title: Cold continuous antegrade blood cardioplegia: high versus low hematocrit.
abstract: OBJECTIVE
  Cold continuous antegrade blood cardioplegia (CCABCP) is used with different hematocrit values. We investigated the consequences of CCABCP with low hematocrit (LH: 20-25%) versus high hematocrit (HH: 40-45%).
  
  
  METHODS
  Anesthetized open chest pigs (25 kg) were placed on cardiopulmonary bypass (CPB). The hearts were arrested for 30 min by 6 degrees C CCABCP with either LH or HH (n=8, each): After an initial 3 min application of high potassium (20 mEq) BCP the hearts were arrested for subsequent 27 min by normokalemic 6 degrees C cold blood delivered continuously antegradely. Thereafter the hearts underwent perfusion with warm systemic blood for an additional 30 min on CPB. Biochemical cardiac data (MVO(2) (ml min(-1)100 g(-1)), release of creatine kinase (CK; units min(-1)100 g(-1))) and lactate (mg min(-1)100 g(-1))) and the coronary vascular resistance index (CVRI (mmHg ml(-1)ming)) were measured during CPB. Total tissue water content (%) and left and right ventricular stroke work indices (LV-and RV-SWI (g m kg(-1))) were assessed 30 min after discontinuation of CPB and compared to pre-CPB controls.
  
  
  RESULTS
  The hearts of the LH group had no biochemical or functional disturbance. The HH group showed marked CK leakage (0.6+/-0.2* vs. 0.1+/-0.1, *P<0.05 for comparison of LH vs. HH with Student's t-test for unpaired data), impaired initial oxygen consumption (4+/-1* vs. 7+/-1) after cardiac arrest, an increased CVRI (82+/-12* vs. 50+/-8), the formation of myocardial edema (81.0+/-1.3* vs. 77.5+/-1.2), and poor functional recovery (LVSWI 0.2+/-0.1* vs. 1.0+/-0.1; RVSWI 0.1+/-0.1* vs. 0.5+/-0.1). The absence of lactate production in both groups was in accord with the non-ischemic protocol.
  
  
  CONCLUSIONS
  CCABCP with a low hematocrit of 20-25% is cardioprotective. In contrast, CCABCP with a high hematocrit of 40-45% jeopardizes the heart despite avoiding ischemic periods, and should be avoided.
authors.affiliation: Division of Cardiothoracic Surgery, UCLA School of Medicine, Los Angeles, CA, USA. baretti@dhzb.de
authors.forename: R
authors.initials: R
authors.lastname: Baretti
authors.forename: A
authors.initials: A
authors.lastname: Mizuno
authors.forename: G D
authors.initials: GD
authors.lastname: Buckberg
authors.forename: H H
authors.initials: HH
authors.lastname: Young
authors.forename: R
authors.initials: R
authors.lastname: Hetzer
mesh_terms: D000818:Animals; D002315:Cardiopulmonary Bypass; D006324:Heart Arrest, Induced / Q000379:methods*; D006400:Hematocrit; D013552:Swine; D014655:Vascular Resistance