Neuromuscular recovery following rocuronium bromide single dose in infants.

Abstract

Rocuronium bromide, a steroid nondepolarizing muscle relaxant, has a rapid onset and an intermediate duration of action in infants, children and adults. However, clinical evidence shows a longer duration of recovery in small infants. The aim of this study was to investigate the influence of age on rocuronium recovery during the first year of life. ASA I-II infants, scheduled for elective surgery under general anaesthesia and intubation were included after ethics committee approval and parents' written consent. According to age the patients were randomly allocated to receive either 0.45 mg.kg(-1) or 0.6 mg.kg(-1) rocuronium bromide in three age-groups: (A) 0-1 month, (B) 2-4 months and (C) 5-12 months. After induction with thiopentone (5-7 mg.kg(-1)), anesthesia was maintained with isoflurane without opioids. Prior to surgery, caudal block with bupivacaine (0.125%) 1.0 ml.kg(-1) and paracetamol 25 mg.kg(-1) rectally were given for analgesia. Efficacy variables were intubation conditions 60 s after administration of muscle relaxant (T(0)) and recovery of neuromuscular blockade measured as T(1) at 10, 25, 50 and 75 % of baseline, train-of-four (TOF) of 0.7 and Recovery Index (RI). Data were characterized by summary statistics and analysis of variance. A total of 61 infants with a median age range of 67 (2-364) days were included. Intubation conditions were excellent or good in all dose and age groups. T(0) in group A was reached in a range of 15-30 s, in others up to 60 s. T(1) recovery (T75) after 0.45 mg.kg(-1) was 56.4 +/- 16 (A), 62.7 +/- 32 (B) and 45.8 +/- 18 (C) min. Recovery times for of 0.6 mg.kg(-1) were 100.8 +/- 35 (A), 70.6 +/- 19 (B) and 63.4 +/- 21 (C) min, respectively. The TOF ratio (0.7) was 62.3 +/- 18 (A), 64.1 +/- 27 (B) and 43.7 +/- 12 (C) min using 0.45 mg.kg(-1) compared with 94.8 +/- 31 (A), 63.8 +/- 14 (B) and 67.5 +/- 18 (C) min with 0.6 mg.kg(-1). The differences of T75 and TOF 0.7 in A and C were significant (P </= 0.05). Recovery of muscle relaxation using rocuronium bromide under isoflurane anesthesia in infants differs widely and shows great differences between age groups as well as dose regimen. A dose of 0.6 mg.kg(-1) resulted in a significantly longer duration of action in group A. The reduced dose of 0.45 mg.kg(-1) resulted in rapid and good relaxation in all infants without very long lasting effects. Reduced doses of rocuronium should be used in newborns and small infants.