Immune system and inflamatory response to cpb(1)

1. IMMUNE SYSTEM ANDIMMUNE SYSTEM AND
INFLAMMATORY RESPONSESINFLAMMATORY RESPONSES
TO CARDIOPULMONARYTO CARDIOPULMONARY
BYPASSBYPASS
Manu Jacob
Perfusionist
KMCT MCH

2. Immune System – in briefImmune System – in brief
Offers protection to organs from
pathalogical insults
Comprises two fundamental features
 Acquired
Innate
The result is inflammatioin

3. Innate SystemInnate System
Phagocytic cells
Neutrophils
Monocytes
Machrophages
Natural killer cells
Endothelial
cells
Soluble factors
Complement
Cytokines
Chemokines
protiens

4. Acquired SystemAcquired System
Memory of prior exposure and recognition
of specific antigens are key features.
There is considerable overlap b/w the two
types.
T lymphocytes B Lymphocytes

5. Factors initiating/aggravatingFactors initiating/aggravating
inflamatory response duringinflamatory response during
cpbcpb
Contact of blood with CPB circuit.
Ischemia
Reperfusion phenomena
Hypoperfusion of various organs during
periods of CPB.
Relative anemia
Anticoagulants

6. What happens?What happens?
1. CPB activates both innate and acquired
system mounting a complex
inflammatory response.
2. CPB induces cellular and humoral
constituents of immune system.
3. This leads to a temporary immuno
deficiency.

7. The systemic inflamatoryThe systemic inflamatory
response to CPBresponse to CPB
Definition:-
Systemic inflamatory response in
general and more specifically in the
context of CPB

9. Copyright ©2006 The Society of Thoracic Surgeons
Kozik D. J. et al.; Ann Thorac Surg 2006;81:S2347-2354S
An overview of the inflammatory response to cardiopulmonary bypass

10. Systemic InflamatorySystemic Inflamatory
Response Syndrome.(SIRS)Response Syndrome.(SIRS)
SIRS is diagnosed if the fallowing conditions
Are met.
1. Body temperature b/w 36deg to 38 deg
C.
2. HR > 90beats/min.
3. Respiratory rate more than 20/mts.
4. Paco2 < 32 mmhg
5. Leukocyte count > 12000cells/mm3 or
< 4000mm3.

11. SIRS contd.,SIRS contd.,
CPB produces “whole-body” inflamatory
response.
The “Post bypass” syndrome is also
known as the “Systemic Inflamatory
response After Bypass”.(SIRAB)

12. Clinical manifestations of SIRABClinical manifestations of SIRAB
A spectrum of injury that includes one or
more of the fallowing
 Pulmonary,GUT,renal CNS,mycocardial
dysfunction.
 Coagulopathy
 Pyrexia
 Increased susceptibility to infection and
leukocytosis.

13. SIRAB contd.,SIRAB contd.,
Systemic inflamatory response is induced
in all patients undergoing CPB.
Severity of response varies.
Only minority develops severe
homodynamic changes or organ failure.
The response is not predictable.
The length of cpb is frequently but not
necessarily regarded as a risk factor.

14. SIRAB contd.,SIRAB contd.,
SIRAB accounts for substantial morbidity
in pediatric surgery, aged and in patients
undergoing complex surgical procedure.

15. Initiation of SIRABInitiation of SIRAB
SIRAB is initiated by the contact of
blood with foreign surface of ECC.
Altered arterial blood flow patterns.
Shear stress generated by blood
pumps.
Cardiotomy suction devices. (including
intra cardiac venting)
Tissue ischemia and reperfusion.
Hypothermia, relative anemia.

16. Initiation of SIRAB contd.,Initiation of SIRAB contd.,
Anticoagulation agents used during CPB.
This response may continue even after
discontinuation of CPB.

17. What SIRAB does?What SIRAB does?
It generates micro emboli.
Cytokine mediated response take place.
This activates vascular endothelium.
This aggravates neutrophil mediated
injury.

18. How?How?
Repeated passage of blood through non
physiological ECC leads to contact
activation response.
Four protiens are involved in contact
activation cascades.
1)Coagulation factors xii & xi
2)Prekallikerein
3)High molecular wt
kininogen (HMWK)

19. The Coagulation CascadeThe Coagulation Cascade
PL
XI
IXa
VIIIa
Intrinsic
XII
XIa
XIIa
HMWK
XI
Extrinsic
Tissue Factor + VII
TF-VIIa
PL
II
Common Pathway
Xa
Va
PL
X
Thrombin
(IIa)
Fibrinogen Fibrin
Clot
XIIIa
XIII

20. Contact Activation in CPBContact Activation in CPB
Negatively Charged
Surface
Plasma
Coagulation
HMWK
Bradykinin
Complement Activation
Fibrinolysis
Impaired
Platelet
Function
Factor XII Factor XIIa
Kallikrein
Plasminogen Plasmin
Prekallikrein
Systemic Inflammatory Response

21. Kinin MechanismKinin Mechanism
 Increased vascular
permeability
 Vasodilatation
 Smooth muscle
contraction
 Inflammation,
phagocytosis
 Pain
 Tissue Repair
Negatively
Charged Surfaces
Inflammatory response and wound healing
Bradykinin
HMWK
Kallikrein Prekallikrein
Factor XII Factor XIIa
Factor XIIa
Fragments

22. HOW? CONTD.,HOW? CONTD.,
The end result is
a) Formation of bradykinin
b) conversion of plaminogen into
plasmin
This initiates fibrinolysis.
May trigger complement cascade.
None of the events occurs in isolation but
simultaneously.

23. The cellular components ofThe cellular components of
bloodblood
Red blood cell.
1. The ecc alters the integrity and function
of RBC.
2. Shear forces causes mechanical damage
to rbcs
3. This reduces rbc deformability and alters
microcirulation
4. Consequence of membrane distortion
rbcs are susceptible to membrane leaks.

24. RBC contd.,RBC contd.,
5) Free hb in plasma is damaging to tissue
function by increasing plasma onc.
pressure and viscosity
6) Cytotoxic o2 free radicals are also
released after auto oxidation of Hb.
7) Adenosine dyphosphate released from
red cells may alter the platelet function
and their ability to contribute to
hemostasis.

25. RBC contd.,RBC contd.,
8) Arrythmias may develope as a
result of k+ release from rbcs.
9) Hemodilution reduces the ability of rbcs
to aggregate triggering pathways
leading to endothelial activation and
compromising tissue oxygenation.

26. Vascular endotheliumVascular endothelium
Vascular endothelium is extremely sensitive to
stimulation associated with cpb such as
1. Hypoxia
2. Surgical manipulation.
3. Cpb also reduces the ability of the endothelium to
produce factors important for promoting vascular
patency and the prevention of thrombosis such
as
Nitric oxide (NO) Prostacyclin and adenosin
.

27. vascular contd.,vascular contd.,
The production of vasoactive factors such
as endothelin and angiotensin is increased
leading to vasomotor and organ
dysfunction.

28. LeukocytesLeukocytes
The recruitment of leukocytes from the
circulation to an inflamatory site is a
multistep process.
CPB activates vascular endothelium
leading to a cascade similar to
complement activation.

29. NeutrophilsNeutrophils
Neutrophil activation and its cytotoxic
capability are an essential aspect of
body’s ability to fight infection.
Neutrophil activation through interaction
with activated vascular endothelium may
be responsible for clinical sequel of SIRAB
The process of neutrophil activation, firm
adhesion and sequestration can lead to
obstruction of capillaries and local
ischemia.

30. Neutrophil contd.,Neutrophil contd.,
The release of cytotoxic products by
activated cells can cause direct cellular
damage.
These cytotoxins present in granules of
neutrophils and newly synthesized molecules.
There are two forms of neutrophil granules
1) Primary azurophilgranules
(predominantly inracellular role)
2) Secondary(extracellular role)

31. Neutrophils contd.,Neutrophils contd.,
These neutrophils synthesize novel substances
including leukotrienes and reactive oxygen
intermediates.
This synthesis is readily detected by dramatical
increase in O2 consumption of cells.
They are largely responsible for ischemia/
reperfusion injury.
Ishemic injury occurs when blood supply to the
tissue is suboptimal during CPB.
The parodox is that a more severe tissue injury
occurs when blood flow is restored upon
reperfusion

32. How reperfusion injury occurs?How reperfusion injury occurs?
1. Anaerobic metabolism results in lactic
acid production and altered cellular
homeostasis with the loss of ion
gradient across cell membranes.
2. Reperfusion injury is initiated by a series
of biochemical events that result in the
generation of reactive oxygen
metabolites.
3. Reduction of oxygen leads to the
produciton of the superoxide anion.

33. How reperfusion contd.,How reperfusion contd.,
4) Superoxide anion penetrates through
cell membrane and gets converted into
more toxic oxygen species
(Hydrogen peroxide,hydroxil radical)
5) The family of reactive O2 intermediates
extends its toxic effect by being highly
reactive agents.
6) This leads to disruption of cellular
function
and eventually cell death.

34. MonocytesMonocytes
These are another type of leukocytes
involved in the systemic inflammatory
process.
Upon migration to tissue they become
tissue macrophages which participates in
both specific and non specific immune
pathways.
Upon activation they play a pivotal role in
inflammation.
Machrophages can exhibit both pro and
anti inflammatory properties depending on
the signal they receive from cells.

35. PlateletsPlatelets
1) CPB decreases platelets function and
count causing derangement in
postoperative heamostasis.
2) Numerous factors associated with cpb
contributes to the platelet changes.
3) Physical factors such as hypothermia
and shear stress.
4) Exposure to artificial surfaces.
5) Hemodilution from priming fluids.

36. Platelets contd.,Platelets contd.,
6) All this contributes to early
thrombocytopenia.
7) Mechanical disruption,adhesion to ecc
and sequestration in organs can cause
a drop in platelet count by 30 to 50%.
8) The response of platelets to cpb is
complex,multifactorial and includes
platelets consumption during cpb.
9) Morphological changes including
spherical appearance and development
of pseudopods as a result of cpb.

37. Platelet ActivationPlatelet Activation
Vascular Injury &
Endothelial Damage
Collagen
Exposure
Platelets
Plasma
Coagulation
Adherence
Aggregation
Platelet Plug
TXA2
Vasoconstriction
Release
Serotonin
ADP
Thrombin
In Presence
of vWF
PF3-Platelet Factor 3

38. Platelets contd.,Platelets contd.,
10) Bleeding time is prolonged after cpb
and is directly relatead to the time
of cpb.
11) Precise mechanism is not clear.
12) Activated platelets attach to
vascular endothelium and cause
neutrophil adhesion and
transmigration.

39. Coagulation cascade
Intrinsic Pathway Extrinsic Pathway
Surface contact Tissue factor
XII XIIa VII VIIa rFVIIa
XI XIa
IX IXa
VII VIIa
X Xa
V Xa
II IIa(Thrombin)
I Ia (Fibrin)

40. Coagulation contd.,Coagulation contd.,
CPB results in the activation of both
clotting and fibrinolysis pathways.
CPB results in increased fibrinolytic
activity caused by elevated levels of factor
xiia and kallikerin and has been linked to
increased postoperative bleeding time,
blood loss, and reduction in platelet
adhesion and aggregation capabilities.

41. Humoral components of bloodHumoral components of blood
The deletrious effect of cpb were secondry to the
exposure of blood to non-endothelial surfaces in
the bypass circuit.
This initiates a whole body inflammatory
response.
This response was characterised by
a) Activation of coagulation system.
b) Kallikerien system.
c) Fibrinolysis
d) Complement activation.

42. Complement System(C)Complement System(C)
Important immunological mechanism in
the inflammatory process.
Consist of more than 30 protiens.
Functions include
a) Meditating inflammation.
b) opsonization of antigenic
particles.
c) Causes membrane damage to
pathogens.

43. Complement system contd.,Complement system contd.,
Product of one reaction forms the enzyme
for the next.
Initial stimulus can trigger a cascade of
activity with consequent biologic
activation and amplification.
5% to 10% of serum protiens are
complement components.
Nearly half the proteins in the
complement system are regulatory
molecules

44. ComplementComplement
 Cascade of enzymatic
reactions
 Complement activation
◦ Foreign substances
(bacteria & viruses)
◦ Components of the
cardiopulmonary bypass
system
◦ Materials used in the
collection and processing
of autologous blood
◦ Damaged red blood cells
- blood recovered from
the operative site for
autotransfusion
 Activation results in:
◦ Macromolecular attack
complex
◦ Cell destruction and
inflammatory response

45. The complement pathwaysThe complement pathways
Classical lectin alternative
Pathway pathway pathway
Terminal pathway
Membrane attack complex
(MAC)
SIRAB

46. Classical pathwayClassical pathway MBL PathwayMBL Pathway AlternativeAlternative
PathwayPathway
C1q Binding to antigenC1q Binding to antigen MBL Binding toMBL Binding to C3 BreakdownC3 Breakdown
antibody complexantibody complex OligosaccharidesOligosaccharides
C1C1 C1C1 MBL active MBL inactiveMBL active MBL inactive C3b + C3aC3b + C3a
inactiveinactive activeactive complex complexcomplex complex
surface- bound C3bsurface- bound C3b
C4 C4b + C4bC4 C4b + C4b
FactorBFactorB
C2C2 C3bBC3bB
Factor DFactor D
C4b2C4b2 C3bBb + BaC3bBb + Ba
Properdin(P)Properdin(P)
C4b2aC4b2a C3bBbPC3bBbP
Terminal PathwayTerminal Pathway C3 ConvertaseC3 Convertase

47. Terminal parthwayTerminal parthway C3 ConvertaseC3 Convertase
C3 C3a + C3bC3 C3a + C3b
C5 ConvertaseC5 Convertase
C5 C5b + C5aC5 C5b + C5a
C6C6
C7C7
C8C8
C5b678C5b678
C9C9
C5b678(9)nC5b678(9)n
MACMAC

48. Complemant Pathway(fig)Complemant Pathway(fig)
Each pathway consist of inactive protiens
that upon activation activates the next
protien in the pathway.

50. Membrane Attack ComplexMembrane Attack Complex
MAC forms a transmembrane channel that
allows the influx of ions and water into the
cell.
The cells become unable to maintain
osmotic and chemical equilibrium.

51. Effects of activation of theEffects of activation of the
complement system.complement system.
Produces anapylotoxins C3a,C4a and C5a
The molecules act on mast cells and
basophils leading to their degranulation
and release of inflammatory mediators.
They also directly act on smooth muscles
and endothelium leading to muscle
contraction and increased vascular
permiability.

52. Contd.,Contd.,
C5a acts as a chemotactic and activating
agents for neutrophils and other myeloid
cells.
This leads to free radical production and
release of lysosomal enzymes.
There is breakdown of C4b and C3b
They are involved in opsonization of
complement coated particles and
clearance of immune complexes

53. When complementWhen complement
activation is observed?activation is observed?
It is observed shortly after CPB mainly
through the alternate pathway.
It is induced by blood contact with non
physiologic surface.
Later by ischemia reperfusion and
protamine administration.

54. When Complement contd.,When Complement contd.,
Heparin-protamine complex can further
activate the complement through the
classical pathway.
This inturn causes cellular damage
endothelial cell and leukocyte
activation,histamine release,increased
vascular permiability and generalised
inflammatory response.

55. Other contributions to SIRABOther contributions to SIRAB
1. Cardigenic shock.
2. Endotoxemia.

56. Cardiogenic shockCardiogenic shock
Prolonged non pulsatile perfusion or
periods of circulatory arrest lead to end
organ ischemia.
End-organ hypoxic insult results in
cytokines and oxygen free radical release.
When reperfusion is initiated ischemic
reperfusion injury results.

57. EndotoxinEndotoxin
It is frequently detected in high conc. in
systemic circulation after cpb.
It is a potent stimulant of both
complement and of endothelial cell
activation.
Precise mechanism of release is not clear
but may derive from a translocation of
bacteria from the gut resulting from
sytemic stress of cpb.
Endotoxin is associated with profound fall
in svr after cpb.

58. Immune response after CPBImmune response after CPB
Immune deficiency and CPB
1. Cardiac surgeries are highly immuno
suppressive.
2. Infections are directly related to duration of
cpb.
3. The immunosupression is also related to
volume of blood transfused
4. The quatitative and qualitative exhaustion of
humoral and cell mediated mechanisms may
have an adverse effect.
5. Sepsis related multiorgan failure can occur in
patients experiencing one or more
complications for example renal failure or low
cardiac output.

59. Humoral immunityHumoral immunity
After cpb there is reduced opsonization of
bacteria.(due to decrease in
immunoglobuliins and complements)
Leuckocyte count fall with the onset of
cpb.
Leukocytes sequesteration in tissue is
increased after their activation by
anaphylotoxins C3a and C5a.

60. Humoral immunity contd.,Humoral immunity contd.,
The secretion of IgG, IgM and IgA by B is
diminished after cpb.
The bacteriocidal activity of serum is
decreased after cpb.
Complement is consumed and all
components of humoral immunity are
decreased due to hemodilution during
cpb.
Immune protiens are denatured due to
their exposure to gaseous and foreign
surface.

61. Natural killer cellsNatural killer cells
They are heterogenous subpopulation of
lymphoid cells.
They produce cytotoxic responses in virus
infected cells.
CPB decreases both the number and
function of natural killer cells.

62. Reticulo endothelialReticulo endothelial
systemsystem
 It is made up of tissue macrophages in
the spleen, lymphnodes, lung and liver.
The normal function of reticuloendothelial
system includes cleaning of bacteria,
endotoxins, platelets, denatured proteins,
plasma hemoglobin, thrombin, fibrin
degradation products, thromboplastin and
plasminogen activator from the circulating
blood.

63. Reticulo endothelialReticulo endothelial
systemsystem contd.,contd.,
CPB depresses the function of reticulo
endothelial system.
This results in increase of microparticles
generated by cpb.

64. T cellsT cells
T cells are lymphocytes that develops in
thymus.
T cells differentiate into two major
peripheral subsets.
1) CD4+ (helper cells)
2) CD8+ (cytotoxic cells)
T helper cells are further differentiated
into TH1 and TH2.

65. T cell contd.,T cell contd.,
T helper cells plays a key role in the
initiation and regulation of acquired
immune response.
Electron microscopic study after cpb
shows profound alterations in plasma
membrane of T cells.
High level of cortisol plays a role in
immunosuppression.

66. T cells contd.,T cells contd.,
Elevation of serum corticosteroids may
cause a decrease in circulating T-cell
levels.
Hemodilution, fluid shifts b/w
extravascular and intravascular
compartments, mechanical destruction
and consumption and T-cell redistribution
are the other likley causes.

67. How to minimize SIRAB?How to minimize SIRAB?
Maintaining an optimal cardiac output
after cpb increases the clearance of
inflammatory protiens and mediators.
Better myocardial preservation and organ
perfusion reduces to some extend the
deletrious effect of humoral activation.
Ideal strategy would be to develop a cpb
system that does not produce contact
activation of blood components.

68. PharmacologicalPharmacological
manipulationsmanipulations
No one single pharmacologic agent can
inhibit effectively all aspects of the
system.
Corticosteroids.
Aprotinin( banned from 2006 due high
incidence of stroke,heart attack and
kidney failure)

69. corticosteroidscorticosteroids
They possess anti-inflammatory
properties
They inhibit the formation of C3 & C5
convertases in vitro
Conflicting reports about their efficacy
during CPB
More potent inhibitor of classical pathway
than alternative pathway

70. Corticosteroids contd.,Corticosteroids contd.,
It can also inhibit leukocyte recruitment,
formation of enzyme for converting
plasminogen into plasmin
This decrease formation of
proinflammatory mediators
Unable to prevent postop decrease in
pulmonary compliance.
Increases the susceptibility to infection by
promoting immunocompromised state

71. Aprotinin (trasylol)Aprotinin (trasylol)
Seine protease inhibitor isolated from
bovine lung.
It inhibits several proteinases, including
trypsin,plasmin,kallikrein and thrombin.
It is effective in reducing bleeding after
cardiac surgery.
It preserves platelet function.

72. Neutrophil activationNeutrophil activation
remodellingremodelling
The prevention of neutrophil activation
would be usefull in preventing SIRAB.
Low temperature reduces adherence of
neutrophils to the endothelium.
The use of monoclonal antibodies has
shown to block neutrophil recuitment in
experimental system.

73. contd.,contd.,
Use of cyclooxygenase inhibitors and
cytokine receptor antagonist results in
inhibition of T and B-cell proliferation and
lymphokine generation.
Gene transfer stratagies using viral or
nonviral method to block signaling
pathway are also being tested.

74. Use of steroidsUse of steroids
High dose methylprednisolone (30mg/kg)
at the time induction reduces complement
activation

75. MechanicalMechanical
manipulationsmanipulations
Conducting CUF and MUF reverses
hemodilution and decreases tissue edema
and circulating inflammatory mediators.
Reducing the number of circulating
leukocytes by using leukocyte depletion
filters.
Reducing the use of Cardiotomy suction
Studies report improved lung function.

76. Mechanical manup contd.,Mechanical manup contd.,
Pulsatile perfusion may be beneficial with
respect to heamodynamics,
microcirculation and organ dysfunction.
Membrane oxygenators.
Heparin coated circuits and oxygenators
reduces the release of proinflammatory
cytokines,complement and platlet
activation.

77. ConclusionConclusion
CPB is far from perfect.
Still no single anti-inflammatory or
immunologic therapy is found for routine
clinical use.