The practice of Emergency Medicine frequently requires access
to a patient’s venous circulation. Venous access allows
sampling of blood as well as administration of medications, nutritional
support, and blood products. Devices such as cardiac pacing wires
and pulmonary artery catheters can be introduced into the patient’s
central venous circulatory system.
Percutaneous, as opposed to surgical, venous access is usually
rapid, safe, and well tolerated. An understanding of the various
techniques available, patient anatomy, and indications for the procedure
allows the practitioner to choose the appropriate site and method
of venous access.
Veins, like arteries, have a three-layered wall composed of an
internal endothelium surrounded by a layer of muscle then a layer
of connective tissue1(Figure 36-1). The muscular layer
of a vein is much 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 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 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 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
36-2). They encourage unidirectional flow of blood back towards
the heart. Venous valves prevent blood from pooling in the dependent
portions of the extremities due to gravitational forces. 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 only permit forward flow, proximally, toward
the right heart. The arrows represent the directional flow of blood.
Veins can be subdivided into ...