applied physiology ii. circulation, haemodynamic support
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Applied physiology II. Circulation, haemodynamic support. Rudas László University of Szeged Department of Anaesthesiology and Intensive Care Medical ICU. The cardiovascular system provides appropriate oxygen and energy supply, via appropriate local circulation to the tissues. - PowerPoint PPT PresentationTRANSCRIPT
Applied physiology II.Circulation, haemodynamic
support
Rudas László
University of Szeged
Department of Anaesthesiology and Intensive Care
Medical ICU
The cardiovascular system provides appropriate oxygen and energy supply, via appropriate local circulation to the tissues.
Circulation consists of macrocirculation and microcirculation
Normal circulation requires:a pump, blood vessels, and normal blood volume
The „Pump”
Say kids!What does theheart generate?
Flow?
Pressure?
Both !
Stroke volume
Pre
ssu
re
Contractility
contractility
The role of contractility
contraktility elastance
Stroke volume
Art
eria
l pre
ssu
re
Arterial elastance
Stroke volume
Art
eria
l pre
ssu
re
elastance
Heart - circulation coupling
Stroke volume
Art
eria
l pre
ssu
re contractility
elastance
HeartCirculation
Coupling Systems
A different view,
(a different representation)
of the „Pump”
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
End-systolicPressure-volume relationship
End-diastolicPressure-volume relationship
Isometriccontraction
Isometricrelaxation
Ejection
Ventricular filling
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
End-systolicPressure-volume relationship
End-diastolicPressure-volume relationship
Isometriccontraction
Isometricrelaxation
Ejection
Ventricular filling
Sympathetic activation
Dyastolic function is dependent on both
normal active relaxation, and passive
distensibility.
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
End-systolicPressure-volume relationship
End-diastolicPressure-volume relationship
Isometriccontraction
Isometricrelaxation
Ejection
Ventricular filling
Systolic dysfunction
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
End-systolicPressure-volume relationship
End-diastolicPressure-volume
relationshipIsometriccontraction
Isometricrelaxation
Ejection
Ventricular filling
Diastolic dysfunction
The „Pump” and theconcept of „preload”
contractility
elastance
Stroke volume
Art
eria
l pre
ssu
re
The role of the end-diastolic volume
12840
5
10
15
20C
ard
iac
ou
tpu
l (l/m
in)
Right atrial pressure (mmHg)
Cardiac function curve
the good old Starling curve
The preload of a muscle strip
Length increase (mm)
0 2 4
Act
ive
ten
sion
(g)
0
4
8
For thick walled spheres=PR/2w
w=wall thicknessP=pressureR=radius
LaPlace formula
The preload is the wall stress of the ventricle prior to ejection.
Clinically it is characterized by the ventricular end-diastolic volume, and/or ventricular end-diastolic pressure.
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
End-systolicPressure-volume
relationship
End-diastolicPressure-volume
relationship
Isometriccontraction
Isometricrelaxation
Ejection
Ventricular filling
The role of the end-diastolic volume
Lef
t ven
tric
ular
pre
ssur
eThe markers of the preload
End-diastolic pressures
End-diastolic volume
Lef
t ven
tric
ular
pre
ssur
eThe markers of the preload
End-diastolic pressures
End-diastolic volume
Which marker is more reliable ??
End-diastolic pressures
End-diastolic volume
Factors to be considered:
1. The end-diastolic pressure-volume relationship is curvilinear.above a certain point monimal volum cshange is mirrored by considerable pressure elevation. The slope of the relatiomship changes from subject to subject
2. The left vantricular diastolic function is very sensitive to ischemia, and injury.Thus end-diastolic pressure may rise without volume change.
Lichtwarck-Aschoff et al. Intensive Care Med1992; 18:142-147
End-diastolic pressures
End-diastolic volume
Factors to be considered:
1. The end-diastolic pressure-volume relationship is curvilinear.above a certain point monimal volum cshange is mirrored by considerable pressure elevation. The slope of the relatiomship changes from subject to subject
2. The left vantricular diastolic function is very sensitive to ischemia, and injury.Thus end-diastolic pressure may rise without volume change.
3. End-diastolic pressure may be influenced by the fact, that left and right heart share location within the pericardial space. Dilation of the right ventricle, or pericardial fluid accumulation may also increases EDP.
Watch out for that kitty !!!
The vasculature
P V
pressure
Vol
um
e
Vascular compliance
3202401608000
1
2
3
4
Rel
atív
e vo
lum
e
241680
pressure (cm water)
AORTA VENA CAVA
Compliance
Intravascular
pressures
Factors to be considered:
1. Vessels could be considered as conduits, connecting the heartto the periphery.
2 Vessels, however are also elastic „containers”, and their capacity to blood is determined by their distending pressure.
3 Pressure could be generated by blood flowing through the tubes.
4 Certain amount of pressure could be also generated by „overstretching” the vessels,
5 The distensibility and the resistance characteristics of the vessels differ tremendously at different sites of the circulation
Arterial pressure generation
Cardiac output
Arterial pressure
The „Ohmic” resistance
Cardiac output 1
300
Cardiac output 2
P1 P2
Generated flow = cardial output (CO)
Generated pressure = mean art. pressure (MAP)– right atrial pressure (RAP)
Systemic Vascular Resistance (SVR = (MAP-RAP)/CO dimension: Hgmm/l/min
SVR index (SVRI) = (MAP-RAP)/CI dimension: Hgmm/l/min/m2
The „overstretching” of the vessels:
I. With „arrested circulation”
During circulatory arrest theblood volume
distrbute according to the distensibility of
the various vascular compartments, and
will exert a steady pressure on the walls.
That pressure is the mean vascular filling
pressure
Pms0 5 10 15 20
BloodVolume
% of control
0
100
Rothe et al. Arch Intern Med 146:977-82, 1986
3.5 l (50 ml/kg) „unstressed volume”
Venous Capacity
Pms0 5 10 15 20
BloodVolume
% of control
0
100
Rothe et al. Arch Intern Med 146:977-82, 1986
Sympathetic blockade
Noradrenalin
Venous Capacity
Pms0 5 10 15 20
BloodVolume
% of control
0
100
Rothe et al. Arch Intern Med 146:977-82, 1986
Sympathetic blockad
Noradrenalin
Reflex compensation range:15-20 ml/kg 1-1.5 l blood
Venous Capacity
Mean systemic filling pressure
During circulatory arrest theblood volume
distrbute according to the distensibility of
the various vascular compartments, and
will exert a steady pressure on the walls.
That pressure is the mean vascular filling
pressure
Circulatory arrest
During circulatory arrest the heart itself will distend as well. (The heart ismuch more compliant, than the arterial system).
The distension of the heart however is not proportional, (The right heart is much more complient than the left)
Intact circulation
Chamberlain D et al. Resuscitation 2008;77:10-15
Cardiac arrest: MRI series
Changes in ventricular volumes following arrest
Mean systemic filling pressure is the
prevailing pressure at the venus
capillary end, in normal basline
conditions it is around 8 mmHg.
The „overstretching” of the vessels:
II. With increasing cardiac output
„compliant ér”
„noncompliant ér”
How this applies
to the total circulation ?
Circulatory arrest Increasing CO
When generating cardiac output, the heart
Translocate blood from the venous compartment
To the arterial compartment
Circulatory arrest Increasing CO
Questions of venous return
- Peripheral passive regulation
Effect of Sympathetic Tone on Auto-Transfusion Splanchnic Regionfrom
Rothe et al. Arch Intern Med 146:977-82, 1986
Time (seconds)
Spl
anc
n i B
lood
Flo
w (m
/mi n
)
0 10 20
100
200
300
Arterial Inflow
Venous Outflow
Arterial Outflow Restriction
45 ml
Questions of venous return
- Peripheral active regulation
Effect of Sympathetic Tone on Auto-Transfusion Splanchnic Regionfrom
Rothe et al. Arch Intern Med 146:977-82, 1986
Time (seconds)
Sp
lan
cni
Bl o
od F
l ow
(m
/ mi n
)
0 10 20 0 10
100
200
300
Arterial Inflow
Venous Outflow
Arterial Outflow Restriction Splanchnic Nerve Stimulation
45 ml 71 ml
Questions of venous return
- Return to the heart
Venous return
Right atrial pressure
Venous return curve
100
Virolainen J. Eur Heart J 1995;16:1293-1299.
Influence of negative intrathoracic pressure on right atrial
and systemic venous drainage
DSA image „Müller manoeuvre” -40 Hgmm
DSA imagenormal inspiration
Right atrial pressure (mmHg)
Ven
ou
s re
turn
(l/
min
)
Car
dia
c o
utp
ut
(L/m
in)
Right atrial pressure (mmHg)
Apart from temporary fluctuations,
cardiac output and
venous return should be equal.
Right atrial pressure (mmHg)
Ven
ous
retu
rn (
l/min
)
/Car
dia
c ou
tpu
t (L
/min
)
The Guyton diagram
Right atrial pressure (mmHg)
Ven
ous
retu
rn (
l/min
)
/Car
dia
c ou
tpu
t (L
/min
)
The Guyton diagram
Cardiac function
- systolic function
contractility
preaload
afterload
heart rate
- diastolic function
structure of the myocardium
Questions of venous return
-Does the pump function
Influence venous return?
Cardiac output and right atrial pressure in pacemaker dependent dogs
Sheriff DD és Mendoza JR. Exerc Sport Sci Rev 2004;32:31-35
Pacemaker dependens alanyok perctérfogat és RAP összefüggései
Sheriff DD és Mendoza JR. Exerc Sport Sci Rev 2004;32:31-35
Pacemaker dependens alanyok perctérfogat és RAP összefüggései
Sheriff DD és Mendoza JR. Exerc Sport Sci Rev 2004;32:31-35
Circulatory arrest Increasing CO
Questions
of the „afterload”
The afterload is the wall stress of the ejecting ventricle.
Clinically it is characterized by the ventricular pressure generated during ejection. (it is certainly an oversimplification).
myocardial wall stress during systolic ejection
afterload
ventricular ventricular myocardial
systolic radius systolic pressure wall thickness
end diastolic radius output impedance normal growth, hypertrophy
systemic arterial pressure outflow tract resistance
diastolic pressure systolic pressure vascular resistance
obstructive CMP
blood volume pulse pressure
total peripheral resistance stroke volume
arterial complianceNorton, Advances in Physiology Education 2001;25:53-61
The abnormal distensibility of ther
conductance vessels (i.e. increased
stiffness), contributes to the
increased central arterial pressure
during ejection.
„Afterload mismatch”: a relative term
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
Lef
t ven
tric
ular
pre
ssur
e
Left ventricular volume
Everybody in the room
who knows 3 ways to increase
Cardiac output raise hand !!
Types of circulatory failure
- a szív csökkent pumpafunkciója - cardiogenic shock
- reduced venous return - hypovolaemic shock
- csökkent artériás tónus a véráramlás abnormális eloszlásával - distributive shock
- outflow obstruction - obstructive shock
Let’s put the puzzle together
(start with normal parameters)
In order to put the puzzle together, I had to
change
the directions of the axes
of certain traditional diagrams.
Do not panick!
Cardiac output
Arterial pressure
Systemic vascular resistance
Cardiac output 1
300
Cardiac output 2
Venous return
Right atrial pressure
Venous return curve
10
Cardiac output / Venous return
Right atrial pressureArterial pressure
Systemic vascular resistance
Cardiac output 1
300
Venous return curve
Cardiac output 2
10
Apart from temporary fluctuations, cardiac output and venous return should be equal.
Arterial pressure
Arterialvolume
300
Arterial compliance curve
Pressure in the great veins
Venousvolume
Venous compliance curve
10
Cardiac output / Venous return
Right atrial pressureArterial pressure
Arterialvolume
Venousvolume
2. Systemic vascular resistance
Cardiac output 1
300
artériás
3. Arterial compliance curve
vénás
4. Venous compliance curve
1. Venous return curve
Cardiac output 2
10
Cardiac output / Venous return
Right atrial pressureArterial pressure
Arterialvolume
Venousvolume
2. Systemic vascular resistance
Cardiac output 1
300
artériás
3. Arterial compliance curve
vénás
4. Venous compliance curve
1. Venous return curve
Cardiac output 2
10
Mechanisms of failure
Mechanisms of failure
Low cardiac output
Cardiac output / Venous return
Right atrial pressureArterial pressure
Arterialvolume
Venousvolume
Systemic vascular resistance
300
artériás
Arterial compliance curve
vénás
Venous compliance curve
Venous return curve
Cardiac output
10
Therapy ?
Limitations of the therapy ?
Mechanisms of failure
Decreased venous return- hypovolemia
Cardiac output / Venous return
Right atrial pressureArterial pressure
Arterialvolume
Venousvolume
Systemic vascular resistance
300
Arterial compliance curve
vénás
Venous compliance curve
Venous return curve
Cardiac output 2
10
Cardiac output / Venous return
Right atrial pressureArterial pressure
Arterialvolume
Venousvolume
Systemic vascular resistance
300
Arterial compliance curve
vénás
Venous compliance curve
Venous return curve
Cardiac output 2
10
Secunder systolic dysfunction
Therapy ?
Limitations of the therapy ?
Mechanisms of failure
Loss of vascular resistance
Cardiac output / Venous return
Right atrial pressureArterial pressure
Arterialvolume
Venousvolume
Systemic vascular resistance
300
artériás
Arterial compliance curve
vénás
Venous compliance curve
. Venous return curve
10
Therapy ?
Diastolic heart failure is suspected in cases
where clinical signs of decompensation are
present, in spite of preserved systolic
function (EF≥50%).
(The diagnosis could be further confirmed by
echocardiography).
myocardial end-diastolic wall stress
preload
end-diastolic end-diastolic myocardial wallradius filling pressure thickness
compliance of total blood volume normal growthventricle and blood volume distribution hypertrophypericardium venous compliance
venous return
Norton, Advances in Physiology Education 2001;25:53-61