INTUBATING CONDITIONS - IMPORTANCE OF THE RATE OF TRAIN-OF-4 REPETITION

Objectives: To assess that neuromuscular relaxation onset of the adduc tor pollicis (AP) is related to neuromuscular stimulation rate. To ass ess that train-of-four (TOF) at 0.05 Hz is a more accurate indicator o f optimal tracheal intubation time and conditions, than TOF at 0.08 Hz . Study design: Prospective, comparative, randomized double-blind stud y. Patients: Forty adults, physical class ASA 1 or 2, undergoing gener al anaesthesia with tracheal intubation were allocated to two groups ( n = 20) according to the sequence of stimulation of the AP : either TO F at 0.05 Hz (test group) or TOF at 0.08 Hz (control group). Methods: Induction of anaesthesia was achieved with thiopentone, fentanyl and v ecuronium (0.1 mg . kg(-1)). Neuromuscular monitoring was obtained wit h force displacement transducers attached to each AP. Tracheal intubat ion was performed once AP muscular response obtained with TOF at 0.05 Hz for test group and TOF at 0.08 Hz for control group was abolished, Results are expressed as X +/- SEM Fisher exact test was used for intu bation conditions comparison. Curarization time between groups was com pared with unpaired Student's t test (P < 0.05 accepted). Results: TOF with 0.05 Hz stimulation significantly increased curarization time: 2 17 +/- 7 versus 162 +/- 6 s (P < 0.001), intubation conditions were ex cellent in 95% and good in 5% of patients in the study group, compared to 15 and 40% in the control group, respectively (P < 0.01). In 45% o f the control group patients coughing at intubation occurred. Conclusi on: Low stimulation rate (TOF at 0.05 Hz) of AP is a reliable techique to determine the appropriate intubation time for patients paralyzed w ith vecuronium.