A fentanyl-, s-ketamine-, and midazolam-based INA protocol was effective and safe for APT and UAS. It should then be considered where intravenous access is impossible or inappropriate.

Single intravenous doses of metamizole used for the prevention or treatment of postoperative pain were well tolerated in more than 1000 children aged up to 6 years. The probability of serious ADRs (haemodynamic, anaphylactic or respiratory reactions) is lower than 0.3%. The sample size and follow-up was not sufficient to detect episodes of agranulocytosis.

Due to possible serious adverse drug reactions (ADRs), the use of metamizole for postoperative pain therapy in infants is a subject of debate. Safety studies with large sample sizes are missing. This prospective multicenter observational study was conducted to evaluate the use of metamizole in infants younger than 1 year undergoing surgery with a particular focus on possible serious ADRs (e.g., hemodynamic, anaphylactic or respiratory reactions, and agranulocytosis). Infants aged up to 1 year (American Society of Anesthesiologists [ASA] I-III) receiving a single dose of metamizole for postoperative pain therapy were enrolled. Patient demographics, main and secondary diagnosis, surgical procedures performed, metamizole dose, hemodynamic data, use of other analgesics and regional blocks, results of pain measurement, and incidence of ADRs were documented using a standardized case report form. A total of 316 infants observed at five pediatric centers were included for analysis (age 4.4 ± 3.7 [0.06-12] months). Mean metamizole dose was 17.8 ± 3.1 (9.2-29.8) mg·kg. Mean arterial pressure (MAP) remained stable during metamizole infusion (MAP before infusion 45 ± 9.5 [25-95] and after infusion 45 ± 9.2 [25-99] mm Hg). Erythema was observed in one patient (ADRs total: 0.3%, 95% confidence interval: 0.27-0.32). No respiratory adverse events directly related to the metamizole administration and no clinical signs of agranulocytosis were reported. Single intravenous doses of metamizole used for prevention or treatment of postoperative pain were safe in more than 300 infants younger than 1 year. The statistical probability of serious ADRs (e.g., hemodynamic, anaphylactic or respiratory reactions) was lower than 1%. The sample size and follow-up were not sufficient to detect agranulocytosis.