Central venous catheterization is essential in the management of critically ill patients seen in the Emergency Department (ED). It allows for fluid resuscitation, central venous pressure monitoring, pacemaker placement, and administration of vasoactive medications. Complications such as arterial puncture, hematoma, pneumothorax, hemothorax, and air embolus have been reported to occur in 5% to 20% of patients.1–3 Unsuccessful cannulation has been reported in up to 20% of cases.4,5 Central venous catheterization has traditionally been performed using surface anatomic landmarks as a guide to locate the veins. Catheterization is not always successful using the landmark method due to anatomical variations or obscured landmarks. Other factors such as obesity, shock, dehydration, intravenous drug abuse, congenital deformities, thromboses, and scarring can complicate the procedure. Ultrasound (US)-guided vascular access is widely supported in current medical practice. The use of US guidance for central venous cannulation has been endorsed by several medical societies and supported by numerous trials in the literature. US guidance has been shown to improve cannulation success rates, reduces mean insertion attempts, and reduce placement failure rates.6–11 US guidance allows the Emergency Physician to more precisely locate target vessels and also provide real time visualization of needle placement.
Peripheral venous access is more commonly performed in the ED than central venous cannulation. Patients with a history of chronic kidney disease, intravenous drug abuse, vascular disease, organ transplantation, and obesity lack easily located peripheral venous sites. Obtaining peripheral intravenous (IV) access in these patients can be a challenge, even for the most experienced medical personnel. Multiple studies have shown US-guided peripheral IV access is safe and successful in these patients.12–17 US-guided peripheral IV access prevents the need for central venous catheterization and the pain of multiple needle sticks in many “hard-to-stick” patients.
It is important to recognize the differences in sonographic appearance between arteries and veins when performing US-guided vascular access. Arteries and veins can be distinguished by their size, shape, location, ability to be compressed, Doppler mode signal, and spectral Doppler waveforms. Arteries have relatively thick and hyperechoic (white) walls and anechoic (black) lumens. Veins have relatively thin and hypoechoic (gray) walls and anechoic (black) lumens. The thin-walled veins are usually oval, easily compressible, and have no pulsations on Doppler mode (Figures 50-1 & 50-2). Arteries are typically round in appearance and pulsatile on Doppler mode (Figure 50-1). Arteries and veins are often found adjacent to each other. Veins are usually larger in diameter than arteries in a well-hydrated patient (Figure 50-1). 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.