Short-axis versus long-axis approaches for teaching ultrasound-guided vascullar access on a new inanimate model

Objectives: To determine whether a short-axis (SA) or long-axis (LA) ultrasound (US) approach to guidance for line placement results in faster vascular access for novice US users. Also, to assess if there was a difference in the number of skin penetrations and needle redirections between the two guidance techniques. Methods: This was a prospective, randomized, observational study of emergency medicine (EM) residents at a Level I trauma center. A gelatin dessert and dietary fiber supplement mixture, providing a realistic US image, were placed inside a synthetic arm skin that is used for training phlebotomists and contains a rubber vein filled with red fluid at a depth of 1.5 cm. After a 30-minute tutorial on US-guided vascular access, EM residents were randomized to one of two groups. Group one attempted SA first and then the LA. Group two tried LA first followed by the SA. Time from skin break to vein cannulation, number of skin breaks and needle redirections, and difficulty of access on a 10-point Likert scale as reported by residents were recorded. Statistical analysis included paired Student's t-test with 95% confidence intervals (95% Cls). Results: Seventeen EM residents participated. The mean times to vein cannulation in SA and LA were 2.36 minutes (95% Cl = 1.15 to 3.58) and 5.02 minutes (95% Cl = 2.90 to 7.13), respectively (p = 0.03). The mean numbers of skin breaks for SA and LA were 4.18 (95% Cl = 1.18 to 7.17) and 5.76 (95% CI = 1.83 to 9.69), respectively (p = 0.49). The mean numbers of needle redirections in the SA and LA were 13.71 (95% CI = 4.51 to 22.89) and 18.17 (95% CI = 7.95 to 28.40), respectively (p = 0.51). The mean difficulty scores for SA and LA were 3.99 (95% CI = 2.42 to 5.67) and 5.86 (95% Cl = 4.32 to 7.40), respectively (p = 0.17). Conclusions: Novice US users obtain vascular access faster with an SA approach on an inanimate model.