Determination of the median effective dose of propofol in combination with different doses of ketamine during gastro-duodenoscopy in children: a randomised controlled trial

Background: Propofol is used to induce deep sedation or general anaesthesia for procedures in children. Adjuvants, such as ketamine, are routinely added to reduce the dose of propofol required and propofol-related adverse events. We conducted a randomised controlled trial to determine the effective bolus dose of propofol in combination with ketamine that induces adequate depth of anaesthesia in 50% of children (ED50) undergoing gastro-duodenoscopy. Methods: Children were randomised to one of four doses of ketamine: 0 (control), 0.25, 0.5, and 1 mg kg(-1), followed by a dose of propofol according to Dixon's up-and-down methodology. Excessive movement, coughing, gagging, or airway obstruction that prevented endoscope insertion was considered a failure. Results: The ED50 of propofol (median, 95% CI) was greater in the ketamine 0, 0.25, and 0.5 mg kg(-1) groups compared with the ketamine 1 mg kg(-1) group (6.1, 4.1-8.1; 4.5, 2.9-6; 4.7, 3.1-6.2 mg kg(-1) vs 1.1, 0.5-1.8 mg kg(-1), respectively, P<0.008). Total dose of propofol administered during the procedure was reduced with ketamine 1 mg kg(-1). The mean arterial pressure was lower in the ketamine 0 mg kg(-1) group compared with the 1 mg kg(-1) group during and immediately after the procedure. The ketamine 1 mg kg(-1) group experienced a higher incidence of nausea and visual disturbances. Conclusions: Ketamine at 0.5-1 mg kg(-1) reduces the dose of propofol required to provide general anaesthesia for gastro-duodenoscopy in children and may reduce the incidence of propofol-related changes in haemodynamics.