Dose—response and minimum time to satisfactory intubation conditions after mivacurium in children

Abstract

SummaryWe assessed neuromuscular blocking effects and tracheal intubation conditions following mivacurium in 121 anaesthetised children aged 1-10 years. The study was conducted in three parts. Parts Key wordsAnaesthesia; paediatric. Intubation; tracheal. Neuromuscular relaxants: mivacurium.Mivacurium is a newer non-depolarising neuromuscular blocking drug with a short duration of action due to its rapid metabolism by plasma cholinesterase [I, 21. In view of its short duration of action, mivacurium may be an alternative to suxamethonium for brief surgical procedures requiring profound muscle relaxation [3-51. While several authors have quantified the neuromuscular blocking effects of mivacurium in children in terms of twitch depression [5-71, there have been no studies to assess the minimum time to achieve satisfactory intubation conditions. Therefore, we undertook the present study to determine the dose-response relationship of mivacurium in children and compare intubation conditions at selected times following a dose of approximately 2 x EDss. Patients and methodsFollowing approval by the local ethics committee and informed parental consent, 61 children aged 1-10 years scheduled to undergo elective general anaesthesia with tracheal intubation were studied. All were ASA physical status 1 or 2 and none were taking drugs known to interfere with neuromuscular transmission. Children whose body weight deviated by more than 20% from the ideal for their height were not studied.All children were premedicated with oral midazolam syrup 0.5 mg.kg -I 3 M O min pre-operatively and EMLA cream was applied to possible venepuncture sites. The study was conducted in three parts: (1) determination of the dose-response relationship; (2) measurement of onset and recovery times after a dose of mivacurium approximately equal to twice the EDss; (3) assessment of intubation conditions at either 60 or 90 s after the same dose of mivacurium.In the first part of the study, anaesthesia was induced in 15 children with thiopentone 6-8 mg.kg-I and alfentanil 50 pg.kg -'. Tracheal intubation was performed after 1 min without using a muscle relaxant.

Age related variability in the effects of mivacurium in paediatric surgical patients

“…However, thiopentone and nitrous o~de without a neuromuscular blocker have been shovm to produce poor or impossible intubation conditions in children. 9 No other studies have compared intubation conditions following mivacurium administration during different types of anaesthesia ha paediatric patients.…”

Role of muscle relaxants in pediatric anesthesia

“…In children anesthetized with thiopental-nitrous oxide, satisfactory intubating conditions were observed in 98 and 100% of cases 90 and 70 s after the administration of 2 Â ED 95 doses of mivacurium or rocuronium, respectively [26,27]. Similarly, in a study of 60 children aged 2-7 years, good/excellent intubating conditions were achieved in all patients at 1 MAC anesthesia with sevoflurane 2 min after injection of rocuronium 0.3 mg/kg (around 1 Â ED 95 ) [28].…”

“…Mivacurium 0.2 mg/kg (around 2 Â ED 95 ) provides satisfactory intubating conditions in 98% of children 90 s after administration during thiopental-nitrous oxide anesthesia [26]. Onset of maximum block occurs in 1-2 min and 25% recovery in 9-10 min.…”

Selection of Anesthesia Techniques for the Neonate

“…Mivacurium 200 μg/ kg IV provides good intubating conditions after 90 s in children [ 213 ]. Several studies showed that fentanyl decreased the number of attempts and the incidence of desaturation during tracheal intubation in premature and full-term neonates [ 185 , 214 ].…”