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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3753_Библиотеки_им_академика_М_И_Перельмана
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300 P. Starinieri
Fig. 2 Advanced modular MiECC for complex surgery
MiECC as an assist device to decompress the
heart.
Minimally invasive extracorporeal circulation
can seamlessly provide maintenance of hemodynamic stability facilitating the surgeon when
manipulating the heart for difficult to reach vessels (lateral or posterior sides of the heart). In this
setting, additional grafts can be performed,
allowing more complete revascularization. This
“hybrid” approach is ideal for the majority of
surgeons who wish to provide the benefits of
beating-heart surgery without compromising the
level of safety associated with stopped heart
procedures. Additionally, it can flatten the steep
learning curve in minimally invasive cardiac
surgery (MICS) by lowering the surgical technical difficulty. MiECC can also facilitate MICS,
accompanied with increased CPB and clamping
times, by minimizing the side effects of these
extended times. We want to share our experience
in multi-vessel coronary bypass surgery by
endoscopic set up in combination with the use of
a minimal invasive perfusion circuit (Video 1 to
Video 15) focusing on overall safety aspects.
3 Team Approach
Prior to induction, the patient’s physi ological
parameters are monitored and self-adhesive sensors containing the infrared light source and light
detectors are placed on both sides of the forehead. In minimal invasive cardiac surgery as
such or in combination with retrograde perfusion,
near-infrared spectroscopy (NIRS) is an interesting tool to monitor cerebral oxygen saturation.
After induction, a transesophageal echocardiography (TEE) probe is inserted into the oesophagus to provide excellent visualization of the heart
and great vessels and to facilitate placement and
confirmation of proper positioning of the various
cannulas and catheters that are used during CPB.
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Video 3 Start CPB (▶ https://doi.org/10.1007/000-a8k)
Video 4 Position table (▶ https://doi.org/10.1007/000-a8m)
302 P. Starinieri
Video 5 Excessive negative pressure (▶ https://doi.org/10.1007/000-a8n)
Video 6 Start air purge control (▶ https://doi.org/10.1007/000-a8p)
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Video 7 Bolus injection medication (▶ https://doi.org/10.1007/000-a8q)
Video 8 Bloodgas sample (▶ https://doi.org/10.1007/000-a8r)
304 P. Starinieri
Video 9 Venous bag empty—add volume (▶ https://doi.org/10.1007/000-a8s)
Video 10 Weaning from bypass patient in trendelenburg (▶ https://doi.org/10.1007/000-a8t)
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Video 11 Reduce RPM (▶ https://doi.org/10.1007/000-a8v)
Video 12 Flush venous line (▶ https://doi.org/10.1007/000-a8w)
306 P. Starinieri
Video 13 Flush antegrade the circuit (▶ https://doi.org/10.1007/000-a8x)
Video 14 Retrieve blood from venous cannula to cellsaver (▶ https://doi.org/10.1007/000-a8y)
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Video 15 Retrieve blood from arterial line to cellsaver (▶ https://doi.org/10.1007/000-a8z)
Proper positioning has becom e increasingly
important with the u se of minimally invasive
techniques that limit the ability to directly visualize the heart and great vessels.
4 Cannulation
The jugular vein or femoral vessels are acceptable vascular access sites for connection to the
heart–lung machine. Vascular access cannulas
used for extra thoracic circulatory procedures are
typically smaller and longer than standard right
atrial cannulas, and some can be inserted
percutaneously.
4.1 Venous Cannulation
If the surgical procedure provides access to the
right atrium, it may be cannulated directly with a
large-bore cannula and drained through gravity
siphon. However, many surgeons have found it
advantageous, especially in MICS, to utilize the
femoral vein to guide an endogenous drainage
cannula into the IVC and right atrium. The right
femoral vein is hereby preferred over the left as it
provides a straighter path for cannulation passage, which may be done percutaneously or
through femoral vein cut down.
The extended length and reduced diameter of
extra thoracic venous cannulae increase the
resistance of blood return. The issue of inadequate venous return during MICS requires
attention of each of the team members. All must
recognize the multiple, frequently covert, technical challenges and mishaps-kinked or obstructed catheters, excessive negative pressure on the
venous return catheters (Video 5), and/or
increased venous capacitance that can lead to
inadequate venous return and inadequate oxygen
delivery.
Good venous drainage requires more than just
a well-designed cannula. The design of the cannula and cannula tip are of great importance and
also the correct choice for a certain procedure.
Reduced venous drainage can lead to flow
reduction. Not only the cannula is responsible for
this problem. Improper placement, smaller
diameter of the venous cannula, resistance,
pressure difference, … all play a role in adequate
venous drainage. Poor venous return from the
308 P. Starinieri
superior vena cava may compromise cerebral
blood flow (MAP-CVP = cerebral perfusion
pressure) leading to neurologic injuries
postoperative.
Although this use of method can create often
only partial support for the circulation, total
cardiopulmonary support through peripheral
cannulas is sometimes difficult to achieve and
assisted drainage is needed.
4.2 VAVD-KVAD
In MICS by groin cannulation, gravity-dependent
venous drainage mostly initiates partial CPB
which indicates the use of assisted venous drainage (AVD). The magnitude of the venous
siphon is gradually increased and pressures of -50
to -80 mmHg are usually adequate without
causing venous conduit “chatter” or collapse. In
contrast to what occurs in conventional CPB,
several minutes usually elapse before a steady
state of extracorporeal circulation is established.
Assisted venous drainage can be proposed for
optimal venous drainage by using a vacuum
source attached to the reservoir or by the use of an
additional centrifugal pump in the venous line.
Using vacuum assisted venous drainage
(VAVD), one must try to avoid excessive VAVD
negative pressures which limits blood trauma and
hemolysis and prevents venous reservoir cracking or implosion. Positive and negative pressure
relief valves must be incorporated into the
reservoir to prevent both overpressure and underpressure to ensure consistent extracorporeal flow
rates. VAVD cannot be applied to closed systems
utilizing a (soft-shell) venous reservoir bag.
Using a soft shell venous reservoir, one can
use an additional centrifugal pump between the
venous cannula and the soft shell reservoir.
Kinetic assisted venous drainage (KVAD) uses a
kinetic pump to mechanically increase venous
drainage. Attention must be made on the fact that
this kinetic pump (usually a centrifugal pump)
can generate significant negative pressures.
MiECC incorporates this assisted venous drainage by using a single centrifugal pump in a
closed circuit and is therefore at higher risk for
venous line cavitation and subsequent air
entrainment because of the direct connection of a
centrifugal pump to the venous cannula. Centrifugal pumps are known to “shred” smaller
amounts of air into microbubbles that the
downstream components need to handle. Therefore is it important that all air is captured by air
handling components (except MiECC Type I)
before it can enter the centrifugal pump. Greater
diligence must therefore be exercised to prevent
air micro-emboli with minimally invasive bypass
techniques. Because small bubbles are not very
buoyant, they advance readily through the entire
perfusion circuit and are expelled through the
arterial cannula.
4.3 Arterial Cannulation
Arterial cannulation strategies are dependent
upon the surgical procedure, but include aortic
cannulation and peripheral vessel cannulation.
When surgical exposure allows direct ascending
aorta cannulation, it is usually the preferred
approach.
The aortic cannula is one of the most critical
components of extracorporeal circulation. A high
flow rate through the narrow lumen of the tip
may lead to a high pressure drop, high local
velocities, turbulence and cavitation, and hereby
cause hemolysis as well as thrombo-embolic
complications by damaging the interior aortic
wall. The choice of area of placement is therefore
of great importance as well as the size and the
direction of the jet flow. The exit flow preferable
points not towards the aorta wall where it can
potentially generate embolization and consequently postoperative neurologic dysfunction can
occur.
When direct ascending aortic cannulation is
not possible, peripheral cannulation may be
achieved at brachial, axillary, and femoral arterial
sites. Femoral cannulation has served as the
standard due to ease and cosmetic scarring considerations. Risks of femoral cannulation include
embolization due to retrograde aortic flow,
femoral or aortic dissections due to vessel
manipulation, and femoral vessel injury with
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hematoma. Retrograde perfusion is therefore not
the best option in calcified peripheral vessels and
central cannulation is preferred to avoid stroke or
cognitive dysfunction.
Besides visualization of proper cannula positioning, TEE is also an excellent means of
detecting and locating retained intracardiac air in
patients on CPB and contributes to the removal
of air before discontinuing CPB and for the
detection of interatrial communication. For
example, a Patent Foramen ovale (PFO) is of
great importance for the perfusionist to choose
the proper circuit for a certain operation. If the
left heart is opened or an aortatomy is performed
in the presence of an existing PFO with single
venous cannulation, air can enter the right side
and cause problems with venous drainage and
air- lock formation in the venous cannula.
A MiECC type IV or “hybrid system” to easily
convert from MiECC to an incorporated “conventional” system is recommended when a PFO
is detected prior to the conduct of bypass providing a safe environment for the team to start
the procedure.
4.4 Safety Concerns
Due to the complexity and extreme invasiveness
of CPB, strict attention needs to be paid to all
aspects of extracorporeal flow, with importance
placed on providing a safe environment for both
the patient and personnel. Technological
advancements, together with an increased
understanding of the pathophysiological effects
of extracorporeal flow, have made the conduct of
CPB both safe and reliable. An essential part of
this success has been the development of monitoring devices that measure both physiological
and mechanical functions.
One of these functions is the removal of
venous air that was suggested in the early nineties for mini-circuits and implemented first in
pediatric practice. This system incorporates a
separate bubble trap in the venous line before the
centrifugal pump with a bubble detector
upstream. With the vent line of the bubble trap
connected through a roller pump to a cardiotomy
reservoir, cell-salvage device or venous storage
bag, the pump can be operated intermittently
based on the bubble alarm to “actively” remove
entrained air from the circuit (Fig. 3 and Video
6). In case of cannula dislodgement, creating a
venous inlet full of air the air handling system
will be likely overwhelmed requiring a second
safety mechanism to step in. The low level alarm
will automatically trigger the arterial clamp
(Fig. 4), giving the opportunity to properly de-air
the venous line retrogradely.
Air can enter the circuit via different ways:
Improper tightening of the venous cannula, direct
air injection with medication bolus administration, cavitation or air coming from vent lines.
4.5 Venting
The left ventricle or aorta is vented to remove
any air that may accumulate. Besides air, blood
may return to the left ventricle through bronchial
vessels and through the lungs pulmonary veins
even if the venous cannula is removing all blood
entering the right atrium. Venting removes blood
that may distend the ventricle. Unless the left
ventricle is completely decompressed, the heart
continues to eject blood which can create an
imbalance in oxygenation between upper and
lower body part when perfusion is done through
groin cannulation.
A vent cannula can therefore be placed
directly in the left ventricle or the aorta can be
vented through a Y-line off the antegrade cardioplegia cannula when cardioplegia is given
antegrade. The venting can also be done through
the right superior pulmonary vein, across the
mitral valve into the ventricle. Large volumes of
continuous air can hereby enter the circuit
requiring a system with proper defoamers and
de-airing capabilities. These de-airing capabilities, as well as the possibil ity to convert to a
conventional circuit are incorporated in a MiECC
type IV or “Hybrid system”. One-way suction
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