Emboli formation rather than inflammatory mediators are responsible for increased cerebral water content after conventional and assisted beating-heart myocardial revascularization in a porcine model.
OBJECTIVE
Emboli and proinflammatory mediators are suspected of generating cerebral edema after coronary surgery. In contrast to cardiopulmonary bypass (CPB), off-pump coronary artery bypass surgery (OPCAB) reduces microemboli count and proinflammatory mediator release but carries the risk of hemodynamic instability. A microaxial blood pump can augment cardiac output.


METHODS
Coronary bypasses were constructed in pigs with CPB and cardioplegia (n=9), OPCAB (n=9), or blood-pump support CAB (n=9). Nine animals underwent sham operation. Embolus count was monitored and regional cerebral blood flow was assessed with microspheres in 21 brain specimens per animal (n=189 per group). Interleukins 6 and 8 and tumor necrosis factor-alpha concentrations were determined. These variables were studied before, during, and for 4 hours after surgery. Finally, cerebral water content was determined.


RESULTS
During CPB and blood-pump CAB, a significant number of emboli were counted in contrast to OPCAB and controls (P<0.05). During CPB, regional cerebral blood flow was affected (32 of 189) and showed reactive hyperemia except in 10 specimens after aortic cross-clamp release. This impairment persisted in 20 specimens. During and after OPCAB, regional cerebral blood flow remained nearly unchanged but showed low flow during (58 of 189) and after (35 of 189) the blood-pump run. A significant increase in proinflammatory mediators was observed only in the CPB group. CPB and blood-pump CAB significantly increased cerebral water content (P<0.05). A strong correlation between embolic load and cerebral water content was observed in all groups. No correlation between proinflammatory mediator release and cerebral water content was detected.


CONCLUSIONS
Emboli formation rather than inflammatory mediators are responsible for increased cerebral water content after conventional and assisted beating-heart myocardial revascularization.
Department of Cardiothoracic and Vascular Surgery, University Hospital Mainz, Mainz, Germany. bier.bach@gmx.de
Benjamin
B
Bierbach
Matthias
M
Meier
Walter
W
Kasper-König
Axel
A
Heimann
Beat
B
Alessandri
Georg
G
Horstick
Hellmut
H
Oelert
Oliver
O
Kempski
D000818:Animals; D001921:Brain / Q000098:blood supply; D001929:Brain Edema / Q000209:etiology* / Q000378:metabolism* / Q000503:physiopathology; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D001026:Coronary Artery Bypass / Q000009:adverse effects; D047549:Coronary Artery Bypass, Off-Pump / Q000009:adverse effects; D004195:Disease Models, Animal; D005260:Female; D018836:Inflammation Mediators / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D020766:Intracranial Embolism / Q000150:complications* / Q000503:physiopathology; D008297:Male; D009204:Myocardial Revascularization / Q000009:adverse effects*; D012039:Regional Blood Flow / Q000502:physiology; D012307:Risk Factors; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D018836:Inflammation Mediators; D015850:Interleukin-6; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha