A 56-year-old male patient with myasthenia gravis (MG) and a severe gagging reflex (GR) was scheduled to undergo intravenous sedation (IVS) for dental treatment. The patient had been diagnosed as having MGFA class Ⅱ (anti-acetylcholine receptor antibody, 32.2 nmol/l) at the age of 52 years, and a thymectomy and partial resectioning of the right upper lobe were performed. An immunosuppressant (tacrolimus) and prednisolone were prescribed.
During a first IVS, the mandibular left second molar was extracted. An initial loading dose of dexmedetomidine (Dex) of 6.0 μg/kg/h for 10 minutes and a maintenance dose of 0.6 μg/kg/h were administered. No GR episodes occurred, and the Ramsay sedation score (RSS) was 2 or 3. The Spo2 was 97-98% without oxygen inhalation. Blood pressure and heart rate were reduced, but remained within the standard range. The recovery time was 70 minutes.
A second IVS was performed to obtain snap impressions. An RSS of 4 was maintained using 3 mg/kg/h of propofol with 3 l/min of O2. However, GR occurred the moment the tray was inserted into his mouth. A bolus administration of propofol, resulting in an RSS of 5-6, was needed to control the GR. The airway was secured by mandibular fisting. The recovery time was 40 minutes.
Finally, a third IVS was performed to acquire a precision denture impression. Dex infusion was started, and propofol was required to control the GR. The dosages of both agents were lower than before. The recovery time was 110 minutes.
The present findings suggest that Dex can be safely used in patients with MG without causing respiratory depression. The disadvantage of its use is the time required to recover and its inability to suppress a GR completely. Propofol was useful for controlling the GR in this presently reported patient.
In conclusion, although the exact dosage of each drug nor the administering time is clear, the expected results of the combined IVS is advantages for MG patients with GR.
