Evaluation of delivery systems for oxygenated cardioplegia.

The oxygen-carrying capacity of four delivery systems for blood and crystalloid cardioplegia was evaluated: nonoxygenated crystalloid cardioplegia, crystalloid cardioplegia oxygenated with a bubbler system and with a membrane system and, finally, blood cardioplegia delivered by the Shiley-Buckberg system. The nonoxygenated crystalloid cardioplegic solution delivered 0.56 ml of oxygen/dl of solution, the bubbler oxygenating system delivered 3.2 ml/dl and the membrane oxygenating system made available 3.7 ml/dl. Blood cardioplegia delivered 4.2 ml/dl when oxygen-carrying capacity was corrected for the shift in the oxyhemoglobin dissociation curve that occurs with hypothermia. There appears to be no advantage between blood and oxygenated crystalloid cardioplegia with respect to the ability of these solutions to provide oxygen to the myocardium during ischemic arrest. However, the bubbler oxygenating system is superior to the membrane and blood delivery systems in that it could administer cold cardioplegia at any time during the operation. In contrast, the membrane and blood cardioplegia delivery systems both depend on integral heat exchangers which limit the delivery of cold cardioplegia to the period of hypothermia.