Semin cardiothorac vasc anesth

530519

SCVXXX10.1177/1089253214530519Seminars in Cardiothoracic and Vascular Anesthesia

Shann and Melnitchouk

research-article2014

1

Massachusetts General Hospital Division of Cardiac Surgery, Boston, 

USA

Corresponding Author:

Kenneth Shann, Massachusetts General Hospital, 55 Fruit Street, 

Edwards 119, Boston, MA 02114, USA. 

Email: [e-mail]

Advances in Perfusion Techniques: 

Minimally Invasive Procedures

Kenneth Shann, CCP

1

, and Serguei Melnitchouk, MD

1

Abstract

There is a growing demand from patients and referring physicians for minimally invasive cardiac surgery. Minimally invasive 

cardiac procedures are technically unique from conventional cardiac procedures and require a thorough understanding 

of the surgical, anesthetic, and perfusion strategies. Strategies include routine use of augmented venous drainage, 

alternative arterial and venous cannulation sites, and special cannulas designed for minimally invasive procedures. The 

following review describes the strategies and safety systems that should be considered when performing minimally 

invasive cardiac surgery.

Keywords

aortic valve replacement, cardiac surgery, cardiopulmonary bypass, minimally invasive surgery, mitral valve

 at UNIV MASSACHUSETTS BOSTON on August 28, 2014

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Shann and Melnitchouk 

147

Unlike a roller arterial pump (pictured in Figure 1), if a 

centrifugal arterial pump is used during VAVD, there is a 

risk of air entrainment via the hollow-fiber membrane 

oxygenator.

18

 Air can be transmitted across the fibers of 

the oxygenator if the RPMs of the centrifugal pump are 

lowered to the point where flow is reversed and negative 

pressure is imparted to the oxygenator. Incorporating a 

1-way flow valve in the tubing between the venous reser-

voir and the oxygenator will prevent retrograde flow and 

the risk of negative pressure.

17

Reports have illustrated that air entrained through the 

venous line of the CPB circuit gets through the reservoir, 

oxygenator, and arterial filter and can be detected in the 

arterial line.

19-21

 In the setting of venous air entrainment, 

relative to gravity drainage, VAVD has been shown to 

increase the rate of entrainment and total number of gas-

eous microemboli.

22

 Therefore, in the setting of venous air 

entrainment, VAVD should be minimized by minimizing 

the level of negative pressure. More important, every effort 

should be made to eliminate the source of any venous air.

CAVD is another method of augmenting venous drain-

age. This strategy may be considered more complicated 

than VAVD because it requires the perfusionist to operate 

2 centrifugal pumps simultaneously. CAVD utilizes a sec-

ond centrifugal pump that is placed in the venous line of 

the CPB circuit and is therefore also more expensive. The 

centrifugal pump creates negative pressure at the inlet and 

actively augments venous flow. As with VAVD, CAVD in 

the setting of venous air entrainment has been shown to 

increase the volume of emboli; however, it has been sug-

gested that CAVD breaks the emboli into smaller emboli 

and allows for easier passage through the CPB circuit.

23

 

The advantages of CAVD include the absence of the risks 

inherent to VAVD—namely, reservoir pressurization and 

oxygenator air entrainment. CAVD also provides the 

option to use a soft shell venous reservoir that has been 

shown in some studies to reduce blood activation and 

improve patient outcome.

24,25

In summary, we recommend the following to safely aug-

ment venous return during minimally invasive procedures:

•

• VAVD with an approved vacuum regulator—for 

example, Boehringer model 3930;

•

• total negative pressure (gravity + applied vacuum) 

should not be less than −100 mm Hg;

•

• use the minimum amount of applied negative pres-

sure to achieve the desired flow;

•

• monitor venous reservoir positive and negative 

pressure with visual and audible alarms;

•

• when using a centrifugal arterial pump, incorporate 

a 1-way flow valve between the venous reservoir 

and oxygenator; and

•

• eliminate venous air entrainment in all clinical situ-

ations, especially during VAVD.

Figure 1.  Schematic of VAVD and CAVD.

Abbreviations: VAVD, vacuum assisted-venous drainage; CAVD, centrifugal-assisted venous drainage.

 at UNIV MASSACHUSETTS BOSTON on August 28, 2014

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Seminars in Cardiothoracic and Vascular Anesthesia 18(2)