Anaesthesia

1. Prof. Jean-Louis TEBOUL
Medical ICU
Bicetre hospital
University Paris-Saclay
France
Basic cardiovascular physiology
What does the intensivist need to know?

2. 2- Mean systemic filling pressure and venous return
1- Cardiac function
Basic hemodynamic physiology

3. Stroke
volume
Ventricular preload
preload responsiveness
preload unresponsiveness
Frank-Starling curve = cardiac systolic function curve

4. Stroke
volume
Ventricular preload
normal heart
failing heart
.
preload responsiveness
preload unresponsiveness
Frank-Starling curve = cardiac systolic function curve

5. LV end diastolic volume
LV end diastolic pressure
A
B
C
D
LV diastolic function curve

6. normal LV compliance
reduced LV compliance
A
C
B
LV end diastolic pressure
LV diastolic function curve
LV end diastolic volume

7. Stroke
volume
Ventricular preload
LVEDP
preload
unresponsiveness
Giving fluid in preload-unresponsive patients
not only does not increase stroke volume
but also increases the LVEDP, and then
the risk of pulmonary edema formation
Importance to identify preload unresponsive pts
before any fluid administration
using dynamic indices of preload responsiveness

8. 2- Mean systemic filling pressure and venous return
1- Cardiac function
Basic hemodynamic physiology

9. Venous return = (Pms – RAP) / Resistance to venous return

10. Mean systemic pressure
is the upstream pressure for venous return
<
Mean systemic pressure is a marker of the effective blood volume
Venous return = (Pms – RAP) / Resistance to venous return

11. According to the Guyton’s model, the systemic venous return
is proportional to the pressure gradient for venous return
and inversely related to the resistance to venous return
Mean systemic pressure, which is a virtual pressure considered to
lie at the level of the venules, is positively related to stressed blood
volume and negatively related to vascular compliance
The pressure gradient for venous return is the difference
between the mean systemic pressure and the right atrial pressure
Capillary
bed
Venules
Veins
Arterioles
Arteries
Pms

12. The stressed blood volume, which represents 30-40 % of the total
blood volume, is hemodynamically active and thus participates in
venous return through its impact on mean systemic pressure.
The unstressed blood volume, which represents 60-70 % of the total
blood volume, is hemodynamically inactive and serves as a blood
reservoir that can be mobilized and be converted to stressed blood
volume under some critical conditions.

13. normal venous return curve
equilibrium point
decreased cardiac contractility
normal cardiac function
increased cardiac
adrenergic activity
Venous return and cardiac output are equal at steady-state
Right atrial pressure
venous return
Cardiac output or
mean systemic pressure

14. • Effects of fluid infusion
Main implications for shock resuscitation

15. Effects of fluid infusion
• Fluid infusion should not affect the Starling curve, as it is expected
not to change cardiac systolic function
• Fluid infusion should increase the mean systemic pressure

16. Pms
at baseline
Pms
after fluid
VR curve
at baseline
VR curve
after fluid
CI
(L/min/m2)
Mean systemic pressure was estimated by end-expiratory and end-inspiratoy occlusion manoeuvres

17. Effects of fluid infusion
• Fluid infusion should not affect the Starling curve, as it is expected
not to change cardiac systolic function
• Fluid infusion should increase the mean systemic pressure
… regardless of the presence of preload responsiveness

18. VR curve
at baseline
VR curve
after fluid
VR curve
at baseline
VR curve
after fluid
in case of preload unresponsiveness
in case of preload responsiveness
The mean systemic pressure increases after fluid infusion
in all cases (preload responsiveness as well as preload unresponsiveness)

19. Effects of fluid infusion
• Fluid infusion should not affect the Starling curve, as it is expected
not to change cardiac systolic function
• Fluid infusion should increase the mean systemic pressure
…. regardless of the presence of preload responsiveness
• … But fluid infusion should increase the venous return pressure
gradient only in case of preload responsiveness

20. Pms2
Pms1
CVP1 CVP2
Effects of fluid infusion in case of preload responsiveness
venous return
Cardiac output or
Increase in the venous return pressure gradient (Pms - CVP) and CO

21. *
Pms - CVP

22. Pms2
Pms1
CVP1 CVP2
venous return
Cardiac output or
No benefit in terms of CO but risks of increase in CVP at too high levels
No Increase in the venous return pressure gradient (Pms - CVP) and in CO
Effects of fluid infusion in case of preload unresponsiveness

23. *
The venous return pressure gradient increased
only in preload responsive patients
Pms - CVP Pms - CVP

24. Effects of fluid infusion
• Fluid infusion should not affect the Starling curve, as it is expected
not to change cardiac systolic function
• Fluid infusion should increase the mean systemic pressure
regardless of the presence of preload responsiveness
• … But fluid infusion should increase the venous return pressure
gradient only in case of preload responsiveness
• Fluid infusion should thus increase cardiac output only in case of
preload responsiveness

26. • Effects of fluid infusion
• Effects of dobutamine
Main implications for shock resuscitation

27. Effects of dobutamine
• Dobutamine should affect the Starling curve, as it is expected
improve the cardiac systolic function (β1 effect).

28. normal venous return curve
equilibrium point
normal cardiac function
increased cardiac
adrenergic activity
with dobutamine
Right atrial pressure
venous return
Cardiac output or
mean systemic pressure
Dobutamine should increase CO
decrease RAP

29. Cardiac index L/min
RAP mmHg
2.4 ± 0.3 2.8 ± 0.3*
10 ± 1 7 ± 1*
Pre-dobutamine Dobutamine

30. • Dobutamine should affect the Starling curve, as it is expected
improve the cardiac systolic function (β1 effect).
• Dobutamine should not change the mean systemic pressure
Effects of dobutamine

31. normal venous return curve
equilibrium point
normal cardiac function
increased cardiac
adrenergic activity
with dobutamine
Right atrial pressure
venous return
Cardiac output or
mean systemic pressure
Dobutamine should increase CO
decrease RAP
not change the Pms

32. Cardiac index L/min
RAP mmHg
Mean systemic pressure mmHg
2.4 ± 0.3 2.8 ± 0.3*
10 ± 1 7 ± 1*
15 ± 2 14 ± 3
Pre-dobutamine Dobutamine

33. normal venous return curve
equilibrium point
normal cardiac function
increased cardiac
adrenergic activity
with dobutamine
Right atrial pressure
venous return
Cardiac output or
mean systemic pressure
Dobutamine should increase CO
decrease RAP
not change the Pms
increase the pressure gradient for venous return

34. Cardiac index L/min
RAP mmHg
Mean systemic pressure mmHg
Pressure gradient for VR mmHg
2.4 ± 0.3 2.8 ± 0.3*
10 ± 1 7 ± 1*
15 ± 2 14 ± 3
6 ± 1 8 ± 2*
Pre-dobutamine Dobutamine

35. • Effects of fluid infusion
• Effects of dobutamine
• Effects of norepinephrine
Main implications for shock resuscitation

36. • Norepinephrine should increase the mean systemic pressure
and thus potentially the venous return (as fluid infusion does)
Effects of norepinephrine

37. • NE increases cardiac preload
• NE increases CO in preload-dependent patients
• NE reduces the degree of preload-dependency
Messages of these two studies
… as fluid infusion does
How does NE impact the venous circulation?
by blood redistribution
from unstressed to stressed volume?
Crit Care Med 2011; 39:689-694

38. 10
CI
(L/min/m²)
CVP
(mmHg)
3
2
1
0
20 40
30
22
32
Experimental points and linear regression line
before the decrease in the dose of norepinephrine.
4
Experimental points and linear regression line
after the decrease in the dose of norepinephrine.
Figure 2
CI
L/min/m2
CVP mmHg
Mean Systemic Pressure
with NE

39. 10
CI
(L/min/m²)
CVP
(mmHg)
3
2
1
0
20 40
30
22
32
Experimental points and linear regression line
before the decrease in the dose of norepinephrine.
4
Experimental points and linear regression line
after the decrease in the dose of norepinephrine.
Figure 2
CVP mmHg
CI
L/min/m2 with NE
before NE
32
22
NE increases both
the Pms and
the resistance to VR

40. with NE
before NE

41. with NE
before NE
In spite of an increase in venous resistance,
venous return increases with NE
through an increase in Mean Systemic Pressure
related to blood redistribution
from unstressed to stressed volume

42. • Norepinephrine should increase the mean systemic pressure
and thus potentially the venous return (as fluid infusion does)
• Norepinephrine should increase the cardiac contractility (β1 effect)
and improve CO (Frank-Starling)
Effects of norepinephrine

43. before NE with NE before NE with NE
In spite of the increase in blood pressure (LV afterload),
all the indices of cardiac systolic function improved with NE
suggesting an improved cardiac contractility
SAP 85 (25) 124 (15)

44. Potential mechanisms:
• Effect on myocardial β1 receptors not yet down-regulated at the early phase
• Increase in coronary perfusion pressure (through increase in DAP)
before NE with NE

45. PRA
Pms2
Pms1
Pra1 Pra2
venous return
Cardiac output or
Increase in contractility
Increase in stressed blood volume
and Pms
Increase in resistance to venous return
Increase in
cardiac output
minor increase
in PRA and CVP
Effects of norepinephrine

46. 2- Mean systemic filling pressure and venous return
1- Cardiac function
Basic hemodynamic physiology

47. Thank you