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Hemodynamic Monitoring 277

TABLE 10-1 Conversions of mm Hg and kilopascal (kPa)

From mm Hg to kPa From kPa to mm Hg

mm Hg 3 0.133 5 kPa kPa 3 7.501 5 mm Hg
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is made possible by using a transducer and an amplifier between the catheter and
monitor. Invasive hemodynamic monitoring uses a transducer to convert a pressure
Invasive hemodynamic signal (in the catheter) to an electronic signal (on the monitor).
monitoring uses a transducer
to convert a pressure signal (in To ensure accurate measurements, the transducer, catheter, and measurement
the catheter) to an electronic site should all be at the same level. Otherwise, the force of gravity will alter the
signal (on the monitor).
actual readings. For example, a higher reading may be obtained if the transducer
and catheter are located lower than the measurement site.
As with other invasive procedures, hemodynamic monitoring should only be used
as indicated because infection, dysrhythmia, bleeding, and trauma to blood vessels
are potential complications.

Units of Measurement

Hemodynamic pressure readings are measured in units of millimeters of mercury
(mm Hg) in the United States and in kilopascals (kPa) in other countries using
Système International (SI) units. The conversion factors in Table 10-1 may be used to
change between mm Hg and kPa pressure units. Hemodynamic readings begin with
the atmospheric pressure as the zero point. Since changes in atmospheric pressure are
gradual and insignificant, adjustments are not necessary in trending measurements.

Types of Catheters

Three different catheters are used in invasive hemodynamic monitoring: arterial cath-
eter, central venous catheter, and pulmonary artery catheter. The arterial catheter is
used to monitor systemic arterial pressure. Central venous pressure is measured by a
catheter in the superior vena cava or right atrium. A pulmonary artery catheter (i.e.,
The proximal opening in Swan-Ganz catheter) is used to measure the pulmonary arterial pressure and pulmo-
the pulmonary artery catheter nary capillary wedge pressure. The proximal opening in the pulmonary artery catheter
can also measure the right
atrial pressure (i.e., CVP). can also measure the pressure in the right atrium. The insertion sites, location, and
uses of hemodynamic catheters are summarized in Table 10-2.

ARTERIAL CATHETER

In hemodynamically unstable patients who are receiving fluid infusion or drugs
to improve circulation, continuous and accurate blood pressure measurements are
essential. With an arterial catheter, most bedside monitors will display a graphic

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