Myasthenia gravis is a neuromuscular disorder characterized by weakness and fatigue of voluntary muscles due to a decreased number of acetylcholine receptors at the neuromuscular junction . The use of muscle relaxants has remained controversial because patients with myasthenia gravis are known to be sensitive to their effects . Experience with the use of propofol induction and maintenance of anaesthesia in patients with myasthenic gravis is limited [3,4].
The aim of this study was to investigate the use of propofol in myasthenic patients by evaluating endotracheal intubation, surgical conditions, undesirable side-effects and duration of postoperative ventilatory support. After institutional Ethics Committee approval and patients' consent, 22 patients with myasthenia gravis were studied. They were all scheduled to undergo transsternal thymectomy. They were classified according to Osserman (8 class IIA; 14 class IIB). All were receiving anticholinesterase drugs and 10 were receiving oral prednisone. This treatment was withdrawn on the morning of surgery. No premedication was used. Anaesthesia was induced using fentanyl 3 μg kg−1 and propofol 2 mg kg−1. Direct laryngoscopy was performed 60 s after propofol injection. Intubating conditions were evaluated by Viby-Mogenson's criteria . Anaesthesia was maintained using a continuous infusion of propofol 10 mg kg−1 h−1 for the first 10 min, 8 mg kg−1 h−1 for the next 10 min and 6 mg kg−1 h−1 thereafter with further titration of the infusion rate as necessary according to haemodynamic response. Mechanical ventilation with oxygen and nitrous oxide (FiO2 of 0.5) was continued throughout anaesthesia. No inhalational anaesthetic agent was used. In cases of poor intubating conditions, vecuronium 0.05 mg kg−1 was used. Unwanted effects (e.g. cough, airway obstruction), patient movement in response to surgery and time to extubation were recorded. Of the 22 patients, two could not be intubated without the addition of vecuronium. Of the remainder, intubating conditions were excellent in 12 cases, and good in 8 cases. No unwanted effects or patient movement were recorded. In 18 patients the trachea was extubated at the end of the anaesthesia. Four required ventilatory support for 1 to 4 h.
Our results suggest that total intravenous anaesthesia with propofol infusion is a suitable technique for transsternal thymectomy in myasthenic patients. It offers a smooth induction and good conditions for tracheal intubation in the majority of patients. Satisfactory surgical conditions, and early extubation and recovery are also benefits.
M. A. Bouderka
1Department of Anaesthesiology and Intensive Care, CHU Ibn Rochd, Casablanca, Morocco
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