Duration of action of vecuronium in infants and children anaesthetized without potent inhalation agents.

The duration of effects of vecuronium has previously been studied in paediatric patients only during inhalation anaesthesia. We therefore studied the age-related differences in duration of action after administration of 0.1 mg kg-1 of vecuronium in 66% N2O in O2, fentanyl anaesthesia without inhalation agents. Forty-nine children (2 wk-14 yr, ASA 1-2) were selected for study and divided into four groups according to age. Evoked EMG monitor (Relaxograph, Datex, Finland) was calibrated with hypothenar muscle recording. The completely restored first twitch (T1) level was used as reference for recovery calculations. In infants (age less than 1 yr) the onset time (68 s) was only 0.6-0.8 times that of older patients (P less than 0.01). In infants the duration of surgical relaxation to T1 10% (42 min) and the recovery index (21 min) were 1.7-2.9 times longer than in older patients (P less than 0.01). It took 55 min from the beginning of recovery to full restoration of T1 in infants, compared with 20-24 min in 3-15-year-old children. Interestingly, the younger the child, the more rapidly train-of-four ratio recovered compared with T1 (P less than 0.01). Because of the age-dependent prolongation of vecuronium relaxation and spontaneous recovery in small children, the level of relaxation should be monitored also in clinical practice.