The smaller peripheral veins in the extremities drain into the subclavian vein, internal jugular vein, and femoral vein, and these vessels constitute the central venous system (Fig. 27.1). The ability to create secure access to the central venous system greatly facilitates the care of many patients. One of the benefits of central venous catheterization is the ability to rapidly dilute therapeutic substances into the blood stream that would be too noxious to deliver through smaller, peripheral veins. Total parenteral nutrition, chemotherapy, and vasopressors are all examples of therapies that require delivery via a large central vein.

Central venous catheterization is also required for therapies such as hemodialysis, continuous venovenous hemofiltration, and plasmapheresis. In these therapies, high rates of blood flow must be generated in order to circulate the patient’s entire volume of blood through an external device. This process requires a large bore catheter that can only be placed in wide diameter vessels such as the central veins.

In certain patients central venous access may be indicated for close hemodynamic monitoring. Measurement of the central venous pressure can be obtained through an indwelling venous catheter with a pressure transducer. This reading can be used to estimate the intravascular blood volume, which can help guide resuscitation decisions. In highly select cases, a pulmonary artery catheter may be indicated to evaluate cardiac function parameters. For this procedure, a long catheter with an inflatable balloon tip is guided into a central vein, then through the right atrium and ventricle, into the pulmonary artery. By inflating the balloon, a measurement can be obtained of the pressure in the pulmonary artery, which indirectly reflects the pressure in the left atrium. In addition, a temperature probe on the pulmonary artery catheter can be used to calculate cardiac output based on thermodilution. These measurements can help guide clinical decisions in critically ill patients.

Finally, central venous access is occasionally indicated in patients who have poor peripheral veins, usually as a result of long inpatient admissions and frequent access attempts. In such patients, central venous catheterization certainly facilitates frequent blood draws or the administration of multiple intravenous medications. However, it is important to note that central venous catheterization should be used as a last resort, and not for convenience, since it exposes the patient to significantly higher risks than peripheral venous access.

Once central venous catheterization is indicated for one of the above reasons, the next step involves choosing which vein should be used. The right and left internal jugular veins, subclavian veins, and femoral veins each have their own advantages and disadvantages that should be considered on a case-by-case basis. The internal jugular veins are generally the preferred site of access because they are associated with the lowest rates of pneumothorax. There is, however, a risk of injury to the carotid artery during this approach. In addition, external catheters on the neck can be uncomfortable for conscious patients. The subclavian veins are advantageous in certain situations: they may provide the easiest access in obese patients in whom landmarks in the neck are not visible. Subclavian line are also generally the most comfortable for the patient. On the other hand, subclavian vein puncture is technically more difficult for the novice; furthermore the vein is not accessible for direct pressure in the event of bleeding. The femoral veins provide quick, easy access with minimal risk of injury. This is particularly useful in frenzied code situations when the intubation team crowds the area around the patient’s head. The femoral veins are also preferred in coagulopathic patients since the site can be compressed with direct pressure. The disadvantage of femoral venous access is that these lines may be more prone to infection. In addition, the location of femoral catheters generally prevents ambulation.

The type of venous access catheter that is selected depends on the indication and anticipated duration of use. Simple external catheters, such as triple lumen catheters, are the best choice for patients who require short-term central venous access during their hospital stay. In general, these lines must be changed every few days to prevent infection. External catheters are not appropriate for outpatients due to the risk of air embolism if the catheter is inadvertently dislodged.

Peripherally inserted central catheters (PICC) are a special type of central line. These long catheters are inserted via the basilic vein in the upper arm, but the tip of the line is located in the superior vena cava. These types of catheters are well suited to outpatients who require days to weeks of intravenous access, such as commonly needed for antibiotic administration.

Tunneled catheters are central lines that are passed through a subcutaneous tunnel before their exit site on the skin. A felt cuff is usually present on the catheter; tissue infiltration of the cuff seals the tunnel site and helps prevent bacterial migration from the skin. These semi-permanent catheters are ideal for patients who require several weeks or months of central venous access, such as patients undergoing plasmaphoresis or hemodialysis.