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Cosmetic procedures might affect accuracy of this technique
- Tomas Tickunas, SP Mackey, KS Orkar (28 September 2009)
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Masseter relaxation also predicts intubating conditions and is required for laryngoscopy
- Kevin D Johnston (27 July 2009)
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Tomas Tickunas, Registrar in Plastic Surgery Queen Victoria Hospital, East Grinstead, UK, SP Mackey, KS Orkar
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Editor – We read with interest the recent article by Lee and colleagues describing the use of action potential monitoring in the corrugator supercilii (CS) muscle to predict intubating conditions. However, as Plastic surgeons, we wish to highlight two potential difficulties with this technique. First, the onset time of rocuronium in the CS muscle may be affected by the presence of Botulinum toxin (Botox®). The incidence of Botox use is increasing dramatically; in 2007 alone 4.5 million Botulinum toxin injections were recorded in the USA. Secondly, previous surgery to the CS, such as in endoscopic brow lifts where the CS is divided, would also affect results. The incidence of the aforementioned aesthetic procedures is increasing and patients may neglect to mention cosmetic work when asked about their medical history, unless they are directly questioned. In conclusion, we believe it is important to ascertain whether a patient has undergone any aesthetic procedures prior to the use of CS as a predictor of optimal intubating conditions. Conflict of Interest:None declared |
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Kevin D Johnston, Specialist Registrar Oxford Radcliffe Hospitals
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Editor – Lee et al report that corrugator supercilii observation predicts reliable intubating conditions faster than adductor pollicis accelerometry. 1 To expand on this, I would like to point out that masseter muscle relaxation may also be used to predict satisfactory intubating conditions and may be somewhat less fiddly to perform. De May et al found that chin accelerometry predicted reliable intubating conditions faster than adductor pollicis accelerometry after 0.6 mg/kg rocuronium2 while de Rossi et al found that the same applied to 1.5 mg/kg suxamethonium.3 The masseter is of course only one muscle contributing to ease of mouth opening. The medial pterygoid contributes and also to an extent, the lateral pterygoid and temporalis muscles. Nevertheless, crude manual assessment of jaw relaxation during the onset of neuromuscular blockade can be useful in predicting the onset of good intubating conditions and requires no specialist apparatus. It is surprising that such an extremely simple manoeuvre has (to my knowledge) not been more completely described elsewhere. When it comes to joints about which to test range of movement in assessing muscle relaxation, the TMJ is closest to hand and during intubation, is usually going to end up manipulated one way or the other. Repeated assessment of jaw opening as muscle relaxation evolves, allows one of the main goals of muscle relaxation to be recognised as soon as it is achieved i.e. mouth opening that is sufficient for the laryngoscope to be inserted. By the time the glottis is seen, then as predicted above2,3, the cords are usually sufficiently abducted to pass an endotracheal tube. I teach new anaesthetists to do this for all rapid sequence inductions and have personally found it particularly useful on occasions when following the administration of suxamethonium, patients have started to desaturate before fasciculations are seen and also when fasciculations are absent either following rocuronium or unexpectedly following suxamethonium. The manoeuvre does not seem to interfere with the application of cricoid pressure. Furthermore, any obvious and unexpected failure of masseter relaxation could prompt the anaesthetist to consider the possibility of malignant hyperpyrexia at an earlier stage and thus seek other features of this rare condition in a timely manner. 1 Lee HJ, Kim KS, Jeong JS, Cheong MA, Shim JC. Comparison of the adductor pollicis, orbicularis oculi, and corrugators supercilii as indicators of adequacy of muscle relaxation for tracheal intubation. Br J Anaes 2009;102:869-74 2 De May JC, De Baerdemaeker L, De Laat M, Rolly G. The onset of neuromuscular block at the masseter muscle as a predictor of optimal intubating conditions with rocuronium. Eur J Anaesthesiol 1999;16:387-9 3 de Rossi L, Preuler NP, Pühringer FK, Klein U. Onset of neuromuscular block at the masseter and adductor pollicis muscles following rocuronium or succinylcholine. Can J Anesth 1999;46:1133-7 Conflict of Interest:None declared |
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