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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3612_Библиотеки_им_академика_М_И_Перельмана
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Key Questions in CONGENITAL CARDIAC SURGERY
400
Figure 11. Avalon Elite
catheter.
Reproduced with permission from Getinge.
®
bi-caval double-lumen
Figure 12. ParaGlide™ ECLS adult veno-veno double-
lumen cannula (Chalise Medical, Worksop, UK).
15 Describe the priming solution used for the institution of
extracorporeal membrane oxygenation
Priming of the entire circuit, oxygenator and pump is performed
•
before cannulating the patient.
Carbon dioxide is flushed through the circuit to displace atmospheric
•
oxygen and nitrogen, followed by an infusion of a balanced crystalloid
prime.
Albumin is then added to coat the prosthetic surfaces and decrease
•
platelet and fibrinogen adherence.
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Finally, blood is used to displace the crystalloid to prevent
•
haemodilution, especially in small patients, with the ideal haematocrit
between 30-40%.
A blood gas analysis of the priming solution is made before
•
connecting the patient to the circuit, with adjustments of the priming
pH and electrolytes frequently required.
When blood is added to the prime, heparin is added to initiate
•
anticoagulation (100 units of heparin per unit of packed red blood
cells), followed by a buffer solution, such as sodium bicarbonate.
16 What are the different cannulation strategies for
extracorporeal membrane oxygenation?
Central cannulation — which is performed via a median sternotomy
•
and usually involves an arterial cannula in the ascending aorta and a
right-angled venous cannula in the right atrium. In some cases, an
additional cannula is inserted through the left atrial appendage or the
right upper pulmonary vein to vent the left atrium. Indications include:
a) post-cardiotomy heart failure, refractory to increasing inotropic
support;
b) post cardiac arrest, refractory to conventional CPR (ECPR).
401
Neck cannulation — which can be used for:
•
a) VA ECMO — where the arterial cannula is placed in the right
common carotid artery (RCCA) and advanced to the aortic
arch, and the venous cannula is placed in the right internal
jugular vein (RIJV) and advanced to the right atrium-IVC
junction. It is mostly used in non-post-cardiotomy neonates and
infants requiring both cardiac and respiratory support. The
right-sided vessels are preferred but in exceptional
circumstances the left neck vessels can be used. If this
cannulation is employed, it is important to ensure patency of
the contralateral arterial and venous vessels;
b) VV ECMO — where a double-lumen cannula is inserted in the
right internal jugular vein and advanced into the right atrium. In
neonates and infants, this is performed by open dissection of
the vessels. In larger patients, the cannulation can be done
percutaneously, using the Seldinger wire technique.
Femoral cannulation — which is used for larger patients, where
•
higher flows are needed both on the venous and/or arterial side. In
VA ECMO, the arterial cannula is placed in the femoral artery and the
Key Questions in CONGENITAL CARDIAC SURGERY
venous cannula in the femoral vein, preferably on the opposite side.
In patients who are supported with ECMO for a prolonged period,
the risk of leg ischaemia, distal to the femoral artery cannulation site,
can be significant. This can be mitigated by the (Figure 13):
a) use of a side graft anastomosed on the femoral artery, which is
subcutaneously tunnelled and exteriorised 4 to 5cm inferiorly,
with a separate incision;
b) positioning of a retrograde reperfusion catheter (smaller in size
to restrict the flow) in the superficial femoral artery, connected
to the femoral arterial cannula.
402
AB
Interposition tube graft
Inguinal ligament
FA
FV
Distal arm
Proximal arm
SFA
Figure 13. Strategies to reduce the risk of leg ischaemia during
prolonged periods of ECMO, including: A) an arterial cannula inserted
into an interposition graft anastomosed to the femoral artery, which
prevents occlusion of the artery; and B) a retrograde reperfusion cannula
inserted in the superficial femoral artery to provide distal perfusion. FA =
femoral artery; FV = femoral vein; SFA = superficial femoral artery.
In VV ECMO, if a double-lumen cannula is not used via the right
•
internal jugular vein in larger children, bilateral femoral venous
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cannulation is used, to drain venous blood from one, and infuse
oxygenated blood into the other.
A combination of neck and femoral vein cannulation can be used to
•
improve venous drainage.
17 What are the indications for a left heart vent in veno-
arterial extracorporeal membrane oxygenation?
Adequate drainage of the right atrium should reduce left ventricular
•
preload, so that even in the absence of significant ejection, the left
ventricle should not distend.
In certain circumstances, however, the left ventricle can distend
•
significantly, even when the pulmonary forward flow is substantially
reduced, where a left atrial vent is beneficial, including:
a) severe LV dysfunction with a prolonged lack of contraction and
ejection — where venting may support recovery by reducing
cardiac workload;
b) mitral regurgitation — where the ejecting ventricles are subject
to volume overload;
c) cyanotic patients — where the pulmonary return may be
increased due to arteriovenous collaterals;
d) significant ventricular return and lack of adequate interatrial
shunting;
e) single ventricle circulations — where deoxygenated blood, due
to mixing, could be ejected into the coronary system, affecting
myocardial recovery;
f) severe ventricular arrhythmias;
g) any situation requiring venting, where percutaneous septal
fenestration cannot be obtained.
403
These indications are weighted against adding a second inflow line
•
to the venous drainage with a ‘Y’ connector and the consequent
increased risk of air embolisation in the circuit.
The left atrium can be accessed via the:
•
a) right upper pulmonary vein;
b) Waterston’s groove;
c) left atrial roof;
d) let atrial appendage;
e) left ventricular apex (uncommon).
404
Key Questions in CONGENITAL CARDIAC SURGERY
18 What are the principles of transitioning a patient from
cardiopulmonary bypass to extracorporeal membrane
oxygenation?
Following cardiac surgery with the patient still in the operating
•
theatre, mechanical support should be considered when cardiac
function is inadequate despite maximal medical therapy.
The institution of ECMO, however, should only be considered when
•
the causes of failure are not attributable to residual surgical lesions,
in which case these should be addressed first. The decision should
be a multidisciplinary team decision, involving the surgeon,
anaesthetist, cardiologist and intensivist.
Once all correctable lesions have been excluded, ECMO may be
•
indicated with:
a) severe right or left ventricular failure (normally myocardial
stunning), with the inability to separate from CPB;
b) rapid haemodynamic deterioration, unresponsive to increasing
inotropic and vasopressor support;
c) rapid deterioration in respiratory function, unresponsive to
conventional ventilation;
d) severe pulmonary hypertensive crisis, unresponsive to inhaled
nitric oxide;
e) cardiac arrest immediately after chest closure, unresponsive to
chest reopening and CPR, or responsive but with residual
myocardial stunning.
One of the challenges faced in such conditions is the choice of the
•
transition method from CPB onto ECMO and depends mainly on the
haemodynamic and respiratory status of the patient. The options
include:
a) completely weaning from CPB, administration of protamine
with blood products and then controlled transition to ECMO.
This is usually used for patients where respiratory failure is the
predominant issue;
b) immediate (or almost immediate) transition from CPB to
ECMO, administering protamine to reach an ACT of
approximately 200 seconds. This is usually used for patients
who do not separate from CPB.
Blood loss while on ECMO cannot be saved and reinfused, leading
•
to multiple blood transfusions and ECMO flow instability. In addition,
surgical haemostasis is more difficult whilst on ECMO and surgical
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manipulation of the heart can impair ECMO flow. A heparin-free run
on ECMO for a limited period of time is an acceptable strategy to
limit severe blood loss in these circumstances.
19 What are the indications for the use of extracorporeal
membrane oxygenation in the intensive care unit?
According to current national standards, fully operational congenital
•
heart disease surgical units are expected to provide ECMO support
for a range of clinical situations, including:
a) haemodynamic and/or respiratory support for patients with
congenital heart disease following cardiac surgery;
b) support for patients with or without structural heart disease,
with acute medical cardiac conditions, such as myocarditis,
malignant arrhythmias, cardiac arrest or failure of the newborn;
c) support for patients with or without structural heart disease
with acute medical non-cardiac conditions, such as sepsis;
d) respiratory support for patients with respiratory failure.
There are two main scenarios in which ECMO is initiated and these
•
can present on the basis on any of the above conditions:
405
a) cardiac arrest and cardiopulmonary resuscitation — where
ECMO is normally instituted due to a failure to re-establish an
adequate circulation or to support a stunned heart following
the arrest. If after 5 minutes of internal CPR, the heart function
has not regained, an ECPR protocol is deployed with central
cardiac VA cannulation and initiation of ECMO. In non-surgical
patients, cardiac surgical patients in whom established
adhesions may delay central cannulation or patients with a
significant risk of bleeding, closed massage and VA ECMO via
neck cannulation should be considered;
b) progressive deterioration of haemodynamic and/or respiratory
function despite full medical support — where controlled
cannulation and initiation of VA ECMO should be performed,
with:
i) neck cannulation for non-cardiac surgical patients;
ii) central cannulation for cardiac surgical patients,
provided there is an acceptable risk of bleeding.
In the majority of units, paediatric cardiac surgeons provide surgical
•
support for institution of ECMO, including participating in the
decision-making process and the provision of surgical cannulation.
406
Key Questions in CONGENITAL CARDIAC SURGERY
Non-cardiac ECMO cannulation is also provided by general
•
surgeons, interventional cardiologists and cardiac anaesthetists.
20 What additional cardiorespiratory support is required
for a patient whilst on veno-arterial extracorporeal
membrane oxygenation?
In general, VA ECMO provides cardiorespiratory support and the
•
need for inotropic, vasopressive and respiratory treatments are
reduced.
After initiation of ECMO, cardiorespiratory medical support is
•
gradually weaned, according to the haemodynamic state of the
patient and ECMO flows.
Whilst adrenaline can be reduced to small doses in the first hour,
•
vasopressors are often still needed in the first few hours following
initiation of ECMO support and in some cases, longer. It is required
to counteract vasodilatation that non-pulsatile flow induces on organ
perfusion, with a non-ejecting heart, especially if concomitant sepsis
is present, where severe vasodilatation could be seen after starting
ECMO flow.
Once ECMO flow balance between preload and afterload is
•
achieved, the need for vasopressor and inotropic support is reduced.
After initiation of ECMO, respiratory support is also reduced but
•
minimal ventilation (on the resting setting) is maintained to guarantee
oxygenation of the blood reaching the left heart, which will allow
oxygenated blood to perfuse the coronary arteries, in case of heart
ejection.
The circulatory management of respiratory VV ECMO can be quite
•
different from the cardiac support required with VA ECMO in the
surgical population.
Patients with patent BT shunts may require increased flows and the
•
medical support needed to compensate for the resulting left-to-right
shunting and reduction in systemic perfusion.
Patients with a single-ventricle circulation may require more afterload
•
reduction to compensate for desaturation and limited systemic
output.
21 What are the exclusion criteria for neonatal
extracorporeal membrane oxygenation support?
Gestational age <34 weeks.
•
Body weight <2kg (limited by venous cannula size).
•
Chronic lung disease >15 days on the ventilator.
•
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Uncontrolled bleeding or coagulopathy.
•
Intracranial haemorrhage (Grade III).
•
Known non-correctable cardiac lesions before or after cardiac
•
surgery.
Known non-cardiac congenital anomalies incompatible with life,
•
including chromosomal abnormalities.
Severe trauma involving the central nervous system.
•
22 What are the indications for extracorporeal membrane
oxygenation in the paediatric population?
In infants and older children, the indications for ECMO include:
•
a) post-cardiotomy cardiac failure, including failure to separate
from CPB;
b) respiratory failure following cardiac surgery;
c) acute cardiac failure following:
i) intractable arrhythmias;
ii) acute myocarditis;
iii) pulmonary hypertensive crisis;
iv) drugs and medication overdose;
v) massive pulmonary embolism;
d) cardiac arrest unresponsive to conventional CPR or
myocardial stunning post-CPR:
i) pre-operatively, in patients with a correctable cardiac
condition;
ii) postoperatively, following cardiac surgery;
e) end-stage cardiac failure, as a bridge to VAD or
transplantation;
f) acute rejection of a transplanted heart or lung;
g) acute medical conditions with failed escalating medical
support, including sepsis or acute anaphylaxis;
h) oncology patients or post-bone marrow transplantation, not
responding to maximal medical support, with survival potential;
i) peri-procedural support for high-risk percutaneous cardiac
interventions.
407
23 What are the exclusion criteria for extracorporeal
membrane oxygenation support in the paediatric
population?
Although exclusion criteria may vary according to institutional
•
protocols developed to account for the local patient population,
408
Key Questions in CONGENITAL CARDIAC SURGERY
expertise and resources, general guidelines provided by the
Extracorporeal Life Support Organization (ELSO) include:
a) cardiac conditions, such as:
i) unrepairable congenital heart disease;
ii) severe aortic regurgitation;
iii) unrepaired aortic dissection;
iv) severe peripheral vascular disease, in older patients
requiring VA ECMO;
v) prolonged cardiac arrest >60 minutes;
vi) repeated cardiac arrests;
vii) failed CPR with evidence of severe multi-organ failure;
viii) unwitnessed cardiac arrest;
ix) out-of-hospital arrest (in some centres);
b) respiratory conditions, such as:
i) >7-10 days on the ventilator, depending on age;
ii) escalating ventilator settings, with PEEP >15cmH
mean airway pressure >25cm H2O, peak inspiratory
pressure >45cm H2O;
iii) severe anatomical lesions or injury;
iv) fixed elevated PVR;
v) chronic lung disease;
c) haematological conditions, such as:
i) major life-threatening haemorrhage;
ii) uncontrolled coagulopathy;
iii) immunosuppression;
iv) disseminated intravascular coagulopathy;
d) neurological conditions, such as:
i) severe central nervous system injury;
ii) infection;
iii) hypoxic damage;
iv) trauma;
v) toxic insult;
e) metabolic conditions, such as:
i) severe chronic organ dysfunction, involving the
hepatobiliary, renal and respiratory systems;
ii) severe metabolic failure (autoimmune disease);
iii) oncological diseases of poor prognosis;
iv) chromosomal abnormalities;
f) infective conditions, such as:
i) uncontrolled septic shock.
O,
2
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24 Which imaging modalities are used for patients whilst
on extracorporeal membrane oxygenation?
Chest radiography can be used to confirm the position of cannulae
•
(Figure 14), immediately after cannulation and thereafter at set
intervals depending on institutional protocols. It is important to note
that cannulae differ slightly in their appearance on the chest
radiograph.
AB
409
Figure 14. Chest radiograph in different patients on veno-arterial
extracorporeal membrane oxygenation, immediately following: A)
central cannulation, with a right-angled venous cannula in the right atrium
and a straight arterial cannula in the aorta; and B) neck cannulation, with
the venous cannula longer, reaching the RA, and armed until
approximately 5cm from the tip, which is not radiopaque.
It is often the first line of investigation to assess cannula dislodgment
•
or malposition, and can also identify any kinks or damage.
It can also be helpful to visualise the endotracheal tube, lung
•
pathology, pleural collections and cardiac shadow.
Echocardiography is critical to confirm the position of the cannulae,
•
cardiac function, the presence of any atrial communication and the
diagnosis of any congenital defect not yet identified (Figure 15).
Importantly, it is also used to indicate the progression of the patient
•
on ECMO and allows plans to be made for weaning and
disconnection from ECMO support.
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