There has been much interest in the provision of effective post-operative pain control for children [1-5], but few studies have examined post-operative pain following dental extraction under general anaesthesia [6,7]. In this practice the proportion of children receiving peri-operative analgesia for day-case extraction was 87 per 1000 in 1993, which may reflect the belief of many anaesthetists that post-extraction pain is not of sufficient intensity to warrant treatment which might delay recovery and increase the incidence of such problems as post-operative nausea and vomiting.
Non-steroidal anti-inflammatory drugs have been found to be effective in the relief of pain following dental extraction in children . The non-steroidal anti-inflammatory drug diclofenac sodium and the partial opioid agonist nalbuphine hydrochloride have previously been shown to provide either effective post-operative analgesia for children [8-12] or following dental extraction in adults .
The aim of this randomized, double-blind trial was to compare the analgesic and behavioural properties of nalbuphine and diclofenac with a control in small children presenting for extraction of carious deciduous teeth under general anaesthesia.
The study was approved by the local Ethics Committee and written informed parental consent was obtained for each patient. We included 60 ASA physical status I or II patients of either sex with a minimum age of 3 years, who required the extraction of carious deciduous teeth under general anaesthesia as outpatients at the London Hospital Dental Institute.
Patients were excluded from the study if they had had a previous or suspected history of bleeding disorder, asthma, atopy, renal dysfunction, history of atypical reaction to opioid or non-steroidal anti-inflammatory drugs. Children were randomly allocated into one of three groups prior to anaesthesia. Those who were given i.v. nalbuphine, those who were given diclofenac suppositories and a control group who received no analgesia.
No premedication was given. The child was accompanied into the dental suite by one of the parents where weight and blood pressure were measured prior to anaesthesia. Anaesthesia was induced using either propofol (1-3 mg kg−1) or inhalation of nitrous oxide, oxygen and halothane. Maintenance of anaesthesia was with 50-67% nitrous oxide in oxygen supplemented with halothane. All patients breathed spontaneously through a Bain system using a nasal mask. A dental pack was inserted by the surgeon prior to extraction. Following induction and prior to commencing surgery the patient received either intravenous nalbuphine 0.3 mg kg−1, one or more 12.5 mg diclofenac suppositories to a dose of 1-2 mg kg−1 or no analgesic as previously allocated.
The extractions in all patients were performed by the same experienced blinded operator who subjectively estimated the amount of bleeding following the surgery on an ordinal scale from 1=minimal, 2=moderate, 3=excessive. Heart rate, non-invasive blood pressure and oxygen saturation were recorded. At the end of surgery the inhalational agent was discontinued, the child given 100% oxygen and positioned laterally and transferred into the recovery area.
On arrival in the recovery area the child was evaluated for pain related behaviour from eye opening and every 5 min for the next 15 min and thereafter at 30 and 45 min. Pain related behaviour was evaluated in all patients by the same blinded observer using an objective pain scale adapted from one previously described by Hannallah and colleagues , see Table 1. The time to eye opening, time to walking and time to negative Romberg test were also noted by the same blinded observer.
Any patient who complained of pain or was felt to be in pain by the recovery staff was offered paracetamol for rescue analgesia; the occurrence of any post-operative nausea and vomiting was also noted. Recovery staff were unaware of the experimental group the patient was in. Patients were discharged from the recovery area when all of the usual discharge criteria were met: children were alert and orientated, had stable signs, could walk with no assistance.
Statistical analysis was performed using standard analysis of variance on parametric data and Kruskal-Wallis analysis of variance on the objective pain scores. A P-value of <0.05 was considered significant.
A total of 60 patients divided into three groups as shown in Table 2 were studied. They were similar in age, weight, fasting time, and sex distribution.
The anaesthetic and surgical details of the three groups are shown in Table 3. There were no statistically significant differences between the groups in the number of teeth extracted, the duration of surgery and the type of induction. However, the duration of anaesthesia was 9.6 (SD 3.5) min in the diclofenac group, compared with only 7.2 (SD 2.6) and 6.9 (SD 3.0) min in the control and nalbuphine groups, respectively, this reached statistical significance (P<0.05).
There were no statistically significant differences in the extremes of mean arterial pressure, oxygen saturation and heart rate recorded for the three groups during the operation. Two patients in the nalbuphine group developed laryngospasm which resolved spontaneously. No patient in either diclofenac or control group developed laryngospasm.
There was no significant difference between the groups with respect to the surgeon's estimate of intraoperative bleeding. Recovery details are shown in Table 4. There was no significant difference in the time to eye opening, time to walking unaided and time to performing a negative Romberg test. There was no clinically significant change in either heart rate, respiratory rate or oxygen saturation during the recovery period. One patient in both the nalbuphine and control group complained of nausea in recovery, compared with none in the diclofenac group. The pain and behaviour scores for each group are shown in Table 5. There was no significant difference between any group in the median objective pain scores in recovery at any time during the period studied. Rescue analgesia consisting of paracetamol suspension was given to five patients in the control group and three patients in the nalbuphine group compared with only one patient in the diclofenac group; however this did not reach statistical significance.
There has been increasing concern about the provision of post-surgical pain relief in children, which in the past has been shown to be either insufficient or inadequate . This study was designed to determine whether the increasing use of either nalbuphine or diclofenac in this practice following extraction of carious deciduous teeth under general anaesthesia could be justified. It has been traditionally thought that pain following extraction of carious teeth is not of sufficient intensity as to warrant treatment intra-operatively. However, there is some evidence to suggest that this may not be the case . Our clinical impression was that there was sufficient pain experienced by children following extraction to warrant treatment. Our study aimed to assess the effectiveness of nalbuphine and diclofenac in this clinical situation.
The non-steroidal anti-inflammatory drug diclofenac has previously been shown to be effective in relieving post-operative pain in children [8-10] and dental extraction in adults . We chose to administer the drug rectally as it was convenient, less painful than intramuscular (i.m.) injections and has been shown to provide effective analgesia in children [16,17]. The administration of rectal diclofenac was carried out following induction of anaesthesia in these unpremedicated children to avoid any possible emotional trauma the child may have experienced if given whilst awake. Previous work suggests that despite possible variable absorption of rectal diclofenac plasma concentrations reach their peak at 30 min  so we would have hoped to demonstrate any analgesic effect within our study period.
Nalbuphine hydrochloride, a partial opioid agonist, has been shown to provide effective analgesia in children equivalent to that provided by morphine [11,12] and to be effective following dental extraction [19,20]. Compared with other partial agonists such as pentazocine it would appear to have a low incidence of nausea, vomiting and psychomimetic effects .
In view of the difficulty of measuring pain in children we decided to use an objective pain score (OPS) first described by Hannallah and colleagues . This has been previously validated in the anaesthetic literature for both infants and children [22,23] and has been shown to have concurrent validity with the Children's Hospital of Eastern Ontario Pain Score (CHEOPS) . The Hannallah OPS scale has been used in many studies of post-operative pain [25-28] and has been used to assess pain in children following bilateral myringotomy, another procedure traditionally associated with minimal post-operative pain . Our study failed to demonstrate any statistically significant differences between any of the groups in terms of the objective pain score (OPS) within the first 45 min from eye opening. There does appear to be a larger difference occurring at 45 min, though this is not statistically significant. Unfortunately the possibility of following up these patients with postal questionnaires was rejected because of previous poor response rates experienced by other co-workers with similar inner city populations .
In retrospect, given the low median scores across all groups including the control group several hundred patients would be necessary to provide an adequate level of power, which may suggest that the effect of treatment is quite small. We believe that the low OPS scores reflect the low incidence of post-operative pain following extraction of carious teeth under general anaesthesia.
We believe it is unlikely that the low OPS scores throughout the 45 min studied could reflect the sedative and behavioural effects of the anaesthetic on the OPS as all mean measures of recovery used, walking unaided and negative Romberg test were not statistically different between the groups (see Table 4). In addition the previous study by Watcha and colleagues  comparing post-operative pain in children following ketorolac, paracetamol and a control group in patients undergoing bilateral myringotomy using halothane anaesthesia showed significantly lower OPS scores from 1-15 min after arrival in recovery in the ketorolac group, also there was no correlation between sedation and low OPS scores as measured by the Aldrete recovery score . We also feel it unlikely that the OPS scores were influenced by the differences in distribution of race or gender in each group as these were not statistically different.
The overall incidence of side effects was low. There was a very low incidence of post-operative nausea and vomiting. Two patients in the nalbuphine group developed laryngospasm compared with none in either the diclofenac and control group; however, these events were probably a result of the nature of the dental surgery and anaesthesia. There were no significant differences in the extremes of heart rate, blood pressure and lowest oxygen saturation during anaesthesia between groups. The significantly increased anaesthetic time for the diclofenac of 9.6 min compared with 7.2 min for control and 6.9 min for nalbuphine may be explained by the extra time required for giving the suppository as all children were partially dressed in their street clothes prior to induction as is our normal practice.
In conclusion, we were unable to demonstrate any statistically significant differences between the analgesic effects of either i.v. nalbuphine or diclofenac suppositories compared with control; however, we believe the low median OPS scores distributed throughout all groups may be clinically significant and may reflect a low degree of post-operative pain following extraction of carious deciduous teeth by an experienced operator during general anaesthesia.
The operating department assistants and nursing staff of Dental Outpatients, The London Hospital Dental Institute.
1 Fell D. Postoperative analgesia in children. Br J Anaesth
2 Lloyd-Thomas AR, Howard R. Postoperative pain control in children. Br Med J
3 Burrows FA, Berde CB. Optimal pain relief in infants and children. Br Med J
4 Lloyd-Thomas AR. Pain management in paediatric patients. Br J Anaesth
5 Goldman A, Lloyd-Thomas AR. Pain management in children. Br Med Bull
6 Fung DE, Cooper DJ, Barnard KM, Smith PB. Pain reported by children after dental extractions under general anaesthesia: a pilot study. Int J Paediatric Dent
7 Moore PA, Acs G, Hargreaves JA. Postextraction pain relief in children: a clinical trial of liquid analgesics. Int J Clin Pharmacol Ther Toxicol
8 Ryhanen P, Adamski J, Puhakka K, Leppaluoto J, Vuolteenaho O, Ryhanen J. Postoperative pain in children. A comparison between caudal bupivacaine and intramuscular diclofenac sodium. Anaesthesia
9 Watters CH, Patterson CC, Mathews HM, Campbell W. Diclofenac sodium for post tonsillectomy pain in children. Anaesthesia
10 Baer GA, Rorarius MG, Kolehmainen S, Selin S. The effect of paracetamol or diclofenac administered before operation on postoperative pain and behaviour after adenoidectomy in small children. Anaesthesia
11 Wandless JG. A comparison of nalbuphine with morphine for post-orchidopexy pain. Eur J Anaesthesiol
12 Krishnan A, Tolhurst-Cleaver CL, Kay B. Controlled comparison of nalbuphine and morphine for post-tonsillectomy pain. Anaesthesia
13 Campbell WI, Kendrick R, Patterson C. Intravenous diclofenac sodium. Does its administration before operation suppress postoperative pain? Anaesthesia
14 Hannallah RS, Broadman LM, Belman AB, Abramowitz MD, Epstein BS. Comparison of caudal and ilioinguinal/iliohypogastric nerve blocks for the control of post-orchidopexy pain in pediatric ambulatory surgery. Anesthesiology
15 Schechter NL. The undertreatment of pain in children: an overview. Pediatr Clin North Am
16 Bone ME, Fell D. A comparison between rectal diclofenac with intramuscular papaveretum or placebo for pain relief following tonsillectomy. Anaesthesia
17 Moores MA, Wandless JG, Fell D. Paediatric postoperative analgesia. A comparison of rectal diclofenac with caudal bupivacaine after inguinal herniotomy. Anaesthesia
18 Landsdorp D, Vree TB, Janssen TJ, Guelen PJM. Pharmacokinetics of rectal diclofenac and its hydroxy metabolites in man. Int J Clin Pharmacol Ther Toxicol
19 Kay B, Lindsay RG, Mason CJ, Healy TEJ. Oral nalbuphine for the treatment of pain after dental extractions. Br J Anaesth
20 Canning HB, Frost DE, McDonald DK, Joyner RW. Comparison of the use of nalbuphine and fentanyl during third molar surgery. J Oral Maxillofac Surg
21 Errick JK, Heel RC. Nalbuphine: a preliminary review of its pharmacological properties. Drugs
22 Norden J, Hannallah R, Getson P, O'Donell R, Kelliher G, Walker N. Reliability of an objective pain scale in children. Anesth Analg
23 Broadman LN, Rice LJ, Raafat S, Hannallah MD. Testing the validity of an objective pain scale for infants and children. Anesthesiology
24 Norden J, Hannallah R, Getson P, O'Donnell R, Kelliher G, Walker N. Concurrent validation of an objective pain scale for infants and children. Anesthesiology
25 Wolf AR, Vally RD, Fear DW, Roy WL, Lerman J. Bupivacaine for caudal analgesia in infants and children: the optimal effective concentration. Anesthesiology
26 Watcha MF, Jones MB, Lagueruela RG, Schweiger C, White PF. Comparison of ketorolac and morphine as adjuvants during pediatric surgery. Anesthesiology
27 Wolf AR, Hughes D. Pain relief for infants undergoing abdominal surgery: comparison of infusions of IV morphine and extradural bupivacaine. Br J Anaesth
28 Atallah MM, Saied MMA, Yahya R, Ghaly AM. Presurgical analgesia in children subjected to hypospadias repair. Br J Anaesth
29 Watcha MF, Ramirez-Ruiz M, White PF, Jones B, Languerala RG, Terkonda RP. Perioperative effects of oral ketorolac and acetaminophen in children undergoing bilateral myringotomy. Can J Anaesth
30 Aldrete JA, Kroulik DA. Postanaesthesia recovery score. Anesth Analg
Keywords:© 1996 European Academy of Anaesthesiology
ANALGESICS, diclofenac, nalbuphine; ANALGESIA, post-operative, paediatric