Holman W L, Spruell R D, Digerness S B, Dudelston J, Pacifico A D
Division of Cardiothoracic Surgery, University of Alabama, Birmingham.
Circulation. 1992 Nov;86(5 Suppl):II339-45.
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.
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).
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.
在人类低温心脏停搏液输注的最初几秒内，冠状窦流出液含有未饱和血液。尽管在低温和碱性pH条件下血红蛋白对氧具有高亲和力，但这种情况仍会发生。本研究对低温心脏停搏期间氧合血红蛋白解离进行了定量分析。
在1小时的心脏停搏期间，向夹闭的主动脉根部输注3次4℃碱性血液心脏停搏液。在开始体外循环之前和之后不久，以及在每次心脏停搏液输注期间的t = 5秒和30秒时，采集配对的主动脉根部和冠状窦血样。在整个研究过程中，主动脉根部血样中的血红蛋白饱和度为100%。低温心脏停搏液输注期间t = 5秒时冠状窦血红蛋白平均饱和度范围为63.0%至66.5%（与主动脉根部血样相比，冠状窦p < 0.05）。低温心脏停搏液输注期间t = 30秒时，冠状窦血红蛋白饱和度接近主动脉根部血红蛋白饱和度。低温心脏停搏液输注期间，主动脉根部血样的平均PO2范围为214至307 mmHg。心脏停搏液输注期间，t = 5秒时冠状窦血样的平均PO2范围为31至39 mmHg，而t = 30秒时冠状窦血样的平均PO2范围为85至119 mmHg（与主动脉根部血样相比，冠状窦p < 0.05）。
在心脏停搏的无灌注阶段，氧从低温、碱性血液心脏停搏液中的血红蛋白解离。然而，在输注低温碱性血液心脏停搏液期间，输送到心肌的唯一氧是物理溶解在溶液中的氧。
