[Ropivacaine volume for ultrasound-guided retrograde infraclavicular brachial plexus block]

The aim of this study was to determine the medium effective volume required to produce an effective retrograde infraclavicular block using an ultrasound (US)-guided technique.

Thirty adults undergoing elective upper limb surgery received a US-guided retrograde infraclavicular block. The initial concentration of 0.5% ropivacaine injected was 30 ml, which was subsequently varied at a ratio of 1:1.2 for each consecutive patient according to the response of the previous patient. The medium effective volume (EV50) was determined using the Dixon and Massey up-and-down method. The effective volume in 95% of patients (EV95) was calculated using probit regression.

The medium effective volume and calculated effective volume in 50% and 95% of patients were 23.6 ml (95% confidence interval, 21.3-26.2 ml) and 32.3 ml, respectively. No patient required a general anesthesia.

The appropriate volume of 0.5% ropivacaine required for US-guided retrograde infraclavicular block was 30 ml in clinical practice.