Download HEMODYNAMIC MONITORING, Part 2

taining the wedge reading, make sure that the catheter has returned to its normal position in the pulmonary artery by evaluating the pulmonary artery pressure waveform. The pulmonary
artery diastolic reading and the wedge pressure reflect the pressure in the left ventricle at end-diastole and are particularly important to monitor in critically ill patients, because they’re used
to evaluate left ventricular filling pressures (preload). At enddiastole, when the mitral valve is open, the wedge pressure is
the same as the pressure in the left atrium and the left ventricle, unless the patient has mitral valve
disease or pulmonary hypertension.
Pulmonary capillary
wedge pressure is a
mean pressure and is
The phlebostatic level is a horizontal line through the phlebostatic axis.
normally 4.5 to 13
The air–fluid interface of the stopcock of the transducer (or the zero
mm Hg. Critically ill
mark on the manometer) must be level with this axis for accurate
patients usually remeasurements. As a patient moves from the flat to erect positions, the
reference level changes, but the phlebostatic level stays horizontal
quire higher left venthrough the same reference point.
tricular filling pressures to optimize cardiac output. These patients may need to
have their wedge pressure maintained as high as 18 mm Hg.
Nursing interventions: Catheter site care is essentially the same
as for a CVP catheter. As in measuring CVP, position the
transducer at the phlebostatic axis to ensure accurate readings.
Watch for complications of pulmonary artery pressure monitoring, which include infection, pulmonary artery rupture, pulmonary thromboembolism, pulmonary infarction, catheter
kinking, dysrhythmias, and air embolism.
——————————————————————————————————————Source: Brunner & Suddarth’s Textbook of Medical-Surgical Nursing, 10th ed,
SC Smeltzer and B. Bare (eds). Lippincott Williams & Wilkins, 2004.
Take5 ©2006 Lippincott Williams & Wilkins
Brought to you by Nursing2006
HEMODYNAMIC MONITORING, Part 2
Critically ill patients require continuous assessment of their
cardiovascular system to diagnose and manage their complex medical conditions. This is most commonly achieved
by using direct pressure monitoring systems, often referred
to as hemodynamic monitoring. Pulmonary artery pressure
(explained here), central venous pressure (CVP), and intraarterial blood pressure (BP) monitoring (covered in Part 1)
are common forms of hemodynamic monitoring; noninvasive hemodynamic monitoring is used in some facilities. For
invasive monitoring, specialized equipment is necessary, including:
• a CVP, pulmonary artery, or arterial catheter, which is
introduced into the appropriate blood vessel or heart chamber
• a flush system composed of intravenous (I.V.) solution
(which may include heparin), tubing, stopcocks, and a flush
device, which provides for continuous and manual flushing
of the system
• a pressure bag placed around the flush solution that’s
maintained at 300 mm Hg of pressure; the pressurized flush
system delivers 3 to 5 mL of solution per hour through the
catheter to prevent clotting and backflow of blood into the
pressure monitoring system
• a transducer to convert the pressure coming from the artery or heart chamber into an electrical signal
• an amplifier or monitor, which increases the size of the
electrical signal for display on an oscilloscope.
Pulmonary artery pressure monitoring
Pulmonary artery pressure monitoring is an important tool used
in critical care for assessing left ventricular function, diagnosing
the etiology of shock, and evaluating the patient’s response to
medical interventions, such as fluid administration or vasoactive
medications.
You’ll monitor pulmonary artery pressure using a pulmonary artery catheter and pressure monitoring system. Catheters
vary in their number of lumens and their types of measurement
(such as cardiac output or oxygen saturation) or pacing capabilities. All types require that a balloon-tipped, flow-directed catheter
be inserted into a large vein (usually the subclavian, jugular, or
femoral vein); the catheter is then passed into the vena cava and
right atrium.
In the right
atrium, the
balloon tip
is inflated,
and the
catheter is
carried rapidly by the
flow of
blood
through the
tricuspid
valve, into
the right
Great vessel and chamber pressures. Pressures are identified in millimeters of mercury (mm
ventricle,
Hg) as mean pressure or systolic over diastolic pressure.
through the
pulmonic valve, and into a branch of the pulmonary artery.
When the catheter reaches a small pulmonary artery, the balloon
is deflated and the catheter is secured with sutures. Fluoroscopy
may be used during insertion to visualize the catheter’s progres-
sion through the heart chambers to the pulmonary artery.
This procedure can be performed in the operating room or
cardiac catheterization laboratory or at the bedside in the
critical care unit. During insertion of the pulmonary artery
catheter, observe the bedside monitor for waveform and
electrocardiogram changes as the catheter is moved through
the heart chambers on the right side and into the pulmonary
artery.
After the catheter is correctly positioned, you can
measure CVP or right atrial pressure, pulmonary artery systolic and diastolic pressures, mean pulmonary artery pressure, and pulmonary artery wedge pressure. If a thermodilution catheter is used, you’ll measure cardiac output and calculate systemic and pulmonary vascular resistance.
Normal pulmonary artery pressure is 25/9 mm Hg,
with a mean pressure of 15 mm Hg. When the balloon tip is
inflated (usually with 1 mL of air), the catheter floats farther
out into the pulmonary artery until it becomes wedged. This
is an occlusive
maneuver that
impedes blood
flow through
that segment of
the pulmonary
artery. A pressure measurement—called
pulmonary artery wedge
You can reference the pressure system to the phlebostatic axis by placing the air–
pressure—is
fluid interface of either the in-line stopcock or the stopcock on top of the transducer at the phlebostatic level.
taken within
seconds after
wedging of the pulmonary artery catheter; then the balloon is
immediately deflated and blood flow is restored. After ob-