Ketamine, but not priming, improves intubating conditions during a propofol-rocuronium induction

Purpose Both ketamine and priming may shorten the onset time of rocuronium. This study investigates the effects of ketamine and priming as components of a propofol induction on intubating conditions and onset of neuromuscular block. Methods This prospective randomized double-blind study was performed in 120 American Society of Anesthesiologists (ASA) I-II patients who were assigned to one of four groups of 30 patients each: control, priming, ketamine, and ketamine-priming. Ketamine 0.5 mg · kg^-1 or saline was given before priming and induction. Rocuronium 0.06 mg · kg^-1 or saline was injected 2 min before propofol 2.5 mg · kg^-1. This was followed by rocuronium 0.6 mg · kg^-1 or by rocuronium 0.54 mg · kg^-1 if priming was given. Intubation was performed one minute later. Intubating conditions were graded as excellent, good, or poor. Heart rate, noninvasive blood pressure, and train-offour (TOF) response were monitored. Results Intubating conditions were graded excellent in 20% of the control group, 30% of the priming group, 47% of the ketamine group, and 57% of the ketamine-priming group. Analysis using forward stepwise regression indicated that ketamine improved intubating conditions (P = 0.001) but priming did not (P = 0.35). Time to reach a TOF count of zero was shortened by ketamine (P = 0.001) but not by priming (P = 0.94): 216 ± 20 s in the control group, 212 ± 27 s in the priming group, 162 ± 18 s in the ketamine group, and 168 ± 22 s in the ketamine-priming group. Conclusion A low-dose ketamine used with a propofol- rocuronium induction improved intubating conditions and shortened onset time. Priming did not influence intubating conditions or onset time.