A trial to compare the accuracy of two methods for delivering Propofol in children

INTERVENTION: Participants will be randomised to receive a propofol intravenous anaesthetic which will be delivered by either the Kataria or Paedfusor algorithm. These algorithms will deliver the "predicted plasma levels" (Cp). The intervention will occur only once: ie each participant will be only randomised once and will only have surgery once. The dose amount given will differ on a case by case basis and propofol delivery will be calculated on target blood level, age and weight. CONDITION: Children having major surgery that necessitates use of an intra‐arterial catheter and who are suitable for an intravenous (Propofol)‐based anaesthetic. PRIMARY OUTCOME: To determine the accuracy of pharmacokinetic algorithms in children. This will be performed by comparing measured arterial plasma concentrations of Propofol (cm) with concurrent predicted (cp) plasma levels. SECONDARY OUTCOME: Bispectral index (BIS) measurements as a surrogate measure of Propofol concentration in the brain. Observation of perceived benefits of Propofol including a possible reduction in post‐operative nausea and vomiting and airway problems. INCLUSION CRITERIA: Children aged 1‐16 yrs old having surgery necessitating insertion of an arterial line for intra‐operative monitoring American Society of Anesthesiologists (ASA) status 1‐3 Surgical procedure expected to last between 1‐8 hours