HESI Critical Care
Cardiac
Hemodynamics
Hemodynamic monitoring common
in critical care unit Studies
relationships among several
variables:
1. Heart rate Blood flow Oxygen delivery Tissue perfusion
Cardiac Output: amt of blood ejected from the heart in every minute
4-8 L per minute
CO = HR (heartbeat) x SV (stroke volume)
SV: amt of blood ejected from the heart in every beat
Preload, Afterload, Contractility
Cardiac Index: Cardiac Output / Body Surface Area
Gives better picture of pts cardiac output based on body size
2-4 L per minute
Ex. You have Shaq & Kevin Hart. Both have cardiac output of 6 L per minute. But CI of Kevin Hart is 3 (warm, alert, strong pulses). CI of Shaq is 1.2 (cold,
weak pulses, neuro changes). CO of 6 L is not normal for Shaq’s body; he probably needs CO of 8 L.
, 4 factors that affect Cardiac Output: Heart Rate:
-Increased heart rate: SVT A-fib/A-flutter. The heart is not filling because the heart is
1. Preload beating too fast.
2. Afterload -Decreased heart rate: AV blocks. The heart is not pumping fast enough to meet the body’s
3. Contractility demands.
4. HR CM: decreased cardiac output
Preload = VOLUME!!! Amt of blood in ventricles at Treatment: Fluids or Blood
the end of diastole.
Frank Sterling Law: the greater the volume, the
greater the stretch & the stronger the contraction.
Ex. Rubber band stretch. Little stretch = doesn’t
go far. Big stretch = goes far.
The stretch should be whatever the heart can physically
handle; normal physiologic stretch.
BAD: Cardiomyopathy or CHF = ventricles get
stretched out too much. The heart becomes
worse because we overstretched.
Increased Preload/Decreased Preload can affect cardiac
output.
Increased
preload:
Causes: fluid overload. Heart failure. Problems
with the heart. Problems with the valves;
valvular stenosis
Clinical Manifestations: edema (R), JVD (R),
crackles (L), pink frothy sputum (L), ascites
(R)
Treatment: diuretics.
Decreased
preload:
Causes: dehydration. Hemorrhage. Burns.
Anything that will cause hypovolemia.
Clinical manifestations: tachycardia. LOC
changes. Orthostatic hypotension. Tenting.
Decreased urine output. Dry mucous
membranes. Weak pulses. Cold.
Cardiac
Hemodynamics
Hemodynamic monitoring common
in critical care unit Studies
relationships among several
variables:
1. Heart rate Blood flow Oxygen delivery Tissue perfusion
Cardiac Output: amt of blood ejected from the heart in every minute
4-8 L per minute
CO = HR (heartbeat) x SV (stroke volume)
SV: amt of blood ejected from the heart in every beat
Preload, Afterload, Contractility
Cardiac Index: Cardiac Output / Body Surface Area
Gives better picture of pts cardiac output based on body size
2-4 L per minute
Ex. You have Shaq & Kevin Hart. Both have cardiac output of 6 L per minute. But CI of Kevin Hart is 3 (warm, alert, strong pulses). CI of Shaq is 1.2 (cold,
weak pulses, neuro changes). CO of 6 L is not normal for Shaq’s body; he probably needs CO of 8 L.
, 4 factors that affect Cardiac Output: Heart Rate:
-Increased heart rate: SVT A-fib/A-flutter. The heart is not filling because the heart is
1. Preload beating too fast.
2. Afterload -Decreased heart rate: AV blocks. The heart is not pumping fast enough to meet the body’s
3. Contractility demands.
4. HR CM: decreased cardiac output
Preload = VOLUME!!! Amt of blood in ventricles at Treatment: Fluids or Blood
the end of diastole.
Frank Sterling Law: the greater the volume, the
greater the stretch & the stronger the contraction.
Ex. Rubber band stretch. Little stretch = doesn’t
go far. Big stretch = goes far.
The stretch should be whatever the heart can physically
handle; normal physiologic stretch.
BAD: Cardiomyopathy or CHF = ventricles get
stretched out too much. The heart becomes
worse because we overstretched.
Increased Preload/Decreased Preload can affect cardiac
output.
Increased
preload:
Causes: fluid overload. Heart failure. Problems
with the heart. Problems with the valves;
valvular stenosis
Clinical Manifestations: edema (R), JVD (R),
crackles (L), pink frothy sputum (L), ascites
(R)
Treatment: diuretics.
Decreased
preload:
Causes: dehydration. Hemorrhage. Burns.
Anything that will cause hypovolemia.
Clinical manifestations: tachycardia. LOC
changes. Orthostatic hypotension. Tenting.
Decreased urine output. Dry mucous
membranes. Weak pulses. Cold.
