Maturation of neuromuscular transmission in the infant.

Twitch tension, train-of-four and tetanus--clinical parameters of neuromuscular transmission--were studied in 37 infants and children anaesthetized with halothane. The contraction time was slower in infants less than 1 month old when compared with their elder counterparts. This may indicate a possible transformation from slow to faster muscle types. The train-of-four reached 100% in most of the infants older than 2 months. The post-tetanic facilitation and the tetanus : twitch ratios were significantly greater in infants older than 2 months when compared with infants less than 1 month. Post-tetanic exhaustion was seen in all the infants and children after stimulation at 100 Hz. Tetanus : twitch ratios were greater in infants more than 2 months old and in children, and the tetanic force was more marked at 50 Hz than at 20 Hz. The data indicate that maturation of neuromuscular transmission occurs in infants in and around the first 2 months of age.