Cannulae - Perfusion.com

Chapter 22 The Manual of Clinical Perfusion
vena cava (SVC) and the other in the IVC. These are connected to a common
venous line with a Y-connector. This type of cannulation also causes the
effect of partial bypass as the two stage cannula does. That is some blood
manages to go around the cannulae, through the heart and to the lungs. When
the cannulae in the SVC and IVC have either a clamp or umbilical tape pulled
around them, all blood coming to the heart is diverted to the cannulae. This is
termed total bypass. This manner of venous cannulation is most often used in
valvular or congenital surgery. A venous cannulae chart will be listed later in
this chapter. This chart suggests the cannulae used with certain weight
categories.
Cardioplegia Cannulae
The other cannulae used during bypass are specific to certain
procedures. Retrograde cardioplegia is a popular technique of giving
cardioplegia. The cannula is placed into the coronary sinus through the right
atrium. The cannula has a balloon near its tip that when inflated prevents the
flow of the cardioplegia back into the right atrium. The flow is, instead, forced
backwards through the coronary veins, capillaries and arteries. The cannulae
are of two basic types: either automatic or manual balloon inflation. Selection
is surgeon preference.
Antegrade cardioplegia is given through a cannula in the aortic root
or directly into the coronary os. (When given directly into the os a coronary
perfusion cannula is used.) These cannulae come in various sizes and in different
configurations. Basically, they have short needle tips that are placed into the
aorta. Cardioplegia is then given into the root. The aortic valve and the aortic
cross clamp prevent flow in either direction and thus force the cardioplegia
into the coronary arteries. Some have an extra arm coming off the side to allow
a vent tubing to be connected and thus provide both functions in turn. The
sizes of these cannulae affect the pressure drop and thus the maximum flow.
Selection is surgeon preference.
Coronary perfusion cannulae come in different sizes and shapes. A
common design is the small hand held cannula with a soft tip that is placed
over the coronary os. Others have tips that engage the coronary os. These
cannulae are used when the aortic root is opened for a valve replacement.
Since the development of the retrograde cannula these cannulae are not often
used. Retrograde delivery is easier and may be done while the surgeon continues
to work.
Vents
The LV vents, PA vents and aortic root vents are the last of the cannulae
types to be discussed. These vents are available in many sizes and shapes.
The type of vent depends on the cannulation site. There are short metal tipped
needles that fit in the aortic root. There are long thin cannulae placed through
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