Abstract
The aim of this prospective, double-blind, randomized, placebo-controlled clinical trial was to investigate whether the administration of ketamine before induction with propofol improves its associated haemodynamic profile and laryngeal mask airway (LMA) insertion conditions. Ninety adult patients were randomly allocated to receive either ketamine 0.5 mg.kg-1 (n=30), fentanyl 1 μg.kg-1 (n=30) or normal saline (n=30), before induction of anaesthesia with propofol 2.5 mg.kg-1. Insertion of the LMA was performed 60s after injection of propofol. Arterial blood pressure and heart rate were measured before induction (baseline), immediately after induction, immediately before LMA insertion, immediately after LMA insertion and every minute for three minutes after LMA insertion. Following LMA insertion, the following six subjective endpoints were graded by a blinded anaesthestist using ordinal scales graded 1 to 3: mouth opening, gagging, swallowing, movement, laryngospasm and ease of insertion. Systolic blood pressure was significantly higher following ketamine than either fentanyl (P=0.010) or saline (P=0.0001). The median (interquartile range) summed score describing the overall insertion conditions were similar in the ketamine [median 7.0, interquartile range (6.0–8.0)] and fentanyl groups [median 7.0, interquartile range (6.0–8.0)]. Both appeared significantly better than the saline group [median 8.0, interquartile range (6.75–9.25); P=0.024]. The incidence of prolonged apnoea (>120s) was higher in the fentanyl group [23.1% (7/30)] compared with the ketamine [6.3% (2/30)] and saline groups [3.3% (1/30)]. We conclude that the addition of ketamine 0.5 mg.kg–1 improves haemo-dynamics when compared to fentanyl 1 μg.kg–1, with less prolonged apnoea, and is associated with better LMA insertion conditions than placebo (saline).