Infusion of atracurium in neonates, infants and children. A study of dose requirements.

The doses of atracurium (by infusion) required to maintain steady-state (90-95%) neuromuscular block were assessed in 75 children aged 9 days to 17 yr during balanced anaesthesia. Following the intubating dose of atracurium 0.4 mg kg-1 and after the recovery of single twitch to 5-10% of control (monitored by evoked EMG of hypothenar muscle), an infusion of atracurium 0.5 mg kg-1 h-1 was started. In 22 of the patients this initial rate resulted in the desired steady state; 32 patients required one, and 21 required two or more adjustments in rate. The mean single twitch value at steady-state was 6.6 +/- 0.3% (SEM), which is equal to 93% neuromuscular block. The infusion requirement to maintain the steady state neuromuscular block in all paediatric patients more than 1 month old was constant (0.53 +/- 0.01 mg kg-1 h-1). The infusion requirement of neonates up to 1 month old was 25% less (0.40 +/- 0.02 mg kg-1 h-1; P = 0.003). A significant correlation (n = 75, r = 0.76, P less than 0.001) was found between the infusion rate (mg m-2 h-1) and the logarithm of the body surface area.