title: Oxyhemoglobin dissociation during hypothermic blood cardioplegia arrest.
abstract: BACKGROUND
  Coronary sinus effluent contains desaturated blood during the first few seconds of hypothermic cardioplegia infusion in humans. This occurs despite the high affinity of hemoglobin for oxygen at a low temperature and alkaline pH. The present study quantitates oxyhemoglobin dissociation during hypothermic cardioplegic arrest.
  
  
  RESULTS
  Three infusions of a 4 degrees C alkalotic blood cardioplegia solution were given into the cross-clamped aortic root during 1 hour of cardioplegic arrest. Paired aortic root and coronary sinus blood samples were obtained before and shortly after initiating cardiopulmonary bypass and at t = 5 seconds and 30 seconds during each cardioplegia infusion. Throughout the study, the hemoglobin saturation in the aortic root samples was 100%. The mean coronary sinus hemoglobin saturation at t = 5 seconds during hypothermic cardioplegia infusion ranged from 63.0% to 66.5% (p < 0.05 coronary sinus compared with aortic root samples). The coronary sinus hemoglobin saturation approximated the aortic root hemoglobin saturation at t = 30 seconds during hypothermic cardioplegia infusion. The mean PO2 of the aortic root samples ranged from 214 to 307 mm Hg during hypothermic cardioplegia infusion. The mean PO2 of the t = 5 seconds coronary sinus samples ranged from 31 to 39 mm Hg, whereas the mean PO2 of the t = 30 seconds coronary sinus samples ranged from 85 to 119 mm Hg during cardioplegia infusion (p < 0.05 coronary sinus compared with aortic root samples).
  
  
  CONCLUSIONS
  Oxygen dissociates from hemoglobin contained in a hypothermic, alkalotic blood cardioplegia solution during the nonperfused phase of cardioplegic arrest. However, the only oxygen delivered to the myocardium during the infusion of a hypothermic alkalotic blood cardioplegia solution is oxygen physically dissolved in the solution.
authors.affiliation: Division of Cardiothoracic Surgery, University of Alabama, Birmingham.
authors.forename: W L
authors.initials: WL
authors.lastname: Holman
authors.forename: R D
authors.initials: RD
authors.lastname: Spruell
authors.forename: S B
authors.initials: SB
authors.lastname: Digerness
authors.forename: J
authors.initials: J
authors.lastname: Dudelston
authors.forename: A D
authors.initials: AD
authors.lastname: Pacifico
mesh_terms: D000818:Animals; D001769:Blood; D002314:Cardioplegic Solutions; D005260:Female; D006324:Heart Arrest, Induced / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism; D010108:Oxyhemoglobins / Q000378:metabolism*; D013552:Swine; D013997:Time Factors
chemical_list: D002314:Cardioplegic Solutions; D010108:Oxyhemoglobins