EC50 of remifentanil to prevent withdrawal movement associated with injection of rocuronium
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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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