Presentation for students

1. Hristo A. Rahman
Department of Cardiovascular Surgery
St. George University General Hospital
CARDIOPULMONARY BYPASS

3. Cardiopulmonary bypass (CPB) was first used successfully by
John Gibbon in 1953;
CPB has revolutionised cardiac surgical practice;
CPB can be employed in any procedure in which the heart and
lungs need to be stopped temporarily and their function
replaced by artificial means;
Prior to J. Gibbon’s work at Jefferson, Philadelphia,(PA), valve
surgery under direct vision would not have been possible nor
would the precise reconstructions needed to treat extensive
coronary artery disease.
Introduction

4. John Gibbon

5. Much of the success of modern CPB is attributable to
the development of new biomaterials and
sophisticated oxygenating devices as well as a greater
understanding of the pathophysiological
consequences.

6. Alternative uses of cardiopulmonary bypass (CPB)
Re-warming from profound hypothermia
Resuscitation in severe respiratory failure
As an adjunct in pulmonary embolectomy
In single- and double-lung transplantation
In cardiopulmonary trauma
In certain non-cardiac surgical procedures
Resection of highly vascular tumours
Large complex arteriovenous malformations
Tumours invading large blood vessels
(e.g. renal or hepatic tumours extending into inferior vena cava, right
atrium or even pulmonary arteries)

7. For most operations, the heart is approached by a median sternotomy
Surgical approach to the heart

8. 1/ Incision:
Jugular (suprasternal notch) to lower end of the
xiphisternum (descending sternotomy)
Sternum is covered with subcutaneous fat and few
pectoral muscle fibres
2/ The sternum is divided and retracted to expose the
thymus superiorly and the pericardium inferiorly

9. 3/ The thymus is divided in its midline with care as it
surrounds the left innominate (brachiocephalic) vein
The thymus ,although atrophic in adults, often remains
relatively vascular.

10. 4/ The pleurae are then dissected from the pericardium
laterally and the pericardium opened
5/ Prior to cannulation the patient is fully heparinized

12. AORTIC CANNULATION:
The great vessels are exposed and a purse string (or 2)
is inserted into the adventitia of the ascending aorta,
proximal to the brachiocephalic artery;
Aortic perfusion cannula is inserted into the ascending
aorta and held in place by the purse string suture;
Air is excluded and the cannula is connected to the
bypass circuit.
Initiating cardiopulmonary bypass

13. Aortic cannulation

14. Alternatively, when it is:
1/ Inadvisable (aortic dissection);
2/ Impractical (aortic arch surgery);
3/ Impossible (severe adhesions) to cannulate the aorta,
Femoro-femoral bypass
Axillary(subclavian)-femoral bypass,
can be employed.
Arterial return to pt. from CPB is via:
1/ Femoral;
2/ Axillary/subclavian;
3/ Common carotid artery
Venous drainage may be from either femoral vein
or right atrium

15. Axillary artery cannulation
INDICATIONS:
1/ Acute aortic dissection
2/ Redo-surgery

16. Femoro-femoral bypass with venous drainage from the
femoral vein offers an alternative particularly during
complex thoracic aortic procedures
Femora-Femoral Bypass in ATAAD (rupture)

17. VENOUS CANNULATION
Purse string suture is inserted into the right atrium by the
appendage;
Single “two stage” (dual) venous return cannula placed in the
right atrium establishes venous drainage;
The venous pipe has end holes that sit in the inferior vena
cava and side holes that sit in the right atrium (to take the
drainage from the superior vena cava);
Alternatively, the superior and inferior vena cavae may be
cannulated separately to gain better control over the venous
return and to facilitate surgery within the right atrium

18. Venous cannulation

19. Once the circuit is connected, the cardiopulmonary
bypass machine (the”pump”) takes over the circulation
and ventilation can be discontinued;
Blood is pumped from a venous reservoir and
oxygenated with a membrane oxygenator that allows
gas exchange across a silicone membrane;
The core systemic temperature may be lowered to
reduce the metabolic demands of the tissues by passing
the returning blood through a heat exchanger

21. The degree of cooling is according to the severity and complexity
of the surgical procedure, as well as the surgeon’s preference;
The blood is also filtered to remove particulate emboli and
infused back into the systemic arterial circulation via a roller
pump;
This returns blood to the patient at an even arterial perfusion
pressure;
Roller pumps produce linear flow;
Although lack of normal pulsatile pressure does not appear
deleterious
The surgeon can now isolate the heart from the rest of the
circulation with suction pumps to keep the area around the heart
clear of blood
Vent suction pump is used to decompress the heart

23. The surgeon can now isolate the heart from the rest of
the circulation with suction pumps to keep the area
around the heart clear of blood;
Vent suction pump is used to decompress the heart

24. To obtain a bloodless operative field, the ascending
aorta is usually cross-clamped once CPB has been
established and blood is diverted away from the heart;
The heart ceases to eject and, as a result of inhibition of
coronary blood flow, becomes anoxic;
Permanent myocardial damage will develop within 30-
40 min.
Myocardial protection

25. Most cardiac operations require some form of
myocardial protection;
Techniques of myocardial protection and the operative
management of the myocardium have had significant
impact on the complexity of cardiac surgery

26. CARDIOPLEGIC ARREST
Most methods involve combinations of topical
cooling and intra-coronary infusions of cardioplegic
solutions;
Modern cardioplegic solutions vary in terms of
temperature, pH, arresting agent, osmolality,
presence of red cells and other factors;
Most solutions contain potassium as the arresting
agent;
Potassium arrests the heart in diastole by
depolarisation of the membrane

27. Cold (4-10 C) isotonic crystalloid or chilled blood
solutions aid myocardial protection by reducing
metabolic requirements through local hypothermia;
This is sometimes combined with topical irrigation of the
heart and pericardial sac with cold (4 C) saline;
Systemic cooling on CPB may provide a margin of safety,
particularly if there are concerns about the degree of
myocardial protection;
With these techniques ,safe cardiac arrest can be
sustained for 2 hours and more

28. The cardioplegia can be infused selectively down the
coronary ostia if the aortic root has been opened as in
aortic valve surgery;
Cardioplegia via a cannula inserted in the aortic root as
in coronary bypass surgery,supplemented via retrograde
perfusion of the coronary venous sinus, which is
particularly useful in the presence of coronary artery
obstruction

29. TOTAL CIRCULATORY ARREST
Circulatory arrest becomes a necessity when visibility and
clarity of the operative area is crucial, as in paediatric
surgery or in surgery of the ascending and arch of the
aorta.
CPB is instituted and core systemic temperature reduced
to 15-18 C (profound hypothermia)
The metabolic rate of all organs of the body is reduced by
50% with every 7 C drop in temperature
With pump switched off at 18 C, circulatory arrest can be
tolerated for 20-30 min.
Additional cerebral protection can be provided with ice-
packs placed around the head
Retrograde and antegrade cerebral perfusion techniques
can also be used

30. Antegrade cerebral perfusion

31. At the end of the procedure, air must be meticulously
excluded from the cardiac chambers;
Once perfusion is restored to coronary arteries, the
heart may beat spontaneously or, if ventricular
fibrillation is present, it may require DC shock
defibrillation;
Epicardial pacing wires may be placed to treat
postoperative bradycardia or heart block
Discontinuing cardiopulmonary bypass

32. The patient is re-warmed, acidosis or hypokalaemia is
corrected, ventilation is restarted, and venous blood is allowed
to fill the right atrium by clamping the venous line of the
bypass machine;
The heart gradually takes over the circulation while the arterial
flow from the cardiopulmonary bypass machine is reduced;
When the blood pressure is acceptable and the surgeon is
confident that the heart function is adequate, CPB is
discontinued and the venous cannula is removed;
Blood from the bypass reservoir may be given through the
arterial cannula while protamine is given to reverse the effects
of heparinasation

33. In the unusual occasion when the patient fails to
maintain adequate perfusion pressures while being
weaned from CPB, the use of inotropic support and
insertion of an intra-aortic balloon pump may allow
CPB to be discontinued and the patient returned to the
intensive care unit (ICU)

34. It is clear that CPB is a complex technique that is both
physiologically threatening and requires technically
precise manouvers;
As such, there are many potentially serious
complications;
Increasingly, “off-pump” coronary artery bypass
grafting is being used to avoid such complications
Complications of CPB

35. Potential complications of CPB
Air embolism Myocardial depression
Bleeding disorders Neurological dysfunction
Cholecystitis Pancreatitis
Constrictive pericarditis Post-cardiotomy syndrome
Infection Pulmonary injury
Intestinal ischaemia/infarction Systemic organ dysfunction
Mediastinal tamponade Vascular injury
Microembolization