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Cold and warm myocardial protection techniques
R A Guyton1, J P Gott, W M Brown
1Department of Surgery, Emory University School of Medicine, Atlanta, Georgia, USA.
Insights
Cold cardioplegia is effective for cardiac surgery. Tepid continuous aerobic cardioplegia offers superior myocardial protection, especially for compromised hearts, reducing stroke rates.
Area of Science:
- Cardiovascular Surgery
- Cardiothoracic Anesthesia
- Myocardial Protection
Background:
- Cold cardioplegia is a standard technique for cardiac operations.
- Crystalloid cardioplegia offers good myocardial protection for metabolically intact hearts.
- Blood cardioplegia may be advantageous for metabolically compromised hearts.
Purpose of the Study:
- To evaluate the efficacy of different cardioplegia techniques for myocardial protection during cardiac operations.
- To compare the outcomes of cold crystalloid, cold blood, and normothermic/tepid blood cardioplegia.
- To identify the optimal cardioplegia strategy for resuscitation of ischemic or compromised myocardium.
Main Methods:
- Comparison of cold oxygenated crystalloid cardioplegia with blood cardioplegia techniques.
- Analysis of clinical results and experimental studies on myocardial resuscitation.
- Evaluation of outcomes associated with normothermic cardiopulmonary bypass and cardioplegia.
- Modification of warm blood technique to tepid temperatures with hyperglycemia prevention.
Main Results:
- Cold crystalloid cardioplegia provides excellent exposure and protection for intact hearts.
- Blood cardioplegia shows an advantage in restoring metabolically compromised myocardium.
- Continuous aerobic cardioplegia techniques are superior to intermittent cold blood techniques for ischemic myocardium resuscitation.
- Normothermic techniques initially showed increased adverse neurologic outcomes.
- Tepid continuous aerobic cardioplegia, with hyperglycemia prevention, reduced stroke rates to previous levels.
Conclusions:
- Tepid continuous aerobic cardioplegia is a superior technique for myocardial resuscitation in cardiac operations as of 1994.
- This technique is particularly beneficial for ischemic or metabolically compromised myocardium.
- Careful temperature and glucose management are crucial for optimizing outcomes with aerobic cardioplegia.
Abstract:
Cold cardioplegia techniques are effective and reliable in most circumstances requiring cardiac operations. The cold oxygenated crystalloid technique used in our institution provides superior exposure of distal anastomoses and excellent protection when the heart is metabolically intact at the onset of the cross-clamp interval. If the heart is metabolically compromised before the cross-clamp interval, blood cardioplegia techniques appear to have a distinct advantage in the restoration of this compromised muscle. The clinical results from Toronto and our own experimental studies strongly suggest that continuous aerobic cardioplegic techniques are superior to intermittent cold blood techniques in the resuscitation of ischemic myocardium. As normothermic cardiopulmonary bypass and normothermic cardioplegic techniques were introduced in our institution, an increased rate of adverse neurologic outcomes was observed. Modification of the warm blood technique to allow mildly hypothermic, or tepid, cardiopulmonary bypass and cardioplegia temperatures along with prevention of hyperglycemia has reduced the stoke rate with continuous aerobic cardioplegia techniques to the level observed with our other methods of myocardial protection. Tepid continuous aerobic cardioplegia may be the superior technique available in 1994 for the resuscitation of ischemic or metabolically compromised myocardium during the performance of cardiac operations.