Hemoglobin solutions in experimental cardioplegia

The addition of stroma-free hemoglobin solution to a standard St. Thomas Hospital cardioplegic solution significantly protected the heart from ischemic damage compared to the effect of the same solution without added hemoglobin. An experimental model of rat heart cardioplegia and transplantation comprising heart arrest for three hours at 20 degrees C was used. The number of hearts performing strong contractions after cardioplegia with iso-oncotic oxyhemoglobin prior to transplantation was close to the results with histidine-buffered cardioplegic solution according to Bretschneider. Comparative biochemical model experiments in vitro confirmed that the positive effect of oxyhemoglobin was due predominantly to its buffering capacity. The role of oxygen transport to tissues by hemoglobin was limited only to the first minutes of cardioplegia since neither recirculation nor reoxygenation took place in the present experimental setting.