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Biers Block: Another Adjuvent?
- David F Maritz, Margaret Coleman, Jean Saunders. (4 January 2007)
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David F Maritz, Department Anaesthesia Limerick Regional Hospital, Limerick, Ireland., Margaret Coleman, Jean Saunders.
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We read with interest the article by Sen and colleagues (The analgesic effect of Lornoxicam when added to Lidocaine for Intravenous Regional Anaesthesia’. Br J Anaesth 2006; 97(3): 408-413) (1). The benefits of Intravenous Regional Anaesthesia (IVRA) are well established, however we have some concerns regarding the clinical and statistical relevance of this article. Firstly from a clinical viewpoint, we question the effect that high dose intramuscular (IM) Midazolam (0.15mg/kg) given as premedication has on Visual Analogue Scale (VAS) and patient satisfaction scores. Intramuscular Midazolam 0.1mg/kg may lead to a decrease in Oxygen Saturation (SpO2) and loss of the eyelash reflex (2). In the elderly, doses as low as 0.06mg/kg can lead to hypotension, hypoxia and deep sedation(2,3). The authors used doses of IM Midazolam 50-70% higher than recommended, surely altering VAS and patient satisfaction scores. Intramuscular Diclofenac is associated with severe pain, tissue necrosis and necrotising fasciitis. There have also been several fatalities reported (4,5). Administration of Diclofenac by other routes would be more acceptable. No mention was made of the total consumption of IM Diclofenac or Paracetamol in the post operative period and many patients were given two drugs from the same class (Lornoxicam and Diclofenac). Regarding the technique of IVRA used by the authors, cyclical deflation of the tourniquet, originally thought to be a safer method may actually place patients at higher risk of local anaesthetic toxicity (6). Lornoxicam’s short half life of 2-3 hours surely is a disadvantage in this setting (7). We should strive to use longer acting drugs with a low side effect profile to minimise the use of stronger analgesics and their associated side effects. The new COX 2 inhibitors are associated with adverse cardiac events. Was this taken into account when selecting patients for this study? There is no formal breakdown of patient clinical details (cardiovascular risk factors, renal function etc) but middle aged male smokers with high lipid levels and hypertension are at risk (8,9,10,11). Based on this study, Lornoxicam may be used in those at high risk of coronary syndromes, for very little clinical benefit. Regarding the statistics, sample size estimation was based on a pilot study (10 cases) but this data was not included in the analysis. The sample size calculations given were correct for the particular parameters quoted however there was no mention of the primary outcome variables to which these calculations refer and none of the variables described in the article have these mean values, differences in means or a standard deviations. Therefore the sample size calculations may not appear to refer to this study or if they do and really came from a pilot study we can only conclude that the pilot study must have produced very different results to the ones reported here or must have used a different primary outcome variable. Furthermore the authors only looked at t-tests between the L-IVRA group and other groups i.e. two tests for each parameter. This would mean that over 30 tests were carried out for the main outcome variables alone, whereas over 40 tests if we include the tests on demographic data. Hence there is a high likelihood of finding a false positive result as no adjustment was made for multiple testing. (We do not understand the argument put forward for not adjusting p-values to allow for this possibility.) If an adjustment had been made, very few of the results would still be significant at the 5% level. The increased rapidity of motor blockade is not really clinically advantageous as in IVRA it is standard practice to wait 8-10 minutes for complete anaesthesia, thus negating this perceived benefit. Do we really need another adjuvant to IVRA which is costly, has potential risk for coronary syndromes (and other NSAIDS side effects) and has a dubious benefit based on clinically irrelevant sensory and motor onset times and marginal improvements in pain scores ( in heavily sedated patients) and in non ambulatory patients. There is good evidence to recommend Ketorolac and clonidine as adjuncts to IVRA which have been shown to improve post operative analgesia and prolong tourniquet tolerance (12,13,14). Even though some of the results in this article may have some statistical significance (assuming there are no major flaws in the analysis), are they really that clinically relevant? The findings of this study do not justify the routine use of this drug in IVRA. References: 1. Sen S, Ugur B, Aydm ON et al. The analgesic effect of Lornoxicam when added to lidocaine for intravenous regional anaesthesia. Br J Anaesth 2006; 97(3): 408-413. 2. Nishiyama T, Matsukawa T, Hanaoka K. The effects of age and gender on the optimal premedication dose of intramuscular midazolam. Anesth Analg 1998; 86(5): 1103-1108. 3. Kain ZN, Sevarino F, Pincus S et al. Attenuation of the preoperative stress response with midazolam: effects on postoperative outcomes. Anesthesiology 2000 Jul; 93(1): 141-147. 4. Orlando A, Marrone C, Nicoli N et al. Fatal necrotising fasciitis associated with intramuscular injection of nonsteroidal anti-inflammatory drugs after uncomplicated endoscopic polypectomy. J Infect 2006 Oct 17; (Epub ahead of print) 5. Pillans PI, O’Connor N. Tissue necrosis and necrotizing fasciitis after intramuscular administration of Diclofenac. Ann Pharmacother 1995 Mar; 29(3): 264-266. 6. Sukhani R, Garcia CJ, Munhall RJ et al. Lidocaine disposition following intravenous regional anaesthesia with different tourniquet deflation techniques. Anesth Analg 1989 May; 68(5):633-7. 7. Skjodt NM, Davies NM. Clinical pharmacokinetics of Lornoxicam. A short half life oxicam. Clinical Pharmacokinet 1998 Jun; 34(6): 421-428. 8. Solomon DH, Schneeweiss S, Glynn RJ et al. Relationship between selective cyclooxygenase-2 inhibitors and acute myocardial infarction in older adults. Circulation 2004 May 4; 109(17): e9039-40. 9. Mamdani M, JuurlinkDN, Lee Ds et al. Cyclo-oxygenase-2 inhibitors versus non-selective non-steroidal anti-inflammatory drugs and congestive heart failure outcomes in elderly patients: a population-based cohort study. Lancet 2004 May 29; 363(9423): 1751-6. 10. Tannenbaum H, Bombardier C, Davis P et al. An evidence-based approach to prescribing nonsteroidal anti-inflammatory drugs. Third Canadian consensus conference. J Rheumatol 2006 Jan; 33(1): 140-57. Epub 2005 Dec 1. 11. Hippisley-Cox J, Coupland C. Risk of myocardial infarction in patients taking cyclo-oxygenase-2 inhibitors or conventional non-steroidal anti- inflammatory drugs: population based nested case-control analysis. BMJ 2005 Jun 11; 330(7504): 1366. 12. Reuben SS, Steinberg RB, Maciolek et al. An evaluation of the analgesic efficacy of intravenous regional anaesthesia with lidocaine and ketorolac using a forearm versus upper arm tourniquet. Anesth Analg 2002 Aug; 95(2): 457-60. 13. Reuben SS, Steinberg RB, Kreitzer JM et al. Intravenous regional anaesthesia using lidocaine and ketorolac. Anesth Analg 1995 Jul; 81(1): 110-3. 14. Choyce A, Peng P. A systematic review of adjuncts for intravenous regional anesthesia for surgical procedures. Can J Anaesth 2002 Jan; 49(1): 32-45. Conflict of Interest:None declared |
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