Central Venous Pressure Monitoring

An estimate of intravascular volume status and right heart function can be assessed with a central venous pressure catheter. Central venous pressure is ideally considered as the mean venous blood pressure at the junction of the right atrium and the inferior and superior venae cavae. The central venous pressure (Tables 2 and 3) is an estimate of right heart filling pressures and may be used to assess both right heart function and the circulating blood volume.

The central venous pressure is dependent on multiple factors, such as intravascular volume, functional capacitance of veins, and status of the right heart. A limitation of central venous pressure monitoring is that it does not give direct information about the left heart. Indications for central venous catheter placement may include monitoring of cardiac filling pressures, administration of drugs, and/or rapid infusion of large amounts of fluids (Table 4).

A typical central venous pressure kit is shown in JPEG 5 (see JPEG 5 on the Companion CD). It is critical to calibrate and position the pressure transducer system properly at the level of the right atrium. Because the numeric value of central venous pressure is small (2-12 mmHg), minor changes in transducer height will cause significant inaccuracies in central venous pressure assessment.

There are multiple sites for placement of central venous catheters. Common sites used in clinical practice are the internal jugular and subclavian veins (see JPEG 6 on the Companion CD). Central venous access is also accomplished by placement of a long catheter via the antecubital, external jugular, and femoral veins. Complications of central venous catheter placement may include inadvertent arterial puncture (i.e., carotid and subclavian arteries), venous air embolism, pneumothorax, chy-lothorax, loss of guide wire, nerve injury, cardiac dysrhythmias, and/or infections.

Fig. 14. High-pressure flush test. 1, In an optimally damped pressure-monitoring system, the pressure wave returns to baseline after one oscillation. 2, In an overdamped system, the wave returns to baseline without any oscillations. The systolic blood pressure is underestimated and diastolic pressure overestimated. 3, In an underdamped system, the wave oscillates multiple times before returning to baseline. The arterial wave is amplified. The systolic pressure is overestimated and diastolic pressure underestimated. The mean arterial pressure usually is not significantly affected by overdamping or underdamping.

Table 2 Intracardiac Pressures

Pressures

Mean

Range

Left atrium

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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