Carbon Dioxide Insufflation on Cerebral Microemboli
Carbon Dioxide Insufflation on Cerebral Microemboli
The purpose of this study is to determine if blowing carbon dioxide into the surgical field
 during open-heart surgery to displace retained chest cavity air from the atmosphere will
 decrease the number of microembolic being introduced into the heart chambers and brain.
Although open-heart surgery is widely used throughout the world, from 1 to 4% of patients
 experience neurological impairment such as impairment of memory, language and motor skills
 after surgery. The cause for such cognitive impairment is thought to be air microemboli (very
 small bubbles of air) being introduced into the blood circulation of the brain from the
 heart. These air microemboli are introduced from the surgical field and/or from the
 heart-lung machine. During open-heart surgery, a patient's blood circulation is supported by
 a heart-lung machine (cardiopulmonary bypass) while the surgeon is replacing or repairing a
 valve or performing coronary artery bypass surgery. During valve surgery, chambers of the
 heart are open to room air, causing an introduction of air into the heart. Despite careful
 de-airing (removal of air) procedures during open-heart surgery, studies revealed that air
 microemboli are still formed. Past research studies have shown that carbon dioxide (CO2)
 filling the chest cavity by means of gravity and replacing the room air may help to decrease
 the amount of microemboli reaching the brain.

 CO2 is 50% heavier than room air. Unlike room air, CO2 dissolves more quickly in blood and
 tissue (> 25 times more soluble in blood and tissue than air) whereas air contains nitrogen,
 which does not dissolve easily in the blood. In either case, the emboli made of air or CO2
 can block the arteries of the brain causing cognitive impairment. Due to the properties of
 air and CO2, CO2 emboli may be tolerated much better than air emboli.

 This is a single-centre, double-blind, placebo-controlled study, randomizing 100 patients
 undergoing elective mitral valve repair +/- coronary artery bypass grafting. Patients will be
 divided into 2 groups: (n=100), 50 patients will be receiving carbon dioxide insufflated and
 50 patients will not. The number of microemboli will be ascertained by an intraoperative
 transesophageal echocardiography and transcranial doppler. Three to seven days after surgery,
 a magnetic resonance imaging of the brain will be done to assess for any cerebral ischemic
 lesions. Plus, a battery of neuropsychologic tests will be done preoperatively and 2 months
 postoperatively.
Inclusion Criteria:

 -  provide informed consent

 -  male or female who are 18 years of age or older

 -  elective patients to undergo mitral valve repair +/- coronary artery bypass surgery

 -  ability to read and write

 Exclusion Criteria:

 -  patients with a history of stroke, TIA, carotid vascular disease

 -  patients with a contraindication to TEE or MRI

 -  patients with an active history of drug/alcohol dependence or abuse history