Avoiding propofol injection pain in children: a prospective, randomized, double-blinded, placebo-controlled study

Background. Pain on injection limits the use of propofol in children. The combination of lidocaine and propofol is widely used to reduce pain. A new solvent [medium-chain triglyceride (mct)/long-chain triglyceride (lct)] has been advocated to be less painful than standard (lct) propofol in adults, but no information is available of its usefulness in pre-school children. We designed a prospective, randomized, double-blinded, placebo-controlled study to assess injection pain with two different propofol emulsions, each given with or without lidocaine in children,7 yr. Methods. A total of 160 ASA I-III children were randomly assigned to receive lct-propofol or mct/lct-propofol, 5 mg kg(-1), with lidocaine 10 mg ml(-1) or saline. The site and size of venous cannulation and restlessness before injection were recorded in each patient. A pain score graded 0-6 was established based on spontaneous verbal and motor reaction during injection, each graded 0-3. Kruskall-Wallis and Mann-Whitney tests were used for statistical analysis. Results. Median pain scores decreased in all groups compared with lct-propofol-saline (P<0.001) and were least in the lct/mct-propofol-lidocaine group (P<0.001). Painless injection (score, 0-2) occurred in 92.5% of patients in the mct/lct- propofol-lidocaine group compared with 41-77% in the others (P<0.001). Conclusions. Mct/lct-propofol caused significantly less pain than lct-propofol in preschool children. Mixing of lidocaine with mct/lct-propofol resulted in a further significant decrease, virtually eliminating the pain on injection.