Cardiopulmonary Bypass Guide

Cardiopulmonary Bypass
Cardiothoracic & Vascular Surgery Department-
Sulaimaniya
By :- Dr. Allaa S. Abdel Majeed

History
 Dr.Gibbons, inventor of the Heart &
Lung machine Also known as, cardio-
pulmonary bypass machine (CPB).
 •1935 –maintained a cat’s circulation on
CPB while closing the pulmonary
artery.
 1953 –Cecelia Bavolek First patient to
undergo open heart surgery using CPB
to repair an atrial septal defect

More than 40 years of Innovation, Research, and
Hard Work

General
Comments
 CPB involves an extracorporeal circuit that
provides oxygenated systemic blood flow.
 Is accompanied by normovolemic hemodilution
and nonpulsatile flow.
 The contact of blood with the extracorporeal
circuit results in the activation of numerous
cascades.
 Among the consequences of this contact are
thrombin generation, the release of
proinflammatory cytokines.
 This systemic inflammatory response may lead
to multiple organ system compromise.

 Use of membrane oxygenators, biocompatible circuits, centrifugal
pumps, leukocytes filtration and intraoperative steroids may reduce
the inflammatory effects of CPB, but have not had a significant
impact on clinical outcomes.
 Despite adequate heparinization, the bypass circuit is a potent
activator of the coagulation system with generation of factor Xa and
thrombin.
 A coagulopathy may develop from activation of platelets and the
fibrinolytic system, as well as from dilution of clotting factors and
platelets during bypass.
 Circuits coated with the Carmeda BioActive surface, heparin
(DurafloII) have been shown to improve biocompatibility, with
reduce platelet activation and less release of proinflammatory
mediators.

Why CPB
To facilitate a surgical intervention
Provide a motionless field
Provide a bloodless field

To whom
Coronary Artery Disease (CAD)
Valve Disease
Congenital Heart Defects
Dissections
Aneurysms :- Aortic, ventricular, giant cerebral
Transplants :- Heart, liver, lung, trachea
Others: limb cancer, hypothermic rescue

Principle of CPB
Deoxygenated blood
(Venous Return) taken
away from the body to
the CPB machine.
Then pumped and
oxygenated to returned
back to the body
(Arterial system)

CPB
 Venous and arterial cannulas
 Venous Reservoir
 Centrifugal pump
 Oxygenator, heat exchanger , venous reservoir
 Microfilter bubble trap on the arterial side
 Suction system for cardiotomy reservoir and filter returns to venous
reservoir
 Field blood washed in a cell saver system returned as packed RBCs.
 Partial and occluding clamps to direct and regulate flow
 Various ports in the system to obtain blood samples.
 Cardioplegic system, LV Vent.

Venous Drainage and Cannulation
 Venous cannulas:- Size
determined by patient
size, anticipated flow
rate, flow characteristics
and resistance
Usually 30F in SVC and
34F in IVC or a single 42F
 3 basic approaches:-
Bicaval, single atrial,
cavoatrial(2-stage
Cannula)

Augmented /Assisted Venous Return
 Negative pressure can be applied using roller pump,
centrifugal pump or regulated vacuum. Augmented negative
pressure increases risk of aspirating air , cerebral injury &
hemolysis.
Complications of Venous drainage
 Arrhythmias
 Atrial or caval tears
 Bleeding
 Air embolization
 Unexpected decanulation
 Improperly placed purestring sutures may obstruct cava when
tied.

Arterial Cannulation
Ascending Aortic
 Tip of arterial cannula is
narrowest part of the
perfusion system
 Distal ascending aorta is
preferred due to ease of
placement and fewest
complications.
 The outflow should be
directed into the arch, not
into the innominate artery.

Complications of AA Cannulation
 Difficult insertion, bleeding, tear in aortic wall, intramural or
malposition of cannula tip, air emboli, plaque emboli, aortic
dissection
 •Atherosclerosis of the ascending ,dislodgement of
plaque/debris lead to Peri-operative Stroke
Aortic dissection0.01-0.09%.
Common in aortic root disease :-discoloration beneath
adventia near cannula site, increase in art line pressure,
sharp reduction in return to venous reservoir.
Emergency Management:
Cannulate peripheral artery or uninvolved distal aorta.
Control BP pharmacologically
Temperature to < 20 ºC
Circulatory arrest and repair aorta.

Femoral Cannulation
 First alternative to aortic cannulation
Indicated for initiating CPB quickly in
cardiac arrest, acute , dissections,
limited access
Complications
 Retrograde arterial dissection (0.2-
1.3%) most serious one with 50%
mortality.
 Tears, late stenosis, thrombosis,
bleeding, lymph fistula, infection in
groin, cerebral or coronary

Axillary Cannulation
 Increasing use in Aortic surgery,
circulatory arrest cases
 Advantage :- freedom from
atherosclerosis, antegrade flow
into arch vessels, protection of
arm and hand by collateral flow
 Disadvantage: Risk of brachial
plexus injury, axillary artery
thrombosis

Venous Reservoir
 Placed immediately before
arterial pump
 Reservoir is high
capacitance (low pressure)
receiving chamber for
Venous Return
 Facilitates gravity drainage
 Can add drugs, fluids, or
blood
 Can hold 1-3L of blood
when patient on full CPB

Pumps
Centrifugal pump
 Propel blood by centrifugal force.
 Can pump small amounts of air but
stopped if > than 50mL of air enters
blood chamber
 Produce pulseless blood flow
Roller Pumps
 Forward flow generated by
roller compression
 Produces a sine wave pulse
blood flow at 5mmHg
 No evidence to produce pulsatile
perfusion during short/long-term
CPB

Heat Exchangers
 Control body temperature.
 Gasses more soluble in cold than
warm blood.
 Rapid rewarming may cause bubble
emboli.
 Temperature difference between
body and perfusate kept <10.
 Temp kept < 40ºC to prevent
denaturation of proteins.
 Cardioplegia requires separate heat
exchanger.

Oxygenator
 Membrane Oxygenators imitates natural
lung by providing a thin membrane
between the gas and blood phases
 Plasma filled pores prevent gas from
entering blood but allows exchange of
Oxygen and CO2.
 Produce up to 470mL of O2 and remove
350mL of CO2 / minute at 1-7L of flow.
 Malfunctioning of oxygenators occurs in
0.02-0.26% of cases most common due to
abnormal resistant of blood.
 Monitoring of blood gasses is very
important to ensure adequate removal of
CO2 and oxygenation.

Heparin Coated Circuits
 Can be attached to blood surfaces of all components of the
CPB.
 An ACT of 350 will be satisfactory for this types of circuits.
 No evidence that heparin-coated perfusion circuits reduce
need for systemic heparin, or reduce bleeding or thrombotic
problems associated with CPB.

Suction
 Blood aspirated from surgical wound maybe directed to
cardiotomy reservoir filtered and added to perfusate
 Negative pressure for suction generated by roller pump.
 Suction is major sources of hemolysis, emboli, platelet injury,
thrombin generation, fibrinolysis.
 Alternate option is cell saver
 Field aspirate blood is diluted with saline and saline
removed to return only pRBC to perfusate

Venting the Heart
 RV distention rarely a problem during
cardiac arrest.
 LV distention is a problem due to:-
Blood atrial or venous cannulas
Blood from coronary sinus.
Bronchial arterial and venous blood.
Blood from Aortic Valve regurgitation.
Unknown sources (PFO, PDA).
 Left Heart Venting:-
Multihole, soft-tip catheter (8-10F) inserted
into RPSV and LA and into LV then connected
to cardiotomy reservoir

Cardioplegia System
 Solution contains 8-20 Meq/L of K+, Mg++,
and other components
 Given Anterograde and/or Retrograde.
 Temp varies (4-37ºC)
 Normothermic circulation continuous
 Cold circulation use intermittent
 Delivered through separate perfusion
system that includes a reservoir, heat
exchanger, roller pump and bubble trap.

The CPB Team Role
 Surgeon:- Determines the planned operation, target
perfusion temperatures, methods of cardioplegia,
cannulations.
Communicates procedural steps
Connecting/disconnecting CPB, perfusion management, surgical exposure
 Perfusionist:- Setting up and priming the CPB machine,
safety checks, monitoring anticoagulation, adding
prescribed drugs, maintaining records.
 Anesthetist:-“Troubleshooter” of complex procedures

CPB Physiology
Hemodilution
Anticoagulation
Hypothermia.
Flow rate & Blood Pressure.
Blood gas control

Priming & Hemodilution
 Adult circuits require 1.5-2L of balanced electrolyte solution.
 Volume ~40% of patient’s blood volume↓ HCT by 1/3 of pre-op
value Sometimes banked blood added to raise HCT.
 Decreased viscosity results in increased tissue perfusion.
 No consensus on optimal HCT usually 20-25%.
 Hct of less than 20% may be associated with significant
increase in risk of renal injury and that less than 15% may lead
to maldistribution of coronary flow away from the
subendocardium in the presence of residual coronary stenosis

 Dilution may also ↓ O2 carrying capacity if this occurs, need
to transfuse or increase pump flow.
 Sometimes, 12.5-50g of mannitol added to stimulate
diuresis.
 Addition of Glucose/Lactate avoided because shown to
increase neurologic deficits.
 Other additives to the prime may include calcium, and
pharmacologic agents such as heparin and aprotinin.

Anticoagulation
 300 – 400 Units/Kg IV heparin given before arterial and venous
cannulation
 Measure ACT 3 minutes after dose.
 ACT must >480 to begin cannulation.
 During off-pump surgery, ACT should reach 250 seconds.
 If ACT not increasing need to increase heparin dose to 500U/kg
 May need FFP (antithrombin)
 ACT measured every 30min.
 Usually 1/3rd of initial heparin dose given every hour to
maintain target ACT

Reversal
 Protamine (1mg/100U of heparin) given
 Heparin-protamine complex activates complement
pathway & lead to hypotension.
 May need to add Calcium (2mg/1mg of protamine)
 After 1/3rd of protamine dose administered blood must not
be returned to the cardiotomy reservoir from the surgical
field
 Neutralization of heparin must be confirmed by an ACT

Hypothermia
 Reduces metabolism and oxygen demand especially by
brain.
 Allows less blood trauma.
 Myocardial protection & Systemic organ protection.
 Provides a margin of safety in the event of equipment
failure.
Types of Acceptable hypothermias:-
 Mild 37° - 32°C < 5 min 32°
 Moderate 32° - 28° < 20 min 28 °
 Deep 28 ° - 18 ° < 45 min 18 °
 Profound < 18 ° < 60 min

Outgassing {Air Emboli}
 Occurs at tissue level when cooling.
 Occurs at heat exchanger when rewarming.
 Maintain a 12°C gradient when rewarming.
 Cool at a rate of 1°C per 1 minute
 Rewarm at a rate of 1°C per 3 minutes
 Protein denaturation occurs at. 42°C

Blood flow rate/Arterial pressure
 Basic CO2 determined by O2 consumption (250ml/min).
 systemic flow rate is calculated based on the BSA and
modified by the degree of hypothermia and the venous
oxygen saturation (SvO2).
 Generally accepted flow rate with HCT 25%, deeply
anaesthetized, muscle-relaxed patient = 2.4L/min/m.sq.
 Also ↓flow = ↓O2 consumption.
 in most practices, as long as the SvO2 exceeds 70%, the flow
rate is considered to be adequate.
 Cerebral autoregulation maintenance cerebral blood flow
down to a MAP of 40–50mmHg, but may be inadequate in HT
or DM, in whom may need high MAP.

 At 24% HCT, MAP between 55-60mmhg, adequate to maintain
autoregulation.
 In older patients with vascular disease, MAP generally
maintained between 70-80mmhg.
 At lower temperatures, a mean pressure of 35 mmHg is still
generally accepted as safe
 Higher MAPs undesirable as it increases blood in the operative
field.
 Hypotension – causes are low pump flow, aortic dissection,
vasodilation
Phenylephrine, vasopressin
 Hypertension
nitroprusside (arterial dilator)
nitroglycerine (venodilator and pulmonary vessel)

Blood Gas Strategies
 pH stat maintain normal temperature corrected values for pH
and PaCO2
 As blood temperature decreases, CO2 becomes more soluble
 2 Strategies:-
pH-stat – maintains pH at 7.40 at all temperatures.
Requires addition of CO2 while cooling
Cerebral blood flow is higher, and uncoupled to cerebral
oxygen demand
Recommended for pediatric surgery

Alpha-stat – pH allowed to increase during cooling
Blood becomes alkalotic.
Cerebral blood flow is lower, autoregulated, and coupled to
cerebral oxygen demand.
Total CO2 remains constant.
pH changes as temperature changes.
 PaO2:-
>150mmHg to assure complete arterial saturation

Step 2 for CPB
Exposure of the heart & Check Aorta.
Pericardial cradle/sutures.

Step 3 for CPB
Check ACT
Aortic Cannulation
Concentric 2-0 Ethibond stitches with sliders
11 Blade and cannula insertion
Snare both stitches securely and tie to cannula
Connect cannula to arterial line.
Check for any bubbles
Ask for pulse pressure
Secure aortic cannula (skin stitch and/or towel
Remove arterial clamp.

Step 4 for CPB
Atrial (venous) Cannulation
Single Prolene or Ethibond stitch for RA appendage followed by slider.
Make incision/dilate.
Insert cannula with hand over the IVC for accurate positioning.
Secure cannula with slider and tie.
Connect to venous line.
Remove venous clamp
Command “On bypass”
Turn lungs ventilation off.

Step 5 for CPB
Place cardioplegia cannula (retro/ante).
Reduce pump flow/Clamp aorta.
Resume full flow/check line pressure.
Start cardioplegia.
Set pt. temperature with perfusionist.

Step 6 for CPB
Release cross-clamp after warm cardioplegia.
Remove all air from heart.
Begin respirations (start lungs).
Check Good contractility & Stable heart rhythm.
No bleeding.
Desired patient temperature.

Step 7 for CPB
Wean slowly from CPB.
Begin Protamine assessing BP, CVP.
When stable: Clamp venous line and remove.
Remove vent/cardioplegia.
Be alert for hemodynamic reactions.
Remove arterial cannula after all protamine in.
Keep lines clamped and ready for any emergency.

Weaning off bypass
 Flow rate gradually decreased.
 Venous line gradually occluded.
 As flow rate approaches zero, volume is added/removed to keep
arterial and venous pressures within physiologic range.
 Cardiac filling, contractility, and repairs are assessed while
weaning.
 Once Sats near 100%, ETCO2 >25mmHg, and SvO2 >65% mean
satisfactory circulation.
 If all satisfied, can give protamine.

Patient Monitors
 Radial/brachial/femoral arterial catheter.
 CVP via jugular venous catheter.
 Routine use of Swan-Ganz PA cath controversial.
 TEE – important tool for cathether and vent insertion, aortic
atherosclerosis, thrombi and air assessment, contractility, valve
function, diagnosis of dissection.
 Urine output.
 Temperature – Nasopharyngeal or tympanic membrane temp
used more commonly.
 Arterial line temp. correlates best with jugular venous bulb
temp (best surrogate for brain temp).

 Before CPB there is electrical activity
on the EKG
 positive pressures from blood present
in the right side of heart
 pulsatile arterial blood pressure.
 On CPB, the hearts electrical activity
can be suspended.
 Therefore the arterial blood pressure
will be nonpulsatile.
 The right side of the heart will be
empty.

Emergencies in CPB
Aortic Dissection with cannulation
Massive Air Embolism
Stop CPB
Place pt in steep head-down position
Remove aortic cannula from asc. Aorta
Purge asc. aorta of air and refill arterial line
Begin retrograde SVC perfusion for 2-3 min until air is cleared
Return cannula to aorta for systemic cooling and ?pharmacologic brain
protection
Post-op-Hyperbaric O2 & hyperventilation.
Clotted Oxygenator
Decreasing PaO2 with metabolic acidosis
Check O2 supply/blender
Emergency oxygenator change-out may be necessary

Severe Protamine Reaction
Anaphylactic reaction with pulm HTN, edema and systemic hypotension.
100%O2, IV fluids, steroids, antihistamines, vasoconstrictors and bronchodilators.
Inadequate CPB Flow
Directly proportional to venous saturation/acid-base status.
Possible reasons:-
Inadequate CPB volume
Aortic dissection
Cannula problems (aortic or venous)
Oxygenator thrombus
Pump head malfunction

Complications
Cardiac
Difficult to decipher post-op cardiac dysfunction
Subject to emboli, cytotoxins
Myocardial “stunning ”reperfusion injury.
Lung
 Pulmonary edema (complement activation )
 CPB reduces effect of natural surfactant .
 CPB increases shunts, reduces compliance and FRV.
 ARDS
Kidney
Hemodilution, microemboli, catecholamines, diuretics, hypothermia, aprotinin all
impair renal function.

GI
Peptic ulcers (surgical stress).
Pancreatitis and mild jaundice.
Gastroenteritis (increase inflammatory response).
Brain
Most sensitive organ exposed to injury by CPB.
Difficult to assess with difficult outcomes as stroke, delirium & coma
Risk increases with age (>60), Proximal aortic atherosclerosis or PHx of
neurologic disease ↑ ↑ ↑ ↑ risk
Mechanism –microemboli (air, debris, fat) or hypoperfusion.
Protection strategies Mild hypothermia, HCT>25%, cerebral perfusion, off-pump.

CPB in Pregnancy
 In additional to effect of (CPB), pregnant women circulation already altered.
 These effects are relatively well tolerated by the mother.
 Pregnant women mortality during CPB is almost similar to that in nonpregnant.
 Cooling and rewarming phases are associated with increased sustained uterine
contractions.
 Higher fetal mortality rate with hypothermic than with normothermic CPB.
 Pulsatile flow in contrast to nonpulsatile flow, preserves endothelial NO synthesis,
decreases the activation of the fetal renin-angiotensin pathway and preserve
lactate level stable.
 the fetal mortality rate during maternal cardiac surgery with CPB ranges of 16% -
- 33%.
 Current evidence favors maintaining normothermic CPB, high HCT , high pulsatile
flow and avoiding the use of vasoconstrictors .

CPB in Renal failure Pt.
 Patients requiring long-term hemodialysis are known to be at a high risk
for both mortality and morbidity during heart surgery
 In the literatures, the mortality of cardiac surgery from CPB is 3.5% for RF
pt.
 The most important electrolyte imbalance in CPB operations is that of
potassium.
 Renal insufficiency with creatinine levels higher than 2.5 mg/dL increases
the risk of postoperative dialysis and prolongs the length of hospital stay.
 Careful intraoperative techniques, such as avoiding myocardial
depressants & low perfusion pressure with using low-dose dopamine, may
be useful for a good operative outcomes.
 The use of intraoperative hemodialysis was advocated by some centers.

Special Types of Extracorporeal
Circulations

A. Deep hypothermic circulatory arrest (DHCA)
Indications for DHCA include:
Severe aortic atherosclerosis
Type A dissections & intraoperative ones.
Descending thoracic aortic surgery.
Resection of IVC tumors.
 patient is cooled systemically to 18 C to achieve (EEG) silence.
 The head is packed in ice, and methylprednisolone 20 mg/kg is
also given.
 The arterial line is clamped and blood is drained from the
circulation, taking care not to allow air entry in the lines.

 Measures that may extend the acceptable period of DHCA
Include antegrade (Axillary Art.) or retrograde (IJV) cerebral
perfusion.
 Extensive cooling and rewarming are often associated with a
coagulopathy.
 gradient between the arterial inflow and the patient’s
temperature should be no more than 10 –12 C to prevent
generation of gaseous emboli.

B. Left-heart bypass for thoracic aortic surgery
 Indicated in aortic procedure involving descending aortic cross-clamping
with risks of paraplegia and renal dysfunction.
 Left-heart bypass entails drainage of oxygenated blood from the left
side of the heart and returning it more distally in the arterial tree.
 The blood does not pass through an oxygenator, although one can be
placed in the circuit to improve oxygenation
 Minimal heparinization is necessary for this setup (about 5000 units to
achieve an ACT of 250 seconds).
 Flow rates of up to 3 L/min can be used, with monitoring of lower-
extremity mean pressures in the femoral artery that should
approximate 50mmHg.

C. Assisted right-heart bypass for off-pump surgery.
 During manipulation of the heart for off-pump surgery, especially
with hypertrophied hearts, there may be compromise of right
ventricular filling.
 Several devices have been designed that provide right-heart assist
by draining blood from the right atrium and pumping it into the
pulmonary artery during these procedures

D. Extracorporeal membrane oxygenation
(ECMO)
 Is a means of providing a prolonged period of cardiopulmonary
bypass.
 It is applicable to patients with severe hypoxemic respiratory
failure, severe myocardial dysfunction and CDH Pt.
 Arterial line usually placed through a side graft sewn to the femoral
artery to ensure distal perfusion of the leg, and venous cannulas in
the femoral and/or jugular vein.
 Either arteriovenous or venovenous access can be used in the patient
with respiratory failure.

E. Ventricular assist devices (VADs)
 consist of extracardiac circuits and pumps that provide hemodynamic
support to patients with severe ventricular dysfunction.
 This may be noted with postinfarction or postcardiotomy cardiogenic
shock, or in patients with end-stage heart failure.
 These devices may be used as a bridge to recovery or
transplantation.
 They function solely for hemodynamic support.
 They do not provide oxygenation.

s
 SABISTON & SPENCER SURGERY OF THE CHEST-8th ed.
 MANUAL of PERIOPERATIVE CARE in ADULT CARDIAC SURGERY 5th ed--Robert M. Bojar.
 Cardiopulmonary Bypass Mora CT.
 Cardiac Surgery during Pregnancy.
Anish Patel, MRCS, Sanjay Asopa, MRCS, Augustine T.M. Tang, MD, FRCS (CTh), and Sunil K. Ohri, MD,
FRCS (CTh).
 Cardiac surgery with cardiopulmonary bypass in patients with chronic renal failure.
İsa Durmaz, MDa, Suat Büket, MDa, Yüksel Atay, MD, Tahir Yağdı, MDa, Mustafa Özbaran, MDa, Mehmet Boğa,
Mda.

Cardiopulmonary Bypass Guide

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