title: Higher bypass temperature correlates with increased white cell activation in the cerebral microcirculation.
abstract: OBJECTIVE
  Cardiopulmonary bypass induces a systemic inflammatory response, which in turn promotes a cascade of leukocyte and endothelial cell activity. We investigated whether differences in bypass temperature and flow rate affect endothelial cell and leukocyte adhesion in the cerebral microcirculation.
  
  
  METHODS
  Thirty-six piglets (13.0 +/- 1.1 kg) had a cranial window placed over the parietal cortex to evaluate the microcirculation by means of intravital microscopy. Animals were cooled to a temperature of 15 degrees C, 25 degrees C, or 34 degrees C on cardiopulmonary bypass with hematocrit levels of 20% or 30% by using pH-stat management, followed by 60 minutes of reduced flow (10, 25, or 50 mL.kg(-1).min(-1)). Rhodamine staining was used to observe adherent and rolling leukocytes in postcapillary venules.
  
  
  RESULTS
  Higher bypass temperature correlated with significantly more adherent and rolling leukocytes during the full 60 minutes of low-flow bypass (P <.05). Poisson regression revealed more adherent leukocytes at 34 degrees C than at 15 degrees C and at a flow rate of 10 mL.kg(-1).min(-1) compared with a flow rate of 50 mL.kg(-1).min(-1). There was an inverse correlation between flow rate and the number of adherent and rolling leukocytes at 30, 45, and 60 minutes of low-flow bypass (P <.05). Temperature was a multivariable predictor of histologic score, with greater neurologic damage found after bypass at 34 degrees C (P <.01).
  
  
  CONCLUSIONS
  Leukocyte activation in cerebral microcirculation is increased with higher temperature and lower flow rate, suggesting that these variables influence the inflammatory response during cardiopulmonary bypass.
authors.affiliation: Department of Cardiovascular Surgery, Children's Hospital Boston, Harvard Medical School, Boston, Mass, USA.
authors.forename: Vesa
authors.initials: V
authors.lastname: Anttila
authors.forename: Ikuo
authors.initials: I
authors.lastname: Hagino
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.forename: Hart G W
authors.initials: HG
authors.lastname: Lidov
authors.forename: Richard A
authors.initials: RA
authors.lastname: Jonas
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000379:methods*; D002450:Cell Communication; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000166:cytology; D005260:Female; D007036:Hypothermia, Induced / Q000379:methods; D007431:Intraoperative Complications / Q000517:prevention & control*; D007958:Leukocyte Count; D007962:Leukocytes / Q000502:physiology; D008297:Male; D008833:Microcirculation / Q000502:physiology; D016343:Monitoring, Intraoperative / Q000379:methods; D011897:Random Allocation; D012680:Sensitivity and Specificity; D013552:Swine; D013696:Temperature