Anesthetic volume for ultrasound-guided "double bubble" infraclavicular block: Comparison of ropivacaine 0.75% 30ml vs 35ml

For an UltraSound guided Infraclavicular Block, a non-inferiority randomized study was conducted comparing two volumes of ropivacaine 0.75%: 35 ml vs 30ml. Fifty 18-70 years old patients undergoing upper limb surgery, ASA I-II were enrolled. Exclusion criteria included existing neurologic disease, coagulopathy, allergy, pregnancy, previous surgery in clavicular region, BMI more than 30 kg/m2 or patients unable to give written consent. Using US guidance, a 22 gauge/80 mm SonoPlex needle (Pajunk®) was advanced until the tip was located dorsally to the artery at a 6-o’clock position. Correct placement was ensuring by a “double bubble” sign. The block was performed by delivering ropivacaine 0.75% via an infusion pump (Alaris® PK) at 600 ml/h. The patients were randomly allocated to receive 30 or 35 ml of anesthetic. Subsequently, the brachial plexus block was evaluated after 30 minutes according to a 3-point scale for sensitive and motor blockade in each nerve field (maximum 16 points). Block was successful if a minimal score of 14 points was achieved. Student’s T test for continuous variables and Chi-Square test for qualitative variables were used. Both groups were homogeneous in terms of anthropometric data. The Block Success rate was 22/25 (88%) regardless of the group of origin (G30 or G35) (p=NS). our data showed that for an Infraclavicular Block achieved by a single injection of ropivacaine 0.75% using the “double bubble” technique a volume of 30 ml is equivalent to 35 ml.