Puncture of a peripheral vein is the most common invasive procedure
performed in the Emergency Department. While some newer point-of-care
testing techniques require only capillary blood, the vast majority
of laboratory studies require venous blood. Cannulation of a peripheral vein
is performed on a daily basis and is the cornerstone of circulatory
resuscitation; it is an essential skill for all emergency personnel,
from phlebotomists to nurses to physicians. A variety of approaches
for obtaining peripheral venous access are described in this chapter.
Veins and arteries are composed of a three-layered wall of internal
endothelium surrounded by a layer of muscle then a layer of connective
tissue1 (Figure 37-1). The muscular layer of a vein is
much thinner and weaker than that of an artery. While veins can
dilate and constrict somewhat on their own, they do so mostly in
response to the pressure within them. Veins with high internal pressures
become engorged and are easier to access. The use of venous tourniquets,
dependent positioning, “pumping” via muscle contraction, and
the local application of heat or nitroglycerin ointment all contribute
to venous engorgement.2 These maneuvers can be used to
aid in the performance of a venipuncture or cannulation of a peripheral
Comparative anatomy of an artery and a vein. Note the
vein’s thinner wall with fewer myocytes and elastic fibers.
This is indicative of the lower pressure within veins compared to
The connective tissue surrounding veins can be a help or a hindrance
during attempts at gaining peripheral venous access. Deficient connective
tissue permits the vein to “roll” from side to
side and evade the needle. Tough connective tissue can impede the
entry of a flexible catheter through the soft tissues and into the
vein. This tissue also serves to stabilize the vein and prevent
Venous valves are an important aspect of peripheral venous anatomy1 (Figure
37-2). Venous valves encourage unidirectional flow of blood back
to the heart. Because of gravitational forces, they prevent blood
from pooling in the dependent portions of the extremities. Valves
can impede the passage of a catheter through and into a vein. Forcing
a catheter past venous valves may damage them and contribute to
later venous insufficiency. Valves are more numerous at the points
where tributaries join larger veins and in the lower extremities.
Valves are almost totally absent within the large central veins,
the veins of the head, and the veins of the neck.
Venous valves. Cross section of converging veins demonstrating
the valve leaflets that permit only forward flow, proximally, toward
the right heart. The arrows represent the directional flow of blood.
Veins can be subdivided into central veins and peripheral veins. ...