The learning process of the hydrolocalization technique performed during ultrasound-guided regional anesthesia

Background: Because poor echogenicity of the needle remains a safety issue, we decided to analyze the learning process of the hydrolocalization technique (Hloc) performed to continuously identify needle‐tip anatomical position during many ultrasound‐guided regional anesthesia procedures. Methods: Ten senior anesthesiologists naïve to the Hloc agreed to participate in the study. They were requested to perform 40 out‐of‐plane (OOP) approach ultrasound‐guided axillary blocks (AB) each using the Hloc. The Hloc, which is a needle‐tip localization principle, was performed by means of repetitive injections of a small amount of a local anesthetic solution (0.5–1 ml) under an ultrasound beam. Details of the learning process and skill acquisition of the Hloc were derived from the following parameters: the duration of block placement, a measure of the perceived difficulty of needle‐tip visualization, a measure of block placement difficulty, and the amount of local anesthetics solution required for the technique. Results: Four hundred ABs were performed. The success rate of an ultrasound‐guided AB was 98%. The Hloc was successful in all patients. Skill acquisition over time of the Hloc was associated with a significant reduction of both the duration and the perceived difficulty of ABs placement. Apprenticeship data revealed that 20 blocks were required to successfully place AB within 5 min in most cases using the Hloc. Conclusion: The Hloc performed during the OOP approach of ultrasound‐guided regional anesthesia is a simple technique with a relatively short learning process feasible for efficient placement of ABs.