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380
Key Questions in CONGENITAL CARDIAC SURGERY
27 What are the strategies to limit or prevent blood loss in
congenital cardiac surgery?
Antifibrinolytic agents — which may reduce the risk of bleeding and
•
total transfusion requirement, including:
a) tranexamic acid — which binds to plasminogen to inhibit
fibrinolysis, thereby reduces bleeding following surgery. It is
given as a 100mg/kg bolus followed by an intra-operative
infusion of 10mg/kg/h;
b) aprotinin — which is a plasmin and kallikrein inhibitor, which
slows fibrinolysis and inhibits factor XIIa formation, and has been
shown to reduce postoperative mediastinal blood loss and
transfusion requirements. It has anti-inflammatory effects that
result in a decreased level of cytokines, including interleukin (IL)6, IL-8, tumour necrosis factor-α, and expression of macrophage
1 antigen. The Blood Conservation Using Antifibrinolytics in a
Randomized Trial (BART) demonstrated that aprotinin is
associated with an increased risk of death, stroke, renal
impairment and heart failure, which led to a temporary
suspension of its use. In 2012, the European Medicines
Regulation Agency, however, reinstituted its use after the results
were not replicated and further data suggested greater benefits
than risks in cardiac surgery. It is given as follows:
i) initial test dose of 1mL = 10,000KIU;
ii) loading dose of 4mL/kg = 40,000KIU/kg (max. 2 million
KIU);
iii) pump prime dose of 4mL/kg = 40,000KIU/kg (max. 2
million KIU);
iv) constant infusion dose of 1-2mL/kg/hr = 10,000-
20,000KIU/kg/hr.
Topical haemostatic agents — which reduce blood loss after cardiac
•
surgery and have a role in reducing both surgical (anastomotic) and
non-surgical (tissue surface) bleeding, including:
a) fibrin sealants — which contain varying combinations of
fibrinogen, thrombin and aprotinin, emulating the final stages of
the clotting cascade, such as Tisseel(Baxter, USA) and
Evicel(J&J Medical Devices, USA);
b) tissue adhesives — which contain bovine serum albumin and
glutaraldehyde, creating a protein hydrogel mechanical seal
independent of the coagulation system, such as BioGlue
10 Cardiopulmonary bypass
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(Cryolife Inc, USA). BioGluecannot be used in children as it
does not allow growth of tissue;
c) gelatin matrices — which swell and control bleeding with a
combination of mechanical tamponade and induction of clot
formation that is thrombin-induced, such as Floseal
Medical Devices, USA), Surgiflo
(Ethicon, USA), Gelfoam(Pfizer, Canada);
d) platelet-rich fibrin — which is used as an autologous fibrin
sealant that is derived from the patient's own blood (usually
120mL of blood taken in the anaesthetic room pre-operatively)
that can be effective with bleeding around suture lines and
supports tissue regeneration and wound healing, such as
Vivostat PRF
Viscoelastic tests — including a thromboelastogram (TEG®) and
•
ROTEM®, that may guide transfusion policy, and the optimisation of
blood and blood products usage.
Filtration — which can remove excess water and small molecules
•
(<12,000Da), thereby concentrating platelets and clotting factors.
Erythropoietin therapy — which, if used pre-operatively, can reduce
•
transfusion requirements in those with a low haemoglobin.
Autologous blood donation — which is only useful over the age of 3
•
years and body weight of >15kg.
®
.
(Baxter, USA), Surgicel
(J&J
381
28 What are the principles of management of
cardiopulmonary bypass in the presence of an
aortopulmonary shunt?
Establishment of cardiopulmonary bypass with cessation of systemic
•
ejection will result in excessive pulmonary run-off from an
aortopulmonary shunt with systemic hypoperfusion.
Examples of aortopulmonary shunts include:
•
a) ductus arteriosus;
b) major aortopulmonary collateral arteries;
c) surgical aortopulmonary shunts, such as a BT shunt or central
Gore-Tex®shunt;
d) multiple small aortopulmonary vessels in the mediastinum of
severely cyanosed patients.
Although aortopulmonary shunts should ideally be controlled prior to
•
commencing CPB, this may not be possible in duct- or shuntdependent circulations, if the shunt is difficult to access, or if there
are multiple small aortopulmonary collaterals.
382
Key Questions in CONGENITAL CARDIAC SURGERY
Shunt-dependent pulmonary circulations should be controlled shortly
•
after commencing bypass. Shunt-dependent systemic circulations
require a period of cooling to help preserve end-organ function until
completion of the surgical repair.
Ejection of the heart during cooling helps to maintain systemic
•
perfusion pressures. Elevated bypass flows and the use of
vasopressors may also be required.
Once the shunt is controlled, bypass and surgical repair can be
•
conducted in the usual fashion.
If the shunt cannot be controlled, hypothermia reduces tissue O
•
demand, thereby allowing a temporary reduction of bypass flow with
a resultant reduction in pulmonary run-off.
The use of deep hypothermic arrest during intracardiac repair may
•
occasionally be necessary to manage the otherwise excessive left
atrial return and to provide adequate visibility in the surgical field.
Once the heart stops ejecting, adequate left atrial drainage is
•
mandatory to avoid severe congestion of the lungs by the significant
pulmonary venous return.
2
Recommended reading
1. Karangelis D, Mazine A, Narsupalli S, Mendis S, Veldtman G, Nikolaides N. Morbidity
after cardiac surgery in patients with adult congenital heart disease in comparison with
acquired disease.
2. Fernandez Suarez FE, Fernandez Del Valle D, Gonzalez Alvarez A, Perez-Lozano B.
Intraoperative care for aortic surgery using circulatory arrest.
9(suppl 6): S508-20.
3. Kramer RS, Herron CR, Groom RC, Brown JR. Acute kidney injury subsequent to
cardiac surgery.
4. Baikoussis NG, Papakonstantinou NA, Verra C, Kakouris G, Chounti M, Hountis P,
Dedeilias P, Argirou M. Mechanisms of oxidative stress and myocardial protection
during open-heart surgery.
5. Durandy YD. Is there a rationale for short cardioplegia re-dosing intervals?
`~кЗбзд
2015; 7(10): 658-64.
6. Hessel EA 2nd. A brief history of cardiopulmonary bypass.
^еЙлнЬ
2014; 18(2): 87-100.
7. McRobb CM, Mejak BL, Elliss WC, Lawson DS, Twite MD. Recent advances in
pediatric cardiopulmonary bypass.
153-60.
8. Saad H, Aladawy M. Temperature management in cardiac surgery.
mê~Åí
2013; 1: 44-62.
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2018; 27(6): 739-44.
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pЙгбе= `~кЗбзнЬзк~Е= s~лЕ= ^еЙлнЬ
2015; 47(1): 16-28.
2015; 18(4): 555-64.
g= qÜçê~Å= aáë
pЙгбе=`~кЗбзнЬзк~Е=s~лЕ
dдзД=`~кЗбзд=pЕб
2017;
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2014; 18(2):
10 Cardiopulmonary bypass
Данная книга находится в списке для перевода на русский язык сайта https://meduniver.com/
9. Hirsch JC, Andropoulos D, Austin EH, Jacobs JP, Licht DJ, Pigula F Tweddell JS,
Gaynor JW. Protecting the infant brain during cardiac surgery: a systematic review.
^åå=qÜçê~Å=pìêÖ
10. Gruenwald CE, Manlhiot C, Crawford-Lean L, Foremna C, Brandao LR, McCrindle
BW, Holtby H, Richards R, Moriarty H, Van Arsdell G, Chan AK. Management and
monitoring of anticoagulation for children undergoing cardiopulmonary bypass in
cardiac surgery.
11. Baikoussis NG, Papakonstantinou NA, Verra C, Kakouris G, Chounti M, Hountis P,
Dedeilias P, Argirou M. Mechanisms of oxidative stress and myocardial protection
during open-heart surgery.
2012; 94(4): 1365-73.
g=bснк~=`зкйзк= qЙЕЬезд
^åå=`~êÇ=^å~ÉëíÜ
2010; 42(1): 9-19.
2015; 18(4): 555-64.
383
384
Key Questions in CONGENITAL CARDIAC SURGERY
Chapter 11
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Extracorporeal membrane oxygenation
Spiros Loggos, Attilio A. Lotto
1 What is extracorporeal life support?
Extracorporeal life support (ECLS) is a general term used to
•
describe any form of extracorporeal support to the heart and/or
lungs, when they are failing and not responsive to conventional
treatments, and includes:
a) extracorporeal membrane oxygenation (ECMO);
b) ventricular assist devices (VAD);
c) cardiopulmonary bypass (CPB).
2 What is extracorporeal membrane oxygenation?
Extracorporeal membrane oxygenation (ECMO) is an extracorporeal
•
life support circulation (ECLS) technique, utilised to provide cardiac,
respiratory or combined support to patients, whose lungs are unable
to provide an adequate gas exchange to sustain life, and/or to
patients whose heart is unable to sustain adequate cardiac output.
The circuit involves draining blood from the venous circulation,
•
pumping it through an oxygenator, where oxygen (O2) is added and
carbon dioxide (CO2) is removed, and then returning the oxygenated
blood back to the patient with an adequate pressure, to either the
venous or arterial circulation, depending on the mode of cannulation
used.
385
3 Describe the history of extracorporeal membrane
oxygenation
ECMO as we intend it nowadays has evolved significantly and has
•
expanded its indications to a larger group of patients.
The first prolonged extracorporeal support was reported by Hill and
•
colleagues in 1972, and historically, was developed for adult patients
with acute respiratory failure refractory to conventional mechanical
ventilation.
386
Key Questions in CONGENITAL CARDIAC SURGERY
In 1976, the first successful support for a neonate who was treated
•
for meconium aspiration syndrome and severe respiratory failure was
reported by Robert Bartlett. She was supported on ECMO for 3
days and recovered fully.
Subsequently, it has been employed in younger patients and also in
•
patients with post-cardiotomy heart failure, unable to wean from CPB
following a cardiac operation.
In the current era, most cardiac units worldwide are able to provide
•
ECMO support. Several technical advances have made ECMO use
safer and easier, with new membrane oxygenators, cannulae and the
introduction of centrifugal pumps, representing some of the
developments.
4 What are the types of extracorporeal membrane
oxygenation?
Veno-venous (VV) ECMO — where blood is drawn with the use of a
•
centrifugal pump from a systemic vein, passed through a membrane
oxygenator and returned to the venous system, ideally near the right
atrium. It provides respiratory support, as it returns oxygenated blood
to the pre-pulmonary circulation and uses the cardiac function to
maintain adequate cardiac output.
Veno-arterial (VA) ECMO — where blood is drawn with the use of a
•
centrifugal pump from the venous system passed through a
membrane oxygenator and returned to the arterial system with an
adequate pressure. It is used for primary cardiac support but also in
heart failure secondary to respiratory failure.
Arteriovenous (AV) ECMO — which uses the patient’s own arterial
•
pressure or incorporates a pump to drive blood across an oxygenator
to partially support the respiratory system by effectively removing
CO2.
5 What is ECPR?
Extracorporeal cardiopulmonary resuscitation (ECPR) refers to the
•
rapid deployment of an ECMO circuit to provide circulatory and
respiratory support during cardiac arrest, when conventional
cardiopulmonary resuscitation (CPR) has failed to provide return of
spontaneous circulation within the expected time frame.
Many studies have shown a superiority of ECPR over conventional
•
CPR in improving survival and neurologic outcome.
11 Extracorporeal membrane oxygenation
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6 What are the differences between extracorporeal
membrane oxygenation and cardiopulmonary bypass
(Table 1)?
CPB is mainly intended to be used during cardiac operations in
•
theatre and consists of a large machine, which requires considerable
priming volume and a larger dose of heparin (300-400 IU/kg), with a
desired activated clotting time (ACT) of >400 seconds. It is prone to
haemolysis and haemodilution, utilises an arterial filter and its
oxygenator can be only used for a relatively short time. Traditionally,
it uses a roller pump and has a blood reservoir (except in mini-bypass
circuits) and is able to provide a wide range of temperature change.
ECMO, however, can only be used to perform a limited number of
•
extracardiac procedures and not open heart procedures but is a
smaller machine, portable and usable by the patient’s bedside, which
only requires a small amount of priming volume and smaller doses of
heparin (50-100 IU/kg), with a lower desired ACT of 150-220
seconds. It has limited haemolytic effects and limited haemodilution,
no separate arterial filter and its oxygenator can be used for longterm support. It has a centrifugal pump, no reservoir and a limited
capability to cool or warm patients.
387
Table 1. Differences between cardiopulmonary bypass (CPB) and
extracorporeal membrane oxygenation (ECMO). ACT = activated clotting
time.
Ideal use
Size and portability
Pumping mechanism
Priming volume
Arterial filters
Venous reservoir
Thermoregulation
Anticoagulation requirements
Haemodilution/haemolysis
Adaptable to haemofiltration
Risk of air embolism
`m_
Cardiac operating theatre
Large, poorly mobile
Roller pumps
Large
Yes
Yes
Wide range
High (ACT >400)
Few hours
No
Low
b`jl
Bedside
Small, highly mobile
Centrifugal pump
Small
No
No
Limited range
Low (ACT 150-220)
Few days
Yes
High
388
Key Questions in CONGENITAL CARDIAC SURGERY
7 What are the differences between veno-arterial and
veno-venous extracorporeal membrane oxygenation?
VA ECMO can be used to support a patient with both respiratory and
•
cardiac failure, maintain higher systemic blood pressures, provide a
variable degree of circulatory support but requires venous and
arterial cannulation. It provides a high O2delivery capacity, has a low
pulse pressure on full flow, and reduces cardiac workload by
reducing preload but it increases the afterload. Coronary perfusion
can be affected by ejection of deoxygenated blood; if not
appropriately vented it can provoke LV distension, and may cause LV
stunning on prolonged use.
VV ECMO, however, cannot be used to support cardiac failure, does
•
not affect directly systemic blood pressure but only requires venous
cannulation (either single or double cannulation). It only provides a
moderate O2 delivery capability, does not reduce cardiac workload,
the pulse pressure is unaffected but increases O2delivery to the
coronary and pulmonary circulation.
8 What are the components of an extracorporeal
membrane oxygenation circuit?
A typical VA ECMO circuit is a complex system (Figure 1),
•
composed of:
a) arterial and venous cannulae;
b) circuit to connect the venous cannula draining from the patient
to the centrifugal pump; from the pump to the oxygenator; and
from the oxygenator to the arterial cannula;
c) magnetically levitating impeller (centrifugal pump) mounted on
a rotating magnet device, controlled by a console (Figure 2);
d) membrane oxygenator to which both the venous and arterial
sides of the circuit are connected (Figure 3);
e) heat exchanger for temperature regulation;
f) air and O2mixer (blender) and sweep gas flow regulator to
optimise O2and CO2gas exchange (Figure 4);
g) side ports (pigtails) used for a wide variety of functions,
including:
i) administration of heparin continuously;
ii) pressure monitoring before and after the oxygenator;
iii) sampling for blood gas analysis;
iv) connecting the venous and arterial sides of the circuit
(bridge) to temporarily isolate the patient from the
ECMO pump without stopping the flow (Figure 5);
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389
Figure 1. Veno-arterial extracorporeal membrane oxygenator (VA
ECMO) circuit: with pigtail 1 used for the venous side of the bridge; pigtail
2 used for inlet pressure monitoring and a large air and fluid line; pigtail
3 used for activated clotting time (ACT) measurement and central venovenous haemofiltration (CVVH) access; pigtail 4 used for CVVH return;
pigtail 5 used for pre-membrane pressure monitoring and heparin
infusion; pigtail 6 used for air removal and addition of volume; pigtail 7
used for post-membrane pressure, gas samples, clotting products (if
there is no patient access); and pigtail 8 used for the arterial side of the
bridge.
v) connecting the circuit to a continuous renal replacement
unit (CVVH);
h) flow sensors.
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