Hemodynamics
5-18-10
Cardiac output
o = HR X Stroke Volume
o Normal stroke volume in an adult = 60-70 cc
o CO – the volume of blood ejected from the LV over 60 seconds.
o Normal CO = 4 - 8 Liters/min
o 4 – 6 Liters/min at rest
o Increases with exercise because HR goes up
o A generic value that tells you for all people this is about normal
Cardiac Index
o CO divided by the body surface area of the patient in meters squared
o Specific to the individual
o Normal value = 2.2 – 4 Liters/min/m2
Stroke Volume
o How much output goes out of the heart with one beat (Normal 60-70 cc)
o Effected by preload, afterload, and contractility
Preload
o Priming of the heart – what is returning to right side of the heart.
o The filling pressure
o CVP (central venous pressure) or RA (right atrial pressure) - Measures the preload to the right side of
the heart. We are measuring the pressure in the superior vena cava or the right atrium. No valve
between these so pressure is the same. Normal = 2 – 5 mmHg (Really on low end)
o If this # has dropped, preload is low, which means they don’t have enough volume. Need to give
them more volume to increase preload.
o If # is high, they are volume high and in heart failure because there is too much returning to the heart.
o PAOP (Pulmonary artery occlusion pressure) or PAWP (Pulmonary artery wedge pressure) or PCWP
(pulmonary capillary wedge pressure) or the wedge. Measures the preload to the left side of the heart,
it is in the pulmonary system. Normal = 5 – 12 mmHg. Higher # because higher pressure system. Left
side of heart higher pressure than right side of heart.
o LVEDP (Left ventricular end diastolic pressure) Normal = 10 – 12 mmHg.
o The wedge we get with a PA catheter
o LVEDP they get in cath lab with invasive lines
o Increases preload:
Fluids
Blood
Albumin
Positioning (head down, feet up)
o Decrease preload:
Diuretics
Some vasodilators if they work on the venous side
Positioning (head up, feet down)
o CVP - if its low it’s because they are hypovolemic, early warning sign for bleeding or vasodilation, if
they diurese a lot their CVP will fall, also if we’ve rewarmed them after surgery (heating up too
quick).
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, o CVP too high: too much fluid or cardiac muscle can’t keep up with it, in heart failure, increases
oxygen demand.
Afterload
o The force the heart must overcome to pump blood out into the system or out into the pulmonary
system.
o SVR (Systemic vascular resistance) - Muscle tone in the arteries. Don’t want them to be floppy and
lose BP or clamped down so hard that the heart can’t get any blood out because its going against all
that pressure.
o Clamped down = SVR goes up
o Dilated = SVR goes down
o SVR is left sided afterload (systemically) Normal = 800-1400 dynes/sec/cm3
o SVRI – systemic vascular resistance index – divide SVR by body surface area. More specific to
patient Normal = 2000-2400 dynes/sec/cm3
o PVR (pulmonary vascular resistance) - Measures tone of muscles in pulmonary artery, which is
afterload for the right side of the heart. Normal = 100-250. Much lower than left side because left side
is a higher pressure system.
o Afterload increased by:
Hypertension
Vasoconstriction
Increased blood volume
Increased blood viscosity (sickle cell anemia)
Levophed/Dopamine
o Afterload decreased by:
Vasodilators – causes vessels to be floppy
Sepsis – causes massive vasodilation – SVR and afterload fall
Contractility
o The squeeze of the heart measure
o Measured using the EF (Ejection Fraction)
o EF measured by echocardiogram or in cath lab
o Normal EF = 55%. <50% in CHF, <30% serious trouble
o Increase contractility by positive inotropes:
Digoxin
Primacor
Inacor
Natracor
Dobutamine
o Decrease contractility by:
Negative inotropes
Beta blockers
CCBs
Hypoxia
Hypercapnia
Metabolic acidosis – caused by:
Not enough oxygen to tissues, go into anaerobic metabolism, end product is lactic
acid which causes lactic acidosis which is metabolic acidosis.
Mean Arterial Pressure (MAP)
o CO X SVR = MAP
o Usually use BP to figure: Systolic + Diastolic + Diastolic / 3 = MAP
Page 2 of 10
5-18-10
Cardiac output
o = HR X Stroke Volume
o Normal stroke volume in an adult = 60-70 cc
o CO – the volume of blood ejected from the LV over 60 seconds.
o Normal CO = 4 - 8 Liters/min
o 4 – 6 Liters/min at rest
o Increases with exercise because HR goes up
o A generic value that tells you for all people this is about normal
Cardiac Index
o CO divided by the body surface area of the patient in meters squared
o Specific to the individual
o Normal value = 2.2 – 4 Liters/min/m2
Stroke Volume
o How much output goes out of the heart with one beat (Normal 60-70 cc)
o Effected by preload, afterload, and contractility
Preload
o Priming of the heart – what is returning to right side of the heart.
o The filling pressure
o CVP (central venous pressure) or RA (right atrial pressure) - Measures the preload to the right side of
the heart. We are measuring the pressure in the superior vena cava or the right atrium. No valve
between these so pressure is the same. Normal = 2 – 5 mmHg (Really on low end)
o If this # has dropped, preload is low, which means they don’t have enough volume. Need to give
them more volume to increase preload.
o If # is high, they are volume high and in heart failure because there is too much returning to the heart.
o PAOP (Pulmonary artery occlusion pressure) or PAWP (Pulmonary artery wedge pressure) or PCWP
(pulmonary capillary wedge pressure) or the wedge. Measures the preload to the left side of the heart,
it is in the pulmonary system. Normal = 5 – 12 mmHg. Higher # because higher pressure system. Left
side of heart higher pressure than right side of heart.
o LVEDP (Left ventricular end diastolic pressure) Normal = 10 – 12 mmHg.
o The wedge we get with a PA catheter
o LVEDP they get in cath lab with invasive lines
o Increases preload:
Fluids
Blood
Albumin
Positioning (head down, feet up)
o Decrease preload:
Diuretics
Some vasodilators if they work on the venous side
Positioning (head up, feet down)
o CVP - if its low it’s because they are hypovolemic, early warning sign for bleeding or vasodilation, if
they diurese a lot their CVP will fall, also if we’ve rewarmed them after surgery (heating up too
quick).
Page 1 of 10
, o CVP too high: too much fluid or cardiac muscle can’t keep up with it, in heart failure, increases
oxygen demand.
Afterload
o The force the heart must overcome to pump blood out into the system or out into the pulmonary
system.
o SVR (Systemic vascular resistance) - Muscle tone in the arteries. Don’t want them to be floppy and
lose BP or clamped down so hard that the heart can’t get any blood out because its going against all
that pressure.
o Clamped down = SVR goes up
o Dilated = SVR goes down
o SVR is left sided afterload (systemically) Normal = 800-1400 dynes/sec/cm3
o SVRI – systemic vascular resistance index – divide SVR by body surface area. More specific to
patient Normal = 2000-2400 dynes/sec/cm3
o PVR (pulmonary vascular resistance) - Measures tone of muscles in pulmonary artery, which is
afterload for the right side of the heart. Normal = 100-250. Much lower than left side because left side
is a higher pressure system.
o Afterload increased by:
Hypertension
Vasoconstriction
Increased blood volume
Increased blood viscosity (sickle cell anemia)
Levophed/Dopamine
o Afterload decreased by:
Vasodilators – causes vessels to be floppy
Sepsis – causes massive vasodilation – SVR and afterload fall
Contractility
o The squeeze of the heart measure
o Measured using the EF (Ejection Fraction)
o EF measured by echocardiogram or in cath lab
o Normal EF = 55%. <50% in CHF, <30% serious trouble
o Increase contractility by positive inotropes:
Digoxin
Primacor
Inacor
Natracor
Dobutamine
o Decrease contractility by:
Negative inotropes
Beta blockers
CCBs
Hypoxia
Hypercapnia
Metabolic acidosis – caused by:
Not enough oxygen to tissues, go into anaerobic metabolism, end product is lactic
acid which causes lactic acidosis which is metabolic acidosis.
Mean Arterial Pressure (MAP)
o CO X SVR = MAP
o Usually use BP to figure: Systolic + Diastolic + Diastolic / 3 = MAP
Page 2 of 10
