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Re: Dose for response?
- Helena Kallio (31 August 2008)
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Dose for response?
- Alfred P J Lake, Mohamed M Abo-Khatwa (14 August 2008)
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Helena Kallio
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Dear Editor, We appreciate the interest by Lake PJ and Abo-Khatwa (1) in our study on the effect of i.v. local anaesthetics on tinnitus. The dose of i.v. lidocaine which has been commonly applied in the treatment of tinnitus is 1.0 – 1.5 mg/kg (2-6). The higher standard dose, 1.5 mg/kg (4-5), was chosen for the present study (6) in order to find a possible therapeutic effect if any. For comparison, we chose a longer-acting local anaesthetic, ropivacaine, and we used a dose as high as possible, within safe limits (7). The very high dose of i.v. lidocaine, 5 mg/kg, as mentioned (probably a printing error) by Lake and Abo-Khatwa (1), cannot be recommended because it exceeds by far the safe dose of any local anaesthetic. The fact remains, however, that in our own study (6) a relatively high (1.5 mg/kg i.v.) of both ropivacaine and lidocaine had no long-lasting clinically significant effect on tinnitus. References (1) Lake APJ, Abo-Khatwa MM. Dose for response? (letter) Br J Anaesth 2008. (2) Ueda S, Aso S, Watanabe Y, Mizukoshi K. Changes in auditory evoked responses during intravenous lidocaine. Acta Oto-Laryngol Suppl 1993;504:89-93. (3) Otsuka K, Pulec JL, Suzuki M. Assessment of intravenous lidocaine for the treatment of subjective tinnitus. ENT-Ear Nose Throat J 2003;82:781-4. (4) Kalcioglu MT, Bayindir T, Erdem T, Ozturan O. Objective evaluation of the effects of intravenous lidocaine on tinnitus. Hear Res 2005;199:81-8. (5) Baguley DM, Jones S, Wilkins I, Axon PR, Moffat DA. The inhibitory effect of intravenous lidocaine infusion on tinnitus after translabyrinthine removal of vestibular schwannoma: a double-blind, placebo-controlled, crossover study. Otol Neurotol 2005;26:169-76. (6) Kallio H, Niskanen ML, Havia M, Neuvonen PJ, Rosenberg PH, Kentala E. I.V. ropivacaine compared with lidocaine for the treatment of tinnitus. Br J Anaesth 2008;101:261-5. (7) Rosenberg PH, Veering BTh, Urmey WF. Maximum recommended doses of local anesthetics: a multifactorial concept. Reg Anesth Pain Med 2004;29:564-75. Conflict of Interest:None declared |
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Alfred P J Lake, Consultant in Anaesthesia and Pain Medicine Glan Clwyd Hospital, Rhyl LL18 5UJ., Mohamed M Abo-Khatwa
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Aware of problems with the effective management of subjective tinnitus through regular contact during ENT sessions the paper was of interest. Tinnitus is considered to be a manifestation of nerve damage but in less than 0.5% of cases is there an identifiable treatable cause, measurement of severity is subjective and external influencing factors feature and so, with these similarities, it is not surprising that medications effective in the management of neuropathic pain have been exhibited but they have met with only limited success 1. As with chronic pain, it is important also to consider interventions which act in concert, no single drug is likely to be effective though lidocaine has shown some consistency and the use of the drug for both conditions has a long history 2,3. We were surprised, however, by the choice of the same 1.5mg.kg-1 dose for both lidocaine and ropivacaine with their well known differing potencies (1:3-4) and maximum recommended doses (2:1). Why, despite the presumed common cause (nerve damage), the intravenous doses exhibited for the two conditions differ so markedly is unclear. In general, those for tinnitus are much lower (original paper references: 6,7,18,19,20) but in respect of chronic pain, 5mg.kg-1 is the most common dose administered by intravenous infusion 4,5,6,7. One could speculate a reason might be that with chronic pain the intervention would be in the hands of someone with anaesthesia training, comfortable to deal with the potential adverse consequences of the administration of a maximum recommended dose. The exact mechanism of the observed prolonged relief of chronic pain remains uncertain 4. Patients who respond positively to intravenous lidocaine for either indication are suitable for repeat treatments (when the duration of benefit is prolonged), mexilitene or appropriate anticonvulsant medication. A formal examination of the efficacy of a 5mg.kg-1 dose in the management of tinnitus would be worthwhile together with an assessment of the number needed to treat (NNT) for any subsequent anticonvulsant to see whether this is similar to that when used for neuropathic pain. 1. Simpson JJ, Davies WE. Recent advances in the pharmacological treatment of tinnitus. Trends Pharmacol Sci 1999; 20: 12-8. 2. Lewy RB, Treatment of tinnitus aurium by the intravenous use of local anesthetic agents. Arch Otolaryngol 1937; 25: 178-83. 3. Edwards WT, Habib F, Burney RG, Begin G. Intravenous lidocaine in the management of various chronic pain states. Regional Anesth 1985; 10: 1 - 6. 4. Tremont-Lukats IW, Challapalli V, McNicol ED, Lau J, Carr DB. Systemic administration of local anesthetics to relieve neuropathic pain: a systematic review and meta-analysis Anesth Analg 2005; 101: 1738-49. 5. Gottrup H, Bach FW, Juhl G, Jensen TS. Differential effect of ketamine and lidocaine on spontaneous and mechanical evoked pain in patients with nerve injury pain. Anesthesiol 2006; 104: 527-36. 6. Finnerup NB, Biering-Sorensen F, Johannesen IL et al. Intravenous lidocaine relieves spinal cord injury pain: a randomized controlled trial. Anesthesiol 2005; 102: 1023-30. 7. Attal N, Gaude V, Brasseur L et al. Intravenous lidocaine in central pain: a double-blind, placebo-controlled, psychophysical study. Neurol 2000: 54: 564-74. Conflict of Interest:None declared |
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