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Prospective to a randomized double-blind controlled trial to assess efficacy of double caudal analgesia in hypospadias repair
Prospective to a Randomized Double-Blind Controlled Trial to Assess Efficacy of Double Caudal Analgesia in Hypospadias Repair By M. Samuel, D. Hampson-Evans, and P. Cunnington London, England
Background/Purpose: A prospective, randomised, doubleblind, controlled trial to evaluate efficacy of double-caudal versus single-caudal injection for postoperative analgesia in hypospadias repair was performed. Methods: Between October 1998 and September 2000, 160 boys underwent distal hypospadias repair. The first 80 boys were analyzed prospectively for postoperative analgesia after double-caudal bupivacaine, which involves the administration of a second bupivacaine injection into the caudal extradural space at the end of surgery. Pain was assessed using the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS). The study groups were: group 1, unstented Thiersch-Duplay urethroplasty (50); and group 2, stented Mathieu type repair (30). Results of this cohort formed the basis for a prospective, randomised, double-blind control trial comparing double-caudal against a single injection before operation. The further 80 patients were allocated randomly: group 3, single caudal injection of 1 mL kg⫺1 of 0.25% plain bupivacaine at the start of surgery with unstented Thiersh-Duplay repair (25); group 4, similar single caudal injection but stented Mattieu type operation (15); group 5, second caudal and at end of operation (0.5 mL kg⫺1 on each occasion) with unstented Thiersh-Duplay repair (25); and group 6, similar to group 5 but with stented Mattieu type repair (15). Results: Patient demographics (age and weight) and mean duration of operative time were similar for all groups. There
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EGIONAL TECHNIQUES such as local caudal blocks have been used in conjunction with general anesthesia to provide intra- and postoperative analgesia, which is a vital part of perioperative care in children undergoing hypospadias surgery. Administration of 0.25% plain bupivacaine into caudal extradural space has been the standard method of providing postoperative analgesia for hypospadias surgery at our institution. Duration of analgesia after caudal injection of bupivacaine
From the Departments of Pediatric Surgery and Anesthesia, St George’s Hospital, London, England. Presented at the 48th Annual International Congress of the British Association of Paediatric Surgeons, London, England, July 18-21, 2001. Address reprint requests to Dr D. Hampson-Evans, St George’s Hospital, London, SW17 OQT, England. Copyright © 2002 by W.B. Saunders Company 0022-3468/02/3702-0006$35.00/0 doi:10.1053/jpsu.2002.30247 168
was no significant difference in early pain scores at 0 to 2 hours with a good correlation coefficient (r ⫽ 0.88). At 4, 6, and 8 hours there was a significant difference in pain scores between double and single caudals (P ⬍ .05). There was a significant difference in mean duration of caudal analgesia and need for oral analgesia between single caudal 3.45 versus 7.85 hours for double caudal (P ⬍ .001). Mean duration of caudal analgesia and requirement for oral analgesia after single caudal in group 3 (unstented) was 3.5 versus 3.4 hours in group 4 (stented). In double caudals this lengthened to 9.4 hours in group 5 (unstented) versus 6.3 hours in group 6 (stented; P ⬍ .05). This also was significant when operation time was excluded.
Conclusions: A prospective study of double caudal analgesia showed good postoperative pain control after hypospadias surgery. This was followed by a prospective, randomised, double-blind controlled trial that has confirmed that double caudal injection of bupivacaine prolonged the duration of pain relief after hypospadias repair. The second or top-up caudal did not increase the total dose but supplemented and prolonged postoperative analgesia. J Pediatr Surg 37:168-174. Copyright © 2002 by W.B. Saunders Company. INDEX WORDS: Double caudal analgesia, 0.25% plain bupivacaine, Children’s Hospital of Eastern Ontario Pain Scale, distal hypospadias repair.
usually is 4 to 6 hours.1-5 This period of analgesia is based on time from injection to requirement of pain medication, and a single injection of bupivacaine may have only a relative short duration of action.1-4 There are many methods to try and prolong duration of caudal analgesia, but these involve the addition of other drugs to bupivacaine. These additives include opiates, clonidine, ketamine, and adrenaline. Opiates carry the risk of respiratory depression and urinary retention. Clonidine may cause sedation and therefore precludes its use in day surgery. Ketamine may cause behavioral changes, and there is debate about long-term changes to nerves. Adrenaline is unreliable in prolonging analgesia.5-8 The advantage of the “double caudal” is that it does not depend on additives. It therefore avoids their side effects and reduces drug error by miscalculation of their dose. To study this simple technique, we audited our double caudals prospectively and then performed a prospective, randomised, controlled trial to close our audit loop. The Journal of Pediatric Surgery, Vol 37, No 2 (February), 2002: pp 168-174
DOUBLE CAUDAL ANALGESIA IN HYPOSPADIAS REPAIR
aim of this prospective, randomised, double-blind controlled study was to compare duration of analgesia for hypospadias surgery produced by 1 mL kg⫺1 of 0.25% plain bupivacaine single caudal block administered after induction of general anesthesia but before start of surgery versus double caudal block, wherein 0.5 mL kg⫺1 of 0.25% plain bupivacaine was administered via an indwelling caudal cannula at start of surgery and a top-up of 0.5 mL kg⫺1 of plain bupivacaine was given at end of surgery. MATERIALS AND METHODS Between October 1998 and September 2000, 160 boys underwent distal hypospadias repair. Eighty patients were analyzed prospectively for postoperative analgesia. The further 80 patients were the subject of a trial of single against double caudal administration of extradural bupivacaine. Methodology in the double caudal groups was identical to that described for single injection into caudal extradural space, but at the end of surgery a second injection was given as detailed below. Behavioral scale for rating postoperative pain was assessed by the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS),10 which assigns scores for crying, facial expression, verbal response, touching the wound and torso, and leg movement.10 Results of this prospective cohort formed basis for a randomised, double-blind, controlled trial to access efficacy and benefit of double-caudal versus single-caudal block for postoperative analgesia in distal hypospadias repair. Local Ethics Committee approval was obtained for the randomised study, and written informed parental consent was obtained for each child. Premedication was not used, and 4% amethocaine (Ametop Gel; Smith & Nephew, Health Care Ltd, Hull, England) was applied to potential venous access sites. However, all children were induced with oxygen and sevoflurane. Neuromuscular block was produced with atracurium 0.5 mg kg⫺1 and trachea intubated. Anesthesia was maintained with 0.5% to 1.5% isoflurane and 70% nitrous oxide in oxygen, maintaining normocapnia by intermittent positive pressure ventilation. All children were monitored and received intravenous crystalloids (0.45% sodium chloride and 5% dextrose) at 10 mL kg⫺1 for duration of anaesthesia. After induction of anaesthesia, patients were placed in the lateral position and a caudal injection performed using an aseptic technique via an ABBOCATH-T 22 G cannula. All boys had repair of distal hypospadias with one surgeon using unstented Thhiersch-Duplay urethroplasty (TD) and the other using Mathieu and “V” incision method (MV).9 The prospective trial consisted of group 1, TD unstented urethroplasty (n ⫽ 50) and group 2, MV stented repair (n ⫽ 25). All patients were given double caudal injections of bupivacaine as described below. Eighty patients were assigned randomly using a computer-generated list into group 3, TD unstented urethroplasty: single-caudal (n ⫽ 25); group 4, MV stented urethroplasty: single-caudal (n ⫽ 15); group 5, TD unstented urethroplasy: double-caudal (n ⫽ 25); group 6, MV stented urethroplasty: double-caudal (n ⫽ 15). Single caudal groups received a caudal injection of 0.25% plain bupivacaine, 1 mL kg⫺1, and the cannula was removed before the start of surgery. Double caudal groups in the randomised group received a caudal injection of 0.25% plain bupivacaine, 0.5 mL kg⫺1, and a capped cannula was left in situ with an aseptic Ensure-it dressing. All 160 patients received rectal acetaminophen (paracetamol) suppository, 20 mg kg⫺1, after induction. Anaesthesia was discontinued on application of Cavi-care foam (Smith & Nephew Medical) penile dressing; residual neuromuscular block was antagonised with glycopyrolate, 10 g kg⫺1, and neostig-
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mine, 50 g kg⫺1, and patient’s trachea extubated before transfer to recovery area. In double-caudal (groups 5 and 6) the caudal cannula was accessed aseptically to deliver a second top-up caudal dose of 0.25% plain bupivacaine, 0.5 mL kg⫺1. At the completion of the procedures anaesthetic agents were discontinued, and patients were transferred to the recovery area. Duration of surgery from completion of induction to antagonism of neuromuscular block was recorded for each patient. Time 0 hour was taken as the time of the first caudal injection after induction of anaesthesia. The first pain score was recorded at 2 hours after time 0 and subsequently at 2-hour intervals for a total period of 14 hours. All patients were allowed to eat and drink immediately after transfer to the surgical ward. On the surgical ward, assessors blinded to the nature of caudal injection, performed 2 hourly observations until 14 hours after caudal injection. CHEOPS was used to assess pain.10 The requirement for analgesia (paracetamol or ibuprofen) was recorded during the 14 hours of pain assessment. The need for oral analgesia as indicated by a rising CHEOPS score was taken as the duration of postoperative caudal analgesia. These times were calculated subsequently to create the mean duration of caudal analgesia in each group. Facial flushing, paucity of leg movement, vomiting, and pruritus were noted if they occurred. In unstented urethroplasty the dressing was removed 24 hours postoperatively, whereas in stented repair, dressing and stent were removed 48 hours postoperatively. Parents were advised to continue regular use of paracetamol and trimethoprim for 5 days in all groups. Parametric data were analyzed by Student’s t test. Nonparametric data (pain scores, analgesia requirements, and incidences of complications) were evaluated statistical by 1-way analysis of variance with Bonferroni’s type I error rate correction for multiple tests of significance with P ⬍ .05 considered statistically significant. Data were correlated by Pearson correlation coefficient, and results are presented as mean ⫾ SD.
RESULTS
Demographic Data There was no statistical significance regarding age (18.6 ⫾ 3.2 months), weight (11.8 ⫾ 2.1 kg), and mean duration of operating time (65.3 ⫾ 14.3 minutes) between unstented and stented urethroplasty (P ⬎ .05; Table 1). No complications or morbidity were observed as a result of general anaesthetic or caudal cannula or caudal analgesia. Prospective Cohort Patients analyzed prospectively showed at 0 to 2 hours no significant difference with a good correlation coeffi-
Table 1. Demographic Data of All 160 Patients (Mean ⴞ SD)
Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 P value R
Age (mo)
Weight (kg)
Duration of Surgery (min)
18.5 ⫾ 2.6 18.4 ⫾ 4 19.2 ⫾ 3.4 18.3 ⫾ 3.3 19.1 ⫾ 3.1 18.3 ⫾ 3.3 ⬎.05 0.87
11.2 ⫾ 1.3 12.2 ⫾ 2.4 11.9 ⫾ 2.5 12.8 ⫾ 3.1 12.1 ⫾ 1.9 11.5 ⫾ 1.2 ⬎.05 0.86
61.3 ⫾ 10.2 67.5 ⫾ 10.6 61.6 ⫾ 12.4 68.13 ⫾ 21 69.1 ⫾ 20.8 70.7 ⫾ 10.5 ⬎.05 0.87
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Fig 1. Mean postoperative pain scores CHEOPS: prospective double caudal study.
cient (r ⫽ 0.88) in early pain scores between unstented and stented urethroplasty (P ⬎ .05; Fig 1). Mean duration of caudal analgesia and requirement for oral analgesia between 2 and 14 hours was 9.35 in the unstented versus 6.19 hours in the stented (P ⫽ .02; Table 2). Figure 2 shows the actual number of patients requiring oral analgesia in this group.
Table 2. Mean Duration of Postoperative Caudal Analgesia in All Groups Groups
P Mean Duration of Caudal Analgesia (h) Value
Prospective double caudal (groups 1 & 2) Unstented TD (50) Stented-MV (30) Randomized patients Unstented TD Group 3 (25), single Group 5 (25), double Stented-MV Group 4 (15), single Group 6 (15), double Prospective and randomized patients Double caudal unstented versus stented repairs Groups 1 & 5 (75), unstented Groups 2 & 6 (45), stented Exclusion of mean operative time in double caudal Unstented TD Group 3 Groups 1 & 5 (64 ⫾ 15) Stented-MV Group 4 Groups 2 & 6 (69 ⫾ 11)
P ⬍ .05 was considered statistically significant.
9.35 6.19
.02
3.5 9.4
.001
3.4 6.3
.02
9.4 6.3
.02
3.5 8.33
.001
3.4 5.15
.03
Randomized Cohort In the 80 randomized patients there was no significant difference with a good correlation coefficient (r ⫽ 0.88) in early pain scores at 0 to 2 hours between unstented and stented (P ⬎ .05; Fig 3). Between 2 and 14 hours there was a significant difference in pain scores between double-caudal and single-caudal (P ⬍ .05; Fig 3). In singlecaudal, there was no significant statistical significance in mean duration of caudal analgesia, that is, requirement for oral analgesia, in the unstented, 3.5 hours, versus 3.4 hours in the stented (P ⬎ .05; Table 2). In double-caudal, there was statistical significant difference in the mean duration of caudal analgesia and requirement for oral analgesia, in the unstented, 9.4 hours, versus 6.3 hours in the stented (P ⬍ .05; Table 2). In the unstented, mean duration of caudal analgesia and requirement for oral analgesia in single-caudal was 3.5 hours versus 9.4 hours in double-caudal (P ⫽ .001; Table 2 and Fig 4). In the stented, mean duration of caudal analgesia and requirement for oral analgesia in single-caudal was 3.4 hours versus 6.3 hours in double-caudal (P ⫽ .02; Table 2 and Fig 4). Therefore, irrespective of the type of hypospadias repair, mean duration of caudal analgesia and, hence, need for oral analgesia between single-caudal was 3.45 hours versus 7.85 hours in double-caudal (P ⫽ .001). Figure 4 shows the actual number of patients needing oral analgesia. The difference between single and double caudal irrespective of repair was significant (P ⫽ .001). Mean duration of caudal analgesia and requirement for oral analgesia in double-caudal (inclusive of patients studied prospectively) was 9.4 hours in the unstented versus 6.3 hours in the stented (P ⫽ .02; Table 2). The results of the double-caudal randomized cohort therefore
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Fig 2. Number of patients needing oral analgesia during the first 14 hours of observation. Prospective study, group 1 (n ⴝ 50), group 2 (n ⴝ 30) and randomized patients, group 3 (n ⴝ 25), group 4 (n ⴝ 15), group 5 (n ⴝ 25), and group 6 (n ⴝ 15).
correlate with the prospective double-caudal study, wherein the duration of caudal analgesia is increased significantly.
minutes, was 5.15 hours versus 3.4 hours in singlecaudal (P ⫽ .03; Table 2).
Variables
There was no incidence of nausea, vomiting, or pruritus in any of the 160 children. With the ThierschDuplay procedure (100), urinary retention was not seen, and mean time of first micturition was 5 hours. Discomfort at first urination in single-caudal occurred in 68% (group 3) versus 12% (group 1) and 16% (group 5), both double-caudal (P ⬍ .05). Paucity of leg movement was significant in double-caudal versus single (P ⬍ .05; Fig 5). Occurrence of facial flushing was similar in all 160 patients. Mean surgical follow-up time in unstented was 13.7 ⫾
The main variable was a urethral stent, and this resulted in a significant difference in pain scores of stented versus unstented double-caudals (P ⬍ .05; Fig 3). Operating time in all groups was similar (Table 1). In unstented, mean duration of caudal analgesia in all patients with double-caudal after exclusion of the operating time of mean 64 minutes was 8.33 hours versus 3.5 hours in single-caudal (P ⫽ .001; Table 2). In stented, the mean duration of caudal analgesia in all patients with doublecaudal after exclusion of operating time of mean 69
Complications
Fig 3. Mean postoperative pain scores CHEOPS: randomized groups. Groups 3 and 4: single caudal. Groups 5 and 6: double caudal.
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Fig 4. Duration of caudal anaesthesia in stented and unstented hypospadias repairs. Single versus double-caudal (P < .05).
5.9 versus 13.5 ⫾ 5.8 months in stented (P ⬎ .05; Table 1). Surgical complications seen in all 160 patients is summarised in Table 3. Cosmetically, all patients have a vertical slit glanudar meatus situated at normal position on the glans. Functionally, all 160 patients pass a good calibre single stream of urine in forward direction. DISCUSSION
Broadman et al in 1987 showed that “Kiddie Caudal” could be used safely to provide adjunct operative anesthesia and postoperative analgesia in children, and its practical advantages outweighed theoretical risks of combining 2 anesthetic techniques. The same author also showed that caudal block using 0.25% bupivacaine was effective and that there was no advantage in using higher concentrations of 0.30% and 0.375% of bupivacaine.12 CHEOPS was used for postoperative pain assessment because it is a very sensitive pain assessment tool and has been shown to have excellent interrater reliability and good evidence of validity when used in young children after surgery.10 Our study shows that 0.25% plain bupiv11
Fig 5. Percentage of patients with motor block post plain bupivicaine caudal injection. A, unstented urethroplasty; B, Stented urethroplasty.
acaine caudal injection administered before start and after completion of hypospadias surgery provides prolonged and effective postoperative analgesia. The prolonged postoperative analgesia was achieved without having to increase the total dose of 1 mL kg⫺1 of 0.25% plain bupivacaine or having to use opioid or nonopioid additives with their inherent risks. This statistically significant prolongation in duration of caudal analgesia holds even when the operating time is excluded from the double caudal groups. Therefore, without question, top-up caudal without increasing the total cumulative dose was an adjunct to intraoperative anaesthesia and supplemented postoperative analgesia. Quality of analgesia was good with no major adverse side effects, and the first urinary void was painless in 86% with unstented hyposapdias repair and double caudal. However, the main variant in the 2 groups was a urethral stent. Stenting the urethra resulted in an earlier need for oral analgesia. In patients with an unstented repair, duration of caudal analgesia was prolonged by 3.1 hours. It is possible that stents may cause local inflam-
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Table 3. Surgical Complications in all 160 Patients
Complications
Urethrocutaneous fistula Glanular dehiscence Meatal stenosis Migration of stent in to the bladder Balanitis xerotica obliterans
Groups 1, 3, & 5 Groups 2, 4, & 6 (MV) (TD) 60 Patients 100 Patients
4 0 2 0 2
2 1 0 1 0
mation and, therefore, pain, or a stent lying on the trigone of the bladder may result in bladder spasms necessitating early oral analgesia. The increased incidence of motor block after double-caudal in children aged 18 to 24 months was not a major handicap. Being aware that the anatomy in children differs from that in adults prevented complication of an extradural catheter such as difficulty in insertion, vascular damage, or leaks. Meticulous attention to site selection and preparation, careful aspiration to be certain that neither a vessel nor subarachnoid space had been entered, and the use of the same aseptic technique at top-up obviated infection and complications. The caudal cannula should be inserted as parallel as possible to the caudal extradural space to prevent a kink. This will facilitate ease of delivering the top-up caudal. In children aged 2 to 4 years, epidural fat is packed loosely and gelatinous, which progresses subsequently to a tightly packed fibrous structure by early adulthood. The diffuse loose epidural fat may allow a greater spread of a given caudal volume. There is a linear correlation between body weight, age, and spinal column length until the age of 2 to 4 years; as a result, a volume of bupivacaine calculated for weight of the child will provide a more cephalad level of anesthesia involving the sacral and lumbar innervations. Terminal half-life of bupivacaine is prolonged in children, although the pharmacokinetics of absorption is similar in children and adults. In our study, caudal analgesia was prolonged without having to increase the total cumulative dose or volume. This was achieved by dividing the total dose (1
mL kg⫺1) into 2 equal parts (0.5 mL kg⫺1) and administrating each at a time interval of approximately 65 minutes. Effective prolonged caudal analgesia by 0.25% plain bupivicaine without additives was achieved by (1) possible decreased leak from the caudal extradural space and therefore away from the site of action because of the relative small volumes used in double caudal compared with single or (2) top-up affecting the pharmacokinetics of bupivacaine. Clinical audit is defined as a clinically led initiative that seeks to improve the quality and outcome of patient care through structured peer review whereby clinicians examine their practices and results against agreed standards and modify their practice where indicated.13 Although the prospective analysis showed that doublecaudal provided good postoperative analgesia after hypospadias surgery, we did not know whether a singlecaudal block could be as effective. We used the prospective analysis as a base for a randomised, prospective, double-blind controlled trial to show the increased duration and quality of pain control of double-caudal. We have therefore effectively closed our audit loop, and double-caudal is now the agreed standard for perioperative analgesia for hypospadias repair in our institution. Double-caudal using bupivacaine prolonged duration of pain relief after hypospadias repair. Top-up caudal without increasing the total cumulative dose was an adjunct to intraoperative anaesthesia and supplemented and prolonged postoperative analgesia. ACKNOWLEDGMENTS The authors thank S. Capps and S-A Boddy for the use of their patients in this study; S-A Boddy for her editorial skills; and Dr J-P van-Besouw, Dr P. Razis, and Dr O. Ross for help in obtaining Local Ethics Committee approval, assisting and supervising the caudal block, and for their expert opinion. The authors also thank Mr I. Burton, Pediatric Operative Department Practitioner, for supervising the smooth running of this project. Thanks to all Specialist Registrars in anesthesia for performing the caudals and all nursing staff on the surgical ward for their help during the study.
REFERENCES 1. Warner MA, Kunkel SE, Offord KO, et al: The effects of age, epinephrine and operative site on duration of caudal analgesia in pediatric patients. Anesth Analg 66:995-998, 1987 2. Cook B, Grubb DJ, Aldridge LA, et al: Comparison of the effects of adrenaline, clonidine and ketamine on the duration of caudal analgesia produced by bupivacaine in children. Br J Anaesth 75:698-701, 1995 3. Naguib M, Sharif AMY, Seraj M, et al: Ketamine for caudal analgesia in children: Comparison with caudal bupivacaine. Br J Anaesth 67:559-564, 1991 4. Prosser DP, Davis P, Booker PD, et al: Caudal tramadol for postoperative analgesia in paediatric hypospadias surgery. Br J Anaesth 79:293-296, 1997
5. Peutrell JM, Cupples PA: Caudal epidural analgesia. Baillie`re’s Clinical Anaesthesiology 14:709-730, 2000 6. Constant I, Gall O, Gouyet L, et al: Addition of clonidine or fentanyl to local anaesthetics prolongs the duration of surgical analgesia after single shot caudal block in children. Br J Anaesth 80:294-298, 1998 7. Kelleher AA, Black A, Penman S, et al: Comparison of caudal bupivacaine and diamorphine with caudal bupivacaine alone for repair of hypospadias. Br J Anaesth 77:586-590, 1996 8. Krane EJ: Delayed respiratory depression in a child after caudal epidural morphine. Anesth Analg 67:79-82, 1988 9. Boddy S-A, Samuel M: Mathieu and ‘V’ incision sutured (M.A.V.I.S) results in a natural glanular meatus. J Pediatr Surg 35:494496, 2000
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10. McGarth PJ, Johnson G, Goodman JT, et al: CHEOPS: A behavioural scale for rating postoperative pain in children. Advances in Pain Research and Therapy 9:395-402, 1985 11. Broadman LM, Hannallah RS, Norden OM, et al: “Kiddie Caudals”: Experience with 1154 consecutive cases without complications. Anesth Analg 66:S18, 1987
12. Broadman LM, Hannallah RS, Norrie WC, et al: Caudal analgesia in pediatric outpatient surgery: A comparison of three different bupivacaine concentrations. Anesth Analg 66:S19, 1987 13. NHS Executive: Clinical Audit in the NHS. Using Clinical Audit in the NHS: A position statement. Catalogue number 96CC0018, Crown Copyright, Produced by Department of Health (13) 1996
Discussion L. Spitz (London, England): Is it indeed a self-fulfilling prophecy that if you give a double dose analgesia you would expect to get double the action? M. Samuel (response): Not necessarily. What we have shown in this study, which nobody else has shown, is that if you give a single dose of the same drug you do not create any drug errors, plus, you are giving the same dose that is 1 mL/kg. All you are doing is dividing into smaller dosages, 1 you give before surgery, and 1 you give after. I think there is less leak along the cannula routes; therefore, the drug reaches the required centres to give a higher number to sacral analgesia. Dr Farrugia (London, England): Thank you for an interesting and practical presentation. My question is, does the length of the operative procedure make any difference. That is, if you were to exclude the operating time, would there be a significant change in the duration of the caudal analgesia? M. Samuel (response): We did look at that, I didn’t have time to press on that particular slide. What we did in the double injection group was we excluded the operating time, which was around 65.3 minutes, which I did say in my demographic data. Even if we exclude that operating time, the duration of analgesia for double was
5.5 to 7.4 hours, and this was highly statistically significant against the single injection, which was 3.45. Mr Sugarman (Leeds, England): I just wanted to know, when you say it is double blinded, who was actually double blinded? Did the anaesthetists give a second shot to the children that had already received 1 mg of the Bupivacaine on the first injection, or was it that the anaesthetists knew what they had given, and you as a surgeon may have known because in one child they would have an epidural catheter sticking out but in another they won’t. Who actually is the double blinded? M. Samuel (response): The people who are double blinded were the ones who were conducting the study. For example, it was a team of 4 people; an anaesthetist, a surgeon, named nurse specialist, and a senior nurse. For example, if I was in the theatre, I did not know who was going to get what, and I used to go out of theatre not knowing what would happen to the child at the end of surgery or at the commencement of surgery, so I was blinded to whether the child received a single or double shot. The other anaesthetist colleague who did the scoring system was totally blinded, because he was not allowed into theatres as he was in PICU, and the 2 nurses were totally blinded to the study.
Background/Purpose: A prospective, randomised, doubleblind, controlled trial to evaluate efficacy of double-caudal versus single-caudal injection for postoperative analgesia in hypospadias repair was performed. Methods: Between October 1998 and September 2000, 160 boys underwent distal hypospadias repair. The first 80 boys were analyzed prospectively for postoperative analgesia after double-caudal bupivacaine, which involves the administration of a second bupivacaine injection into the caudal extradural space at the end of surgery. Pain was assessed using the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS). The study groups were: group 1, unstented Thiersch-Duplay urethroplasty (50); and group 2, stented Mathieu type repair (30). Results of this cohort formed the basis for a prospective, randomised, double-blind control trial comparing double-caudal against a single injection before operation. The further 80 patients were allocated randomly: group 3, single caudal injection of 1 mL kg⫺1 of 0.25% plain bupivacaine at the start of surgery with unstented Thiersh-Duplay repair (25); group 4, similar single caudal injection but stented Mattieu type operation (15); group 5, second caudal and at end of operation (0.5 mL kg⫺1 on each occasion) with unstented Thiersh-Duplay repair (25); and group 6, similar to group 5 but with stented Mattieu type repair (15). Results: Patient demographics (age and weight) and mean duration of operative time were similar for all groups. There
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EGIONAL TECHNIQUES such as local caudal blocks have been used in conjunction with general anesthesia to provide intra- and postoperative analgesia, which is a vital part of perioperative care in children undergoing hypospadias surgery. Administration of 0.25% plain bupivacaine into caudal extradural space has been the standard method of providing postoperative analgesia for hypospadias surgery at our institution. Duration of analgesia after caudal injection of bupivacaine
From the Departments of Pediatric Surgery and Anesthesia, St George’s Hospital, London, England. Presented at the 48th Annual International Congress of the British Association of Paediatric Surgeons, London, England, July 18-21, 2001. Address reprint requests to Dr D. Hampson-Evans, St George’s Hospital, London, SW17 OQT, England. Copyright © 2002 by W.B. Saunders Company 0022-3468/02/3702-0006$35.00/0 doi:10.1053/jpsu.2002.30247 168
was no significant difference in early pain scores at 0 to 2 hours with a good correlation coefficient (r ⫽ 0.88). At 4, 6, and 8 hours there was a significant difference in pain scores between double and single caudals (P ⬍ .05). There was a significant difference in mean duration of caudal analgesia and need for oral analgesia between single caudal 3.45 versus 7.85 hours for double caudal (P ⬍ .001). Mean duration of caudal analgesia and requirement for oral analgesia after single caudal in group 3 (unstented) was 3.5 versus 3.4 hours in group 4 (stented). In double caudals this lengthened to 9.4 hours in group 5 (unstented) versus 6.3 hours in group 6 (stented; P ⬍ .05). This also was significant when operation time was excluded.
Conclusions: A prospective study of double caudal analgesia showed good postoperative pain control after hypospadias surgery. This was followed by a prospective, randomised, double-blind controlled trial that has confirmed that double caudal injection of bupivacaine prolonged the duration of pain relief after hypospadias repair. The second or top-up caudal did not increase the total dose but supplemented and prolonged postoperative analgesia. J Pediatr Surg 37:168-174. Copyright © 2002 by W.B. Saunders Company. INDEX WORDS: Double caudal analgesia, 0.25% plain bupivacaine, Children’s Hospital of Eastern Ontario Pain Scale, distal hypospadias repair.
usually is 4 to 6 hours.1-5 This period of analgesia is based on time from injection to requirement of pain medication, and a single injection of bupivacaine may have only a relative short duration of action.1-4 There are many methods to try and prolong duration of caudal analgesia, but these involve the addition of other drugs to bupivacaine. These additives include opiates, clonidine, ketamine, and adrenaline. Opiates carry the risk of respiratory depression and urinary retention. Clonidine may cause sedation and therefore precludes its use in day surgery. Ketamine may cause behavioral changes, and there is debate about long-term changes to nerves. Adrenaline is unreliable in prolonging analgesia.5-8 The advantage of the “double caudal” is that it does not depend on additives. It therefore avoids their side effects and reduces drug error by miscalculation of their dose. To study this simple technique, we audited our double caudals prospectively and then performed a prospective, randomised, controlled trial to close our audit loop. The Journal of Pediatric Surgery, Vol 37, No 2 (February), 2002: pp 168-174
DOUBLE CAUDAL ANALGESIA IN HYPOSPADIAS REPAIR
aim of this prospective, randomised, double-blind controlled study was to compare duration of analgesia for hypospadias surgery produced by 1 mL kg⫺1 of 0.25% plain bupivacaine single caudal block administered after induction of general anesthesia but before start of surgery versus double caudal block, wherein 0.5 mL kg⫺1 of 0.25% plain bupivacaine was administered via an indwelling caudal cannula at start of surgery and a top-up of 0.5 mL kg⫺1 of plain bupivacaine was given at end of surgery. MATERIALS AND METHODS Between October 1998 and September 2000, 160 boys underwent distal hypospadias repair. Eighty patients were analyzed prospectively for postoperative analgesia. The further 80 patients were the subject of a trial of single against double caudal administration of extradural bupivacaine. Methodology in the double caudal groups was identical to that described for single injection into caudal extradural space, but at the end of surgery a second injection was given as detailed below. Behavioral scale for rating postoperative pain was assessed by the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS),10 which assigns scores for crying, facial expression, verbal response, touching the wound and torso, and leg movement.10 Results of this prospective cohort formed basis for a randomised, double-blind, controlled trial to access efficacy and benefit of double-caudal versus single-caudal block for postoperative analgesia in distal hypospadias repair. Local Ethics Committee approval was obtained for the randomised study, and written informed parental consent was obtained for each child. Premedication was not used, and 4% amethocaine (Ametop Gel; Smith & Nephew, Health Care Ltd, Hull, England) was applied to potential venous access sites. However, all children were induced with oxygen and sevoflurane. Neuromuscular block was produced with atracurium 0.5 mg kg⫺1 and trachea intubated. Anesthesia was maintained with 0.5% to 1.5% isoflurane and 70% nitrous oxide in oxygen, maintaining normocapnia by intermittent positive pressure ventilation. All children were monitored and received intravenous crystalloids (0.45% sodium chloride and 5% dextrose) at 10 mL kg⫺1 for duration of anaesthesia. After induction of anaesthesia, patients were placed in the lateral position and a caudal injection performed using an aseptic technique via an ABBOCATH-T 22 G cannula. All boys had repair of distal hypospadias with one surgeon using unstented Thhiersch-Duplay urethroplasty (TD) and the other using Mathieu and “V” incision method (MV).9 The prospective trial consisted of group 1, TD unstented urethroplasty (n ⫽ 50) and group 2, MV stented repair (n ⫽ 25). All patients were given double caudal injections of bupivacaine as described below. Eighty patients were assigned randomly using a computer-generated list into group 3, TD unstented urethroplasty: single-caudal (n ⫽ 25); group 4, MV stented urethroplasty: single-caudal (n ⫽ 15); group 5, TD unstented urethroplasy: double-caudal (n ⫽ 25); group 6, MV stented urethroplasty: double-caudal (n ⫽ 15). Single caudal groups received a caudal injection of 0.25% plain bupivacaine, 1 mL kg⫺1, and the cannula was removed before the start of surgery. Double caudal groups in the randomised group received a caudal injection of 0.25% plain bupivacaine, 0.5 mL kg⫺1, and a capped cannula was left in situ with an aseptic Ensure-it dressing. All 160 patients received rectal acetaminophen (paracetamol) suppository, 20 mg kg⫺1, after induction. Anaesthesia was discontinued on application of Cavi-care foam (Smith & Nephew Medical) penile dressing; residual neuromuscular block was antagonised with glycopyrolate, 10 g kg⫺1, and neostig-
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mine, 50 g kg⫺1, and patient’s trachea extubated before transfer to recovery area. In double-caudal (groups 5 and 6) the caudal cannula was accessed aseptically to deliver a second top-up caudal dose of 0.25% plain bupivacaine, 0.5 mL kg⫺1. At the completion of the procedures anaesthetic agents were discontinued, and patients were transferred to the recovery area. Duration of surgery from completion of induction to antagonism of neuromuscular block was recorded for each patient. Time 0 hour was taken as the time of the first caudal injection after induction of anaesthesia. The first pain score was recorded at 2 hours after time 0 and subsequently at 2-hour intervals for a total period of 14 hours. All patients were allowed to eat and drink immediately after transfer to the surgical ward. On the surgical ward, assessors blinded to the nature of caudal injection, performed 2 hourly observations until 14 hours after caudal injection. CHEOPS was used to assess pain.10 The requirement for analgesia (paracetamol or ibuprofen) was recorded during the 14 hours of pain assessment. The need for oral analgesia as indicated by a rising CHEOPS score was taken as the duration of postoperative caudal analgesia. These times were calculated subsequently to create the mean duration of caudal analgesia in each group. Facial flushing, paucity of leg movement, vomiting, and pruritus were noted if they occurred. In unstented urethroplasty the dressing was removed 24 hours postoperatively, whereas in stented repair, dressing and stent were removed 48 hours postoperatively. Parents were advised to continue regular use of paracetamol and trimethoprim for 5 days in all groups. Parametric data were analyzed by Student’s t test. Nonparametric data (pain scores, analgesia requirements, and incidences of complications) were evaluated statistical by 1-way analysis of variance with Bonferroni’s type I error rate correction for multiple tests of significance with P ⬍ .05 considered statistically significant. Data were correlated by Pearson correlation coefficient, and results are presented as mean ⫾ SD.
RESULTS
Demographic Data There was no statistical significance regarding age (18.6 ⫾ 3.2 months), weight (11.8 ⫾ 2.1 kg), and mean duration of operating time (65.3 ⫾ 14.3 minutes) between unstented and stented urethroplasty (P ⬎ .05; Table 1). No complications or morbidity were observed as a result of general anaesthetic or caudal cannula or caudal analgesia. Prospective Cohort Patients analyzed prospectively showed at 0 to 2 hours no significant difference with a good correlation coeffi-
Table 1. Demographic Data of All 160 Patients (Mean ⴞ SD)
Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 P value R
Age (mo)
Weight (kg)
Duration of Surgery (min)
18.5 ⫾ 2.6 18.4 ⫾ 4 19.2 ⫾ 3.4 18.3 ⫾ 3.3 19.1 ⫾ 3.1 18.3 ⫾ 3.3 ⬎.05 0.87
11.2 ⫾ 1.3 12.2 ⫾ 2.4 11.9 ⫾ 2.5 12.8 ⫾ 3.1 12.1 ⫾ 1.9 11.5 ⫾ 1.2 ⬎.05 0.86
61.3 ⫾ 10.2 67.5 ⫾ 10.6 61.6 ⫾ 12.4 68.13 ⫾ 21 69.1 ⫾ 20.8 70.7 ⫾ 10.5 ⬎.05 0.87
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Fig 1. Mean postoperative pain scores CHEOPS: prospective double caudal study.
cient (r ⫽ 0.88) in early pain scores between unstented and stented urethroplasty (P ⬎ .05; Fig 1). Mean duration of caudal analgesia and requirement for oral analgesia between 2 and 14 hours was 9.35 in the unstented versus 6.19 hours in the stented (P ⫽ .02; Table 2). Figure 2 shows the actual number of patients requiring oral analgesia in this group.
Table 2. Mean Duration of Postoperative Caudal Analgesia in All Groups Groups
P Mean Duration of Caudal Analgesia (h) Value
Prospective double caudal (groups 1 & 2) Unstented TD (50) Stented-MV (30) Randomized patients Unstented TD Group 3 (25), single Group 5 (25), double Stented-MV Group 4 (15), single Group 6 (15), double Prospective and randomized patients Double caudal unstented versus stented repairs Groups 1 & 5 (75), unstented Groups 2 & 6 (45), stented Exclusion of mean operative time in double caudal Unstented TD Group 3 Groups 1 & 5 (64 ⫾ 15) Stented-MV Group 4 Groups 2 & 6 (69 ⫾ 11)
P ⬍ .05 was considered statistically significant.
9.35 6.19
.02
3.5 9.4
.001
3.4 6.3
.02
9.4 6.3
.02
3.5 8.33
.001
3.4 5.15
.03
Randomized Cohort In the 80 randomized patients there was no significant difference with a good correlation coefficient (r ⫽ 0.88) in early pain scores at 0 to 2 hours between unstented and stented (P ⬎ .05; Fig 3). Between 2 and 14 hours there was a significant difference in pain scores between double-caudal and single-caudal (P ⬍ .05; Fig 3). In singlecaudal, there was no significant statistical significance in mean duration of caudal analgesia, that is, requirement for oral analgesia, in the unstented, 3.5 hours, versus 3.4 hours in the stented (P ⬎ .05; Table 2). In double-caudal, there was statistical significant difference in the mean duration of caudal analgesia and requirement for oral analgesia, in the unstented, 9.4 hours, versus 6.3 hours in the stented (P ⬍ .05; Table 2). In the unstented, mean duration of caudal analgesia and requirement for oral analgesia in single-caudal was 3.5 hours versus 9.4 hours in double-caudal (P ⫽ .001; Table 2 and Fig 4). In the stented, mean duration of caudal analgesia and requirement for oral analgesia in single-caudal was 3.4 hours versus 6.3 hours in double-caudal (P ⫽ .02; Table 2 and Fig 4). Therefore, irrespective of the type of hypospadias repair, mean duration of caudal analgesia and, hence, need for oral analgesia between single-caudal was 3.45 hours versus 7.85 hours in double-caudal (P ⫽ .001). Figure 4 shows the actual number of patients needing oral analgesia. The difference between single and double caudal irrespective of repair was significant (P ⫽ .001). Mean duration of caudal analgesia and requirement for oral analgesia in double-caudal (inclusive of patients studied prospectively) was 9.4 hours in the unstented versus 6.3 hours in the stented (P ⫽ .02; Table 2). The results of the double-caudal randomized cohort therefore
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Fig 2. Number of patients needing oral analgesia during the first 14 hours of observation. Prospective study, group 1 (n ⴝ 50), group 2 (n ⴝ 30) and randomized patients, group 3 (n ⴝ 25), group 4 (n ⴝ 15), group 5 (n ⴝ 25), and group 6 (n ⴝ 15).
correlate with the prospective double-caudal study, wherein the duration of caudal analgesia is increased significantly.
minutes, was 5.15 hours versus 3.4 hours in singlecaudal (P ⫽ .03; Table 2).
Variables
There was no incidence of nausea, vomiting, or pruritus in any of the 160 children. With the ThierschDuplay procedure (100), urinary retention was not seen, and mean time of first micturition was 5 hours. Discomfort at first urination in single-caudal occurred in 68% (group 3) versus 12% (group 1) and 16% (group 5), both double-caudal (P ⬍ .05). Paucity of leg movement was significant in double-caudal versus single (P ⬍ .05; Fig 5). Occurrence of facial flushing was similar in all 160 patients. Mean surgical follow-up time in unstented was 13.7 ⫾
The main variable was a urethral stent, and this resulted in a significant difference in pain scores of stented versus unstented double-caudals (P ⬍ .05; Fig 3). Operating time in all groups was similar (Table 1). In unstented, mean duration of caudal analgesia in all patients with double-caudal after exclusion of the operating time of mean 64 minutes was 8.33 hours versus 3.5 hours in single-caudal (P ⫽ .001; Table 2). In stented, the mean duration of caudal analgesia in all patients with doublecaudal after exclusion of operating time of mean 69
Complications
Fig 3. Mean postoperative pain scores CHEOPS: randomized groups. Groups 3 and 4: single caudal. Groups 5 and 6: double caudal.
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Fig 4. Duration of caudal anaesthesia in stented and unstented hypospadias repairs. Single versus double-caudal (P < .05).
5.9 versus 13.5 ⫾ 5.8 months in stented (P ⬎ .05; Table 1). Surgical complications seen in all 160 patients is summarised in Table 3. Cosmetically, all patients have a vertical slit glanudar meatus situated at normal position on the glans. Functionally, all 160 patients pass a good calibre single stream of urine in forward direction. DISCUSSION
Broadman et al in 1987 showed that “Kiddie Caudal” could be used safely to provide adjunct operative anesthesia and postoperative analgesia in children, and its practical advantages outweighed theoretical risks of combining 2 anesthetic techniques. The same author also showed that caudal block using 0.25% bupivacaine was effective and that there was no advantage in using higher concentrations of 0.30% and 0.375% of bupivacaine.12 CHEOPS was used for postoperative pain assessment because it is a very sensitive pain assessment tool and has been shown to have excellent interrater reliability and good evidence of validity when used in young children after surgery.10 Our study shows that 0.25% plain bupiv11
Fig 5. Percentage of patients with motor block post plain bupivicaine caudal injection. A, unstented urethroplasty; B, Stented urethroplasty.
acaine caudal injection administered before start and after completion of hypospadias surgery provides prolonged and effective postoperative analgesia. The prolonged postoperative analgesia was achieved without having to increase the total dose of 1 mL kg⫺1 of 0.25% plain bupivacaine or having to use opioid or nonopioid additives with their inherent risks. This statistically significant prolongation in duration of caudal analgesia holds even when the operating time is excluded from the double caudal groups. Therefore, without question, top-up caudal without increasing the total cumulative dose was an adjunct to intraoperative anaesthesia and supplemented postoperative analgesia. Quality of analgesia was good with no major adverse side effects, and the first urinary void was painless in 86% with unstented hyposapdias repair and double caudal. However, the main variant in the 2 groups was a urethral stent. Stenting the urethra resulted in an earlier need for oral analgesia. In patients with an unstented repair, duration of caudal analgesia was prolonged by 3.1 hours. It is possible that stents may cause local inflam-
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Table 3. Surgical Complications in all 160 Patients
Complications
Urethrocutaneous fistula Glanular dehiscence Meatal stenosis Migration of stent in to the bladder Balanitis xerotica obliterans
Groups 1, 3, & 5 Groups 2, 4, & 6 (MV) (TD) 60 Patients 100 Patients
4 0 2 0 2
2 1 0 1 0
mation and, therefore, pain, or a stent lying on the trigone of the bladder may result in bladder spasms necessitating early oral analgesia. The increased incidence of motor block after double-caudal in children aged 18 to 24 months was not a major handicap. Being aware that the anatomy in children differs from that in adults prevented complication of an extradural catheter such as difficulty in insertion, vascular damage, or leaks. Meticulous attention to site selection and preparation, careful aspiration to be certain that neither a vessel nor subarachnoid space had been entered, and the use of the same aseptic technique at top-up obviated infection and complications. The caudal cannula should be inserted as parallel as possible to the caudal extradural space to prevent a kink. This will facilitate ease of delivering the top-up caudal. In children aged 2 to 4 years, epidural fat is packed loosely and gelatinous, which progresses subsequently to a tightly packed fibrous structure by early adulthood. The diffuse loose epidural fat may allow a greater spread of a given caudal volume. There is a linear correlation between body weight, age, and spinal column length until the age of 2 to 4 years; as a result, a volume of bupivacaine calculated for weight of the child will provide a more cephalad level of anesthesia involving the sacral and lumbar innervations. Terminal half-life of bupivacaine is prolonged in children, although the pharmacokinetics of absorption is similar in children and adults. In our study, caudal analgesia was prolonged without having to increase the total cumulative dose or volume. This was achieved by dividing the total dose (1
mL kg⫺1) into 2 equal parts (0.5 mL kg⫺1) and administrating each at a time interval of approximately 65 minutes. Effective prolonged caudal analgesia by 0.25% plain bupivicaine without additives was achieved by (1) possible decreased leak from the caudal extradural space and therefore away from the site of action because of the relative small volumes used in double caudal compared with single or (2) top-up affecting the pharmacokinetics of bupivacaine. Clinical audit is defined as a clinically led initiative that seeks to improve the quality and outcome of patient care through structured peer review whereby clinicians examine their practices and results against agreed standards and modify their practice where indicated.13 Although the prospective analysis showed that doublecaudal provided good postoperative analgesia after hypospadias surgery, we did not know whether a singlecaudal block could be as effective. We used the prospective analysis as a base for a randomised, prospective, double-blind controlled trial to show the increased duration and quality of pain control of double-caudal. We have therefore effectively closed our audit loop, and double-caudal is now the agreed standard for perioperative analgesia for hypospadias repair in our institution. Double-caudal using bupivacaine prolonged duration of pain relief after hypospadias repair. Top-up caudal without increasing the total cumulative dose was an adjunct to intraoperative anaesthesia and supplemented and prolonged postoperative analgesia. ACKNOWLEDGMENTS The authors thank S. Capps and S-A Boddy for the use of their patients in this study; S-A Boddy for her editorial skills; and Dr J-P van-Besouw, Dr P. Razis, and Dr O. Ross for help in obtaining Local Ethics Committee approval, assisting and supervising the caudal block, and for their expert opinion. The authors also thank Mr I. Burton, Pediatric Operative Department Practitioner, for supervising the smooth running of this project. Thanks to all Specialist Registrars in anesthesia for performing the caudals and all nursing staff on the surgical ward for their help during the study.
REFERENCES 1. Warner MA, Kunkel SE, Offord KO, et al: The effects of age, epinephrine and operative site on duration of caudal analgesia in pediatric patients. Anesth Analg 66:995-998, 1987 2. Cook B, Grubb DJ, Aldridge LA, et al: Comparison of the effects of adrenaline, clonidine and ketamine on the duration of caudal analgesia produced by bupivacaine in children. Br J Anaesth 75:698-701, 1995 3. Naguib M, Sharif AMY, Seraj M, et al: Ketamine for caudal analgesia in children: Comparison with caudal bupivacaine. Br J Anaesth 67:559-564, 1991 4. Prosser DP, Davis P, Booker PD, et al: Caudal tramadol for postoperative analgesia in paediatric hypospadias surgery. Br J Anaesth 79:293-296, 1997
5. Peutrell JM, Cupples PA: Caudal epidural analgesia. Baillie`re’s Clinical Anaesthesiology 14:709-730, 2000 6. Constant I, Gall O, Gouyet L, et al: Addition of clonidine or fentanyl to local anaesthetics prolongs the duration of surgical analgesia after single shot caudal block in children. Br J Anaesth 80:294-298, 1998 7. Kelleher AA, Black A, Penman S, et al: Comparison of caudal bupivacaine and diamorphine with caudal bupivacaine alone for repair of hypospadias. Br J Anaesth 77:586-590, 1996 8. Krane EJ: Delayed respiratory depression in a child after caudal epidural morphine. Anesth Analg 67:79-82, 1988 9. Boddy S-A, Samuel M: Mathieu and ‘V’ incision sutured (M.A.V.I.S) results in a natural glanular meatus. J Pediatr Surg 35:494496, 2000
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10. McGarth PJ, Johnson G, Goodman JT, et al: CHEOPS: A behavioural scale for rating postoperative pain in children. Advances in Pain Research and Therapy 9:395-402, 1985 11. Broadman LM, Hannallah RS, Norden OM, et al: “Kiddie Caudals”: Experience with 1154 consecutive cases without complications. Anesth Analg 66:S18, 1987
12. Broadman LM, Hannallah RS, Norrie WC, et al: Caudal analgesia in pediatric outpatient surgery: A comparison of three different bupivacaine concentrations. Anesth Analg 66:S19, 1987 13. NHS Executive: Clinical Audit in the NHS. Using Clinical Audit in the NHS: A position statement. Catalogue number 96CC0018, Crown Copyright, Produced by Department of Health (13) 1996
Discussion L. Spitz (London, England): Is it indeed a self-fulfilling prophecy that if you give a double dose analgesia you would expect to get double the action? M. Samuel (response): Not necessarily. What we have shown in this study, which nobody else has shown, is that if you give a single dose of the same drug you do not create any drug errors, plus, you are giving the same dose that is 1 mL/kg. All you are doing is dividing into smaller dosages, 1 you give before surgery, and 1 you give after. I think there is less leak along the cannula routes; therefore, the drug reaches the required centres to give a higher number to sacral analgesia. Dr Farrugia (London, England): Thank you for an interesting and practical presentation. My question is, does the length of the operative procedure make any difference. That is, if you were to exclude the operating time, would there be a significant change in the duration of the caudal analgesia? M. Samuel (response): We did look at that, I didn’t have time to press on that particular slide. What we did in the double injection group was we excluded the operating time, which was around 65.3 minutes, which I did say in my demographic data. Even if we exclude that operating time, the duration of analgesia for double was
5.5 to 7.4 hours, and this was highly statistically significant against the single injection, which was 3.45. Mr Sugarman (Leeds, England): I just wanted to know, when you say it is double blinded, who was actually double blinded? Did the anaesthetists give a second shot to the children that had already received 1 mg of the Bupivacaine on the first injection, or was it that the anaesthetists knew what they had given, and you as a surgeon may have known because in one child they would have an epidural catheter sticking out but in another they won’t. Who actually is the double blinded? M. Samuel (response): The people who are double blinded were the ones who were conducting the study. For example, it was a team of 4 people; an anaesthetist, a surgeon, named nurse specialist, and a senior nurse. For example, if I was in the theatre, I did not know who was going to get what, and I used to go out of theatre not knowing what would happen to the child at the end of surgery or at the commencement of surgery, so I was blinded to whether the child received a single or double shot. The other anaesthetist colleague who did the scoring system was totally blinded, because he was not allowed into theatres as he was in PICU, and the 2 nurses were totally blinded to the study.