Does mouth opening in patients with dental infections improve after induction of anaesthesia? A prospective observational study

ABSTRACT

Dental infection can cause reduced mouth opening which may make tracheal intubation after induction of general anaesthesia difficult. Although it is widely quoted in the literature that reduced mouth opening secondary to dental infection might not improve post-induction of anaesthesia,1 the evidence base for this is limited. The 4th National Audit Project in Anaesthesia highlighted that airway complications often resulted from poor assessment, inadequate planning of management, and a reluctance to use advanced airway techniques.2 An improved understanding and awareness of the effect of dental infection on mouth opening could help highlight potential airway difficulty, improving planning of airway management and the use of appropriate techniques to do this. We conducted a prospective observational study at the Royal Hallamshire Hospital, Sheffield. After study approvals (REC ref 18/LO/1134, IRAS ID 264468) were obtained, 11 patients presenting with dental infection requiring surgical management under general anaesthetic were recruited between December 2018 and January 2020. Maximal mouth opening was measured immediately before and after the induction of general anaesthesia using a TheraBite® ROM scale.3 The presence of a number of parameters associated with the severity of dental infection was also recorded. The mean pre-induction maximal mouth opening of the study participants was 18 mm (standard deviation [SD], 5.16 mm) whereas the mean post-induction maximal mouth opening was 22.3 (5.56) mm. Although the maximal mouth opening of 3 (17%) patients improved by more than 10 mm after induction of anaesthesia, the other 8 (73%) patient’s maximal mouth opening improved by less than 2 mm. Unfortunately, there was a large under-recruitment to the study in part owing to difficulties resulting from the COVID-19 pandemic. The study was therefore underpowered to perform further statistical analysis of the influence of induction of anaesthesia on a patient’s maximal mouth opening or to examine the influence of the presence of parameters associated with the severity of dental infection on maximal mouth opening. To our knowledge, this is the first study to look at the change in maximal mouth opening after induction of anaesthesia as a primary endpoint in patients with dental infection. Even in the context of the small sample size, the finding that 73% of the patients in the study had a less than 2 mm improvement in maximal mouth opening after induction is clinically highly relevant. A lack of improvement in reduced mouth opening has significant implications on airway management. This study clearly shows there is a reasonable prospect of this scenario in patients with dental infection and supports the practice of assuming mouth opening will not improve after induction of anaesthesia when planning airway management in these patients. References 1. Morosan M, Parbhoo A, Curry N. Continuing Education in Anaesthesia Critical Care & Pain 2012;12 257–62 2. Cook TM, Woodall N, Frerk C. On behalf of the Fourth National Audit Project. Br J Anaesth 2011;106 617–31 3. TheraBite® Range of Motion Scale. Available from accessed date as 5th November 2021