A 27-year-old female was admitted with a history of speech and swallowing difficulties associated with ptosis for 6 months. There was progressive wors-ening of the symptoms with weakness that involved the facial and respira-tory muscles. The patient had no significant concurrent illness. A provisional diagnosis of myasthenia gravis in crisis was made and confirmed by appro-priate investigations. Computed tomography showed thymic enlargement. Trans-sternal  thymectomy  was  done  because  prior  plasmapheresis  treat-ment  with  pyridostigmine,  azathioprine  and  prednisolone  was  unsuccess-ful.  The  use  of  neuromuscular  blockers  with  anesthesia  was  avoided  to  facilitate extubation at the end of the surgery in the absence of residual paralysis associated with muscle relaxants under neuromuscular transmis-sion (NMT) monitoring. On postoperative day 3, the patient developed pto-sis, breathing difficulties and respiratory arrest because the primary care physician had attempted to decrease the pyridostigmine dose, resulting in emergency intubation and mechanical ventilation. The pyridostigmine dose was gradually increased to 120 mg every 6 hours over 2 days. The patient’s condition steadily improved, allowing the withdrawal of ventilatory support and the patient was returned to a ward, with strict instructions regarding dosage and timing of the medications.

The patient was readmitted the following week with respiratory diffi-culty, mild ptosis, and swallowing difficulties. It was found that the patient irregularly took her medications. The pyridostigmine dose was adjusted to 120 mg every 6 hours. Intermittent noninvasive ventilation (NIV) was also performed. It was observed that the patient regularly experienced inter-mittent breathing difficulties approximately 4 hours after each pyridostig-mine dose. Thus, we provided intermittent NIV to maintain adequate and satisfactory  ventilation  and  oxygenation  during  this  transitional  period  (Figure 1), and thus avoid intubation. The pyridostigmine dose was further adjusted to 120 mg every 4 hours. Over the following 3 days the patient’s condition  improved  and  she  was  able  to  manage  her breathing without intermittent NIV. The spiro-metric findings at the time of discharge were sug-gestive  of  improved  muscle  power,  with  1-second  forced  expiratory  volume  (FEV1)  of  1.84  L  (82%  of  the  predicted  value),  forced  vital  capacity  (FVC)  of 1.92 L (72%), peak expiratory flow of 4.32 L/sec (66%), and FEV1/FVC of 95.8 (114%).

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Figure 1 Dosing interval. *Dosing interval can be adjusted to 4 hours if needed; †intravenous anticholinergic agents (e.g. neostigmine) can supplement noninvasive ventilation (NIV) if needed.

NMT monitoring is a standard diagnostic modal-ity in patients with myasthenia gravis in the peri-operative period because patients are given agents that  influence  NMT,  including  inhalational  agents  and neuromuscular blockers. NMT monitoring was performed  at  the  end  of  surgery  to  aid  the  deci-sion  on  extubation.  However,  because  anesthetic  adjuvants were not used in our patient, NMT moni-toring was not considered necessary in the inten-sive care unit. In addition, NMT monitoring cannot differentiate between cholinergic and myasthenic crisis, supporting our decision not to perform NMT monitoring in the intensive care unit.

Remission  and  relapse  are  common  problems  observed  in  the  preoperative  and  postoperative  periods. These events warrant adjustments in the dose and timing of anticholinesterase medication, the primary treatment during a crisis, as well as the need  for  ventilatory  support.  An  abrupt  increase  in dose can induce a cholinergic crisis; therefore, changes in dose should be done gradually. Respira-tory insufficiency most commonly occurs between the  pyridostigmine  doses.  Standard  practice  is  to  give a small dose of the parenteral anticholinergic drug  (e.g.  neostigmine)  to  provide  cover  for  this  short-duration weakness until the next dose is due. Respiratory  insufficiency  can  also  occur,  warrant-ing  intubation  and  ventilatory  support.  However,  because  endotracheal  intubation  and  mechanical  ventilation may cause injury, NIV has been proposed as  the  preferred  method  of  providing  ventilatory  support  for  respiratory  distress  in  patients  with  neuromuscular diseases.¹⁻⁴

In summary, we wish to raise awareness that a gradual increase in the dose of anticholinesterase drugs and provision of intermittent NIV during the dosing interval is a safe and easy method of manag-ing respiratory difficulties in patients with myasthe-nia gravis crisis during the perioperative period.