Ultrasound provides a reliable test of local anesthetic spread.

Background And Objectives: We predicted that practitioners could identify injectate spread in a model of ultrasound-guided peripheral nerve block.

Methods: Both novices and experts in ultrasound-guided peripheral nerve block were asked to recognize the spread of local anesthetic in a gelatin ultrasound phantom. In a blinded and randomized fashion, these participants were observed to either successfully or unsuccessfully state whether an injection had been made.

Results: Twelve novices and 8 experts each completed the trials. Accuracy, Sensitivity and specificity were calculated for all trials. Users attained a very high accuracy and sensitivity (> 85%) as well as specificity (> 90%) with ultrasound in this model.

Conclusions: This study shows that ultrasound is a reliable method of detecting injectate spread in a gelatin phantom model.