Central venous catheterization (CVC) is essential in the management of critically ill patients seen in the Emergency Department (ED). It allows for administration of vasoactive medications, central venous pressure monitoring, fluid resuscitation, and pacemaker placement. Complications (e.g., air embolism, arterial puncture, hematoma, hemothorax, and pneumothorax) have been reported to occur in 5% to 20% of patients.1-3 Unsuccessful CVC has been reported in up to 20% of cases.4,5 CVC has traditionally been performed using surface anatomic landmarks as a guide to locate the veins. CVC is not always successful using the landmark method due to anatomic variations or obscured landmarks. Factors (e.g., congenital deformities, dehydration, intravenous drug abuse, obesity, scarring, shock, and thromboses) can complicate the procedure. Ultrasound (US)-guided vascular access is widely supported in current medical practice. The use of US guidance for CVC has been endorsed by several medical societies and supported by numerous clinical trials in the literature. US guidance has been shown to improve CVC success rates, reduce mean insertion attempts, and reduce placement failure rates.6-15 US guidance allows the Emergency Physician to more precisely locate target vessels and provide real-time visualization of needle placement.
Peripheral venous access is more commonly performed in the ED than CVC. Patients lack easily located peripheral venous sites in many cases (e.g., chronic kidney disease, intravenous drug abuse, obesity, organ transplantation, and vascular disease). Obtaining peripheral intravenous (IV) access in these patients can be a challenge, even for the most experienced medical personnel. Multiple studies have shown that US-guided peripheral IV access is safe and successful in these patients.16-22 US-guided peripheral IV access prevents the need for CVC and the pain of multiple needle sticks in many “hard-to-stick” patients.23
ANATOMY AND PATHOPHYSIOLOGY
It is important to recognize the differences in sonographic appearance between arteries and veins to perform US-guided vascular access. Arteries and veins can be distinguished by their ability to be compressed, Doppler mode signal, location, shape, size, and spectral Doppler waveforms. Arteries have relatively thick and hyperechoic (i.e., white) walls and anechoic (i.e., black) lumens. Veins have relatively thin and hypoechoic (i.e., gray) walls and anechoic (i.e., black) lumens. The thin-walled veins are usually easily compressible, have no pulsations on Doppler mode, and are oval-shaped (Figures 64-1 and 64-2). Arteries are typically round in appearance and pulsatile on Doppler mode (Figures 64-1 and 64-2). Arteries and veins are often found adjacent to each other. Veins are usually larger in diameter than arteries in a well-hydrated patient (Figure 64-1). The anatomy relevant to the sonographic evaluation of central and peripheral veins is described in the following sections.
US image of the neck vessels. The internal jugular vein (IJV) is thin-walled and oval. The carotid artery (CA) is thick-walled and round.