Results:
The maximum number of 1151 articles were selected using the descriptors “dipyrone or metamizol and postoperative pain”. The number of articles found in EMBASE was 1,151, in PUBMED 336 and in VHL 345. When the descriptor “children” was introduced to the previous search, the corresponding numbers were 120, 49 and 42. When adding “randomised clinical trial”, the corresponding numbers were 31, 13 and 19. It was decided not to use the last search and the abstract, and the materials and methods of each article obtained from the search with the descriptors “dipyrone or metamizole and postoperative pain and children” were manually reviewed. Nine randomised clinical trials were identified evaluating the postoperative analgesic effect of dipyrone in isolation or associated with one of the groups. When only studies dealing with tonsillectomy were selected, 3 remained and it was seen that there was a duplicate of one. The final search result was 2 randomised clinical trials that evaluated the effect of dipyrone against placebo, one in pre-emptive and the other in the postoperative analgesia, in children undergoing tonsillectomy, with or without adenoidectomy or placement of ventilation tubes.
Tables 1, 2 and 3 show information on the 2 articles included. Table 1 shows the study identification, investigational model, follow-up time, inclusion criteria, age, sex and the sample size.
(Table 1: Characteristics of selected articles.)
The studies had short follow-up times (maximum 24 hours). While the first study involved only older children, the second study included children from 3 years old. While in the first study, only cases of isolated tonsillectomy were evaluated, in study 2, tonsillectomy either with or without associated adenoidectomy and / or placement of ventilation tubes was allowed.
Table 2 shows the description of the data referring to the intervention groups (random number and number who completed the study in each group), type of analgesia and form of administration of dipyrone. Both studies had a 100% completion rate for the randomised sample. While in the first study analgesia was post-operative, in the 2nd it was applied pre-emptively, thus, making it difficult to directly compare the two studies. The first study brought an innovation to the paediatric surgery postoperative period, in the use of PCA (patient-controlled analgesia).
(Table 2: Description of the intervention groups, type of analgesia and form of administration of dipyrone.)
Table 3 describes the strengths and weaknesses of each study, the primary and secondary outcomes, the results, the level of evidence according to Oxford criteria, the levels of evidence and degrees of recommendation according to the GRADE classification and the Jadad scores.
(Table 3: Strengths and weaknesses, primary and secondary outcomes, main results and Oxford, GRADE and Jadad classifications of studies.)
It is evident that both studies demonstrated care in their methodological approach. For this reason, the Jadad classification for the first paper was excellent (score = 5) and the second was classed as good (score = 4). The study by Kocum et al. lost a point for not explicitly describing withdrawals and losses. The other classifications were equal for both studies. Regarding the analgesic results measured by validated pain scales in childhood, dipyrone and paracetamol were superior to placebo and similar to each other in many measured intervals. The same was observed for the use of rescue pethidine, and this did not differ between active comparison groups.