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Two difference Oxygenators avilable

Membrane oxygenator--sheaves of hollow fibers (120 to 200 um) with 0.3-0.8 um pores. produce less particular and gaseous micro-emboli, less reactive to blood elements, and allow superior control of blood gases

Bubble oygenators--cheaper, produce more gaseous micro-embolic and therefore rarely used.


Types of Cardiopulmonary bypass pumps

Roller Pumps--produce flow by compression of the heparin-coated tubing using two rollers 180 degrees apart. The flow rate is determined by
a) rate of rotation of the rollers
b) degree of compression
c) length and diameter of the tubing being compressed

Centrigular pumps--flow by using a rotating impeller. The flow rate is determined by
a) speed of rotation of the impeller
b) afterload within the circuit, distal to the pump


Name 3 filters available within the CPB system

1) Arterial line filters (40um) used to reduce the cerebral embolic load

2) Leucocyte depleting filters removed activated neutrophils and therefore may reduce the system inflammatory response

3) Ultrafiltration and modified ultrafiltation, which remove excess fluid. Also good for filtering cytokines.


How does Protamine work

Protamine is a cation (comes from salmon sperm) that binds with the anion, to form stable heparin-protamine complexes

For each 100U of heparin given then 1mg of protamine should be injected IV.

Should be given over 15 minutes


Describe Horrow Classification of Protamine Reaction

Class 1: Hypotension--caused by rapid administration of protamine. Triggered by a histamine release and can usually be treated by fluid resuscitation and vasopressor

Class 2:
IIa (true anaphylaxis)--hypotension, brochospasm and angioedema---mediated by anti-protamine immunoglobine E antibody, histamine, prostaglandins, and kinins. Patients with fish allergies and those exposed to protamine.
IIb (immediate anaphylactoid) and IIc (delated anaphlactoid) less severe--mediated by complement
Class 3: Catastrophic pulmonary vasoconstriction--complement activation and release of thromboxane A2 (RV failure, circulatory shock, severe broncospam)


5 Complication of CPB

Systemic inflammatory response
Renal and splanchnic hypoperfusion
Cerebrovascular accident


5 things to check before going on CPB

arterial line pressure
decompression of heart
venous drainage
systemic arterial and venous pressure
arterial blood oxygen cocentration

once bypass is started should wait 2 minutes to make sure that hemodynamic factors are stable, lung ventilation is off, systemic cooling is happening, and then cross clamp aorta


Principles of managing an IVC tear during venous cannulation

Advance the venous cannula into the IVC beyond the tear to obtain venous drainage along with cardiotomy suction return
use additional purse string to secure the venous cannula
cool to 18 degrees
during circulatory arrest the IVC can be repaired by direct suture or using a bovine pericardial patch


Management of massive airlock in venous line

Stop CPB
separate the venous cannula from the venous line
manually fill the venous line with saline
reconnect the venous cannula to the venous line
If there is a small to moderate amount of air it can be chased back into the reservoir by progressively lifting the venous line


management of massive arterial air embolism

Stop CPB---clamp both arterial and venous lines
place pt in steep Trendelenburg position
Remove arterial cannula and aspirate any air at the site of entry
Remove the venous cannula
Place the arterial cannula via the right atrium into the SCV and snare
Start retrograde cerebral perfusion at 400 to 500 ml/min for 3 minutes
Mannitol, dexamethasone, and ice packs around the head
Antegrade circulation is then recommenced withe DHCA for 30 minutes
The perfusion pressures are kept relatively high (70 to 80 mmHg) and 100% Fio2
TEE to look for residual air
Hyberbaric chamber/disclose to family


Management when arterial cannula falls out

Stop CPB
Clamp venous line
Flush the arterial line and forward flow from pump
Replace the arterial cannula
Reconnect the arterial line and the arterial cannula, ensuring the absence of air bubbles


Signs of iatrogenic aortic dissection

Spreading hematoma with bleeding at point distal to the cannulation site
Classically a boggy mass may be palable
failure of blood to rise to the top of arterial cannula
Poor swing on the arterial line following removal of the line clamp
High line pressure when fluid is infused via the arterial cannula
Profound hypotension with poor venous return


Principles of managing iatrogenic aortic dissection

Stop CPB and clamp both arterial and venous lines
Insert the aortic cannula into the right atrium and rapidly infuse volume as required
Inset an arterial cannula into a peripheral artery or uninvolved distal aorta
Following DHCA (18) the ascending aorta is opened and inspected for dissection at the orginal site of cannulation
The aorta can then be repaired using a direct suture, patch, or interposition graft depending on the extent of the dissection
It is important to recognise and treat iatrogenic aortic dissection immediately, to limit the extent of the injury and restore the systemic perfusion--when recongnised early survival rates are 66-85% but when discovered late its only 50%.


Describe de-airing routine for AVR

Prior to tying down the aortotomy suture
1) patient in Trendelenburg position
2) venous line is partially occluded to fill the heart
3) heart is gently agitated while keeping the aortotomy open with forceps to allow release of trapped air
4) lung are inflated to displace any air in the pulmonary veins
5) aortic cross clamp is removed and the aortotomy suture is tied
6) aortic root is turned onto suction

TEE to confirm de-airing process


Indications for Deep Hypothermic Circulatory Arrest

Aortic dissection
Arch aneurysms
Thoraco-abdominal aneursyms
Renal tumors invading the IVC and right atrium
Complex congenital cardiac surgery
Porcelain aorta
Pulmonary thromo-endarterectomy
Blood loss during resternotomy
Repair of ruptured thoracic aorta


What are safe periods of circulatory arrest

Temp Duration of safe CA (min)
36 1
32 5
28 10
24 20
20 30-40
16 45-60


What strategies exist in the management of acid-base metabolism during DHCA

pH stat
--adding CO2 to keep the PaCo2 and pH at 7.4 which are normal levels in arterial blood at 37 degrees
-advantage of a more rapid and homogenous cooling but an increased risk of cerebral embolism

alpha- stat
--- not adding CO2 thereby allowing the pH and PaCO2 to drift as dictated by the solubility at a given temperature, producing alklotic blood during the cooling process.
--- has the advantage of reducing the risk of cerebral embolism and the alkalosis produced may also be beneficial in terms of reducing cerebral and mycardial metabolism.

pH stat on cooling enhances cerebral perfusion by maintaing PaC02 and facilitates cooling and alpha stat on rewarming to reduce the miroemboli load on the circulation.


Names different options for blood conservation

Tranexamic acid
recombinant EPO
delaying surgery in patients on ASA/Plavix.
Autologous pre-donation
Intra-operative cell salvage
Auto-transfusion of washed shed post operative mediastinal fluid
Meticulous hemostasis
consider fibrin glue
Low threshold for resternotomy for bleeding


2 studies examining Aprotinin

IMAGE trial showed aprotinin:
reduces postoperative mediastinal blood loss
reduces the need for postoperative blood transfusions
reduces the need for post operative platelets
reduces the resternotomy for blooding
possible reduction of graft patency when you have poor run off
Increased incidence of mortality
renal impairment
heart failure and myocardial infarction


What is heparin resistance

failure to achieve the desired effect on the coagulation system with the standard, or increasing doses of Heparin. Once > 500u/kg
1. Recent administration of Heparin
2. Congenital AT III deficiency (0.2 to 0.3%) of the general population
3. Hepatic or renal failure
4. Premature or cyanotic infants
5. Synthetic estrogen use
6. chronic illness and cachexia


Describe steps of routine weaning from CPB

check lines for kinks, lab values (K, Hg, Can, pH), temperatture, rhythm, ST segments, suction the chest, atrial and ventricular pacing

If failed once
a. Go back on CPBN (reperfuse) for 15 minutes
b. correct metabolic defects
c. rewarm, assess for ischemia, intracoronary air
d. consider and start inotropes
e. consider IABP
f. TEE review


List advantages of alpha vs pH stat

No added CO2
better subendocardial blood flow
lower CBF may cause ischemia
changed defibrillation threshold
used in most adults

Co2 added/
Better brain protection/used in neonates/higher CBF and may cause edma and emboli


8 factors that protect the brain during DHCA

Steep head down position
Ice packing around the head
antegrade cerebral perfusion
tight glucose control
retrograde cerebral perfusion


Describe antegrade cerebral perfusion technique

continuous perfusion of the brain with oxygenated blood independently of the rest the body, at physiological flow and pressure of 10 to 20 ml/min and 40 to 50 mmHg (via right radial artery.

Two options are 1) non selective (cannulation of right axillary artery with left hemisphereic perfusion dependent on patent circle of willis) or 2) selective cannulation of both left common carotid and innominate artery.

Advantages: potential for proloned safe time on circulatory arrest; improved cerebral cooling, potential for moderate instead of deep.


What is strategy for retrograde cerebral perfusion

RCP flow of 300 to 500 ml/min retrogradely through the SVC to maintain a pressure between 20 to 35 mmHg.

opportunity for de-airing
may remove sold emboli
avoids manipulation of atheromatous arch vessels
mild evidence that blood reaches the cerebral target (only 2 to 10% of blood is directed at brain 90% deviates through the azygos)


What are causes of heparin resistance

Recent administration of Heparin
Congenital AT III deficiency
Hepatic or renal failure
premature or cyanotic infants
synthetic estrogen use
chronic illness and cachexia


What is acceptable retrograde myocardial protection values

Coronary sinus pressure of 15 to 30 mmHg and a flow rate of 150 to 200ml/min

pressure higher then 200 mmHg increases the risks of rupture and leads to increases shunting of cardioplegia flow to the RV


What are problems with retrograde cardioplegia

Inadequate myocardial protection
RV usually underprotected. Common placement of catheter too deep into the CS
Perforation of the coronary sinus
slow arrest
myocardial edema


How is Cerebral perfusion pressure caculated


(ICP) intracranial pressure


What are risks for a pregnant lady undergoing CPB

Avoid hypothermia--body temperature of < 35 may trigger uterine contractions
Increase the pump output by 25%
Heparinazation is unchanged
Maternal risk of death is similar to the risk of a non-pregnant women
the risk of fetal death is 10 to 50% and its related to the duration of CPB


List deleterious effects of CPB circuit

activation of complement
release of endotoxin
activation of leukocytes
increased expression of adhesions molecules
release of inflammatory mediators, including cytokines, free radicals
resulting in
third-space fluid retention
subtle end-organ dysfunction


Describe the easiest classification of protamine reactions

Type 1: Transient hypotension and low cardiac output due to compliment/histamine release

Type 2: Anaphylactic reaction due to IgE and IgG antibodies. High risk for this to ccur again. Responds to Epi and steroids

Type 3: Pulmonary hypertension due to release of Thromboxane A2.


What is treatment for protamine reaction

Use Protamine
test dose 1 to 10 mg followed by slow administration over 10 to 300 minutes
discontinue bypass and wait for the heparin to wear off
Use alternate treatments
Methylene blue
Consider off pump


What other drugs and dose can you give as alternative to heparin

Argatroban at 2 u/kg/min--no reversal agen
Lipirudin infusion


What are rates of dispersion for Cardioplegia when given retrograde

55% returns to Left Coronary
15% to the right Coronary
30% to the Right ventricle


What are retrograde parameters that should be used

Coronary sinus pressure of 15 to 30 mmHg
Flow rate of 150 to 200 ml/min
A pressure in CS of higher then 200 mmHg increases the risk of rupture and leads to increased shunting of carioplegia flow to the RV


List problems with retrograde carioplegia

Slow arrest
myocardial edema
Perforation of CS
Inadequate myocardial protection because it's placed too deep


List reasons why antergrade cardioplegia not arresting the heart

Aortic root vent is not clamped and cardioplegia solution circulated to the vent
No K in cardioplegia
Unable to close the aoric valve (too slow administration)
Severe AR
High grade proximal or ostial coronary disease
Aortic dissection


What are principles of deairing the heart

minmize air entrapment (keep the heart full of blood)
reperfuse and allow the heart to beat before coming off CPB
Aspirate pockets of air before ejection
Apply continuous suction on the aortic root during the initial period of cardiac ejection


What is in St. Thomas solution

St Thomas sol’n:
Bicarb 10mEq/L
Ca2+ 2.4mEq/L
K+ 100mEq/L or 30mEq/L
Cl 244 mEq/L
Na+ 120 mEq/L
Mg2+ 32 mEq/L
osmolarity 324 mOsm/L
pH 7.4


What can be done on CPB with renal failure

prime sol’n should have little K+ (< 5mEq/L)
cardioplegia should be avoided or completely scavenged
hemodialysis should occur the day b4 surgery or in OR just prior to surg
should be prepared for dialysis on pump
monitor electrolytes carefully and any volume changes


At start of plegia note precipitates in cardioplegia: diagnosis

cold agglutination is an IgM mediated response
autoantibodies against red cell antigens are activated by cold
diagnosed by direct Coombs’ test at various temps


What are harm and harmful cold aggultins

harmless cold agglutinins
found in normal pts
have narrow thermal range of 0-4˚C
produce reversible agglutination
harmful cold agglutinins
hemolytic anemia
peripheral vascular obstruction
complement activation (typically below 32˚C)


What is management of Cold Agglutins problem

know antibody titre and critical temp
don’t let blood temp or pt temp fall below critical temp of antibody
consider pre-op plasmapheresis w/ FFP to lower plasma antibody titre
hemodilute to decrease titre
use warm crystalloid cardioplegia (to wash out antibody) followed by warm blood cardioplegia
adequately rewarm pt
employ regional hypothermia
watch for Reynaud’s or hemolysis
azothioprine or cyclophosphamide to depress antigen/antibody formation


What are factors of cardioplegia

Most of the data for the negative results of crystaloid cardioplegia comes from the a sub study of the CABG patch Trial which showed in 885 patients with low ejection fraction that pts who had crystaloid cardioplegi vs blood cardioplegia had a 10% vs 2 % rate of post op MI, and 21 vs 12 % conduction abnormalities. However, despite this higher operative mortality there was no difference in early or late mortalities.


Describe hypothermic fibrillatory arrest

Patient is cooled down to 28C
heart is allowed to fibrillate
Systemic perfusion is maintained between 80 and 100 mmHg
Myocardial revascularisation can be performed
Limitations of this technique:
The surgical field may be obscured by blood during revascularization
Ventricular fibrillation is associated with increased muscular tone, which can limit the surgeon's ability to position the heart for optimal exposure
It is generally not applicable for intracardiac procedures.


What are types of crystalloid solution

Intracellular: Absent or low concentrations of sodium and calcium
Extracellular: High concentrations of sodium, calcium and magnesium.
Both contain potassium ranging from 10 to 40 mmol/l, bicarbonate buffer and are osmotically balanced


Describe cold blood cardioplegia

most commonly used type of cardioplegia
Different formulations but basically consists off: a) autologous blood from the extracorporal circuit mixed with crystalloid solution of
b) citrate-phosphate-dextrose (CPD) ( to lower ionic calcium)
c) tris-hydroxymethyl-aminomethane (tham)
d) bicarbonate buffer ( to keep pH alkaline at 7.8)
e) potassium chloride ( to arrest the heart, around 30 mmol/l)
The temperature is lowered to between 4 and 12 C
The ratio of blood to crystalloid varies e.g. 8:1, 4:1, 2:1
“ Miniplegia”: undiluted blood cardioplegia.


List benefits of blood over crystalloid

provide an oxygenated environment.
provide a method for intermittent reoxygenation of the heart during arrest.
Limit hemodilution when large volumes of cardioplegia are used.
excellent buffering capacity.
excellent osmotic properties.
The electrolyte composition and pH are physiologic.
contains a number of endogenous antioxidants and free radical scavengers.
Less complex than other solutions to prepare.


List 3 adverese events of CPB

Neurological deficits (stroke, coma, post op neuro dysfunction)
Renal dysfunction
Systemic Inflammatory response syndrome


Two main types of Venous reservoir

1) Open reservoirs (rigid, hard plastic canisters)--Large capacity for storage of circulating volume, allow vacuum-assisted venous drainage, easier to prime, aless expensive, can incorprorate filters and allow for volume measurements and management of venous air

2) Close reservoirs (collpasible, soft plastic bags)--less versatile, eliminating the blood-gas interface, able to reduce the systemic inflammatory response, lower risk for producting gas micro-emboli

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