title: Ropivacaine in ultrasound-guided femoral nerve block: what is the minimal effective anaesthetic concentration (EC90)?
abstract: The 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.
authors.affiliation: Department of Anaesthesia, Ain Shams University, Cairo, Egypt; Department of Anaesthesia, Abu Dhabi Knee and Sports Medicine Centre, Abu-Dhabi, UAE.
authors.forename: A M
authors.initials: AM
authors.lastname: Taha
authors.forename: A M
authors.initials: AM
authors.lastname: Abd-Elmaksoud
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005267:Femoral Nerve / Q000187:drug effects*; D006801:Humans; D007717:Knee / Q000601:surgery; D008297:Male; D009407:Nerve Block / Q000379:methods*; D000077212:Ropivacaine; D018084:Ultrasonography, Interventional / Q000379:methods*
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine