Cannulation Strategy and setting up of cardiopulmonary bypass:
Our preference is antegrade perfusion if at all feasible. Due to the
ease and relatively rapid initiation of cardiopulmonary bypass, we have
of late preferred to use the direct ascending aorta true lumen
cannulation over a guidewire under echocardiographic guidance. In
patients who present with rupture or contained rupture of the ascending
aorta/root, and/or are extremely unstable to even allow us to do a
sternotomy, femoral artery cannulation can still be used. On occasions
when the intimal flap has been found occluding the origin of arch
vessels, double cannulation with axillary artery plus central or femoral
artery cannulation has been performed to maintain both upper and lower
body perfusion and achieve uniform systemic cooling.
For venous cannulation, we prefer the right atrium. Often times we
cannulate the superior vena cava as well. This additional cannula can be
used for retrograde cerebral perfusion during circulatory arrest.
However, in an unstable patient with ruptured ascending aorta/root and
cardiac tamponade, opening the pericardium can potentially lead to
sudden hypertension and potential exsanguination of the patient. In such
patients cannulating the femoral vein with a multistage venous cannula
is an option. Once on pump and with ongoing systemic cooling,
pericardium is opened to allow for controlled decompression. If then the
drainage is believed to be inadequate, one can switch to right atrial
cannulation.
Most often, Type-A dissection leads to significant aortic regurgitation
due to loss of commissural support. This leads to left ventricular
distension, especially as the heart fibrillates with systemic cooling.
Hence venting of left ventricle is critical. A left ventricle vent
advanced through the right superior pulmonary vein is the commonest
approach.