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Acute trismus can be caused by pain, muscle spasm, swelling or mechanical obstruction. Unfortunately, the cause is not always obvious during pre-operative airway assessment. In this pilot study, we prospectively evaluated mandibular nerve block as a pre-operative tool to identify patients with reversible causes of trismus, namely pain or spasm, in order to allow safe anaesthetic induction. Six patients with unilateral fractured mandibles and trismus received a mandibular nerve block before induction of general anaesthesia. There was an increase in maximal inter-incisor gap after the blocks (median (range) distance: pre-block 16.5 (14-30) and post-block 34 (32-35) mm; p = 0.027), and no further improvement after induction of general anaesthesia (post-induction 37 (30-40) mm; p = 0.276 compared with post-block). There was an improvement in pain scores (p = 0.027), and no side-effects were detected. Pre-operative mandibular nerve blockade appears to reverse trismus caused by pain and muscle spasm, allowing the anaesthetist to decide whether awake intubation is genuinely indicated.

Both the American Society of Anesthesiologists and the Difficult Airway Society of the United Kingdom have published guidelines for the management of unanticipated difficult intubation. Both algorithms end with the 'can't intubate, can't ventilate' scenario. This eventuality is rare within elective anaesthetic practice with an estimated incidence of 0.01-2 in 10,000 cases, making the maintenance of skills and knowledge difficult. Over the last four years, the Department of Anaesthetics at the Royal Perth Hospital have developed a didactic airway training programme to ensure staff are appropriately trained to manage difficult and emergency airways. This article discusses our training programme, the evaluation of emergency airway techniques and subsequent development of a 'can't intubate, can't ventilate' algorithm.