Accelerated onset and delayed recovery of d-tubocurarine blockade with pancuronium in infants and children

The effect of cardiac output on the onset of neuromuscular block by vecuronium

A relationship between cardiac output and the onset time of neuromuscular blockade administered into a peripheral vein was evaluated in 41 adult patients. Anaesthesia was induced with midazolam and fentanyl and maintained with intermittent doses of fentanyl and 66% nitrous oxide in oxygen. After immobilisation of the forearm in a splint, the ulnar nerve in the other arm was stimulated supramaximally every 10 s and the adduction force of the thumb was recorded. The times from administration of vecuronium 0.08 mg.kg-1 to first and 95% depression of twitch response was 82.4 (18.0) s and 191.7 (33.5) s (mean, SD), respectively. A significant correlation between cardiac index and the onset time of blockade was observed. This study demonstrated that the rapidity of the onset of paralysis in the adductor pollicis muscle after vecuronium injection into a peripheral vein is clearly related to cardiac output.

The influence of the duration of control stimulation on the onset and recovery of neuromuscular block

The onset of action of atracurium 450 micrograms/kg, mivacurium 160 micrograms/kg, and vecuronium 80 micrograms/kg was measured after train-of-four (TOF) stimulation had been applied for 1, 5, 10, 15, or 20 min in groups of 10 patients each during anesthesia with thiopental, nitrous oxide-oxygen, and fentanyl. TOF stimulation was applied to the ulnar nerve at 2 Hz every 12 s and the force of contraction of the adductor pollicis muscle recorded. There was a progressive and significant reduction in the time to onset of maximum block with increasing times of control stimulation with all three relaxants (P < 0.0001). The mean +/- SD times to onset of maximum block decreased from 224 +/- 103 to 73 +/- 28 s with atracurium, 239 +/- 81 to 101 +/- 33 s with vecuronium, and 198 +/- 72 to 106 +/- 23 s with mivacurium as the period of control stimulation increased from 1 to 20 min. The time to recovery of T1 (first response in the TOF stimulation) to 25% of control (duration of clinical relaxation) increased from 33 +/- 5.7 to 52 +/- 13.4 min with atracurium, 25 +/- 7.6 to 38 +/- 9.4 min with vecuronium, and 13 +/- 2.5 to 18 +/- 3.5 min with mivacurium with the period of control stimulation increasing from 1 to 20 min. The differences were significant for atracurium and vecuronium (P < 0.05-0.0001). We conclude that increasing periods of control stimulation are associated with decreasing time to onset of neuromuscular block with atracurium, vecuronium, and mivacurium at the adductor pollicis muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuromuscular blocking agents in paediatric patients: influence of age on the response

This paper reviews the studies in which neuromuscular blocking drugs were compared in at least two different age groups of patients. Most recent studies have lead to a uniform concept of the variation of the effect of these drugs in different age groups. In general, the dose of a nondepolarizing agent required to produce a particular degree of relaxation is similar in neonates (less than one month), infants (one to twelve months) and adolescents (more than thirteen years). However, in children from three to ten years the dose is significantly greater. The maximal effect is reached more quickly in neonates and infants than in the older children and adolescents. These results can be explained by changes in sensitivity, distribution volume and muscle mass. The duration of effect of a nondepolarizing agent is significantly altered by age only in the case of vecuronium, which has a prolonged action in neonates and infants. Suxamethonium remains as the agent with the most rapid onset.