Letter to the editor
Stop before you (bite) block
I read with interest the case reported by Kidwai and colleagues  of a fractured reinforced LMA, near-transected by their patient biting down on it at emergence. Whilst I agree with their learning point that ‘deep’ removal of the LMA may have been preferrable in this particular patient (both to prevent the specific problem they encountered, and to minimise any unwanted increases in intraocular pressure), I would like to express some reservations regarding their recommendation of using either a guedel airway or sterile gauze roll as a bite block. Both of these suggested devices are likely to have been ineffective in the case they describe, and in fact, potentially harmful.
The maximum bite forces generated by a human have been reported to be as high as 1240 Newtons  and clearly anything capable of severing a metal reinforced tube will obliterate any number of rolled up gauze swabs. Furthermore, the use of gauze rolls, whilst commonplace, can be associated with the additional risks of soft tissue/dental trauma (on insertion), hypoglossal nerve injury (if the tongue is accidentally folded over during placement) and airway obstruction (if accidentally retained at the end of anaesthesia, much like a throat pack). The use of a guedel airway in this instance is likely to have incurred significant dental injury to the incisors given the huge forces being applied upon this hard and unforgiving oropharyngeal device.
Rather than employing these rather make-shift and potentially harmful devices, I would recommend the Breathesafe TM bite block (OGM Ltd, Eynsham, UK). This particular bite block is placed between the patient’s molars rather than incisors, is comprisesd of a rigid plastic body but with a soft intermolar section (so preferrable to the guedel), is capable of withstanding compression forces of up to 1500 Newtons , and crucially, is able to maintain an intermolar distance sufficent to prevent occlusion/transection of an LMA or endotracheal tube at emergence.
No competing interests.
Dr Patrick Ward, Clinical Fellow in Anaesthesia, Hong Kong
1. Kidwai U, Sri-Ganeshan P, Surve P, Dalal V, Cozma R. Bite block or not? Journal of Anaesthesia Practice, Oct 2015.
2. Shepherd J. Bite blocks and tube obstruction. Anaesthesia, 2006; 61: 406-407.
3. Gibbs CH, Anusavice KJ, Young HM, Jones JS, Esquivel-Upshaw JF. Maximum clenching force of patients with moderate loss of posterior tooth support: a pilot study. Journal of Prosthetic Dentistry, 2002; 88: 498-502.