Improved cerebral protection through replacement of residual intracavital air by carbon dioxide: a porcine model using diffusion-weighted magnetic resonance imaging.
BACKGROUND
Major risk of central or peripheral organ damage is attributed to air embolism from incompletely de-aired cardiac chambers after cardiac operations. Replacement of air by carbon dioxide insufflation into the thoracic cavity is widely used. Diffusion-weighted magnetic resonance imaging of the brain detects ischemia within minutes after onset. The reversibility of ischemia in cerebral tissue after massive gaseous emboli has not yet been described.


METHODS
After selective catheterization of a common carotid artery in 15 pigs, boli of 1 mL/kg body weight of air (n = 5) or carbon dioxide (n = 5, "low dose") were applied. Five pigs received 2 mL/kg body weight of carbon dioxide ("high dose"). Diffusion-weighted magnetic resonance imaging of the brain was performed 2, 5, 10, 15, and 25 minutes after embolization.


RESULTS
All animals of the "air" group showed important circulatory reactions leading to death of 2 animals. In the whole group, diffusion-weighted magnetic resonance imaging revealed irreversible hyperintense signals in both hemispheres. In the low-dose group, no change in signal intensity was observed in 2 pigs, and 3 others showed reversible changes in signal intensity, without important circulatory reactions. In 3 animals of the high-dose group, hyperintense signals were reversible, but 2 others presented with bilateral, irreversible signals in diffusion-weighted magnetic resonance imaging, accompanied by minor circulatory reactions.


CONCLUSIONS
In contrast to the dramatic effect of air emboli, identical quantities of carbon dioxide injected into cerebral arteries of the pigs were not associated with major clinical symptoms. The early reversibility of ischemic reactions visualized in diffusion-weighted magnetic resonance imaging encourages the use of carbon dioxide insufflation as a protective method in cardiac surgery.
Martens
S
S
Department of Thoracic and Cardiovascular Surgery, University Hospital J. W. Goethe, Frankfurt am Main, Germany. martens.herz@gmx.de
Theisen
A
A
Balzer
J O
JO
Dietrich
M
M
Graubitz
K
K
Scherer
M
M
Schmitz
C
C
Doss
M
M
Moritz
A
A
D000818:Animals; D002545:Brain Ischemia / Q000175:diagnosis* / Q000517:prevention & control*; D002245:Carbon Dioxide / Q000494:pharmacology*; D016893:Carotid Stenosis; D002560:Cerebrovascular Circulation / Q000502:physiology; D038524:Diffusion Magnetic Resonance Imaging; D004195:Disease Models, Animal; D004618:Embolism, Air / Q000517:prevention & control*; D005260:Female; D007269:Injections, Intra-Arterial; D008297:Male; D011897:Random Allocation; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013552:Swine; D014654:Vascular Patency / Q000502:physiology; D014656:Vascular Surgical Procedures / Q000009:adverse effects / Q000379:methods
D002245:Carbon Dioxide