Welcome to Hemodynamics!
Hemodynamics is the continuous movement of blood; it's pressures and volumes. Our focus here
will be the placement of a flow directed catheter (FDC), aka Swan Ganz, for the purpose of
obtaining pressures and volumes which cannot be obtained from any other source. Individuals
should be familiar with the results received from the FDC, as misdiagnosis, mistreatment, and
ultimate harm may come to the patient.
In the late 1960's Doctors Swan and Ganz were successful in the placement of a FDC into a
patient's pulmonary artery. The typical FDC is approximately 110 cm. in length and is made
from PVC. It has an inflation balloon at its distal tip for the purpose of:
A. insertion, and
B. obtaining pulmonary capillary wedge pressures (PCWP) or left ventricular end diastolic
pressures.
These will be discussed in detail later. It should be noted that the balloon ONLY be inflated for
the former two reasons and should be then deflated, or pulmonary necrosis may result. There is
not one-way valve (similar found on most endotracheal tubes). Once the inflation syringe is
removed, the balloon should deflate.
Why use a FDC?
The NUMBER 1 REASON to insert a FDC is that the information obtained
CANNOT come from any other source!
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Other indications include:
cardiovascular instability
shock
pulmonary instability
fluid management (trauma, burns, sepsis, acute renal failure)
Insertion
The 110 cm catheter is inserted into one of the following veins:
right internal jugular or subclavian vein
right or left femoral vein
right or left basilic vein (arm)
During insertion, the distal balloon is inflated, and the physician notes the location of the catheter
on the pressure monitor. Once inside the heart, the right atrial pressure waveform should
resemble Waveform #1.
From there, he/she will advance the catheter into the right ventricle (Waveform #2). Note the
higher systolic pressure, yet still has minimal diastolic pressures without a dicrotic notch. From
the right ventricle, the catheter is now advanced into the pulmonary artery (Waveform #3). Note
the higher diastolic pressure and the dicrotic notch now appears.
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What's a transducer??
A transducer converts mechanical energy into electrical signals. The mechanical energy of blood
pressure presses against the transducer which converts the pressure into a numeric signal. The
transducer must be accurately calibrated to ensure accurate readings. The first step is to place the
transducer at the level of the patient's heart and open the transducer vent port to air. The monitor
should be adjusted to read ZERO. If the transducer is placed at a level ABOVE THE LEVEL OF
THE HEART, THE READINGS WILL BE INACCURATELY TOO LOW. Since water has
pressure (hydrostatic), positioning the transducer LOWER THAN THE LEVEL OF THE
ATRIUM, THE RESULTING PRESSURE WILL READ INACCURATELY TOO HIGH!! (see
page 341 in Wilkins' Clinical Assessment in Respiratory Care)
Common Insertion Sites
Not in any particular order, these sites include:
1. right internal jugular or
2. subclavian vein
3. right or left femoral vein
4. right or left basilic vein (arm)
Hazards
The major hazards associated with the FDC include:
 arrhythmias
 infection at the site of insertion
 PA thrombus or hemorrhage
 pneumothorax
 valve disorders
 air embolus
Risks
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Placing the catheter when you can receive the information from other, non-invasive
ways,
Misinterpreting the data received, causing the patient to have inaccurate or
unnecessary treatment.
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Pressures
The FDC measures many intra-cardiac pressures, and pressures that can assist in the treatment
of patients.
Two of these pressures are Pulmonary Vascular Resistance (PVR), and Systemic Vascular
Resistance
(SVR).
Pulmonary Vascular
Systemic Vascular
Characteristics
Resistance (PVR)
Resistance (SVR)
Normal values
150-250 dynes/sec/cm5
900-1400 dynes/sec/cm5
What it reflects
Resistance that the RIGHT
ventricle must pump or
work against. This is
called afterload or the load
after the RIGHT ventricle.
Resistance that the LEFT
ventricle must pump or work
against. This is called
afterload or the load after the
LEFT ventricle.
Why are the values
different?
SVR measures pressures in
the systemic vascular bed (all
PVR measures pressures in
arteries, arterioles, capillaries,
the pulmonary vascular
etc) which is a greater
bed which is a smaller
network compared to the
network compared to the
pulmonary circulation. Think
systemic circulation.
of Poiseuille's Law of
resistance. R = ΔP/flow
What will cause these
values to INCREASE?
PVR will increase with
CHF from the left heart,
pulmonary embolus,
hypoxemia, acidosis,
hypercapnia, and/or any
narrowing of the
pulmonary arteries and/or
veins. Think of the person
with pathologic lungs (i.e.
COPD).
What will cause these
values to DECREASE?
SVR will decrease with
Everything that is
hypoxia, hypercapnia,
corrected in the box above,
hypotension, dehydration,
or septic shock will cause
medications which will dilate
a fall in PVR.
the vasculature.
SVR will increase with
hypertension, fluid overload,
increased blood viscosity, any
narrowing of the systemic
vasculature.
Intra-cardiac pressures
The FDC frequently measures pressures inside the heart. Please refer to the following table for
these pressures:
Pressure
CVP
(Central Venous Pressure)
Where is it?
Right atrium
Normal ranges
1-6 torr
RV (right ventricular)
Right ventricle but is only
15-30 torr systolic
measured upon insertion of
0-8 torr diastolic
the FDC
PAP (pulmonary artery
pressure)
Directly inside the
pulmonary artery
PCWP (pulmonary capillary
wedge pressure)
15 - 30 torr systolic
5 - 15 torr diastolic
4 - 12 torr. NOTE:
Normally, this value is
The FDC is now "wedged" almost identical to the PAP
downstream from the
diastolic pressure. If one
pulmonary artery while the received correlation with
catheter's balloon is
the PCWP and the PAP
inflated.
diastolic pressure,
"wedging" can be kept at a
minimum.
LVP (Left ventricular pressure,
Same as PCWP
filling and preload*)
Same as PCWP
(*preload) - is the stretch of the ventricular muscle just prior to contraction.
Mean Pressures
Any mean, hemodynamic pressures are calculated by adding the systolic pressure to double, the
diastolic pressure. This value is then divided by 3.
Example: Mean arterial pressure (MAP) = (systolic or 120 torr) + (diastolic or 80 torr x
2) = 120 + 160
3
3
MAP = 280/3 or 93 torr. Normal range for MAP is 70 - 100 torr
Cardiac Output (C.O.) and Index (C.I.)
OK, if we know that normal C.O. ranges between 4 - 8 L/min., what is normal for a female,
Olympic gymnast, may not be normal for a Cleveland Browns' linebacker. The gymnast's C.O.
of 5 L/min. may cause problems for the linebacker, who, due to his large size, requires more
output. This is why the cardiac output must be "indexed" to that particular patient. The C.I. is
C.O. divided by the person's body surface area (BSA). A "normal" male's BSA is 2 square
meters or 2 m2. That is, if we could take all of your tissues and spread them out on the floor and
measure them, they could equate to 2 square meters. It simply eliminates body size as a variable.
Normal C.I. is 2.5 - 4 L/min/m2.
Example: C.O. = 6 L/min and the person's BSA = 1.8 m2 , the C.I. = 3.33 L/min/m2.
BSA
(m2)
C.O.(L/min)
C.I.(L/min/m2)
How to treat???
1.4
8
5.7
Either lower the C.O. or increase
the BSA. More appropriate to lower
the C.O.
1.9
6
3.15
Nothing as this is a normal C.O. for
this person's size.
1.8
Either increase the C.O. or lower
the BSA. Faster to increase the C.O.
but if the person is morbidly obese,
dietary restrictions or surgery may
help.
2.2
4
Thermodilution C.O.
Thermodilution C.O. can only be obtained via a FDC. The process consists of injecting a bolus
(approximately 10 mL.) of iced or room temperature fluid (dextrose in water or normal saline)
referred to as the injectate, through the PROXIMAL port (CVP) of the FDC. The injectate exits
the catheter in the RA (CVP or proximal port) and travels to the P.A. where the thermistor
resides at the distal tip of the catheter. The change in injectate temperature is registered and
converted into C.O. This process is sometimes referred as "shooting" a cardiac output.
Maybe you can visualize what the temperature of the injectate would be registered as, if the C.O.
fell or was below normal for that person. Let's say it started at 0 degrees C., entered the RA and,
due to the slow C.O. warmed quickly before being measured in the P.A. at the thermistor.
Example: Injectate starting temp.= 0 degrees. Measured temp. in the P.A. = 20 degrees C.
C.O. extrapolated at 4 L/min.
NOW, the C.O. is increased due to the administration of a positive inotrope.
Injectate starting temp.= 0 degrees. Measured temp. in the P.A. = 15 degrees C.
C.O. extrapolated at 5 L/min.
So, we can infer that the WARMER the injectate is measured in the P.A., the SLOWER the
C.O.
The "COLDER" the injectate is measured in the P.A., the HIGHER the C.O.
Sv02
Some FDC have the ability to consistently measure Sv02 at their distal tip. This is a great feature as we can obtain C.O.
measurements indirectly, without "shooting" C.O.'s. One simply reads the mixed venous saturation, and derives its
change into an increased or decreased C.O. One must also realize that tissue metabolism of 02 is also a factor in Sv02!
Therefore, if metabolism remains the same, changes in Sv02 is relative to changes in C.O.
As C.O. INCREASES, MORE 02 is available at the venous level and Sv02 INCREASES*.
As C.O. DECREASES, LESS 02 is available at the venous level, therefore Sv02
DECREASES*.
*as long as tissue metabolism remains unchanged
If we simplify tissue metabolism as Pac Man eating dots, Pac Man represents the
tissues' rate of 02 consumption and the dots being 02. As metabolism increases, Pac
Man (tissue) eats more dots (02). If the tissue consumes more 02, there will be less
left at the venous level (decreased Sv02), traveling back to the lungs, even if C.O.
remains unchanged. If metabolism decreases its rate of 02 consumption, there will be more dots
(02) traveling in the venous circulation, moving toward the lungs, therefore, Sv02 increases.
Cardiac Output and Pac Man: If tissue metabolism remains unchanged, but C.O. changes, this
will also affect Sv02. If the dots (02) fly past Pac Man (tissues' rate of 02 consumption) at a high
rate of speed (higher C.O.) Pac Man cannot eat many dots (02), therefore, leaving many dots (02)
at the venous end, increasing Sv02. If the rate of dots slows (lower C.O.) Pac Man will eat many
dots leaving few at the venous end, therefore, lower Sv02.
Sv02 Summary
Less 02 at the venous end
Metabolism High More 02 consumed
Sv02 low
C.O. high
Less 02 consumed
More 02 at the venous end
Sv02 high
Metabolism low
Less 02 consumed
More 02 at the venous end
Sv02 high
C.O. low
More 02 consumed
Less 02 at the venous end
Sv02 low