Campbell in 1933 first described caudal block for paediatric urological interventions, since then it has evolved to become the most popular regional anaesthetic technique for use in children. The reason for the widespread use of this block both by the fulltime paediatric anaesthetist, as well as those undertaking occasional paediatric cases, is that it can be used for most of the operations that make up the large bulk of every day paediatric anaesthesia (e.g. inguinal hernia repair, hydrocoele, orchidopexy, circumcision, orthopaedic interventions on the lower limb, anorectal procedures) and can also be used for certain types of abdominal surgery. The block is perhaps the most easily learned and mastered of all regional anaesthetic techniques and Jöhr and co-workers have shown that only 32 blocks are needed for an anaesthetic registrar to reach about the same skill level as older and more experienced colleagues.2 As with any medical intervention caudal block is associated with the potential for some complications, such as unintentional dural puncture with total spinal anaesthesia or inadvertent intravascular injection of local anaesthetics.
However, the incidence is low if a proper technique is used and a prospective large-scale international study did not find any case with long-term sequelae or medico-legal action.3 Although it is a versatile block one of the major limitations of the single-injection technique is the relatively short duration of postoperative analgesia (4–6 h) that accompanies the use of even long-acting local anaesthetics. This problem can easily be circumvented by the use of a continuous catheter technique as despite the proximity to the anorectal area continuous caudal analgesia has been found safe, from an infectious point of view, for at least 48 h.4 However, most standard paediatric operations do not merit the use of such a complicated analgesic regimen as a continuous catheter technique and, thus, practitioners have tried to find other ways to enhance the efficacy of single injection caudal analgesia.
One of the most frequently used method to further prolong postoperative analgesia following caudal block is to add different adjunct drugs to the local anaesthetics solution. Epinephrine was the earliest adjunct drug used but is now less frequently administered. This may be because the newer long-acting local anaesthetics are not available as epinephrine containing solutions but may also be a result of the current availability of more potent adjunct options. During the second half of the 1980s neuroaxial administration of opioids became the established practice in adult anaesthesia and Krane and colleagues in 1988 published dose–response data for morphine as an adjunct to caudal anaesthesia in children.5 Soon after this, the successful use of both racemic ketamine and clonidine was described.6–8 During the following years a large number of studies on the adjunct use of these drugs in caudal anaesthesia have been published and this literature has recently been the focus of a number of review articles.9–11
A survey by Sanders in 20029 reported that the use of adjuncts was so popular that a majority of British paediatric anaesthetist (58%) used an adjunct drug when performing caudal block, with the most commonly used being ketamine, clonidine, fentanyl and diamorphine. Although the choice of opioids as adjuncts has been questioned, because of the high incidence of side-effects associated with their use,12 there is no doubt that the use of opioids, ketamine or clonidine as an adjunct does result in clinically relevant prolongation of postoperative analgesia. The recommended doses for morphine, S(+)-ketamine and clonidine are 33–50 µg kg–1, 0.5–1.0 mg kg–1 and 1–2 µg kg–1, respectively.13 14 .Recently the combined use of S(+)-ketamine and clonidine without local anaesthetics as a single injection technique has been reported to result in approximately 24 h of adequate postoperative analgesia after inguinal hernia repair.15 Thus, at present we have an adequate choice of drug options that are capable of achieving the set goal of prolonged postoperative analgesia. The widespread use of these drugs also has shown that these drugs are associated with an adequate safety profile, although not all are licensed for caudal epidural use. Whether these adjunct drugs should be administered with or without local anaesthetics or if certain adjuncts are more beneficial compared with the others in specific circumstances is currently not clear but deserves investigation in future prospective, randomized studies.
One of the less bright and more worrisome aspect of the use of adjuvant drugs for caudal blocks is the use of other drugs, which have not undergone adequate safety testing (some drug preparations may contain potentially toxic preservatives), and only producing limited prolongation of postoperative analgesia, or are associated with clearly unacceptable side-effects still remain the focus for research. The most obvious recent example is neostigmine as an adjunct. Abdulatif and colleagues, in 2002,16 reported a seemingly good effect of adjunct neostigmine but approximately 30% of the patients experienced postoperative nausea and vomiting (PONV). Despite this high incidence of PONV, a further study on the use of caudal neostigmine has recently been published.17 In this study the use of S(+)-ketamine, with or without 10 µg kg–1 of preservative-free neostigmine, was compared. The results showed a marginal prolongation of postoperative analgesia by the addition of neostigmine but the incidence of PONV increased from zero in the ketamine group to an unacceptable 30% in the combined neostigmine+ketamine group. In The field of pediatric anesthesia research should be pursued albeit with even more rationalism than say that for adults.
There are a number of drugs in our armamentarium of adjuvants for enhancement of post operative analgesia after caudal block that are both effective and have an acceptable side-effect and safety profile there appears to be little justification to investigate new drugs only out of academic curiosity. The road forward should follow one of the following three different but eventually converging paths. First, individual anaesthetists should change their current clinical practice regarding adjuncts to caudal block to better adhere to the existing literature and evidence base. Secondly, working groups of accepted relevant specialist bodies’ should issue guidelines to help the clinician to identify what is to be considered a standard of care. Thirdly, new alternatives to opioids, clonidine, and ketamine should only be tested in prospective, randomized trials of adequate size and such new alternatives should only be incorporated in clinical practice if they provide improved analgesia, combined with an acceptable safety and side-effects spectrum, compared with the already existing alternatives. This shall go long way in preventing the undue disrepute of a safe procedure like caudal block and also limit any occurrence of serious neurological adverse effects of adjuvant drugs in children .
1 Campbell MF. Caudal anesthesia in children. Am J Urol 1933; 30: 245–9
2 Schuepfer G, Konrad C, Schmeck J, Poortmans G, Staffelbach B, Johr M. Generating a learning curve for pediatric caudal epidural blocks: an empirical evaluation of technical skills in novice and experienced anesthetists. Reg Anesth Pain Med 2000; 25: 385–8
3 Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-Language Society of Pediatric Anesthesiologists. Anesth Analg 1996; 83: 904–12
4 Kost-Byerly S, Tobin JR, Greenberg RS, Billett C, Zahurak M, Yaster M. Bacterial colonization and infection rate of continuous epidural catheters in children. Analg Anesth 1998; 86: 712–6
5 Krane E, Tyler DC, Jacobson LE. The dose response of caudal morphine in children. Anesthesiology 1989; 71: 48–52
6 Naguib M, Sharif AMY, Seraj M, El Gammal M, Dawlatly AA. Ketamine for caudal analgesia in children: comparison with caudal bupivacaine. Br J Anaesth 1991; 67: 559–64
7 Lee JJ, Rubin AP. Comparison of a bupivacaine-clonidine mixture with plain bupivacaine for caudal analgesia in children. Br J Anaesth 1994; 72: 258–62
8 Jamali S, Monin S, Begon C, Dubousset AM, Ecoffey C. Clonidine in pediatric caudal anesthesia. Anesth Analg 1994; 78: 663–6
9 Sanders JC. Paediatric regional anaesthesia, a survey of practice in the United Kingdom. Br J Anaesth 2002; 89: 707–10
10 Ansermino M, Basu R, Vandebeek C, Montgomery C. Nonopioid additives to local anaesthetics for caudal blockade in children: a systematic review. Paediatr Anaesth 2003; 13: 561–73
11 de Beer DA, Thomas ML. Caudal additives in children—solutions or problems? Br J Anaesth 2003; 90: 487–98]
12 Lonnqvist PA, Ivani G, Moriarty T. Use of caudal-epidural opioids in children: still state of the art or the beginning of the end? Paediatr Anaesth 2002; 12: 747–9
13 Marhofer P, Krenn CG, Plochl W, et al. S(+)-ketamine for caudal block in paediatric anaesthesia. Br J Anaesth 2000; 84: 341–5
14 Klimscha W, Chiari A, Michalek-Sauberer A, et al. The efficacy and safety of a clonidine/bupivacaine combination in caudal blockade for pediatric hernia repair. Anesth Analg 1998; 86: 54–61
15 Hager H, Marhofer P, Sitzwohl C, Adler L, Kettner S, Semsroth M. Caudal clonidine prolongs analgesia from caudal S(+)-ketamine in children. Anesth Analg 2002; 94: 1169–72
16 Abdulatif M, El-Sanabary M. Caudal neostigmine, bupivacaine, and their combination for postoperative pain management after hypospadias surgery in children. Anesth Analg 2002; 95: 1215–18
17 Almenrader N, Passariello M, D’Amica G, Haiberger R, Pietropaoli P. Caudal additives for postoperative pain management in children: S(+)-ketamine and neostigmine. Pediatr Anesth 2005; 15: 143–7
Syed Kamran Habib
Assistant Professor, Department of Anaesthesiology.
Qazi E Ali
Associate professor, Department of Anaesthesiology.
M Salahuddin Ansari
Senior Resident, Department of Anatomy.
S. Kamran Habib, H.No. 4/275 Bait-ul-Habib, Sir Syed Nagar, Civil Lines.Aligarh(U.P)INDIA.
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