Are children just little adults when it comes to propofol injection pain?

thetic agent in pediatric practice, with the well-known benefits of smooth induction characteristics, antiemetic effect, rapid recovery and pleasant emergence. The drug appears to have a wide margin of safety and is less likely to cause significant hypotension than in the elderly population. With the exception of concerns that have been raised with its use for long-term sedation in the pediatric critical care environment,1 there appear to be few safety issues to unduly concern the anesthesiologist. Minor complications are a different issue. Most of these, such as excitatory events upon induction, are generally of a trivial nature, but the troublesome issue of pain on injection still remains and has never been consistently eradicated.2 Consider the following scenario. A happy little fellow arrives with doting parents for his hernia repair. A preoperative tour some days previously has helped reassure the family and the child is orientated to the hospital by child-life workers. On the day of surgery, local anesthetic cream is applied to the child’s hand. The family meets with the anesthesiologist and it is planned to have a parent present for the induction. Everyone is happy and the anesthesiologist impresses everyone, including him/herself, by painlessly introducing the iv catheter into the appropriate vein. When the propofol starts to run in, however, the child lets out a piercing scream and complains loudly about the “big owee!” in his arm. No one is that impressed any more. Will the child remember this event? Quite possibly. The parent will certainly remember. Fortunately, this type of event is not that common, as most anesthesiologists administer lidocaine, either prior to the propofol with venous occlusion, or mixed with the propofol solution. There are some details of technique that seem to be important. Picard’s large meta-analysis3 would suggest that lidocaine is most efficacious when given in advance of the propofol and by applying a tourniquet for up to 120 sec. Although a total of 6,246 patients were included in this analysis, most of the patients were adult. In practice, many children, particularly in the younger age group, object to a tourniquet being applied for this length of time. Whilst a circumferential squeeze with a pair of warm hands may be somewhat less threatening to the child, the reliability of this as a tourniquet may be questionable. Many pediatric anesthesiologists therefore add lidocaine to propofol and have good success with this mixture. Important points seem to be to add the lidocaine just prior to injection and to use an adequate amount of lidocaine.4 Morton5 has reported complete abolition of pain with a freshly prepared mixture of propofol (3 mg·kg–1) and lidocaine (1 mg·kg–1). This brief report was conducted in 50 unpremedicated children and the injections were made via a vein on the dorsum of the hand. The only concern with this mixture is that some children require higher doses of propofol (4–5 mg·kg–1) for induction, particularly if used as a sole agent. When the induction dose is high, therefore, the lidocaine dose increases and toxicity becomes a concern. Can other strategies reduce the pain on injection of propofol more than the appropriate use of lidocaine? Many approaches have been tried in the past, with mixed success. Two techniques are evaluated and presented in this month’s Canadian Journal of Anesthesia. Rachel Pollard and colleagues, from B.C. Children’s Hospital, Vancouver, have compared the effect of lidocaine and thiopental when added to propofol.6 The incidence of injection pain in the propofol/thiopental (P/T) group was 14%, compared to 35% in the propofol/lidocaine (P/L) group. Some questions arise from this study. Firstly, it is not clear why the incidence of pain in the P/L group was as high as 35%. Morton, using the same dose of lidocaine 1016 EDITORIAL