title: Can hypocapnia reduce cerebral embolization during cardiopulmonary bypass?
abstract: 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.
authors.affiliation: Department of Cardiothoracic and Vascular Anesthesiology and Intensive Care, University of Vienna, Austria. walter.ploechl@univie.ac.at
authors.forename: W
authors.initials: W
authors.lastname: Plöchl
authors.forename: C G
authors.initials: CG
authors.lastname: Krenn
authors.forename: D J
authors.initials: DJ
authors.lastname: Cook
authors.forename: E
authors.initials: E
authors.lastname: Gollob
authors.forename: T
authors.initials: T
authors.lastname: Pezawas
authors.forename: H
authors.initials: H
authors.lastname: Schima
authors.forename: O
authors.initials: O
authors.lastname: Ipsiroglu
authors.forename: G
authors.initials: G
authors.lastname: Wollenek
authors.forename: G
authors.initials: G
authors.lastname: Grubhofer
mesh_terms: 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
chemical_list: D002245:Carbon Dioxide