Masseter muscle spasm following atracurium.

Abstract

We would like to report a case of masseter muscle spasm (MMS) following administration of atracurium. A 29 year-old lady presented for elective diagnostic laparoscopy. Her past medical history included mild asthma and uneventful general anaesthesia for a laparotomy. Pre-operative assessment of her airway revealed a Mallampatti score of 2 with good mouth opening. Anaesthesia was induced with fentanyl 100 µg, propofol 150 mg and atracurium 40 mg. Her lungs were ventilated for 3 min with a facemask with nitrous oxide 30% in oxygen and isoflurane 1%. The airway was easy to maintain, however, direct laryngoscopy was not possible due to severely restricted mouth opening. The possibility of inadequate anaesthesia and muscle relaxation was considered and a further 20 mg of atracurium was given followed by a further 3 min of bag-mask ventilation. A second attempt at direct laryngoscopy was unsuccessful due to same restricted mouth opening. Blood pressure, heart rate, oxygen saturation and end-tidal carbon dioxide remained stable throughout. There were no other signs of developing Malignant Hyperthermia (MH). The temperature measured during and after the procedure was within normal limits. The trachea was successfully intubated orally using a fibre-optic laryngoscope and anaesthesia maintained using a propofol infusion. The surgery was completed without further complications. The paralysis was reversed with neostigmine 2.5 mg and glycopyrrolate 500 µg and the trachea was extubated when spontaneous ventilation was established. She was admitted overnight for observation and made an uneventful recovery. Serum creatinine kinase measured post operatively was within normal limits. The Malignant Hyperthermia Centre at St James University Hospital, Leeds was contacted for advice regarding further testing. They felt that lack of other signs of MH and the short period of exposure to isoflurane did not justify further investigation in this patient. MMS following induction of anaesthesia is a rare phenomenon and can be an early sign of MH. It is most commonly associated with succinylcholine and volatile agents, although non-depolarising muscle relaxants have been implicated [1]. We feel it is most likely that our patient developed MMS following administration of atracurium. MMS can result in difficulties with airway management, in particular inability to remove secretions from the airway and achieve tracheal intubation. With appropriate airway management MMS should not be life threatening.