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3. Hessel EA 2nd. What’s new in

cardiopulmonary bypass.

J Cardiothorac Vasc Anesth.

August, 2019;33(8):2296–2326.

4. Ramchandani M, Al Jabbari O,

Abu Saleh WK et al. Cannulation

strategies and pitfalls in

minimally invasive cardiac

surgery. Methodist Debakey

Cardiovasc J.January–March,

2016;12(1):10–3.

Christiana Burt, Timothy A Dickinson, Narain Moorjani and Caitlin Blau

Chapter

Minimal Invasive Extracorporeal Circulation

Kyriakos Anastasiadis, Polychronis Antonitsis, Helena Argiriadou and

Apostolos Deliopoulos

Minimal invasive extracorporeal circulation (MiECC)

is a recent development in perfusion science.

MiECC’s unique characteristics include advances

such as closed circuits with elimination of blood-air

interaction, reduced hemodilution, biocompatible

surfaces, and lack of scavenging and reinfusion of

unprocessed shed blood. Contemporary hybrid

(modular) systems allow perfusionists to safely

employ MiECC in the full spectrum of cardiac sur-

gery. MiECC provides the base for developing a mul-

tidisciplinary intraoperative strategy which

encompasses a surgeon’s particular technique and

goal-directed perfusion, as well as modified heparin/

protamine management. Proponents of MiECC are

convinced that it will ultimately replace conventional

CPB and become standard practice in cardiac surgery

once the potential clinical benefits have been widely

accepted. As with traditional extracorporeal circula-

ton (ECC) techniques, MiECC requires close collab-

oration of surgical, anesthesiology and perfusion

colleagues for optimal outcome.

The Evolution of Minimal Invasive

Extracorporeal Circulation

MiECC has its roots in Extracorporeal Life Support

(ECLS), where a single circui t with low systemic

inflammation, low hemodilution, and enhanced bio-

compatibility to reduce anticoagulation is required.

The successful use of such systems opened a new era

in short-term mechanical circulatory support.

Subsequently, during the mid-90s multidisciplinary

teams developed minimally invasive CPB systems

for coronary surgery. These first systems comprised

of short arterio-venous lines without cardiotomy res-

ervoir in order to reduce hemodilution and transfu-

sion requirements. Kinetic venous drainage with

integration of a centrifugal pump allowed for a com-

pact closed circuit that could be installed close to the

patient’s chest. In order to improve biocompatibility,

to reduce injury to blood cells and to minimize

expression of inflammatory mediators, all lines and

oxygenator were coated with heparin, while priming

volume was reduced to a minimum. Shed blood from

the surgical field was collected, washed and transfused

with a cell salvage device, avoiding the adverse effects

of recirculating unprocessed shed blood from the

operating field into the CPB circuit.

The last two decades have witnessed numerous

additional advancements in MiECC technology along

with encouraging clinical results. This evolution led to

the foundation of the multidisciplinary Minimal

Invasive Extracorporeal Technologies International

Society (MiECTiS) in order to promote research,

clinical use and standards to further develop minim-

ally invasive perfusion. MiECTiS advocates a multi-

disciplinary strategy invol ving surgery, anesthesiology

and perfusion to promote maximum benefit from this

technology.

The term MiECC has replaced all other descriptive

terminology previously used for minimal extracor-

poreal circulation circuits, such as: miniaturized

extracorporeal circulation (MECC), mini extracor-

poreal circulation (mECC), minimized extracorporeal

circulation or mini cardiopulmonary bypass (mCPB,

mini-CPB).

Table 8.1 summarizes the mandatory and add-

itional components of a contemporary MiECC

circuit.

Classification of MiECC systems

MiECTiS has adopted a classification of MiECC

systems that reflects how they have evolved over the

last decade. Figure 8.1 illustrates a Type III / IV

circuit, which is the type most commonly used today.



Type I

systems are derived from ECLS circuits

with the addition of a line to administer

cardioplegia. These systems are suitable for

performing closed-heart surgeries. Soon after

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their introduction significant safety concerns

emerged: there was a risk of air entrainment and

air lock, requiring stopping the pump and

manually de-airing the circuit.



Type II

circuits addressed the air entrainment

issue seen with Type I systems by integrating a

venous bubble trap or air removal system.



Type III

systems were driven by the desire to use

MiECC technology for open-chamber heart

surgery, such as valve replacement. The addition

of a soft-bag or soft-shell reservoir allows for the

management of the circulatory volume during

CPB, which is particularly important in patients

with preoperative volume overload, such as in

aortic or mitral insufficiency.



Type IV

are modular, hybrid systems which

integrate a heparinized venous reservoir as a

standby component, readily available for

conversion to an open, conventional CPB system.

This configuration allows the use of MiECC in the

full spectrum of cardiac surgery including

Table 8.1. Components of MiECC

Mandatory

Components

Closed CPB circuit

Biocompatible surfaces

Reduced priming volume

Centrifugal pump

Membrane oxygenator

Heat exchanger

Cardioplegia system

Venous bubble trap/venous air

removing device

Shed blood management system

Additional

Components

Vents



Aortic root



Pulmonary artery / vein

Reservoir



Soft bag / soft-shell



Hard-shell (modular

systems)

Regulated smart suction

Arterial line filter

Soft bag

reservoir

Vent

Oxygenator heat

Cardioplegia

Bubble

trap

Hard shell

reservoir

Centrifugal

pump

Roller

pumps

Figure 8.1 Typical Type III circuit, which can easily be converted into Type IV by removing the clamps from the afferent and efferent tubing

from the hardshell reservoir. Any cell salvage, if used, needs to be reinfused into the hardshell reservoir.

Kyriakos Anastasiadis, Polychronis Antonitsis, Helena Argiriadou and Apostolos Deliopoulos

complex patients and procedures, as any

unexpected perfusion scenarios, such as massive

air entry to the venous side of the circuit or

accidental excessive blood loss to the

mediastinum, can be managed by an easy switch

to standard CPB.

The Team Approach to MiECC

It is of utmost importance that all members of the

team not only comprehend perfusion technology, but

that they understand the unique characteristics of

MiECC, particularly what it can and what it cannot

deliver. Continuous excellent communication with

the perfusionist is of utmost importance, particularly

during critical moments, such as during retrograde

priming of the circuit with patient blood via the aortic

cannula (retrograde autologous prime [RAP]), when

securing the vent for the cardioplegia line or when

removing a vent, in order to avoid accidental air

entrainment into the system.

Surgeon’s perspective

Firstly, the surgeon must appreciate that when oper-

ating on MiECC shed blood does not recirculate into

the bypass circuit and is not available for the circulat-

ing volume. Meticulous operative technique is man-

datory and special attention must be paid to avoiding

blood loss, not dissimilar to requirements of beating-

heart surgery.

Secondly, all cannulation sites must be secured in

a way that provides an airtight seal. The venous can-

nula is commonly secured with two purse-string

sutures and two silk ties; some surgeons arm the

purse strings with Teflon pledgets, particularly when

the right atrial appendage is of poor quality tissue.

Some advocate double-snaring the inferior and super-

ior vena cava cannulae during mitral valve surgery to

mitigate against air entrainment. Any manipulations

of the heart must be done very carefully in order not

to displace the venous cannula(e). Lines are connected

with due diligence to avoid introducing air. Accurate

positioning of the venous cannula is essential to

achieve optimum drainage, which can be assisted by

placing a pulmonary artery vent.

Anesthesiologist’s perspective

MiECC systems are closed and, without the option of

easily adding fluids as necessary, they effectively make

the patient’s venous compartment the reservoir. This

means that fluids have to be used judiciously, i.e.

filling up the venous compartment sufficiently with-

out losing the benefit of minimal hemodilution with

low prime volume. Appropriate use of vasocon-

strictor or inotropic support before initiating CPB

can help maintain hemodynamic goals.

Standard perioperative hemodynamic monitoring

with invasive, continuous mean arterial pressure

(MAP), central venous pressure (CVP) and transeso-

phageal echocardiography (TEE) is often expanded by

using pulmonary artery catheters (PAC) and continu-

ous cardiac output (CCO). Some centers opt to use

near infrared spectroscopy (NIRS) monitoring of

cerebral oxygenation as an index of global perfusion.

Some advocates of MiECC use its unique charac-

teristics – minimal hemodilution, biocompatible sur-

faces, elimination of blood-air interaction and

elimination of unprocessed shed blood reinfusion –

to use less anticoagulation, aiming for an ACT value

>300 seconds for coronary surgery and >400 seconds

for valve and more complex procedures.

Perfusionist’s perspective

MiECC integrates all advancements in perfusion tech-

nology in a single circuit, but also provides a chal-

lenge for the perfusionist.

Centrifugal pump flow is largely dependent on a

balance between the filling status of the patient and

the systemic vascular resistance and therefore needs

regular adjusting. All commercially available centrifu-

gal pumps are fitted with bubble detectors, which

cause the pump to stop when air reaches the sensor.

In that case the perfusionist has to immediately de-air

the bubble trap by applying suction to it, while at the

same time adding volume to the circuit. Devices that

can purge air automatically can be integrated into the

circuit, removing the need for the perfusionist

to intervene.

The perfusionist has to appreciate the principles of

a closed circuit, where the patient’s venous compart-

ment acts as the reservoir. The patient’s volume status

is monitored via several surrogate measures: negative

venous drainage pressure, arterial pressure, cardiople-

gia pressure and the amount of blood drained from

the aortic root vent. Pump flow is another sensitive

parameter, as it decreases with hypovolemia. Moving

the operating table into Trendelenburg position and

volume replacement and/or administration of

Chapter 8: Minimal Invasive Extracorporeal Circulation

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vasoconstrictors are measures to increase the preload.

On the other hand, hypervolemia can cause difficul-

ties in off-loading the heart and in obtaining a blood-

less surgical field. In this case, surplus blood volume

can be decanted into the soft-shell reservoir or the

table can be moved into the reverse-Trendelenburg

position.

Understanding the principles of kinetic-assisted

venous drainage produced by the centrifugal pump is

of paramount importance as the negative pressure at

the venous line provides important information on the

filling status of the patient. Exceeding 70 mmHg can

result in cavitation with the creation of gaseous micro-

emboli and can lead to high blood velocity thereby

increasing shear stress and hemolysis at the level of

the entrance holes of the cannula and at the wall of the

cannula. Increasing the assisted venous, and thus the

negative pressure, is not a solution for correcting

improper cannula position or hypovolemia.

Major determinants of negative pressure are the

type, the size and the position of the venous cann ula.

When increasing the negative pressure, drainage ini-

tially increases linearly with pressure until any further

increase collapses the surrounding venous wall and no

further advantage in flow will be seen. The ratio

between the diameter of the cannula and the vein

should be around 0.6 in order to avoid collapse of

the vein around the side holes of the cannula. Re-

positioning of the venous cannula may be required to

provide appropriate flow. In case of bicaval cannula-

tion, the perfusionist should prom pt the surgeon to

check flow in every cannula separately.

In case of a temporary excess in negative pressure

due to venous cannula displacement while lifting the

heart, the perfusionist might need to add volume to

compensate and ensure adequate flow.

During surgery with MiECC it is imperative to use

blood mini-cardioplegia (i.e. Calafiore regime) in

order to avoid excessive volume. The cardioplegic

solution is delivered with a roller pump in combin-

ation with a high-speed syringe driver. Hyperkalemia

during cardioplegia delivery can cause transient vaso-

dilation but rarely warrants an intervention.

Since there is no cardiotomy reservoir in the

MiECC circuit, shed blood is collected into a cell

saver. The collected blood is processed and adminis-

tered as required after weaning off CPB. In case of

excessive bleeding, the collected blood can be given

back into the circuit directly. Type IV circuits are best

equipped to deal with sudden massive blood loss.

Advantages of a Modular Design

Modular MiECC systems (i.e. Type IV) represent the

latest evolution in the field of extracorporeal circula-

tion. They integrate contemporary advancements in

perfusion technology and address safety concerns. As

previously described, they are Type III circuits with a

standby hard-shell reservoir connected in parallel to

the venous line to allow immediate conversion into a

conventional circuit if required. The circuit configur-

ation of the AHEPA University Hospital Thessaloniki

prototype Type IV MiECC circuit is shown in

Figure 8.2.

Two recently published series show that modular

configuration ensured 100% technical feasibility for

performing every type of cardiac surgery including

aortic arch replacements. They reported conversion

rates to conventional CPB of 0.8 and 6%. Modular

configuration is advocated for all cardiac surgical

procedures, including isolated coronary artery bypass

grafting, in order to promote more widespread adop-

tion of MiECC technology in modern cardiac surgical

practice.

Training

A MiECC training program can be divided into five

stages (see Figure 8.3). After appropriate proctorship,

a dedicated team of surgeon, anesthesiologist and

perfusionist can start operating on coronary cases,

using at least a Type II MiECC system. Experience

shows that tangible results, particularly in reducing

transfusion requirements, materialize after about

50 cases.

After having completed 50 cases, it is feasible to

progress to uncomplicated open-chamber heart sur-

gery, such as aortic valve replacement. Although these

operations are doable with a Type II circuit, the

integration of a soft-shell reservoir (Type III circuit)

is highly recommended for volume management.

After gaining experience in aortic valve cases,

more complex mitral and tricuspid valve procedures

can be pursued with a Type III circuit, although a

modular design is advocated as a “safety net.” With a

high level of expertise and confidence in using Type

IV circuits, any cardiac procedure, even emergency

aortic dissection repair or demanding redo cases, can

be performed using MiECC technology.

Type IV circuits can obviously be used even from

the first coronary cases, obviating the need for a

staged approach, as part of the learning strategy.

Kyriakos Anastasiadis, Polychronis Antonitsis, Helena Argiriadou and Apostolos Deliopoulos

Figure 8.2 The prototype modular type IV AHEPA MiECC circuit (left). Schematic configuration (right). PA: pulmonary artery, VARD: venous air

removal device.

Figure 8.3 Proposed MiECC training pathway. Ao arch: aortic arch, AVR: aortic valve replacement, CABG: coronary artery bypass grafting, MVR:

mitral valve replacement, TVR: tricuspid valve replacement.

Chapter 8: Minimal Invasive Extracorporeal Circulation

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The Quest for “Physiologic” Perfusion

Development of MiECC has initiated a multidisci-

plinary strategy toward “physiologic” perfusion in

cardiac surgery. Despite all advances in surgical tech-

niques and cardiac anesthesia, this concept could

never have been introduced in clinical practice with-

out the concomitant advancement in CPB technology.

Figure 8.4 proposes a monitoring algorithm through-

out the perioperative period. Hemodynamic

management during the pre-CPB and post-CPB

period – either with the help of inotropes or vasocon-

strictors, with optimizing volume status or by increas-

ing pump flow – aims to keep cardiac output (CO) >

2.4 L/min/m

and mixed venous oxygen saturation

(SvO

) > 70%. During CPB the perfusionist adjusts

their strategy to goal-directed perfusion, maintaining

oxygen delivery (DO

i) > 272 ml/min/m

and an

oxygen delivery to carbon dioxide production ratio

(DO

i/VCO

i) > 5, while the oxygen extraction

ratio (O

ER) should be kept at <30. Cerebral

oximetry monitoring serves as a ‘ level alarm’ on-

and off-CPB and a drop of >20% from the baseline

needs to prompt immediate intervention. While

aiming to reduce transfusion, hemoglobin level

should be kept >8 g/dl.

Evidenced-Based Clinical Advantages

of MiECC

As the amount of evidence increases, the use of

MiECC is gaining traction in various guidelines. The

2019 joint guidelines on adult cardiopulmonary

bypass in cardiac surgery by the European Societies

of Cardiac and Thoracic Surgery, Cardiac Anaesthesia

and the European Board of Cardiac Perfusion

(EACTS, EACTA and EBCP) state that:



MiECC should be considered over standard

conventional CPB systems to increase the

biocompatibility of ECC. (Class of

recommendation: IIA, Level of evidence: B.)



MiECC should be considered over standard

conventional CPB systems to reduce blood loss

and the need for transfusion. (Class of

recommendation: IIA, Level of evidence: B.)



A combination of MiECC features – such as

coating, the centrifugal pump, the separation of

Figure 8.4 Schematic diagram of perioperative strategy to optimize the use of MiECC. CCO: continuous cardiac output; CO: cardiac output/

circulatory flow; CPB: cardiopulmonary bypass; Ht: hematocrit, Lac: lactate levels; POC: point-of-care; rSO

: cerebral oxygen saturation; TEE:

transesophageal echocardiography.

Kyriakos Anastasiadis, Polychronis Antonitsis, Helena Argiriadou and Apostolos Deliopoulos

cardiotomy suction blood and the use of closed

systems – should be considered to improve

conventional CPB. (Class of recommendation:

IIA, Level of evidence: C.)

The 2017 EACTS/EACTA guidelines on patient blood

management for adult cardiac surgery recommend

considering MiECC to reduce perioperative blood

transfusion. A position paper produced by MiECTiS

in 2016 provides a detailed overview of practice rec-

ommendations, which are summarized in Table 8.2

A meta-analysis including 2,700 patients from

24 randomized controlled trials showed that MiECC

is associated with reduced postoperative morbidity

and lower mortality (0.5% versus 1.7%; p = 0.02) in

coronary surgery when compared to conventional

CPB. A large network analysis including 22,778

patients showed that MiECC and OPCABG reduce

the odds of 30-day all-cause-mortality, and particu-

larly stroke, new onset atrial fibrillation and renal

dysfunction, over CABG done on conventional CPB.

There was no difference in the odds for developing a

postoperative myocardial infarction. The authors

conclude that MiECC may represent an attractive

compromise between OPCAB and conventional CPB.

Incorporating the Lessons Learnedfrom

MiECC into Practice

Cardiac surgery is by definition a “non-physiologic”

intervention. MiECC attempts to apply physiology to

perfusion. On a cellular level it shows less impairment

of microcirculation and a faster recovery of physiolo-

gic flow compared with conventional flow. At least in

low-risk coronary surgery, this seems to translate into

improved organ protection and clinical outcomes

appear to be better than those of patients operated

on using conventional CPB (see Figure 8.5).

Some teams have introduced the term “optimized

ECC” (opECC), representing a shift from conventional

Table 8.2. MiECC Practice Recommendations

Level of

Evidence

Class I

MiECC systems reduce hemodilution and better preserve hematocrit as well as reduce postoperative

bleeding and the need for RBC transfusion.

MiECC systems reduce the incidence of postoperative atrial fibrillation. A

MiECC systems preserve renal function. A

MiECC is associated with improved myocardial protection. A

Class IIA

Inflammatory response assessed by specific inflammatory markers is attenuated with use of MiECC. B

MiECC systems can reduce cerebral gaseous microembolism and preserve neurocognitive function. B

MiECC exerts a subclinical protective effect on end-organ function (lung, liver, intestine) which is

related to enhanced recovery of microvascular organ perfusion.

Class IIB

Within a MiECC strategy, less thrombin generation may permit reduced heparin dose targeted to

shorter ACT times. When such a strategy is followed, individual heparin dose should be determined

using heparin dose-response monitoring systems.

MiECC appears to offer survival benefit in terms of lower 30-day mortality after CABG procedures. B

Use of short-acting opioids in combination with propofol or volatile anesthetics, and hypnotic effect

monitoring by processed EEG, is recommended for induction and maintenance of anesthesia for

MiECC-based surgery. TEE findings pertinent to institutional management of MiECC should be

communicated during the preoperative surgical safety time out.

ACT: Activated Clotting Time; CABG: Coronary Artery Bypass Grafting; EEG: Electroencephalogram; MiECC: Minimal Invasive Extracorporeal

Circulation; RBC: Red Blood Cells

Chapter 8: Minimal Invasive Extracorporeal Circulation

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CPB to advanced perfusion circuits. This trend high-

lights the change in mindset that MiECC has offered to

perfusion, leading perfusionists to improve CPB tech-

nology. An opECC circuit often follows a custom-made

design, incorporating relatively easy-to-make changes,

such as using short tubing with biocompatible surfaces,

centrifugal pumps, low prime oxygenators and assisted

venous drainage. They might not reach the efficacy of a

MiECC system but are a step toward more physiological

perfusion becoming global practice.

The success of MiECC depends on the engagement of

all three stakeholders of the cardiac surgical team in

order to obtain the maximum benefit. Combining a

multidisciplinary strategy with technological advances

has the potential to make MiECC a “therapy” for

cardiac surgery. The evidence is not strong enough

at present, but it could at some point in the future

replace conventional CPB and become standard prac-

tice in cardiac surgery.