• Andreas Koköfer, Jürgen Nawratil, Thomas K Felder, Ottokar Stundner, Nina Mader, and Peter Gerner.
• From the Department of Anaesthesiology, Perioperative Medicine and Intensive Care (AK, JN, OS, PG), Department of Laboratory Medicine (TKF), and Department of Vascular and Endovascular Surgery, Paracelsus Medical University, Salzburg, Austria (NM).
• Eur J Anaesthesiol. 2015 Nov 1; 32 (11): 781-9.

BackgroundCarotid endarterectomy is widely performed under regional anaesthesia. Ultrasound guidance is increasingly used in many regional anaesthetic procedures to improve safety and efficacy, and because it can reduce the amount of local anaesthetic required. Despite this, an ideal approach and dosing regimen for cervical plexus block remain elusive.ObjectiveThe aim of this study was to compare two different concentrations of ropivacaine in terms of analgesic adequacy, haemodynamic effects and plasma concentration using an ultrasound-guided triple approach for intermediate cervical plexus blockade.DesignA randomised, placebo-controlled, blinded study.SettingUniversity Clinic Salzburg, Department of Anaesthesiology, Perioperative Medicine and Intensive Care, Paracelsus Medical University, Salzburg, Austria, from 16 November 2012 to 17 September 2013.PatientsForty-six patients prospectively randomised to receive ultrasound-guided intermediate cervical block with either 20 ml ropivacaine 0.75% or 20 ml ropivacaine 0.375% each with 20 ml prilocaine 1%.InterventionAfter subcutaneous infiltration, blocks were performed using ultrasound-guided infiltration below the sternocleidomastoid muscle, and ultrasound-guided infiltration of the carotid sheath. Ropivacaine and prilocaine plasma concentrations were measured at intervals.Main OutcomeThe primary study endpoint was the volume of supplementary lidocaine 1% required to achieve adequate surgical anaesthesia. Perioperative haemodynamic variables and pain scores were recorded.ResultsThere was no statistical difference in the volume of supplementary lidocaine given: 5.0 (±3.63) ml in the ropivacaine 0.375% group and 5.17 (±2.76) ml in the ropivacaine 0.75% group (P = 0.846). Pain scores were similarly low across both groups. Measured concentrations of ropivacaine and prilocaine did not reach toxic levels in either group. Levels of ropivacaine were approximately two-fold higher in the 0.75% group [mean area under the curve (AUC) 10 531.11 (±2912.84) vs. 5264.34 ng (±1594.69), P < 0.0001]. Perioperative cardiovascular stability was excellent in both groups. There were no serious block-related complications.ConclusionAn ultrasound-guided intermediate block provides adequate anaesthesia for carotid thrombendarterectomy with a little need for supplementary local anaesthetic. Use of 0.375% ropivacaine provided similarly effective analgesia as 0.75%, but resulted in significantly lower plasma concentrations.Trial RegistrationThe study was registered at the European Clinical Trial Database (Eudra CT No.: 2012-002769) as well as at ClinicalTrials.gov (NCT01759940).

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