• A M B Heard, R J Green, D A Lacquiere, and P Sillifant.
• Royal Perth Hospital, Perth, Australia. Andrew.Heard@health.wa.gov.au
• Anaesthesia. 2009 Nov 1;64(11):1196-8.

AbstractAcute 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.

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