Propofol is an IV hypnotic that is made in a soy-based emulsion containing soybean oil, egg lecithin, and glycerol.  It has a very rapid onset time (10-50 seconds) and a brief duration of action making it ideal for ED sedation.  Children have a more rapid metabolism of propofol than adults.  Propofol has been shown to be safe and effective for Pediatric ED sedation in several studies.  

Pearls on Propofol

• Dosing is 1mg/kg bolus than 0.5 mg/kg IV q 1-2 min until desired sedation occurs
• Due to high lipid concentration can cause pain at injection site in up to 70% of patients.  This can be prevented by applying a rubber tourniquet well above IV site and injecting 0.5 mg/kg of lidocaine 30 seconds before injecting the propofol. 
• Use is contraindicated in those with allergies to Eggs, Soy, or sulfites, or those with mitochondrial disorders
• PRIS (Propofol Infusion Syndrome) was described in 1992 with case reports of children dying due to metabolic acidosis, rhabdomyolysis, and refractory heart failure when receiving high doses (>4mg/kg/h) for >48 hours.  And it is more associated with children < 4 years old. 
• So while safe for pediatric procedural sedation don't use propofol as a drip for intubated children.

References

Lopez M, Beltran G. Pediatric Procedural Sedation.  Pediatric Emergency Medicine Reports. Dec 2008.