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Ketamine gargles for post operative sore throat
- Trevor A King (9 May 2008)
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Throat packs may cause more pain than tracheal intubation
- Francis E Arnstein (4 May 2008)
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Ketamine gargle
- James S Dawson (23 April 2008)
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Trevor A King
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Editor - Canbay et al (1) quite rightly conclude that a drawback of their study was the absence of measurements of plasma ketamine levels. The possible action of ketamine on peripheral NMDA receptors needs to be challenged at two levels. Firstly, sore throat from intubation is likely to be due to superficial trauma at glottic and sub-glottic level. During the act of gargling, these areas are well protected by pharyngeal and glottic reflexes. If they were not, patients would cough considerably during and after the act of gargling. It is unlikely, therefore, that the ketamine gargles made significant contact with the areas concerned. Secondly, ketamine is absorbed both via the oral (2) and transmucosal (3) routes. The act of gargling would effectively keep ketamine in contact with oral mucosa for a period of time, allowing for systemic absorption and avoiding first pass metabolism. Furthermore, following gargling, the natural reflex is to swallow, allowing any remaining ketamine to be ingested together with saliva. Even if the quantities of absorbed ketamine were small, they may have significant analgesic effect. Studies have shown that low, sub-anaesthetic doses of ketamine given systemically may have good analgesic properties (4). I therefore do not think that any definite conclusions can be drawn from this paper regarding the topical effect of ketamine on peripheral NMDA receptors. 1)Canbay O, Celebi N, Sahin A, Celiker V, Ozgen S, Aypar U. Ketamine gargle for attenuating postoperative sore throat. Br J Anaesth 2008; 100(4): 490-3. 2)Petros AJ. Oral ketamine. Its use for mentally retarded adults requiring day care dental treatment. Anaesthesia 1991; 46(8): 646-647. 3)Cioaca R, Canavea I. Oral transmucosal ketamine: an effective premedication in children. Pediatric Anaesthesia 1996; 6(5): 361-365. 4)Adam F, Chauvin M, Du Manoir B, Langlois M, Sessler DI, Fletcher D. Small-dose ketamine infusion improves postoperative analgesia and rehabilitation after total knee arthroplasty. Anesth Anal 2005; 100 (2): 475-80. TA King Eastbourne, UK Conflict of Interest:None declared |
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Francis E Arnstein St John's University Hospital, Livingston
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O'Canbay et.al. demonstrate nicely that gargling ketamine appears to be useful in reducing post-operative sore throat. However, I would contend that their suggestion that this is necessarily caused by tracheal intubation in their patient series may be erroneous as their patients had gauze naso-pharyngeal packs inserted during the procedures. This is mentionned but not emphasised. Throat packs, I believe, are well recognised to cause significant post-operative discomfort. In the regional head and neck unit that I work, we abandonned tracheal intubation and throat packs for almost all upper airway ENT procedures some years ago, using flexible laryngeal mask airways instead. We believe there are a number of advantages to this approach including being able to abandon the throat pack. Sore throats still occur, possibly associated with the LMAs, but rarely do patients complain of the severe discomfort previously noted. Conflict of Interest:None declared |
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James S Dawson, Anaesthetic Registrar United Lincolnshire Hospitals NHS Trust
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Dear Sir I read with great interest the research by Canbay and colleagues1 looking at the role ketamine may have to play in attenuating postoperative sore throat, a problem frequently encountered by all of us who instrument the patients airway. I wish to make comment on several aspects of this paper; the first relates to the study design, implementation and presentation of the research, and the second to the authors interpretation of their findings. Firstly the authors fail to acknowledge whether several important factors were standardized between the two groups, any of which may have greatly affected the observed outcomes. These include: if the same anaesthetist administered the anaesthetic for all patients; if endotracheal tubes were consistently lubricated or not; if gum elastic bougies were used; grade of view at laryngoscopy; timing of extubation (deep or wide awake); use or not of airway adjuncts (oropharyngeal airways); use of anti-emetics and incidence of post-operative vomiting; force used and method of insertion of gauze to pack the posterior nasopharynx; vasoconstrictor or local anaesthetic use by the operating surgeon. In addition, all patients were given 500mg of acetaminophen (paracetamol) irrespective of the individuals body weight; while mean weight in the two groups was similar, the very large standard deviation of the control group suggests they were less homogenous compared to the study population. Secondly, table 1 documents ‘time taken for tracheal intubation (min)’ though I am unsure if this represents the time taken to perform laryngoscopy and insert the endotracheal tube (in which case the units should presumably be seconds given the values are 55 and 61), or if it represents the total duration of time the endotracheal tube was in situ. Thirdly, it is also unclear from the paper if the 30ml volume of fluid to be gargled was given as a single gargle or as repeated smaller attempts in the allotted 30 seconds. Having experimented myself and on several colleagues, 30ml is a large volume to gargle in a single attempt and results in much coughing, swallowing (ingestion) and ‘patient’ displeasure. Fourthly, I agree with the authors in acknowledging that failing to measure plasma ketamine is a major weakness in this study. Even if just 10ml of the study solution was ingested, this would equate to an oral dose of about 0.2mg kg-1 of ketamine. Previous work has shown that an oral dose of 0.5mg kg-1 of ketamine has very clear analgesic effects2, so it would seem reasonable that the results in this study could be in part attributable to the systemic effects of ketamine. Finally, in their discussion, the authors appear to promote the idea that the action of ketamine in this study is a topical effect, though all the papers they cite to support this theory have all used systemically administered ketamine (enterally or parenterally). I personally find it hard to believe that a 30 second exposure to topical ketamine can provide effective analgesic and anti-inflammatory properties in the throat lasting for 24 hours, and unfortunately the evidence in this paper fails to convince me otherwise for the reasons cited. I look forward to a follow-up study using a more standardized technique, in patients who do not require ‘throat packs’ and in which plasma levels will be assayed. 1 Canbay O, Celebi N, Sahin A, Celiker V, Ozgen S, Aypar U. Ketamine gargle for attenuating postoperative sore throat. Br J Anaesth 2008; 100: 490-3 2 Grant IS, Nimmo WS, Clements JA. Pharmacokinetic and analgesic effects of i.m. and oral ketamine. Br J Anaesth 1981; 52: 805-10 Conflict of Interest:None declared |
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