Can hypocapnia reduce cerebral embolization during cardiopulmonary bypass?
BACKGROUND
Cerebral embolization is a major cause of central nervous dysfunction after cardiopulmonary bypass. Experimental studies demonstrate that reductions in arterial carbon dioxide tension (PaCO2) can reduce cerebral embolization during cardiopulmonary bypass. This study examined the effects of brief PaCO2 manipulations on cerebral embolization in patients undergoing cardiac valve procedures.


METHODS
Patients were prospectively randomized to either hypocapnia (PaCO2 = 30 to 32 mm Hg, n = 30) or normocapnia (PaCO2 = 40 to 42 mm Hg, n = 31) before aortic cross-clamp removal. With removal of the aortic cross-clamp embolic signals were recorded by transcranial Doppler ultrasonography for the next 15 minutes.


RESULTS
Despite significant differences in PaCO2, groups did not differ statistically in total cerebral emboli counts. The mean number of embolic events was 107 +/- 100 (median, 80) in the hypocapnic group and 135 +/- 115 (median, 96) in the normocapnic group, respectively (p = 0.315).


CONCLUSIONS
Due to the high between-patient variability in embolization, reductions in PaCO2 did not result in a statistically significant decrease in cerebral emboli. In contrast to experimental studies, the beneficial effect of hypocapnia on cerebral embolization could not be demonstrated in humans.
Plöchl
W
W
Department of Cardiothoracic and Vascular Anesthesiology and Intensive Care, University of Vienna, Austria. walter.ploechl@univie.ac.at
Krenn
C G
CG
Cook
D J
DJ
Gollob
E
E
Pezawas
T
T
Schima
H
H
Ipsiroglu
O
O
Wollenek
G
G
Grubhofer
G
G
D002245:Carbon Dioxide / Q000097:blood*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D002560:Cerebrovascular Circulation; D017548:Echocardiography, Transesophageal; D005260:Female; D006801:Humans; D016857:Hypocapnia; D020766:Intracranial Embolism / Q000097:blood / Q000000981:diagnostic imaging / Q000209:etiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D017585:Ultrasonography, Doppler, Transcranial
D002245:Carbon Dioxide