Does the newer preparation of propofol, an emulsion of medium/long chain triglycerides cause less injection pain in children when premixed with lignocaine?

Background: Injection pain during propofol administration can be particularly distressing in children. The newly available emulsion of propofol in medium and long chain triglycerides (LCT) is reported to cause less injection pain because of lower concentrations of free propofol. This study compared the incidence of injection pain during administration of propofol emulsion of LCT and propofol emulsion of medium and long chain triglycerides (MCT/LCT) both premixed with lignocaine in children. Methods: This prospective, randomized, double blind study was conducted after obtaining institutional ethics committee approval, parental consent and included 84 children aged 5-15 years. Preoperatively, an intravenous cannula was inserted in all children. four children were excluded. Those included, depending on the randomization, received 3 mg·kg^-1 of either propofol LCT or propofol MCT/LCT both premixed with lignocaine (0.1%). The incidence and intensity of injection pain was assessed. Results: Pain on injection of propofol LCT with lignocaine was observed in 16/40 children (40%), five of these children complained of severe pain. In comparison, 14/40 (35%) children complained of pain following propofol MCT/LCT premixed with lignocaine (P = 0.644), the intensity being severe in two children (P = 0.698). Conclusions: Propofol MCT/LCT and propofol LCT premixed with lignocaine are both associated with pain on injection in children; the incidence and intensity of the injection pain are similar.