Perioperative changes in cerebral blood flow after cardiac surgery: influence of anemia and aging.
BACKGROUND
Stroke occurs in 2% to 5% and cognitive dysfunction occurs acutely in 60% to 80% of patients early after cardiac surgery. Both may have long-term consequences. Research into mechanisms behind these sequelae has been focused intraoperatively, although there is little reason to believe that injury is limited to this period. Aging prominently increases the incidence of these sequelae. Anemia with cardiac surgery is acute and severe, should cause an increase in cerebral blood flow (CBF), and may impact stroke and cognitive function in this setting. To better understand changes in perioperative CBF physiology we have measured changes in CBF and the influence of anemia and aging on these changes.


METHODS
Cerebral blood flow was measured using the noninvasive continuous arterial spin labeling perfusion magnetic resonance imaging method. Cerebral blood flow, mean arterial pressure, hemoglobin, hemoglobin oxygen saturation, and cardiopulmonary bypass time were recorded in 12 subjects before and 6 +/- 2 days after cardiac surgery.


RESULTS
Cerebral blood flow increased from 44.6 +/- 15.6 mL100 g(-1)min(-1) to 64.4 +/- 20.1 mL100 g(-1)min(-1) after cardiac surgery, or 49.1% +/- 26.7%, (p < 0.0001). The absolute change in CBF (DeltaCBF) was predicted by the following regression model: DeltaCBF = -55 + 0.64(Age) + 0.53(CBF(Pre)) -3.3(DeltaHgb); R(2) = 0.81; p = 0.003, where CBF(Pre) is the baseline preoperative CBF and DeltaHgb is the change in hemoglobin from preoperative to postoperative periods.


CONCLUSIONS
Cerebral blood flow increases after cardiac surgery, and anemia appears to be an important cause. Age appears also to be an important covariate, with advancing age further increasing the magnitude of this hyperemia. The interrelationship of aging and anemia, in determining perioperative changes in CBF, and potentially cerebral oxygenation, may have important implications for the understanding of perioperative stroke and cognitive dysfunction after cardiac surgery.
Floyd
Thomas F
TF
Department of Anesthesia, University of Pennsylvania, Philadelphia, Pennsylvania, USA. floydt@uphs.upenn.edu
McGarvey
Michael
M
Ochroch
E Andrew
EA
Cheung
Albert T
AT
Augoustides
John A
JA
Bavaria
Joseph E
JE
Acker
Michael A
MA
Pochettino
Alberto
A
Detre
John A
JA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000740:Anemia / Q000503:physiopathology*; D001783:Blood Flow Velocity; D006348:Cardiac Surgical Procedures; D002560:Cerebrovascular Circulation; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D010100:Oxygen / Q000097:blood
D006454:Hemoglobins; D010100:Oxygen