In-plane ultrasound-guided venipuncture: The underestimated risk of slice thickness artefact and strategies for safe...

In-plane (IP) ultrasound-guided venipuncture is widely used for its recognized advantages, including improved needle tip identification and a shallower puncture angle, which enhances echogenicity, reduces posterior wall injury, and facilitates guidewire insertion. These benefits, however, can create a false sense of security if the inherent limitations of ultrasound imaging are not appreciated. Among these, slice thickness artefact, caused by the finite elevational thickness of the ultrasound beam, is frequently overlooked in clinical practice. This narrative review examines the mechanisms, clinical implications, and strategies to mitigate slice thickness artefact during IP venipuncture, with particular emphasis on factors influencing artefact magnitude and needle tip visualization. Slice thickness artefact projects echoes from structures outside the imaging plane onto the two-dimensional image, making the needle tip appear intraluminal while it actually lies in a parallel, off-plane trajectory. Misinterpretation may increase the risk of injury to adjacent arteries, nerves, or other critical structures and lead to inadvertent extravascular catheter placement. The magnitude of the artefact depends on imaging depth, focal zone alignment, beam divergence, and transducer design, and is particularly relevant for deep, small-caliber veins and low-frequency or handheld devices. Mitigation strategies include awareness of beam limitations, careful probe selection, optimization of depth and focal zone, dynamic probe manipulation, controlled needle advancement, backflow verification, and complementary out-of-plane confirmation. When recognized and managed appropriately, slice thickness artefact can be minimized, preserving the procedural advantages of IP guidance. Understanding ultrasound beam geometry and applying targeted technical strategies are essential to optimize needle tip visualization, procedural safety, and patient outcomes.