Summary
A 6.4% stroma-free solution of hemoglobin, containing a cardioplegic additive (Mg-aspartate, K-aspartate and procaine), was used for improved myocardial protection during cardiac arrest. This cardioplegic solution produces optimal and easily reversible cardiac arrest, together with optimal oxygen transportation to and oxygen yield in the myocardium, similar to that provided by whole blood.
A one-hour period of normothermic cardiac arrest was produced in ten dogs, using a room-temperature hemoglobin solution which contained the cardioplegic agent and was saturated with oxygen. After this period, all the hearts recovered promptly and, after a 10-15-minutes recovery phase showed normal pressures and output. Metabolic investigations of left ventricular myocardial tissue showed a fall in adenosine triphosphate of up to 46% after 60 minutes, and a 63% fall in phospho creatine as compared to the initial levels. Resumption of perfusion after 30 minutes' ischemia led to a more rapid increase in the low ATP and PKr levels during the reperfusion phase.
Comparative studies of myocardial metabolism showed that this level of energy-rich phosphates and lactic acid was achieved at 15 minutes of pure normothermic ischemia. It was also shown that cardioplegia with Mg-aspartate-procaine and mild hypothermia offer similar myocardial protection for only 40-45 minutes, as compared with one-hour protection from normothermic hemoglobin cardioplegia.
Key-Words:
Myocardial protection - Cardioplegic hemoglobin perfusion - Open heart surgery - Different cardioplegic methods
