The train of four ratio decreases to zero in anesthetized children is the guide to achieve a satisfactory intubation condition.

The purpose of this study is to investigate the satisfactory (excellent or good) intubation conditions attained when the TOF ratio was zero in anesthetized children. Sixty children undergoing elective ophthalmic surgery were allocated randomly into three groups. Anesthesia was induced with thiopentone 4 mg/kg and halothane in combination with 66% N2O and O2 (2 L/min). Patients maintained spontaneous breathing with assisted ventilation to limit the values of end tidal CO2 within the range of 36-44 mmHg, maintained the stable end tidal expiratory 1 MAC halothane concentration for three minutes and followed by 0.1 mg/kg vecuronium in group 1, 0.6 mg/kg rocuronium in group 2, and 0.9 mg/kg rocuronium in group 3. Intubation was attempted as the TOF ratio decreased from 1.0 to 0. The intubation condition was scored by assessing the degree of jaw relaxation, vocal cord opening grades, and cough responses. The overall intubation conditions were graded as excellent, good, fair, and poor on the basis of the scores. Excellent or good intubation conditions were considered satisfactory. After neuromuscular blockade administration, TOF ratio required 160.5 +/- 28.9 seconds in group 1, 70.7 +/- 18.5 seconds in group 2, and 55.7 +/- 13.5 seconds in group 3 to decrease to zero. There is a significant difference between group 1 and group 2 and 3 (p < 0.001, group 1 vs group 2 and group 3). All children were intubated, during which procedures satisfactory intubation conditions were observed in all of the group 3 patients, in 17 of the 20 group 2, and in 16 of the 20 group 1 patients. We concluded that zero of TOF from monitoring the adductor pollicis muscle indicated the proper moment for intubation in anesthetized pediatric patients and it was a reliable guide in adequately anesthetized children to achieve satisfactory intubation conditions following 0.9 mg/kg rocuronium administration.