Microemboli in Aortic Valve Surgery: Minimized Extracorporeal Circulation vs. Classic Extracorporeal Circulation.

Microemboli are an important risk factor for neurological damage after cardiac
surgery. The cause of the neurological damage in cardiac surgery is
multifactorial. The extracorporeal circulation circuit (ECC) is one of the
primary causes of microemboli during operation. Minimized extracorporeal
circulation (MECC) is developed in attempt to reduce this and other side effect
of ECC. The MECC system is associated with a significant reduction in embolic
count measured with Transcranial Doppler (TCD) monitoring during coronary
bypass surgery compared to conventional ECC (CECC). Patients undergoing aortic
valve surgery are at higher risk for developing a stroke and therefore
reduction of the microemboli could improve the neurologic outcome after aortic
valve surgery. Beside neurological complications extracorporeal circulation
effects the imflammatory respons and bloodloss.

We hypothesize that the use of the MECC system in patient undergoing aortic
valve surgery is associated with and a reduction in HITS determined by TCD, a
reduction in the transfusion of RBC and FFP and a better QOL.

This study is performed to asses the effect of MECC system compared to CECC in
patients undergoing aortic valve surgery on microemboli in the form of high
intensity transient signals (HITS) detected by Transcranial Doppler
Ultrasonography (TCD). Adjacent to the detection of microembolization with
intra operative bilateral TCD, the QOL and neurocognitive functioning will be
assessed in both groups. To complete the MRI of the brain will be used to
identify new cerebral ischemic areas.

Next to the neurocognitive analysis the circulation and inflamatory respons
will be assessed with peri-operative with Side Stream Dark Field -imaging
(SDF), quantification of the transfusion of bloodproducts ( RBC and FFP) and
organ specific biomarkers.

This is a prospective, randomized trial to evaluate the effect of two applied
cardiopulmonary bypass techniques, minimized extracorporeal circulation (MECC)
versus conventional cardiopulmonary bypass in patients undergoing aortic valve
replacement on the intraoperative high intensity transient signals (HITS)
detected by Transcranial Doppler ultrasonography (TCD).

Beside HITS determination for emboli detection neurocognoitive analysis take
place with a Quality of Life assessment, neuropsychological analyses.

Next to the neurocognitive analysis the circulation and inflamatory respons
will be assessed with peri-operative with Side Stream Dark Field -imaging
(SDF), quantification of the transfusion of bloodproducts (RBC and FFP) and
organ specific biomarkers. Patients undergoing aortic valve replacement meeting
the inclusion criteria will be enrolled. Comparative and descriptive statistics
will be used to summarize patient outcomes for specific study endpoints

One group of patients will undergo aortic valve replacement with the minimized
extracorporeal circulation (MECC) and the other group of patient will be
treated with the CECC.

Minimized Extra Corporeal Circulation

The MECC system consist of a closed system containing a centrifugal pump (
Rotaflow; Jostra) and a membrane oxygenator (Quadox HE;Jostra). The Venous line
is connected to the centrifugal pump via a venousbubble trap (VBT 160). All
components are Bioline coated ( Jostra). Priming volume of the system is 700 ml
of NaCl 0,9 %( this solution contains 14.4. % hydoxyethyl starch). Retrograde
autologous priming is used in hemodynamical stable patients. Myocardial
protection is performed by using a modified Calafiori technique. (potassium
blood cardioplegia every 15 - 20 minutes) Blood from the surgical field will be
collected by a cell-saving device (BRAT 2; Cobe). Anticogulationis attained by
administration of 150 IU/KG heparin to achieve an activated clotting time of
longer than 300 seconds. The left ventricle is vented via a vent in the
pulmonary artery. Continuous carbondioxide (CO2) insufflation is used during
the procedure. Dexamethasone (1mg/kg) was administrated at induction of the
anesthesia.

Conventional Extra Corporeal Circulation

The ECC closed circuit is composed of a centrifugal pump (Jostra), a hollow -
fiber polypropylene oxygenator (CTRBE-HMO 1010; Jostra) , a venous reservoir
(BMR 1900G; Jostra), a cardiotomy reservoir ( Quadrox BE-AC2811;Jostra), and
Rehau Bioline-coated tubing ( Maquet/Jostra). The pump is primed with 1600 mL.
Myocardial protection is performed by using a modified Calafiori technique
(blood cardioplegia every 15 -20 minutes.) Anticoagulation was attained by
administration of 300 IU/KG heparin to achieve an activated clotting time of
longer than 400 seconds. Blood from the surgical field will be drained to the
venous reservoir. Left ventricle is vented via a vent in the right upper
pulmonary vein. Continuous carbondioxide (CO2) insufflation is used during the
procedure. Dexamethasone (1mg/kg) was administrated at induction of the
anesthesia.

There is no expected associated risk with participation in this trial. Both
CECC and MECC are successfully performed in the St. Antonius Hospital. Patients
will ask to fill out the 12 questionnaire pre-operative, at 3 months and 6
months postoperative. Neuropsychological testing will be performed
pre-operative, at discharge and at 3 and 12 month postoperative.
Microcirculation assessment is performed during the operation and direct
postoperative and is performed without discomfort for the patient. Blood
analysis is part of standard procedure pre and postoperative treatment. Extra
blood investigations will be embedded in these standard analyses. TCD is not a
standard procedure during aortic valve replacement. TCD is performed during the
procedure while the patient is under general anaesthesia and terminates at the
completion of the procedure. Therefore we anticipate no physiological and
physical discomfort with participation. Diffusion weighted MRI is done
preoperative and at discharge and is not part of routine patient care.