Applied physiology II. Circulation, haemodynamic support

1. Applied physiology II.Circulation, haemodynamic support Rudas László University of Szeged Department of Anaesthesiology and Intensive Care Medical ICU

2. 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

3. The „Pump”

4. Say kids! What does the heart generate?

5. Flow ?

6. Pressure ?

7. Both !

8. Contractility contractility Pressure Stroke volume

9. The role of contractility contraktility elastance Arterial pressure Stroke volume

10. Arterial elastance Arterial pressure elastance Stroke volume

11. Heart - circulation coupling contractility elastance Arterial pressure Stroke volume

12. Coupling Systems Heart Circulation

13. A different view, (a different representation) of the „Pump”

14. End-systolic Pressure-volume relationship End-diastolic Pressure-volume relationship Ejection Left ventricular pressure Isometric contraction Isometric relaxation Ventricular filling Left ventricular volume

15. Sympathetic activation End-systolic Pressure-volume relationship End-diastolic Pressure-volume relationship Ejection Left ventricular pressure Isometric contraction Isometric relaxation Ventricular filling Left ventricular volume

16. Dyastolic function is dependent on both normal active relaxation, and passive distensibility.

17. Systolic dysfunction End-systolic Pressure-volume relationship End-diastolic Pressure-volume relationship Ejection Left ventricular pressure Isometric contraction Isometric relaxation Left ventricular volume Ventricular filling

18. Diastolic dysfunction End-systolic Pressure-volume relationship Ejection End-diastolic Pressure-volume relationship Left ventricular pressure Isometric contraction Isometric relaxation Ventricular filling Left ventricular volume

19. The „Pump” and the concept of „preload”

20. The role of the end-diastolic volume contractility elastance Arterial pressure Stroke volume

21. 20 15 10 5 0 4 8 12 Cardiac function curve Cardiacoutpul (l/min) the good old Starling curve Right atrial pressure (mmHg)

22. The preload of a muscle strip

24. LaPlace formula For thick walled spheres =PR/2w w=wall thickness P=pressure R=radius

25. 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.

26. The role of the end-diastolic volume End-systolic Pressure-volume relationship Ejection Left ventricular pressure Isometric contraction Isometric relaxation End-diastolic Pressure-volume relationship Ventricular filling Left ventricular volume

27. The markers of the preload Left ventricular pressure End-diastolic pressures End-diastolic volume

28. The markers of the preload Which marker is more reliable ?? Left ventricular pressure End-diastolic pressures End-diastolic volume

29. Factors to be considered: • 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 • The left vantricular diastolic function is very sensitive to ischemia, and injury. • Thus end-diastolic pressure may rise without volume change. End-diastolic pressures End-diastolic volume

30. Lichtwarck-Aschoff et al. Intensive Care Med1992; 18:142-147

31. End-diastolic pressures End-diastolic volume • Factors to be considered: • 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 • The left vantricular diastolic function is very sensitive to ischemia, and injury. • Thus end-diastolic pressure may rise without volume change. • 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.

32. Watch out for that kitty !!!

33. The vasculature

34.  V  P Vascular compliance Volume pressure

35. 4 3 2 1 0 0 8 16 24 0 80 160 240 320 Compliance Relatíve volume AORTA VENA CAVA pressure (cm water)

36. Intravascular pressures

37. Factors to be considered: • 1. Vessels could be considered as conduits, connecting the heart • to the periphery. • Vessels, however are also elastic „containers”, and their capacity to blood is determined by their distending pressure. • Pressure could be generated by blood flowing through the tubes. • Certain amount of pressure could be also generated by „overstretching” the vessels, • The distensibility and the resistance characteristics of the vessels differ tremendously at different sites of the circulation

38. Arterial pressure generation

39. The „Ohmic” resistance Cardiac output Cardiac output 2 Cardiac output 1 300 P1 P2 Arterial pressure

40. 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

41. The „overstretching” of the vessels: I. With „arrested circulation”

42. 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

46. Blood Volume % of control Venous Capacity 100  3.5 l (50 ml/kg) „unstressed volume” 0 0 5 10 15 20 Pms Rothe et al. Arch Intern Med 146:977-82, 1986

47. Blood Volume % of control Venous Capacity Sympathetic blockade 100 Noradrenalin 0 0 5 10 15 20 Pms Rothe et al. Arch Intern Med 146:977-82, 1986

48. Blood Volume % of control Venous Capacity Sympathetic blockad Noradrenalin 100 Reflex compensation range: 15-20 ml/kg  1-1.5 l blood 0 0 5 10 15 20 Pms Rothe et al. Arch Intern Med 146:977-82, 1986

49. Mean systemic filling pressure

50. 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