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

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.

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 x kg(-1) or saline was given before priming and induction. Rocuronium 0.06 mg x kg(-1) or saline was injected 2 min before propofol 2.5 mg x kg(-1). This was followed by rocuronium 0.6 mg x kg(-1) or by rocuronium 0.54 mg x 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-of-four (TOF) response were monitored.

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.

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.