'Jaws of steel' after rocuronium.

Abstract

Sir, A 60-year-old lady was admitted to the Intensive Care Unit of our hospital with complaints of shortness of breath. She was a diagnosed case of dilated cardiomyopathy with left ventricular failure. Arterial blood gas analysis revealed severe hypoxia with metabolic acidosis. Adrenaline infusion was started to optimise blood pressure. Intravenous frusemide was administered to relieve pulmonary oedema. Bilevel positive airway pressure was applied to improve oxygenation. After 1 h, patient was still hypoxic with laboured respiration; hence, it was decided to intubate patient electively and start mechanical ventilation. Her airway assessment revealed Mallampati class of 2 with good mouth opening. Intravenous midazolam 1 mg and fentanyl 50 µg were given; as bag and mask ventilation was adequate, rocuronium intravenous 50 mg was administered to facilitate muscle relaxation for intubation. After 1 min, an attempt was made to open the mouth, but severe jaw stiffness did not allow it. Injection rocuronium 20 mg was repeated, and bag and mask ventilation was continued for another 2 min. Oxygen saturation was maintained at 95% on 100% oxygen with bag and mask ventilation. Again, intubation attempt was made; however, jaw could not be opened with any force. As last resort, blind nasal intubation was done. Bilateral chest auscultation confirmed tracheal intubation. Except for the jaw muscle rigidity, other muscle spasm or rigidity in the body was not observed. The patient's body temperature was 36°C. End tidal expired CO2 was 32 mm Hg with tidal volume of 400 ml and respiratory rate of 12/min on mechanical ventilation. Haemodynamics were deteriorating despite maximal inotropic therapy with progressively increasing metabolic acidosis. The patient had repeated episodes of ventricular fibrillation and received multiple defibrillatory shocks. The patient could not be revived despite all efforts. Masseter muscle rigidity (MMR) also referred as ‘jaw of steel’ is severe stiffness of the jaw, with inability to open the mouth causing difficult or impossible laryngoscopy.[1] MMR is commonly seen after administration of succinylcholine and volatile agents.[2] MMR has also been quoted as an early sign of malignant hyperthermia (MH).[3] Muscle spasm following succinylcholine causing masseter spasm can lead to clinical MH in 30% of cases.[4] However, implications related to non-depolarising muscle relaxants have also been reported.[5] Jenkins reported a case of MMR after vecuronium.[6] Masseter spasm after pancuronium administration in a patient undergoing aortic valvulotomy has been reported.[7] A similar case of persistent masseter spasm during anaesthesia has been reported, where the authors attributed the spasm to increased extreme pre-operative anxiety rather than rocuronium.[8] Fentanyl in high dose can cause rigidity but in the present case, it was used in a low dose. Masseter spasm has the potential to complicate airway management, but no reported case has been shown to progress to generalised rigidity and MH. In the present case, we did not observe any signs of MH such as raised temperature, raised EtCO2 and generalised muscle rigidity. Non-depolarising muscle relaxants can be used safely in MH patients. Failed intubation in such scenario can be an important cause of morbidity and mortality. Nasopharyngeal airways can be placed and ventilation carried out and can be life saving. Sporadic case reports have suggested different techniques for airway management after MMR like fibreoptic nasotracheal intubation, retrograde endotracheal intubation, surgical cricothyrotomy and use of Trachlight®.[9] Though rare, one must be aware of MMR after using muscle relaxants. In case of any incident of masseteric spasm, the aim should be to maintain adequate oxygenation by any means. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.