Wpływ sewofluranu na zapotrzebowanie na miwakurium podawane w ciągłym wlewie u dzieci^*)

Bogumiła Wołoszczuk-Gębicka

Summary
Background. Sevoflurane, like other volatile halogenated agents, potentiates the neuromuscular block produced by mivacurium. The dose of mivacurium should therefore be reduced appropriately from that used during opioid/nitrous oxide anaesthesia. The purpose of the study was to determine the dose requirements for mivacurium, when administered by continuous infusion to maintain a stable 90-99% twitch depression in children, during N₂ O/O₂ -fentanyl or sevoflurane anaesthesia. Methods. Twenty-four ASA I or II children, aged 3-11 yrs, were randomly allocated to two groups to receive N₂ O/O₂ -fentanyl or N₂ O/O₂ /sevoflurane(1HAC) anaesthesia. Electromyographic response of the adductor pollicis to train-of-four stimulation, applied to the ulnar nerve, was recorded using a Relaxograph (Datex, Helsinki, Finland). A 0.2 mg kg^-1 bolus dose of mivacurium was followed by a continuous infusion delivered by an infusion pump working in a closed loop system with the Relaxograph and a personal computer, programmed to maintain a stable 90-99% block. Results. The mivacurium requirement was significantly decreased in the sevoflurane group (6.5 ± 2.6 mcg kg^-1 min^-1), when compared with the fentanyl group (13.0 ± 6.5 mcg kg^-1 min^-1) (p= 0.007). There was a significant negative correlation of the mivacurium requirement with the duration of neuromuscular block after the first bolus dose of mivacurium (R² = 0.35 for all patients, R² = 0.52 for the fentanyl group). Discussion and conclusion. The mechanism of potentiation of neuromuscular block by volatile anaesthetic agents is not fully understood, but it is obvious and clinically significant. Since mivacurium requirement is related to serum pseudocholinesterase activity, the duration of action of the intubating dose may serve as an indicator of mivacurium requirement during anaesthesia. Due to large individual variability, monitoring of neuromuscular transmission during mivacurium infusion should be mandatory during longer procedures in children.

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