Carbon Dioxide Insufflation on Cerebral Microemboli

Effects of Carbon Dioxide Insufflation on Cerebral Microemboli During Cardiopulmonary Bypass: A Randomised Trial Correlating Embolic Load & Neurologic Outcomes.


Lead Sponsor: University Health Network, Toronto

Source University Health Network, Toronto
Brief Summary

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.

Detailed Description

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.

Overall Status Terminated
Start Date 2008-04-01
Completion Date 2011-10-01
Primary Completion Date 2010-04-01
Phase Phase 2/Phase 3
Study Type Interventional
Primary Outcome
Measure Time Frame
Primary outcome will be the number of emboli as measured by transesophageal echocardiogram and transcranial doppler. intraoperative
Secondary Outcome
Measure Time Frame
Secondary outcome will be the prevalence of new ischemic lesions on diffusion weighted magnetic resonance imaging and neuropsychological impairments 2 months
Enrollment 20

Intervention Type: Procedure

Intervention Name: Carbon dioxide insufflation

Description: For baseline evaluations, all patients will undergo a battery of neuropsychological testing after obtaining written informed consent and before cardiac surgery. A transesophageal echocardiography and a transcranial doppler will be performed for intraoperative evaluations. For post-operative evaluations, patients will undergo a diffusion-weighted magnetic resonance imaging three to seven days after surgery and have a repeat neuropsychological assessment at six to eight weeks post cardiac surgery. All patients will undergo cardiopulmonary bypass using the same equipment and technique. Patients in both groups will receive a jackson-pratt drain as a gas diffuser. The jackson-pratt drain will be placed 5 cm below the cardiothoracic wound opening adjacent to the diaphragm and if the patient is randomized to carbon dioxide, the flow will be set at 2 litre/min.

Arm Group Label: 2



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



Minimum Age:

18 Years

Maximum Age:


Healthy Volunteers:


Overall Official
Last Name Role Affiliation
Patricia Murphy, BSc, MD, FRCPC Principal Investigator University Health Network, Toronto
Facility: Toronto General Hospital/ University Health Network
Location Countries


Verification Date


Responsible Party

Type: Sponsor

Has Expanded Access No
Condition Browse
Number Of Arms 1
Arm Group

Label: 2

Type: Experimental

Study Design Info

Allocation: Randomized

Intervention Model: Parallel Assignment

Primary Purpose: Prevention

Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)

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