 1, 2

Pyridostigmine has reduced plasma cholinesterase activity, which can prolong the effects of certain neuromuscular blocking agents (NMBAs) like succinylcholine and mivacurium if these are needed for ongoing sedation or procedures 1, 2
Discontinuing pyridostigmine on the day of surgery or during critical illness increases sensitivity to non-depolarizing NMBAs, which may be advantageous when precise neuromuscular blockade control is needed 2

Hold pyridostigmine immediately upon intubation and initiation of mechanical ventilation for myasthenic crisis (MGFA Class III-V with respiratory failure) 4, 5
The focus shifts to immunomodulatory therapy: IVIG 2 g/kg IV over 5 days (0.4 g/kg/day) or plasmapheresis for 5 days, plus high-dose corticosteroids (methylprednisolone 1-2 mg/kg/day or prednisone 1-1.5 mg/kg/day) 4, 5

Myasthenia gravis patients have heightened sensitivity to non-depolarizing NMBAs due to reduced functional nicotinic receptors, requiring reduced NMBA doses based on peripheral nerve stimulation (PNS) with train-of-four (TOF) monitoring 1, 2
Pyridostigmine interferes with accurate TOF monitoring by increasing acetylcholine at the neuromuscular junction, making it difficult to assess the degree of neuromuscular blockade from administered NMBAs 3, 1

Pyridostigmine should be reintroduced during the weaning phase from mechanical ventilation, when the patient begins to resume spontaneous breathing efforts and needs respiratory muscle support 4
Monitor for adequate reversal of neuromuscular blockade (TOF ratio ≥0.9) before extubation to ensure sufficient muscle strength for airway protection and spontaneous ventilation 3
Daily neurologic review is essential to assess improvement in muscle strength and readiness for weaning from mechanical ventilation 6, 4