Update March 23, 2017
Determine central venous pressure (CVP) during
administration of fluid to treat hypovolemia and shock, infusion of caustic drugs and total parenteral nutrition, aspiration of air emboli, insertion of transcutaneous pacing leads, and gaining venous access in patients with poor peripheral veins. With specialized catheters, central venous catheterization can be used for continuous monitoring of central venous oxygen saturation.
Relative contraindications include tumors, clots, or tricuspid valve vegetations that could be dislodged or embolized during cannulation. Other contraindications relate to the cannulation site. For example, subclavian vein cannulation is relatively contraindicated in patients who are receiving anticoagulants (due to the inability to provide direct compression in the event of an accidental arterial puncture). Some clinicians avoid central venous cannulation on the side of a previous carotid endarterectomy due to concerns about the possibility of unintentional carotid artery puncture. The presence of other central catheters or pacemaker leads may reduce the number of sites available for central line placement.
Central venous cannulation involves introducing a catheter into a vein so that the catheter’s tip lies just superior to or at the junction of the superior vena cava and the right atrium.
When the catheter tip is located within the thorax, inspiration will increase or decrease CVP, depending on whether ventilation is controlled or spontaneous.
Measurement of CVP is made with a water column (cm H2O), or, preferably, an electronic transducer (mm Hg). The pressure should be measured during end expiration.
Compared with other sites, the subclavian vein is associated with a greater risk of pneumothorax during insertion, but a reduced risk of other complications during prolonged cannulations (eg, in critically ill patients). The right internal jugular vein provides a combination of accessibility and safety. Left-sided internal jugular vein catheterization has an increased risk of pleural effusion and chylothorax. The external jugular veins can also be used as entry sites, but due to the acute angle at which they join the great veins of the chest, are associated with a slightly increased likelihood of failure to gain access to the central circulation than the internal jugular veins. Femoral veins can also be cannulated, but are associated with an increased risk of line-related sepsis. There are at least three cannulation techniques: a catheter over a needle (similar to peripheral catheterization), a catheter through a needle (requiring a large-bore needle stick), and a catheter over a guidewire (Seldinger’s technique; Figure 5-16). The overwhelming majority of central lines are placed using Seldinger’s technique.
For CVP monitoring, a 14-gauge IV catheter is inserted into the central venous circulation through the internal jugular or subclavian vein (see Chapter 13). A pressure transducer and monitor connected to the catheter provide the measurements. A CXR is required to confirm the position of the catheter in the superior vena cava. The zero point for the transducer is the level of the right atrium in a supine patient; this phlebostatic axis is usually 5 cm caudal to the sternal notch in the midaxillary line.
The transduced CVP reflects right atrial pressure, and by association, right ventricular filling pressure or preload. Although CVP is a relatively inaccurate indicator of preload, trends in relation to volume status and hemodynamics may be clinically useful.
Right Atrial Pressure (RAP) – Central Venous pressure (CVP)
| Reading (mm Hg) | General Description | Clinical Implications |
|---|---|---|
| < 3 | Low | Intravenous fluids may be administered |
| 3–10 | Midrange | Probable clinical euvolemia |
| >10 | High | Suspect fluid overload, CHF, CP, COPD, tension PTX |