Materials & Methods:
This study is a systematic review of the literature, which involved the work of two researchers independently evaluating the quality of each article. The formulation of the research question was based on the PICO strategy29. The following questions guided the bibliographic search: Is the action of dipyrone indicated for pre-emptive or postoperative analgesia in tonsillectomy in children? Are there any positive or negative influences? The search was carried out in the databases MEDLINE / PubMed, EMBASE and Virtual Health Library (VHL / Lilacs), using separate and combined terms, with the Boolean operator OR and, using the following subject descriptors in health sciences from BIREME (DeCS): dipyrone OR metamizole AND postoperative pain; dipyrone OR metamizole AND postoperative pain AND children, dipyrone OR metamizole AND tonsillectomy, dipyrone OR metamizole AND tonsillectomy AND children, dipyrone AND metamizole AND pre-emptive analgesia, dipyrone OR metamizole AND pre-emptive analgesia AND children. Additionally, the references of the selected articles were reviewed in the search for other relevant publications. The selection of articles was carried out in the months of June / 20 and July / 2020.
The inclusion criteria were as follows: studies that addressed the treatment of pain with dipyrone in a pre-emptive way or after the end of surgery in children. This was then refined for studies with a randomised clinical trial design and that dealt exclusively with tonsillectomies, with dipyrone alone or in combination with another drug in one of the comparison groups. There was no time limit for publications, and we included all articles available in full in Portuguese, English, Spanish and German. As exclusion criteria, the following were adopted: publications corresponding to theses, dissertations, abstracts of congresses and annals and all articles that exclusively included evaluation of chronic pain and studies in adults.
The studies were classified according to the level of evidence, following the Oxford Centre for Evidence Based Medicine recommendations30. The studies were also described according to the GRADE31 classification, which takes into account the quality of the evidence (high or level A, moderate or level B, low or level C and very low or level D) and the degree of recommendation (strong or weak). Finally, the two included studies were classified according to the Jadad32 scores, which assess the methodological quality of the study using specific criteria: poor (scores 0-2), good (3-4) or excellent (score 5 or more). The PRISMA strategy (Preferred Reporting Items for Systematic Reviews and Meta-Analysis)33 was used in this review in order to qualify the work when performing a critical analysis of the selected studies. Figure 1 shows the flowchart of identification, selection and inclusion of studies based on the PRISMA recommendation.
(Figure 1: PRISMA flowchart)