EC50 of remifentanil to prevent withdrawal movement associated with injection of rocuronium
Various strategies have been studied to reduce the discomfort of rocuronium injection. This study was designed to determine the effect-site target concentration (Ce) of remifentanil at which there was a 50% probability of preventing movement from pain in response to the injection of rocuronium (EC50).
Anesthesia was induced with a propofol target-controlled infusion (TCI, Marsh model) and remifentanil TCI (Minto model). Effect-site target concentration of propofol was 3 μg/ml. Ce of remifentanil for the first patient started at 2.0 ng/ml. Ce of remifentanil for each subsequent patient was determined by the response of the previous patient by the Dixon up-and-down method with an interval of 0.5 ng/ml. After both drugs reached target concentration, rocuronium 0.8 mg/kg was administered, and the pain response was observed.
The EC50 of remifentanil was 1.5 ± 0.45 ng/ml by Dixon’s up-and-down method. From probit analysis, the EC50 of remifentanil was 1.37 ng/ml (95% confidence limits, 0.69–2.15 ng/ml), and the EC95 was 3.19 ng/ml (95% confidence limits, 2.31–11.24 ng/ml).
The EC50 of remifentanil to blunt the withdrawal responses to rocuronium injection was 1.37–1.5 ng/ml during 3 μg/ml propofol TCI anesthesia.
KeywordsEC50 Remifentanil Rocuronium Up-and-down method
This work was supported by a clinical research grant from Pusan National University Hospital in 2008.
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