Evaluation of artery and vein differentiation methods using ultrasound imaging among medical students

Abstract

Editor—Central venous catheters (CVCs) provide vascular access for fluid resuscitation, drugs, and antibiotics and allow haemodynamic monitoring and cardiac pacing. Central venous catheters also help to achieve higher peak drug concentrations and shorter circulation times compared with peripheral venous administration. Recently, the ultrasound-guided CVC (US-CVC) technique has become available, which allows differentiation between veins and arteries and improves CVC safety with a visible guidewire to facilitate catheter progression.1Tokumine J Lefor AT Yonei A Kagaya A Iwasaki K Fukuda Y. Three-step method for ultrasound-guided central vein catheterization.Br J Anaesth. 2013; 110: 368-373Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar However, novices and medical students with less experience may find it difficult to distinguish between veins and arteries, which is the first important step. Here, we conducted a survey on the subjective difficulty of ultrasound-based methods to distinguish between veins and arteries among medical students. Ethical approval was deemed unnecessary by the Research Ethics Committee of Osaka Medical College. From December 2015 to February 2016, we conducted a questionnaire survey of 31 fifth year medical students who had no experience with internal jugular vein ultrasound imaging as a part of their routine training at Osaka Medical College. At our institution, we teach artery (common carotid artery) and vein (internal jugular vein) differentiation in healthy volunteers using an ultrasound system with a 5–10 MHz transducer (iLook™; SonoSite, Inc., Bothell, WA, USA). We introduced the following four differentiation methods: arterial pulse (pulse), colour Doppler, compression (vein reduction), and Valsalva (vein expansion) methods. At the end of training, participants rated the difficulty of the four methods on a visual analog scale, which ranged from 0 (extremely easy) to 100 mm (extremely difficult).2Komasawa N Mihara R Fujiwara S Minami T. Significance of basic airway management simulation training for medical students.J Clin Anesth. 2016; 32: 29Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar Results obtained from each trial were compared using one-way repeated measures analysis of variance. A value of P < 0.05 was considered statistically significant. The subjective difficulty of each differentiation method is shown in Fig. 1. There was no significant difference in subjective difficulty between pulse and colour Doppler methods (P = 0.99). The compression method was easier than colour Doppler and pulse methods (P < 0.001 each). The Valsalva method was less difficult compared with the other three (P < 0.001 vs pulse or colour Doppler). Differentiation between the internal jugular vein and the common carotid artery is the first and most important step in US-CVC. According to our survey, medical students found arterial pulse and colour Doppler methods more difficult than other ultrasound image-based methods. This might be associated with the fact that the vein often shows pulsatory motion with artery, and colour Doppler also captures venous flow. In contrast, vein collapse by the compression method and vein enlargement by the Valsalva method were considered relatively easy even for novices. A combination of the compression and Valsalva methods may be effective for novice doctors to differentiate between the internal jugular vein and the common carotid artery on ultrasound images. None declared.