1 Manchester, UK 2 Albuquerque, USA
EditorCaudal analgesia is commonly used for postoperative pain relief in children of all ages having surgery below the diaphragm, as confirmed in Sanders recent survey of UK practice of paediatric regional anaesthesia.1 Bupivacaine is named as the most common local anaesthetic drug of choice, and it would have been interesting to know what dose of local anaesthetic was used. The isomer levobupivacaine (Chirocaine®) is now regularly used in the Manchester Childrens Hospitals, for theoretical reasons of improved safety.2 I have conducted an audit, looking retrospectively at the doses of levobupivacaine used in the caudal space over the last six months by anaesthetists at Booth Hall Childrens Hospital in Manchester.
I studied the operating theatres recovery book, and extracted the case numbers of all patients recorded as having caudal analgesia during the period March to September, 2002. I then looked at the patient records and noted the dose of local anaesthetic used and the weight of the patient. I calculated the dose of levobupivacaine received in mg kg1 and plotted this on a scatter chart (Fig. 1).
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Although levobupivacaine 1.25 mg kg1 each side is recommended for ilio-inguinal nerve block,3 there is no evidence to support the recommended maximum dose of levobupivacaine for caudal analgesia in children. Is it assumed to be the same as the limit recommended for bupivacaine at 2 mg kg1 (although this drug is not yet licensed for use in children)? In this audit, more than one-third of patients received a dose in excess of this, but came to no harm. Further formal studies are needed, but I have shown that administering a dose of levobupivacaine 2.5 mg kg1 into the caudal space in children is a common practice at our hospital and has produced no clinical problems.
R. H. Smith
Manchester, UK
EditorThank you for the opportunity to reply to Dr Smiths letter on the dosing of levobupivacaine in paediatric caudal analgesia. Although much potentially valuable data was not analysed from the 35/79 (44%) medical records, which could not be located, some interesting points arose.
In 42/44 (95%) of caudals in Smiths report, levobupivacaine was the local anaesthetic of choice. In my survey, levobupivacaine was used by only 7/210 (3%) of respondents.1 It is exciting to see development and change for the patients benefit in our practice, brought about by new evidence on the possible reduced toxicity of levobupivacaine compared with bupivacaine. This is the sort of fact-based, highly transferable knowledge alluded to in my paper that can spread rapidly in the medical community. In Smiths report, only 3/44 (7%) of local anaesthetic doses had an adjuvant added. Lack of opiate adjuvants could be because the cases reported were suitable for day surgery. Of more interest, is the lack of use of epinephrine. Although the interpretation of test doses can be difficult in the anaesthetized child, many authorities recommend the use of epinephrine in test doses and monitoring for heart rate changes as well as changes in ECG morphology.4 5 It would be useful to know how test doses were interpreted.
My survey did not attempt to record the doses of local anaesthetic used in caudal analgesia. Doses are dependent not just on weight, but also on operative site and the age of the patient. Toxicity of local anaesthetics is potentially increased in infants, and especially neonates, because of decreased plasma protein binding of the drug and increased elimination half-time. Consequently, recommended bupivacaine doses are reduced by half in the neonate.6 An analysis of dosing by age in the report would have been of interest. If reduced toxicity is a prime concern, ropivacaine has been shown to be less toxic than levobupivacaine and bupivacaine in isolated heart preparations,7 and whole animal preparations.8 Ropivacaine has been available for longer than levobupivacaine and there are a substantial number of clinical studies supporting its use. For all of these drugs, maximum allowable doses must be considered carefully, as toxicity depends not only on dose of the drug and the weight of the patient, but also on age, physiological status, speed of injection, and site of injection. Although no adverse events were reported in the records reviewed, care must be taken in generalizing on the safety of the doses reported, especially in the very young, the acidotic patient, or those with decreased levels of -1 acid glycoprotein and albumin.
J. C. Sanders
Albuquerque, USA
References
1 Sanders JC. Paediatric regional anaesthesia, a survey of practice in the United Kingdom. Br J Anaesth 2002; 89: 70710
2 Gristwood RW. Cardiac and CNS toxicity of levobupivacaine: strengths of evidence for advantage over bupivacaine. Drug Saf 2002; 25: 15363[ISI][Medline]
3 Gunter JB, Gregg T, Varughese AM, et al. Levobupivacaine for ilioinguinal/iliohypogastric nerve block in children. Anesth Analg 1999; 89: 6479
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7 Mazoit JX, Decaux A, Bouaziz H, Edouard A. Comparative ventricular electrophysiologic effect of racemic bupivacaine, levobupivacaine and ropivacaine on the isolated rabbit heart. Anesthesiology 2000; 93: 78492[CrossRef][ISI][Medline]
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