The physiologic basis of warm cardioplegia.
BACKGROUND
Advances in myocardial protection have been instrumental in making cardiac surgery safer. Debate exists over the optimal medium and the optimal temperature for cardioplegia. Currently blood cardioplegia is preferred over crystalloid; the optimal temperature, however, remains controversial.


METHODS
Both warm and cold blood cardioplegia use potassium-induced electromechanical arrest, thereby reducing oxygen consumption by 90% in the working heart. Hypothermic blood cardioplegia given every 15 to 30 minutes provides a bloodless operative field and reduces oxygen consumption an additional 5% to 20%. Continuous warm cardioplegia avoids the deleterious effects of hypothermic ischemia and minimizes reperfusion injury. Perfusion is often interrupted for 5 to 10 minutes to allow adequate visualization of the operative site. Both warm and cold cardioplegia can be given either antegrade or retrograde.


RESULTS
Retrospective studies from Toronto support the safety and efficacy of warm cardioplegia. Two large prospective, randomized trials of warm cardioplegia versus intermittent cold blood or cold crystalloid cardioplegia demonstrated equally low incidences of death, perioperative myocardial infarction, and need of intraaortic balloon pump support.


CONCLUSIONS
Warm blood cardioplegia represents the latest development in myocardial protection. Preliminary studies support its efficacy. Additional studies are needed to determine the ideal route of delivery and to identify any risks associated with the inherent warm cardiopulmonary bypass required.
Mauney
M C
MC
Department of Surgery, University of Virginia Health Sciences Center, Charlottesville, USA.
Kron
I L
IL
D001769:Blood; D006348:Cardiac Surgical Procedures; D002314:Cardioplegic Solutions; D003080:Cold Temperature; D006324:Heart Arrest, Induced / Q000379:methods*; D006801:Humans; D007036:Hypothermia, Induced; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control; D010101:Oxygen Consumption; D010827:Physiology; D011188:Potassium; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D013696:Temperature
D002314:Cardioplegic Solutions; D011188:Potassium