Perioperative assessment of cerebral ischemia in patients undergoing aortic arch surgery

The risk of neurological complications after aortic arch surgery is high,
mainly as a result of peri-procedural ischemia. Aortic arch surgery is
associated with a disturbance of the normal state of cerebral autoregulation,
especially during and after extracorporal circulation, deep hypothermia and
circulatory arrest. The optimal cerebral perfusion pressure under these
circumstances is unknown. Hypoperfusion can potentially cause a mismatch
between cerebral oxygen demand and supply. Both anesthesia and hypothermia
decrease the metabolic decrease the metabolic demand of the brain. Whether this
decrease in metabolism is proportional to the changes in cerebral blood flow is
unknown.

The primary objective is to measure the dose of cerebral ischemia, as a measure
of cerebral hypoperfusion, before, during and after aortic arch surgery.
Secondary objectives include parameters that influence the occurrence of
cerebral ischemia (dynamic autoregulation, cerebral blood flow velocity,
arterial blood pressure, PaCO2 and PaO2, cerebral aerobic and anaerobic
metabolism and neuronal activity) and the effects of cerebral ischemia on the
brain (functional neurological and cognitive testing, incidence of delirium,
biomarkers of cerebral ischemia)

Observational study

The burden for the patients is minimal. Procedures related to this study are
mostly non-invasive (transcranial Doppler, NIRS, and Finger
photoplethysmography, with no risk. Patients <70 years need to spend an extra
15-20 minutes during the pre- and postoperative visit, during which
non-invasive measurements are performed. Patients >70 years do not need to
spend extra time during the visits, as they are already visiting a
geriatrician. The measurements will take about 10 minutes after equipment. Some
patients might experience the measurements as annoying, but the measurements do
not relate to any health risk.
Peri-operative monitoring (EEG, TCD, NIRS and Jugular bulb measurements) will
be continued after admission to the ICU. During the first hours of ICU
admission, patients are sedated and monitoring will not cause any (additional)
discomfort. Upon awakening, EEG will be discontinued. No invasive measurements
will be necessary, and the burden for the patients minimal. Blood (for
measurement of bloodgas and neurospecific markers) will be drawn from an
arterial catheter, to a maximum amount of 20 ml in 48 hrs.
A jugular bulb catheter will be inserted at the operating theatre, together
with a standard* central venous catheter in the jugular vein. Catheters will
be placed by experienced anesthesiologist, under ultrasound guidance after the
patient is sedated (sedation for the surgery, not for line placement). The
potential risk of jugular bulb catheterization are similar to other central
venous catheterizations and include hemorrhage, bleeding, arterial
catheterization, pneumothorax, thrombosis and infection. These risks are
estimated to be < 1%. Removal of this catheter will occur within 72 hours after
insertion, thus minimizing the risk of infection or thrombosis. A jugular bulb
catheter (next to a normal jugular catheter) will not cause extra discomfort
for the patient; removal is without risk or burden