This was a prospective, randomized, observational study evaluating ultrasound-guided vascular access in the short axis of the vessel using an echo-enhanced needle (EchoTip Needle, Cook, Bloomington, IN, USA) compared to a standard needle using a phantom vascular access model (Blue Phantom, Advanced Medical Technologies, LLC, Kirkland, WA, USA). This study was reviewed and approved by the Institutional Review Board for verbal consent for all participants.
Study setting and population
This study was conducted in the emergency departments of two Midwestern urban tertiary care centers with a shared emergency medicine residency program. Both residents and staff physicians participated on a voluntary basis. As part of their training, emergency medicine residents are instructed in ultrasound techniques through a combination of didactic lectures, lab time, and a 1-month dedicated rotation in emergency medicine ultrasound. Following this baseline training, residents are expected to incorporate ultrasound into their daily patient care practices. Skills in ultrasound-guided vascular access are taught through lectures and direct supervision by attending physicians certified in the technique.
A random number generator with a ten-subject block design was used to randomly assign which needle each participant would use first. Each subject was then shown a 10-min video describing ultrasound-guided vascular access (produced by Blue Phantom, Advanced Medical Technologies, LLC, Kirkland, WA, USA). They then attempted to obtain vascular access with both standard and echo-enhanced needles. Ultrasound imaging was performed with the Sonosite Titan ultrasound machine (Sonosite, Bothell, WA, USA), with a 38-mm broadband (10-5 MHz) linear array transducer (Titan L38, Sonosite, Bothell, WA, USA).
The Blue Phantom vascular access model is a durable anthropomorphic phantom that images similar to real tissue with ultrasound and contains simulated blood vessels. For this study, the phantom was modified to further obscure the embedded vessel such that there were no visual or palpable anatomic clues for vascular access. This was done by placing a separate rectangular flap made of the same material as the phantom over the phantom obscuring any visualized vessels. This added approximately 1.0 cm extra depth, an insignificant amount, but provided excellent camouflage of the vessel. The same phantom was used for each study participant. We did our best to reposition the flap after multiple uses to hide obvious needle sticks. The vessel was 8 mm in diameter and was filled with a blood simulation material (water colored with red food dye).
Participants attempted to obtain vascular access with the 18-gauge standard needle and echo-enhanced needle in the short axis view. A successful attempt was defined as a flash of dye returned into the syringe. Residents and staff members were not allowed to observe others attempting to gain vascular access.
Physicians were directly observed by a trained research assistant during all of their attempts to gain vascular access. Using a stopwatch, time from ultrasound probe placement on the phantom until dye flash within the cannula was measured. The research assistant also recorded the number of needle sticks required and the number of needle redirections.
Median differences between echo-enhanced and standard needles for the variables – time to dye flash, number of sticks, and number of redirects were calculated by subtracting the standard needle tip value from the EchoTip value. A positive value corresponded to higher echo-enhanced needle values and negative values indicated a higher standard needle value. Wilcoxon rank sum testing was used for analysis with a p < 0.05 taken to indicate statistical significance. All analyses were done using the SAS® software, version 9.1 (Cary, NC, USA).