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CARDIO-PULMONARY BYPASS
1. Technology rules the world…..
• A physician at the bedside of a child dying of an
intracardiac malformation as recently as 1952
could only pray for a recovery. Today correction
is routine.
• And about 2,000 such surgeries performed
every 24 hours worldwide these days.
2.
3. • Why do we bypass the cardiac and
pulmonary system?
• How is it possible??
• How does the tissues supplied if the heart is
not pumping?
• We know if the heart stops beating, the
person dies. Then how CPB saves the pt??
• Taken out blood clots easily, then how could
the whole blood is bypassed without
clotting?
4. Definition
• Cardiopulmonary bypass is a form of extra
corporeal circulation.
• It temporarily takes over the function of the
heart and lungs during surgery maintaining
the circulation of blood and oxygen content
of the body.
• Heart–lung machine
5. Goals of CPB
The CPB circuit has 4 major functions
• Diversion of blood from heart to provide
blood less & stable surgical field.
• Circulation of blood.
• Oxygenation & carbon dioxide elimination.
• System cooling and rewarming.
6. History
• The first operation – 5th April 1951- Dr. Clarence
Dennis (University Of Minnesota) following 4 years
of experiment with dogs.
• The first successful open heart procedure on a
human using bypass machine – 6th May 1953,
John Gibbon (Philadelphia) correction of
ASD in an 18 year old girl.
9. Surgical procedures in which
cardiopulmonary bypass is used
• Coronary artery bypass surgery.
• Cardiac valve repair and/or replacement.
• Repair of large septal defects.
• Repair and/or palliation of congenital heart
defects.
• Transplantation.
• Repair of some large aneurysms.
• Pulmonary thrombectomy.
12. BYPASS SYSTEM
• Basic bypass system
– Blood drained from the venous system using
gravity through,
• Cannulas in SVC & IVC
• Single cannula in RA in to the venous reservoir.
• It is pumped into the membrane oxygenator .
• Returned to the systemic circulation via a cannula
usually placed in distal ascending aorta.
15. Basic components of CPB
• Venous cannula
• A venous reservoir
• An oxygenator
• A heat exchanger
• The main pump
• An arterial filter
• Aortic cannula
• Accessory pumps and devices
17. Venous cannulas
• Made of flexible plastics
Size (According to )
• Pt size
• Anticipated flow rate
• Index of catheter: flow index
For an average adult
• 30F SVC + 34F IVC
• Single 42F (Single cavoatrial)
19. Venous reservoir
Venous blood enters the circuit by gravity into a
reservoir placed 40-70cm below the level of heart.
The amount of blood drained is determined by,
CVP, Resistance in cannula, tubing, and connectors &
Absence of air with in the system.
Volume
Adult-4000-5000ml
Paediatrics-3500-4000ml
Infants-1000-1500ml
20. Basic components of CPB(contd..)
Main pump
Roller pump/ peristaltic pump
Rotating motor-driven pumps – Peristaltic
"massage“ of tubing gently propels the blood
through the tubing.
22. In CPB there are 4 pumps:
1. To pump the oxygenated blood to patient.
2. To induce negative pressure to operate the
cardiotomy suction system.
3. To deliver the cardioplegic solution to perfuse the
coronary arteries during open operations
involving the aortic root.
4. To actively vent the left heart.
23. Basic components of CPB(contd..)
Heat exchanger
Whole body hypothermia has been widely used
to reduce metabolic demand and to protect vital
organs.
For every 1 °C decrease in brain
temperature, cerebral
metabolic rate decreases by 7%.
24. Basic components of CPB(contd..)
Oxygenator
• This serves as the lung and is designed to
expose the blood to oxygen.
• Disposable & membrane is permeable to gas
but impermeable to liquid blood.
• Blood flows on one side of the membrane
while oxygen on the other.
25. Oxygenator…
• The rate of oxygen addition is similar to that of
normal respiration.
• Blood flow is 3-5 liters/min and gas flow is
between 40-60% of blood flow.
27. Basic components of CPB(contd..)
Aortic cannula
It is usually the narrowest part of the
extracorporeal circuit.
• High flow
• High pressure gradients
• High velocity of flow
• Turbulence
28. Basic components of CPB(contd..)
Accessory pumps and devices
Considerations in the selection of tubing and
connectors.
• Minimization of blood trauma
• Prime volume
• Resistance to flow
• Avoidance of leaks
30. Tubing
• Medical grade polyvinyl chloride (PVC)
(e.g., Tygon)
• Silicone or latex rubber tubing is sometimes
used in roller pumps.
• New formulations of PVC are being developed
for use in roller pumps.
31. Cardiotomy Suction System
• 2 handheld suckers, connecting
tubing, one roller pump, and a
combined blood filter and a
reservoir unit.
• Return blood spilled in the
operative field directly into the
perfusion circuit.
32. LV Venting
VENTRICULAR VENTING :
• LV venting done to keep the operative field clear
• Maintain Low LA & pulmonary venous pressure
• Remove air from cardiac chamber.
• Blood from LV goes to reservoir bag
33. Cardioplegia
• A separate circuit for infusing a solution into the
heart to produce cardioplegia (i.e. to stop the heart
from beating), and to provide myocardial
protection(i.e. to prevent death of heart tissue).
39. Precaution
• If venous return is poor check cannulas for
proper placement, kink, airlock etc.
• The pump flow should be slowed until the
program is resolved.
• Search for evidence of SVC obstruction
High CVP
Facial engorgement
40. Assess arterial inflow
• Is Arterial blood is oxygenated?
• Is the flow is appropriate?
• Evidence of arterial dissection (persistent low
MAP in presence of high inflow line pressure
and falling of reservoir level).
41. Causes of aortic cannula high line pressure
• Kink in the arterial cannula or line
• Cannula improperly positioned
• Cannula too small
• Arterial systemic blood pressure very high
• Aortic dissection
• Blockage in arterial filter
42. Continuous monitoring during CPB
• Reservoir level
• Blood flow @ proper rate or flow rate
• Pressure line / arterial line pressure
• Arterial blood pressure
• Oxygen saturation
• Temperature
• ECG
• Venous oxygen saturation
• Central venous pressure
43. Intermittent monitoring during CPB
• Blood gas
• Urine output : Urine output is monitored
using a freely draining urinary catheter.
• Electrolyte
46. Before Surgery – Pt Mx
• Routine preoperative care.
• NPO
• Antiseptic bath
• Autoclaved clothes
• High risk consent
• Various investigation reports should be attached to the
patient file.
• Articles needed in the surgery should be ready with the
client.
• Pre operative vitals monitoring and recording.
• Make sure that patient has no allergy to
heparin/shell fish.
47. Management of Pt
• Information from the patient's chart is
obtained regarding the proposed surgical
procedure and relevant history.
• Equipment is then selected appropriate to
surgical and patient needs.
• Blood grouping and matching done.
• Arranged for blood.
48. Before Sx - Management of Tubing
• CPB circuit must be primed with fluid and all
air expunged before connection to the
patient.
• The circuit is primed with a crystalloid solution
and sometimes with blood products .
• The patient must be fully anti-coagulated
with an anticoagulant such as heparin.
• The circuit may be briefly flushed with filtered
100% carbon dioxide to displace room air.
49. During surgery
• Patient is prepared.
• Circuits kept in a secure area with sealed ports
and vents to maintain sterility of the blood-
contacting surfaces.
• Sequence of circuit done in a consistent
manner.
• Heat exchanger and cardioplegia delivery
system are turned on and tested.
50. Preparation for bypass
• Full anticoagulation (heparin 300IU/kg)
• Bypass circuit primed with crystalloid, heparin
+/- mannitol just before aortic cannulation.
• Prepare and pressurize cardioplegia to
300mmHg.
51. Anticoagulation-heparin
• Heparin is given soon after the
chest is opened.
• After a control activated clotting
time(ACT) is obtained, a loading
dose of 300 IU/Kg heparin is
given through central venous
line.
52. During Surgery
• When the surgeon is ready to begin CPB, the
heart–lung machine console is positioned
near the operating table.
• Pump should be placed to minimize tubing
lengths to the cannulation sites to reduce
Prime volume
Pressure gradient (resistance to flow)
Blood trauma
53. Connection of patient to circuit
• After administration of systemic heparin
• Verify CPB circuit for any visible gas bubbles.
• Arterial and venous lines are clamped at the
pump and table.
• The surgeon or assistant divides the
arterial/venous recirculation loop.
54. • Upon instruction from the surgeon, CPB
begins by removing the clamp(s) on the
arterial line and activating the systemic pump
speed control.
• After removal of the arterial line clamp at the
field, the perfusionist should manually palpate
or observe pulsation on an arterial flow line
pressure monitor.
55. Establishing extracorporeal blood flow
• Full CPB flow can be established in most cases
within 30 seconds.
• Starts flow in the systemic pump before
releasing the venous line.
• As the volume of perfusate in the CPB
reservoir decreases, the venous line clamp or
occluder is released.
56.
57. During bypass
• Turn off ventilator
• Propofol 6mg/kg/hr OR midazolam OR volatile
agent on bypass machine
• MAP maintained at 50-70mmHg by altering
SVR
• Pressure maintained with vasopressors and
vasodilators
• Hypothermia to 28-34˚C used
59. Coming off bypass
• Warm to 37˚C
• K+ 4.5-5.0
• HCT >20%
• Normal acid-base status
• HR 70-100/min (ideally SR)
• 100% O2
• Venous line progressively clamped
60. • Heart gradually fills.
• Start inotropes if inadequate cardiac output
• Protamine (3mg/kg)
• Restart volatile and opioid
• Removal of aortic cannula is the final step.
61. Protamine
• Once bypass is terminated, and
after removal of venous
cannula,protamine is given to
reverse heparin, usually during a
5-10 min period.
• The reversing dose is
approximately 1.3mg of
protamine for 100 U of heparin.
62. Bypass catastrophes
• Supply failure - pump stops working
• Inadequate anticoagulation - circuit clots
• Oxygenation failure - hypoxaemia and ischemia
• Disconnection, empty reservoir - RV distension,
increased PAP - cardiovascular collapse
• Gas emboli - into system circulation
• Aortic dissection - renal failure, bowel ischaemia,
paraplegia, cardiac tamponade, limb ischemia,
stroke
• Hemolysis
64. After Surgery
• Preparing the ICU environment for the patient.
• Make sure the functioning of equipment.
• To warm the patient after surgery , a
hyperthermia blanket is placed on the bed.
• All the emergency equipments including IABP
machine and all the emergency drugs should be
available.
• After receiving the patient baseline vitals should
be checked.
65. After Surgery
• Closely monitor the hemodynamic parameters of
the patient.
• Clotting time,Hct. ,Na,K,ABG should be
monitored frequently.
• Look for any signs of complications.
• Closely monitor the IV fluid input and urine
output, chest drainage.
• Document all the findings.
• Once the patient is stabilized, an ECG and upright
chest X ray are routinely performed.
66. Complications
• Swelling of the brain
• Infections
• Arrhythmia
• Kidney stress
• Blood vessel damage
• Need for transfusion
• Low output syndrome
• Weight gain
• Release of cytokines leading to a variety of physiologic
events
• Difficulty planning out complex actions
• Irritability
68. Off pump surgeries
• The off pump technique is very similar to the
conventional Coronary Artery Bypass Grafting
(CABG) procedure. OPCAB still utilizes a
medial sternotomy, however the important
difference is that the cardiopulmonary bypass
pump is no longer employed.
69. Extracorporeal membrane oxygenation
(ECMO)
• Partial CPB that diverts a fraction of systemic
venous return (maximum 75%) to an oxygenator
and thus temporarily supports the heart and lung
function.
INDICATIONS FOR ECMO
• Preoperative cardiopulmonary support.
• Management of failure to wean from the
cardiopulmonary bypass.
• Resuscitation after cardiac arrest in the post
operative period.
With the exception of pumps most of the apparatus is now made of disposable plastics.
In early practice ice packs were applied to the body- long cooling time as well as not much effect on organs.
membrane oxygenators have supplanted bubble oxygenators since the 1980s. Another type of oxygenator gaining favour recently is the heparin-coated blood oxygenator which is believed to produce less systemic inflammation and decrease the propensity for blood to clot in the CPB circuit. Most oxygenators come with a manufacturer's recommendation that they are only used for a maximum of 6 hours, although they are sometimes used for up to 10 hours, with care being taken to ensure they do not clot off and stop working. For longer periods than this, an ECMO (extra-corporeal membrane oxygenation) or VAD (ventricular assist device) circuit is used, which can be in operation for up to 31 days.
The oxygen partial pressure is around 65%. As the blood passes through the oxygenator, the blood comes into intimate contact with the fine surfaces of the device itself.
Oxygen gas is delivered to the interface between the blood and the device, permitting the blood cells to absorb oxygen molecules directly.
The aortic cannula is always placed prior to the venous cannulas (and removed last), because in the event of an emergency, the perfusionist can temporarily initiate cardiopulmonary bypass via a single aortic cannula (i.e. without venous cannulation). “Crashing” onto bypass is short-lived, however, as the CPB machine’s reservoir is quickly depleted, thus the central veins need to cannulated quickly and venous return to the pump established as soon as possible. Note that the aortic cannula does not have to enter directly via the aorta – an arterial cannula can be threaded into the aorta via the femoral artery and in some instances, via the subclavian artery
Excessive suction lead to excessive RBCs trauma
Excessive suction to cell saver - blood volume depletion
After establishing full flow with appropriate VR, the following tasks will be checked within 5 minutes from the start of CPB.
0.5-1 ml/hr
F
In some hospitals, a circuit is assembled (but not primed) and kept available at all times in the event CPB is needed urgently. The tubing or device manufacturer may preconnect some components for more rapid assembly and convenience.
clamp is to avoid exsanguinating the patient into the CPB circuit in the event of a pump malfunction.
– can block the circuit (particularly the oxygenator) or send a clot into the patient.
(lose blood perfusion of tissues)
