Cardiopulmonary Bypass evolution, technical, physiological, surgical aspects.

1. CPB (Clinical Methodology)
Dr Akshay Ravindra Deshmukh
NICS

2. John Heysham Gibbon Jr
During his research fellowship at Harvard in1931, he got the idea for
Cardiopulmonary Bypass.
He began his machine experimentation on cats and was able to
maintain the cardiorespiratory function for about 4 hours.
On May 6, 1953 he performed first OPEN heart procedure, an ASD
closure, on an 18 year old patient using TOTAL cardiopulmonary
bypass. Patient went on to live for 30 years post surgery.

3. Why the need for CPB?
• For operating on a part of the body, the part has to steady, dry
(blood free) and relaxed.
• Steady, so surgeon can dissect & place incisions accurately
• Dry, to allow surgeon to view the operating area well
• Relaxed so that, it can be retracted to provide access.

4. Some Historical Landmarks
• Clarence Dennis (1951)- First attempt to use pump oxygenator for
clinical cardiac surgery (ASD repair).
• C. Walton Lillehei (1954)- Series of surgeries in paediatric patients
with “Controlled Cross Circulation” with father or mother as the
oxygenator.
• John Kirklin (1955)- Series of intracardiac procedures with Pump
Oxygenator at Mayo Clinic

7. Present Day CPB Machine

8. SystemicPump
•Roller Pump
•Centrifugal Pump

9. Roller Pump
• Devised by DeBakey for blood transfusion
• Set at ‘near occlusion’
• Under occlusion is unable to maintain flow across varying pressures
from 30 to 300 mmHg
• Over occlusion causes trauma to blood elements
• Tubings- Tygon (polyvinyl chloride) or Silicone

10. Controlled Vortex (centrifugal) Pump
• Flow varies with changes in resistance to flow in and out of the
system.
• If pressure is +500mmHg in outflow or -500mmHg in inflow, both
inflow and outflow stop. That way, in this pump pressure can not raise
above 500mmHg.
• So in case of any occlusion accidental or intentional, tubings will not
rupture.

11. • Hemolysis is same in both roller and centrifugal pump.
• Both can transmit air entrapped to arterial lines. But in case of vortex
pump the air is broken down into microbubbles while roller pump will
push forward gross air presented to it.

12. Venous Input
• By negative pressure gradient from patient to machine which is
generated by
1)Creating a controlled vacuum in the venous reservoir
2) Using a siphon system in which gravity creates the negative
pressure
3)Using a controlled vortex pump to create the negative pressure
within the venous line from the patient

13. Vacuum Assisted Venous
Return
• Ideal method
• Input pressure and output
pressures are independent
• VAVR permits use of smaller
venous cannulae, smaller
reservoirs, considerably shorter
tubing, and low priming
volume
Siphon (Gravity) Drainage
• Narrow range of generated
negative pressure.
• The need for a reservoir
increases the priming volume
of the pump-oxygenator
• Decreases hematocrit

14. Venous Reservoir
• Screen Filter- for venous input
• Depth Filter- for suction lines

15. Oxygenator
• Regulates tension of gases in arterial blood
• This is the largest area of foreign surface blood comes into contact
with and therefore probably the component of the pump-oxygenator
where the most blood damage occurs.
• Has integrated heat exchanger.
• Types-
-Bubble
-Rotating Disc/ Cylinder
-Vertical Screen
-True Membrane

16. • All the above mentioned types (expt True Membrane) have blood gas
interface where the damage to blood occurs.
• In True Membrane type with silicone rubber or microporous
polymethylepentene membrane, there is no blood gas interface. This
type can be used for more than 24 hours with reasonable safety. E.g.
In ECMO.
• PaO2 is maintained at 250 mmHg, higher PaO2 can cause oxygen
toxicity and bubble formation.
• PaCO2 is controllable during CPB by varying the ratio between gas
flow through the oxygenator and blood flow through the Oxygenator.
• PaCO2 and pH calibration varies as per the temperature

17. Alpha stat Strategy
• Ventilation of the Oxygenator is
maintained at level appropriate
for body temperature of 37°c
irrespective of the hypothermia
• This hyperventilation in
hypothermia causes decrease in
PaCO2 and increase in pH.
• But at low body temperatures
neutrality exists at higher pH so
this strategy has no effect on
various enzyme systems which
keep functioning optimally.
• Low PaCO2 results in pulmonary
vasodilation which diverts blood
away from cerebral perfusion
pH stat Strategy
• Ventilation is adjusted to
hypothermia ie hypoventilation
which causes respiratory acidosis.
• This causes increased cerebral
blood flow which is considered
advantageous during deep
hypothermic CPB.
• Several studies suggest that pH stat
Strategy has better neurological
outcome.

18. Heparin
• Dose- 300 to 400 U/kg (3 to 4 mg/kg)
• Binds to Antithrombin 3 and amplifies its effect.
• Inhibits activation of Factor 7 and inactivates factors 9,10,11,12 and
hence conversion of fibrinoagen to fibrin
• Metabolized in liver.
• Derived from porcine intestinal mucosa or bovine lung.
• For CPB purpose, lung heparin is superior as it has better protamine
neutralization response.
• Satisfactory anticoagulation for CPB is ACT of >480 seconds

19. Trouble shooting for low ACT
• If ACT <480
1) Give additional heparin 100 U/kg
2) Check ACT in two different machines
Still ACT low?
Suspect Antithrombin 3 deficiency
Give FFP at 10 to 15 ml/kg

20. • Most common cause AT3 deficiency is previous exposure to
heparin.
• Around 1 to 5 % patients who receive unfractionatedheparin
develope HIT antibodies with concomitant
thrombocytopenia.
• In such patients heparin can not be used so the alternative
BIVALIRUDIN maybe used.

21. Circuit Selection
• Depends on
1) Body surface area
2) Age
3) Sex
4) Surgical Procedure

23. Priming
Serves the purpose of de-airing of the circuit.
Each component of CPB adds to priming volume.
DNS is avoided as the extra sugar gets converted to the extra lactic acid
during hypoperfusion and causes acidosis.
• Composition of prime
1) RL 1.5 litre
2) 20% mannitol (0.4 gm/kg)
3) 7.5% NaHCO3 (25 to 50 ml/L)
4) Heparin (50 mg/L)
5) Blood products if required.

24. Additivesto prime
1) Mannitol- reduces myocardial edema, acts as free radical scavenger
2) Glucose- to maintain level at 350mg/do, also causes diuresis
3) Furosemide- causes diuresis
4) Phentolamine- inhibits vasoconstriction and allows even cooling
5) Nitroprusside- even cooling and rewarming
6) Corticosteroids- improve tissue perfusion and attenuate
compliment acrivation
7) Antifibrinolytic- reduce bleeding and thus need for BT

25. Hb Concentration
• At normothermia, the normal hematocrit of 0.40 to 0.50 is optimal
for oxygen transport.
• Hypothermia increases blood viscosity therefore at low temperatures,
a lower hematocrit is more appropriate than at 37°C.
• Hematocrit of about 0.20 to 0.25 may be optimal during moderately
and deeply hypothermic CPB.

26. • During rewarming, a higher hematocrit is desirable because of
increased oxygen demands, which may be achieved by Ultrafiltration.
• If the calculated hematocrit is lower than desired, an appropriate
amount of blood is added.

27. Hypothermia
• The patient’s body temperature is the most important determinant of
the length of safe circulatory arrest time.
• Allows CPB to be flexible.
• Allows use of lower pump flow with less blood trauma, achieves
better myocardial protection and protection of other organ systems.
• Acts as a margin of safety for organ protection in case of equipment
failure.
• Mild hypothermia (31° to 34°C) is essential.
• Even cooling is achieved by combination of surface cooling and core
cooling by CPB.

28. Relationship of O2 consumption to flow rate and temperature

29. AorticCannulation
• Cannulation site is proximal to the origins of brachiocephalic artery.
• Llittle to left of anterior aortic surface and directed towards left
shoulder. ( vice versa in right sided aortic arch)
• In elderly its beneficial to do Epiaortic USG scan to look for any
atheroma before cannulation to avoid its dislodgement.
• 2 purse string sutures are placed catching only adventitia without
going in the lumen.

31. Venous Cannulation
Two venous cannulae
• Two venous cannulae may be
used as a routine or only for
congenital heart disease
operations, including those in
infants, and operations
involving the right atrium, such
as tricuspid valve surgery.
Single 2 stage venous cannula
• CABG, operations on the aortic
valve, mitral valve, and
ascending aorta; some
operations for congenital heart
disease and combinations of
these procedures.
• Efficiently decompressed the
right heart.

32. 2 stage venous cannula

33. Aortic cannula selection

34. Venous cannula selection

35. Commencing Bypass and Left Heart Venting
• Flow is gradually increased to 2.2 L/min/sqm
• After proper flow is obtained, perfusion cooling is started.
• Heart is carefully observed for any distension.
• If distension occurs, pump flow is reduced and venous cannulae are
readjusted.
• Around 50ml of blood from each cardiac output returns back to LA via
bronchial veins opening into pulmonary veins.
• This volume gets accumulated, distends the heart, warms it.

36. • To prevent this, the left heart venting catheter is inserted from LA
through a purse string stitch situated at junction of RSPV and LA.
• In right sided heart surgeries, the same catheter can be introduced to
left side from a patent foreman ovale or an ASD.
• If neither foreman or ASD is present a direct stab incision can be
made into fossa ovalis bellow superior limbus.
• Alternatively RSPV or RIPV or apex of left ventricle can be used.

39. AorticCross Clamping
• Cross clamp causes separation of systemic outflow from heart which
is taken over by the CPB.
• Check list for cross clamping
1) No resistance to arterial line
2) Venous Reservoir is adequate, RA is empty, MPA is soft
3) Cardioplegia is ready to be delivered.
4) All the sutures, valves, patches and instruments are ready.

40. • Complications of cross clamping
1) Incomplete clamping of aorta if the aorta is tense and dilated. Can
be prevented by making aorta soft by reducing flows before
clamping.
2) Accidental clamping of tip of cannula may result in sudden rise in
arterial line pressure which may result in line rupture.
3) Accidental clamping of cardioplegia cannula
4) Partial clamping of MPA (Due to inadequate dissection between
aorta and pulmonary artery.)
5) Injury to right pulmonary artery.

41. Cardioplegia
• Aspects of myocardial protection are
1) Cardioplegia
2) Prevention of LV distension at all times
3) Prevention of rewarming of the heart.
Cardioplegia can be delivered antegrade or retrograde.
1) Antegrade- through Aortic root/ coronary ostia
2) Retrograde- through coronary sinus

42. • Antegrade root cardioplegia
1) Aortic root should be distended and should not be too tense (seen
in coronary block) or too soft (seen in AR).
2) Absence of LV distension.
3) Distended and turgid coronaries on the anterior surface of the
heart.
4) Veins should be distended and their colour should change from,
initial dark blue to later bright red as the delivery of cardioplegia
progresses.
5) Quick diastolic arrest of heart.

43. • Cardioplegia is delivered retrogradely when,
a) antegrade delivery is not feasible due to coronary ostial block,
coronary artery disease, coronary ostium is difficult to visualise.
or
b) surgeon does not want interruptions during a prolonged surgery
During retrograde cardioplegia delivery, the coronary veins are tense
and red in colour and the blood coming retrogradely through the
coronary arteries or ostia is dark in colour.
• Blood cardioplegia is delivered at 8°C
• Cardioplegia dose is 20ml/kg for adults and 30ml/kg for paediatric.
• In coronary patients cardioplegia pressure can be around 120 to 150
mmHg.

44. Principles of Cardioplegic protection

45. Cardioplegia solutions
• St Thomas (BCD 1:4)
• Del Nido (BCD 4:1)
• CAPS Buckberg
• Bretshneider
• ViaSpan UW

47. St Thomas Cardioplegic Solution
• 1 part crystalloid,4 parts blood.
• Composition
1) KCL – provides arrest
2) NaCl – isotonicity
3) MgCl2 dihydrate – Ca channel blocker
4) CaCl2
5) NaHCO3
Plegia time of 20 minutes.

48. del Nido Cardioplegic sollution
• 4 parts crystalloid, 1 part blood
• Composition
1) Plasma-Lyte A
2) Mannitol 20%
3) Magnesium sulphate
4) Na Bicarbonate
5) Lidocain 1%
6) KCl
1000ml
16.3ml
4ml
13ml
13ml
13ml

50. De-Airing the Heart
• The heart is filled with fluid (blood or electrolyte solution) before
closing to minimize air entrapment.
• The heart must be reperfused and beating.
• Residual air is aspirated from the heart before allowing it to eject.
• The lungs are intermittently ventilated to express air from the
pulmonary veins.
• Continuous suction is applied on a needle vent or catheter in the
ascending aorta as the heart commences ejecting blood to retrieve
any air that may have remained in the heart or pulmonary veins
(alternatively, a freely bleeding stab wound may be used)
• Transesophageal two dimensional echocardiography (TEE) can be done
to look for any entrapped air.

51. Protamine
• Given at the end of CPB after removal of all the cannulae.
• Derived from salmon sperm.
• Is a heparin antagonist, forms heparin-protamine complex.
• Dose- 1 to 1.5 mg / 100 U of heparin administered.
• 1 mg of protamine neutralizes 85 U of heparin

52. Ultrafiltration
• During CPB, if there is excess volume in the pump-oxygenator, the
hemofilter device is activated for removal of serum water by
ultrafiltration.
• This devices contain semi permeable membrane which allows
removal of excess fluid and electrolytes but not blood cells, albumin
and coagulation factors
• Two methods of Ultrafiltration
1) Conventional Ultrafiltration (CUF)
2) Modified Ultrafiltration (MUF)

53. CUF
• Filtration done while patient is
on CPB.
• Blood is drawn from venous line
or the reservoir, filtered,
concentrated and given back to
venous line or reservoir
• Hemofilter is in series with the
pump.
• Both CUF and MUF cause
removal of some amount of
inflammatory mediators as well
as heparin from blood.
MUF
• Practice of withdrawing blood
from patient for filtration after
weaning from CPB.
• Blood is usually drawn from
arterial cannula and after
hemoconcentration, pumped
back to venous line.
• Used in all neonates and
paediatric weighing <10kg.
• Amount of blood removed from
Aorta should not exceed 5
ml/kg/min to prevent cerebral
steal.

54. Coming off bypass
• After complete deairing, aorta is declamped.
• As the myocyardium gets perfused and warm, it starts beating
• These initial contraction are not sinus and are not powerful,so it’s
better to keep heart empty by LV vent.
• After adequate contractility is achieved, Venous cannulae are
gradually clamped (25% f/b 50% f/b 75% f/b 100%).
• Heart is increasingly filled with guidance of CVP and PA diastolic
pressure.

55. • Prerequisite for going off CPB
1) Nasopharyngeal temperature of 37°C
2) Sinus rhythm. If chronic AF, ventricular rate should be >100/min.
3) Adequate cardiac contractility, well perfused myocardium (looks
red). Assessed by giving slight volume load, which causes rise in BP
without rise in CVP and produces a pulsatile waveform on monitor
4) Both lungs can be ventilated well
5) Blood electrolytes and pH is within normal limits.
Once Haemodynamics are good after going off CPB, venous cannulae
are removed.
Residual volume in the reservoir is returned via aortic cannula.

56. • Prerequisite for aortic decannulation
1) Procedure is completed
2) No need to go back on CPB for achieving Haemodynamic stability.
3) All the blood from venous reservoir is returned back.
Aortic cannula is removed and purse strings are tied.

57. Agents of damagein CPB
1) Foreignsurfaces - produce damage to blood products, activate immune
response which may lead to SIRS.
2) Shear Stresses – Generated by blood pumps, tubings, abrupt
accelerations and deccelerations of flow which leads to hemolysis.
3) Foreignsubstances – Air bubbles, particulate from Oxygenator, dentured
proteins, atheroma, platelet aggregates, chylomicrons may get
disseminated to cause microembolisation.
4) Heparin- being an imperfect anticoagulant,permits formation of
microthrombi on Oxygenator membrane which may embolise
5) Protamine – Activates compliment via classicalpathway, provokes
temporary severe bronchospasm.

58. Safe duration of CPB
• Partial CPB is better tolerated than Total CPB.
• Duration of CPB is a proven risk factor for post op morbidity and
mortality
• Normothermia is a risk factor for increased morbidity.
• Absence of hemodilution is a risk factor
• Safe duration can be increased with moderate to deep hypothermia.

60. Surgeries should be well planned in advance
and procedural steps should be calculated to
minimise the CPB time.
Failing to plan is planning to fail!!

61. THANK YOU

62. • Dr Chandrashekhar
• Dr Tamasa
• Dr Sendur
• Dr Swetcha
• Dr Shamanth
• Dr Hemapriya
• Dr Purvang
CVS Embryology
Anatomy of Thorax
Cardiac Anatomy
Valve Apparatus
Coronary Anatomy
Cardiac Cycle
Cardiac Pharmacology

63. University of
Minnesota Hospital,
on September 2,
1952 near the end
of the first
successful open
heart operation in
medical history. On
that date, Dr. F. John
Lewis closed by
suture an atrial
secundum defect (2
cm in diameter)
under direct
visualization using
inflow stasis and
moderate total body