• A M Taha and A M Abd-Elmaksoud.
• Department of Anaesthesia, Ain Shams University, Cairo, Egypt; Department of Anaesthesia, Abu Dhabi Knee and Sports Medicine Centre, Abu-Dhabi, UAE.
• Anaesthesia. 2014 Jul 1;69(7):678-82.

AbstractThe objective of this study was to estimate the minimal effective anaesthetic concentrations of ropivacaine required to block the femoral nerve in 90% of patients. Forty-five patients who had knee surgery received ultrasound-guided femoral nerve block using 15 ml ropivacaine. The ropivacaine concentration given to a patient relied on the efficacy of the block in the previous patient, using the biased-coin design up-down sequential method. In the event of successful block, the next patient was randomly assigned to receive either the same ropivacaine concentration or a concentration 0.02% w/v less. In the event of a failed block, the next patient received a concentration 0.02% w/v higher. Successful block was defined as complete sensory and motor block before surgery together with pain-free surgery. The minimal effective ropivacaine concentration was estimated to be 0.167% w/v (95% CI 0.14-0.184%). Perineural injection of 15 ml ropivacaine 0.167% w/v under ultrasound guidance can provide successful femoral nerve block in 90% of patients.© 2014 The Association of Anaesthetists of Great Britain and Ireland.

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