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* From the Department of Anesthesiology and
Surgery, Children’s Hospital of Eastern Ontario, Ottawa, Ontario, Canada.
Address for correspondence: Dr. Sanjay M. Bhananker, Department of Anesthesiology, Box 359724, Harborview Medical Center, 325, 9th Avenue, Seattle, WA 98104, USA. Phone: 206-731-3059; Fax: 206-731-8624; E-mail: sbhanank{at}u.washington.edu
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Abstract |
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Methods: In a randomized, prospective, double-blind trial, we studied 124 patients, six months to eight years, ASA physical status I or II, undergoing elective BMT under general anesthesia. The patients in Group I received acetaminophen 30 mg·kg–1 orally in a grape flavoured syrup 30 to 60 min before surgery and 0.9% saline drops (placebo) in each ear upon insertion of tympanostomy tube. Patients in Group II received a placebo (grape flavoured syrup) before surgery and 2% lidocaine, 0.5 mL in each ear when ear tubes were inserted. Postoperative pain assessments were recorded every five minutes in the postanesthesia care unit, and every 15 min in the day care surgical unit (DCSU) using the modified Children’s Hospital of Eastern Ontario pain scale (mCHEOPS), a ten-point scale. Pain at home was documented by parents using a 0 (no pain) to 10 (worst pain imaginable) scale.
Results: The median (range) mCHEOPS scores in the DCSU at 15 and 30 min were similar, i.e., 5 (4–9) in the acetaminophen group and 4 (4–8) in the lidocaine group. The proportion of patients receiving supplemental analgesics in the 24 hr following surgery was similar in both groups (45% and 42% respectively).
Conclusion: Topical lidocaine and oral acetaminophen in a dose of 30 mg·kg–1 provide similar analgesia following BMT.
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Introduction |
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The optimal method of controlling postoperative pain in children would be effective for extended periods of time and have no adverse effects. There are disadvantages to both the oral and rectal routes of administration of analgesics. Postoperative nausea and vomiting may lead to unpredictable absorption of drugs administered orally in the postoperative period. Children often refuse to swallow unpalatable medication formulations and many parents prefer to avoid suppositories. Use of topical analgesia avoids these limitations.
The purpose of this study was to compare the analgesic efficacy and side effects of preoperative oral acetaminophen administration 30 mg·kg–1 with topical 2% lidocaine applied to the external auditory canal in children undergoing BMT. We hypothesized that these interventions would provide similar postoperative analgesia.
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Methods |
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Using a computer-generated random number table, subjects were assigned to one of two groups: Group I – acetaminophen, and Group II - topical lidocaine. Subjects in Group I received acetaminophen 30 mg·kg–1 orally in a grape-flavoured syrup 30 to 60 min before the scheduled start of their surgery, and 0.5 mL of 0.9% saline was administered into each ear upon insertion of the tympanostomy tube. Patients in Group II received oral placebo in the form of an equivalent volume of grape-flavoured syrup 30 to 60 min before surgery and upon the insertion of a tympanostomy tube, 0.5 mL of 2% lidocaine solution eardrops were administered bilaterally. A nurse who was not a part of the investigation was responsible for randomization and administration of the oral syrup administration. Premedication with oral midazolam 0.5 mg·kg–1 was administered 20 to 30 min before the surgery when deemed necessary by the attending anesthesiologist. No other premedication (including atropine) was used. Intraoperative monitoring included an electrocardiogram, non-invasive blood pressure measurement, pulse oximetry, and the inspired and end-tidal concentrations of nitrous oxide and inhalation agent. Induction of general anesthesia was achieved by inhalation of either halothane or sevoflurane in a mixture of nitrous oxide and oxygen, or administration of propofol 2.5–3.5 mg·kg–1 iv. Anesthesia was maintained with 60–70% nitrous oxide in oxygen and halothane or sevoflurane via a face mask. No opioids or non steroidal anti-inflammatory drugs were administered in the perioperative period. Nausea, vomiting, oxygen saturation less than 90% and other adverse events such as laryngospasm were recorded perioperatively.
Pain assessment
Postoperative pain intensity was assessed in the PACU every five minutes using a modified Children’s Hospital of Eastern Ontario pain scale (mCHEOPS)A scoring system (Appendix
). A nurse who blinded to the randomization sequence recorded the pain scores. Whenever the pain score was 
6, subjects received acetaminophen 15 mg·kg–1 po as the rescue analgesic. Subjects were transferred from PACU to DCSU upon achieving an Aldrete recovery room score of 10.6 In the DCSU, acetaminophen was administered for mCHEOPS scores 6 or upon parental request even if the mCHEOPS score was < 6. Pain unresponsive to acetaminophen was treated with codeine phosphate 1 mg·kg–1 po (maximum 30 mg). Pain after hospital discharge was evaluated by the parents, who were asked to assess and record pain on a 0 to 10 scale. Parents were also instructed to administer acetaminophen 10 mg·kg–1 po every six hours for pain scores > 4. A research assistant contacted the parents the day after surgery and to document the at-home pain scores, use of acetaminophen, and any adverse events such as vomiting or tinnitus.
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Data management and statistical analysis
Normally distributed continuous data were compared using the Student’s t test. Proportional data, such as gender distribution, were compared by Chi-square analysis. Data that were non-normally distributed, and/or not continuous, such as mCHEOPS scores, were compared using the Kruskal-Wallis rank test. The number of patients who required rescue analgesia in the PACU and DCSU were compared by Chi-square analysis. A statistically significant difference was assumed when P < 0.05. Based on chart review and previous investigations, we expected the incidence of significant pain (requiring rescue analgesic) in the PACU to be 20%. We set 
at 0.05 and ß at 0.20. We considered that a clinically significant difference between the study groups was 20%. Using Blackwelder and Chang’s graphics,7 the estimated sample size was 60 patients per group (120 patients total). An additional 20 subjects, for a total of 140, were enrolled to compensate for possible dropouts.
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Results |
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). The two study groups were comparable with respect to demographic data (Table I).
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). Sixty-nine percent of children in the acetaminophen group received a supplemental dose of acetaminophen in the DCSU as compared with 60% of patients in the lidocaine group (P = 0.25, Table II). No child required codeine for pain unresponsive to a rescue dose of acetaminophen. Most patients in both groups had a pain score < 4 upon their arrival at home (Table II). Pain scores were similar in the two groups at bedtime and the morning after surgery. There was no emesis in the PACU, while the overall incidence of emesis was 3% in the DCSU.
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Discussion |
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Several studies have investigated the effectiveness of acetaminophen in minimizing pain after BMT. Doses of 10 to 15 mg·kg–1, administered orally, do not provide effective postoperative pain relief following BMT.1,8–10 Ragg and Davidson noted a higher success rate with a dose of 20 mg·kg–1 given preoperatively.11 Bolton et al. reported that the analgesic efficacy of oral acetaminophen 40 mg·kg–1, defined as the absence of need for supplemental analgesics, was 87% until discharge from hospital and 57% for the first 24 hr after surgery.12 The failure of acetaminophen to provide sufficient analgesia in earlier studies could be attributed to the lower dosages of acetaminophen. Nahata and Powell reported that oral acetaminophen 24–30 mg·kg–1 is needed to achieve blood concentrations in the antipyretic range, and even higher doses would be required to achieve analgesic blood concentrations.B These data have been supported by others.4,13 Since both 20 mg·kg–1 and 40 mg·kg–1 doses of acetaminophen have been shown to be effective,11,12 we chose an intermediate dose of 30 mg·kg–1. We observed that 45% of patients in the acetaminophen group required supplemental analgesia at home. The use of higher doses of acetaminophen, as recommended by Bolton et al.12 might have improved the 24-hr analgesic efficacy. On arrival at home, by bedtime, and on the following morning, the pain perception as judged by the parents, was similar in the two groups. Forty-five percent of children in the acetaminophen group and 42% of children in the topical lidocaine group required one more dose of acetaminophen at home. Nearly 60% of children from both groups had pain scores < 4 at home in the 24 hr following surgery. This is comparable to the observations of Bolton et al. who investigated a 40 mg·kg–1 dose of acetaminophen. Fifty seven percent of patients in that study did not require additional analgesics during the next 24 hr.12
Several other investigators have undertaken studies have to evaluate the effectiveness of topical anesthesia for BMT. Lawhorn et al. compared topical 4% lidocaine with placebo instilled into the external auditory canal. Postoperative analgesia was significantly better in the lidocaine group.14 Derkay et al. also found that 4% topical lidocaine mixed with antibiotic ear drops is an effective analgesic following BMT.15 Topical tetracaine has also been shown to provide effective analgesia in adult patients.16 We observed that 58% of patients in the lidocaine group did not require analgesic medications at home in the 24 hr following surgery, a proportion similar to that reported by Derkay et al.15 There are many advantages to using topical lidocaine for analgesia following BMT. The therapy is simple and easy to use, does not need the cooperation of the infant/child, is inexpensive, and a single dose provides pain relief for up to 24 hr, by which time pain does not seem to be a major concern. Acetaminophen can then be used as a rescue analgesic without concern for overdose.
There were no between-group differences in the incidence of postoperative vomiting, and the overall incidence of emesis was strikingly low (3%). Pappas et al. observed a similar incidence of emesis when opioids were avoided in the perioperative period in children undergoing BMT.10 Tinnitus and vertigo were not observed in any patient of either group. Vertigo following topical tetracaine16 and 4% lidocaine14 has been described, and hence we chose to use a lower lidocaine concentration (2%) in our study.
We used a validated pain score (mCHEOPS). Behaviour-based pain scores, such as mCHEOPS, may potentially be affected by emergence delirium. In our practice, and in similar investigations,17 a mCHEOPS score 6 was considered to indicate pain whereas a score 
5 indicates adequate analgesia.
Sixty-nine percent of the patients in the acetaminophen group and 60% of those in the lidocaine group received additional acetaminophen in the DCSU. Nurses in the DSCU were permitted to give acetaminophen in consultation with the parents, even if the mCHEOPS score was < 6. Therefore, acetaminophen administration in the DSCU could not be considered as one of the outcomes of the study. Because the proportion of children who received acetaminophen was similar in the two groups, outcome data, such as mCHEOPS scores and pain at home, can be compared without undue bias. No patient in either group needed codeine for pain unresponsive to acetaminophen.
There are several limitations to our study. We did not include a true placebo group (po placebo + placebo ear drops). In view of the high incidence of pain following BMT,1 and the high proportion of patients receiving analgesics in our institution in the PACU/DCSU following BMT, we viewed it to be unethical to include a true placebo arm to the study. Also, each of the study interventions, oral acetaminophen4 and topical lidocaine,14 has been shown to be superior to placebo. We used simple randomization instead of random permuted blocks, and this resulted in an unequal distribution of subjects in the two groups. Additionally, the anesthetic regimen, including pre-medication, was not rigidly standardized. This makes our results more generalizable, but reduces the specificity. Previous studies have shown similar recovery times and pain levels following BMT with the use of different anesthetic agents.18,19 Finally, as mentioned earlier, our study design allowed the use of acetaminophen in DCSU in consultation with parents, even with an mCHEOPS score < 6.
In conclusion, acetaminophen 30 mg·kg–1 po and topical lidocaine 2% instilled into the ear canal confer a similar degree of analgesia following bilateral myringotomy and tube placement surgery in children. Both treatment modalities were devoid of any serious side effects. Further trials, using a combination of acetaminophen and topical lidocaine, may show improved postoperative pain relief in children undergoing BMT.
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Footnotes |
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Funding: Departmental funding for research assistant.
Competing interests: None declared.
Accepted for publication February 27, 2006. Revision accepted May 3, 2006. Final revision accepted August 9, 2006.
A Splinter WM, Semelhago LC, Chou S. The reliability and validity of a modified CHEOPS pain score. Anesth Analg 1994; 78: S413 (abstract). 
B Nahata MC, Powell DA. Kinetics of acetaminophen following single strength vs. double strength administration to febrile children. Clin Res 1982; 30: 634A (abstract).
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2 American Academy of Pediatrics. Committee on Psychosocial Aspects of Child and Family Health. Task Force on Pain in Infants, Children, and Adolescents. The assessment and management of acute pain in infants, children, and adolescents. Pediatrics 2001; 108: 793–7.
3 Munro HM, Malviya S, Lauder GR, Voepel-Lewis T, Tait AR. Pain relief in children following outpatient surgery. J Clin Anesth 1999; 11: 187–91.[Medline]
4 Korpela R, Korvenoja P, Meretoja OA. Morphine-sparing effect of acetaminophen in pediatric day-case surgery. Anesthesiology 1999; 91: 442–7.[Medline]
5 Anand KJ, Scalzo FM. Can adverse neonatal experiences alter brain development and subsequent behavior? Biol Neonate 2000; 77: 69–82.[Medline]
6 Chung F. Discharge criteria--a new trend. Can J Anaesth 1995; 42: 1056–8.
7 Blackwelder WC, Chang MA. Sample size graphs for "proving the null hypothesis". Control Clin Trials 1984; 5: 97–105.[Medline]
8 Bennie RE, Boehringer LA, McMahon S, Allen H, Dierdorf SF. Postoperative analgesia with preoperative oral ibuprofen or acetaminophen in children undergoing myringotomy. Paediatr Anaesth 1997; 7: 399–403.[Medline]
9 Tobias JD, Lowe S, Hersey S, Rasmussen GE, Werkhaven J. Analgesia after bilateral myringotomy and placement of pressure equalization tubes in children: acetaminophen versus acetaminophen with codeine. Anesth Analg 1995; 81: 496–500.[Abstract]
10 Pappas AL, Fluder EM, Creech S, Hotaling A, Park A. Postoperative analgesia in children undergoing myringotomy and placement equalization tubes in ambulatory surgery. Anesth Analg 2003; 96: 1621–4.
11 Ragg P, Davidson A. Comparison of the efficacy of paracetamol versus paracetamol, codeine and promethazine (Painstop) for premedication and analgesia for myringotomy in children. Anaesth Intensive Care 1997; 25: 29–32.[Medline]
12 Bolton P, Bridge HS, Montgomery CJ, Merrick PM. The analgesic efficacy of preoperative high dose (40 mg·kg– 1 oral acetaminophen after bilateral myringotomy and tube insertion in children. Paediatr Anaesth 2002; 12: 29–35.[Medline]
13 Anderson BJ, Holford NH, Woollard GA, Kanagasundaram S, Mahadevan M. Perioperative pharmacodynamics of acetaminophen analgesia in children. Anesthesiology 1999; 90: 411–21.[Medline]
14 Lawhorn CD, Bower CM, Brown RE Jr, et al. Topical lidocaine for postoperative analgesia following myringotomy and tube placement. Int J Pediatr Otorhinolaryngol 1996; 35: 19–24.[Medline]
15 Derkay CS, Wadsworth JT, Darrow DH, Strasnick B, Thompson GK, O’Master J. Tube placement: a prospective, randomized double-blind study. Laryngoscope 1998; 108: 97–101.[Medline]
16 Hoffman RA, Li CL. Tetracaine topical anesthesia for myringotomy. Laryngoscope 2001; 111: 1636–8.[Medline]
17 Kim J, Azavedo L, Bhananker S, Bonn G, Splinter W. Amethocaine or ketorolac eyedrops provide inadequate analgesia in pediatric strabismus surgery. Can J Anesth 2003; 50: 819–23.
18 Hallen J, Rawal N, Gupta A. Postoperative recovery following outpatient pediatric myringotomy: a comparison between sevoflurane and halothane. J Clin Anesth 2001; 13: 161–6.[Medline]
19 Galinkin JL, Fazi LM, Cuy RM, et al. Use of intranasal fentanyl in children undergoing myringotomy and tube placement during halothane and sevoflurane anesthesia. Anesthesiology 2000; 93: 1378–83.[Medline]
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