Sonographic identification of needle tip by specialists and novices: a blinded comparison of 5 regional block needles in fresh human cadavers.

BACKGROUND AND OBJECTIVES: Needle visibility using ultrasound remains problematic at steep insertion angles. Despite modified techniques, steep approaches are still needed, particularly in the obese, neuraxial anesthesia or pain blocks around the spine. We describe a novel technique for objective assessment of needle-tip identification and present data on a new needle. METHODS: Five needles were compared for accuracy of tip position identification. Pajunk facet-tipped, Tuohy-tipped, Polymedic Ultrasound, Hakko EchoStim, and a new intermittently textured needle (T). Static ultrasound images were obtained of the needles in first-thaw, unembalmed cadavers at shallow, moderate and steep angles. Actual tip position was defined. Images were presented in blinded, random order to 10 experienced and 10 novice anesthetists who estimated tip position. Distance between true tip position and estimated position was measured ("tip error"). Secondary objectives included subjective measures of visibility and differences between needles at shallower insertion angles and between novice and expert observers. RESULTS: At steep angles, study needles varied significantly with regard to tip error (P < 0.0001). Needle T scored highest for confidence and subjective visibility at moderate and steep angles. There was no significant difference between novice and experienced anesthetists for tip error or visibility. Experts were more confident in their estimates. CONCLUSIONS: Needle T demonstrated good properties even at steep insertion angles. Tip location was accurate, and observers rated it highly visible. Ability to identify needle-tip position can be objectively assessed.