title: Low postoperative hematocrit increases cerebrovascular damage after hypothermic circulatory arrest.
abstract: OBJECTIVE
  The objective of this study was to evaluate the systemic and cerebral effects of different postoperative hematocrit management following cardiopulmonary bypass and deep hypothermic circulatory arrest.
  
  
  METHODS
  Animal case study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Four-week-old Yorkshire piglets.
  
  
  METHODS
  Twelve piglets were subjected to cardiopulmonary bypass (hematocrit = 25%) and 100 mins of deep hypothermic circulatory arrest (15 degrees C). After weaning cardiopulmonary bypass, they were randomized to either group L or H, in which the postoperative hematocrit was maintained approximately 20% vs. approximately 30%, respectively, and survived for 6 hrs.
  
  
  RESULTS
  Changes in body weight, bioimpedance, and colloid oncotic pressure were assessed. Near-infrared spectroscopy and immunohistochemical assays for cerebral transforming growth factor-beta(1) and caspase-3 were performed. Postoperative weight gain (kg) and decreases in bioimpedance (ohms) were significantly less in group H (1.5 +/- 0.2 [H] vs. 2.4 +/- 0.6 [L], p = .01; 39.3 +/- 15.5 [H] vs. 89.1 +/- 29.6 [L], p = .01). Mean colloid oncotic pressure (mm Hg) was significantly higher in group H (10.8 +/- 1.6 [H] vs. 8.2 +/- 0.8 [L], p = .01) at 6 hrs postoperatively. Oxyhemoglobin, oxidized cytochrome aa(3) (muM x differential path-length factor), and tissue oxygenation index (%) were significantly better in group H (65.7 +/- 31.8 [H] vs. -104.7 +/- 55.2 [L], p = .0001; 0.52 +/- 4.1 [H] vs. -12.8 +/- 6.1 [L], p = .0001, and 55.7 +/- 4.6% [H] vs. 45.3 +/- 6.4% [L], p = .004, respectively). Cerebral transforming growth factor-beta(1) and caspase-3 scores were significantly better in group H (3.0 +/- 0.6 [H] vs. 1.9 +/- 0.9 [L], p = .04 and 1.8 +/- 0.5 [H] vs. 3.2 +/- 0.8 [L], p = .02, respectively). Mean arterial pressure (mm Hg) was consistently higher with group H (94.7 +/- 13.0 [H] vs. 78.3 +/- 11.5 [L], p = .003) despite comparable central venous pressure ( approximately 11 mm Hg).
  
  
  CONCLUSIONS
  Lower postoperative hematocrit was associated with increased fluid retention, lower perfusion pressure, and worse cerebrovascular injury following deep hypothermic circulatory arrest. Postoperative hematocrit management may have profound systemic and cerebral effects after deep hypothermic circulatory arrest and merits further investigation.
authors.affiliation: Divisions of Cardiac Surgery, The Montreal Children's Hospital, McGill University Health Center, 1650 Cedar Avenue, Montreal, Quebec H3G 1AM, Canada. dominique.shum-tim@muhc.mcgill.ca
authors.forename: Dominique
authors.initials: D
authors.lastname: Shum-Tim
authors.forename: Derek
authors.initials: D
authors.lastname: MacDonald
authors.forename: Saito
authors.initials: S
authors.lastname: Takayuki
authors.forename: Eric
authors.initials: E
authors.lastname: Laliberté
authors.forename: Jenny
authors.initials: J
authors.lastname: Chen
authors.forename: Al-Maleek
authors.initials: AM
authors.lastname: Jamal
authors.forename: Anie
authors.initials: A
authors.lastname: Philip
authors.forename: Robert
authors.initials: R
authors.lastname: Platt
mesh_terms: D000818:Animals; D001834:Body Water; D001835:Body Weight; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000379:methods; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D002561:Cerebrovascular Disorders / Q000209:etiology*; D017097:Electric Impedance; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D007036:Hypothermia, Induced / Q000009:adverse effects*; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D011184:Postoperative Period; D013552:Swine; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C100003:deoxyhemoglobin; D053148:Caspase 3; D020169:Caspases