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Optimal flow rates for retrograde warm cardioplegia
J S Ikonomidis1, T M Yau, R D Weisel
1Department of Clinical Biochemistry, Toronto Hospital, Ontario, Canada.
The Journal of Thoracic and Cardiovascular Surgery
|February 1, 1994
Summary
Optimal warm retrograde cardioplegia flow rates are crucial for cardiac surgery. Delivering at least 200 ml/min ensures adequate myocardial perfusion and metabolic stability during coronary artery bypass operations.
Area of Science:
- Cardiovascular Surgery
- Cardiothoracic Anesthesia
- Cardiopulmonary Bypass
Background:
- Retrograde warm blood cardioplegia is used in coronary artery bypass grafting.
- Potential for inadequate perfusion of certain heart regions exists.
- Optimal flow rates require further investigation.
Purpose of the Study:
- To determine the optimal flow rate for warm retrograde cardioplegia.
- To assess the impact of different flow rates on myocardial metabolism and perfusion.
Main Methods:
- Two studies involving 62 patients undergoing elective coronary artery bypass.
- Low flow study: 50, 75, 100 ml/min.
- High flow study: 100, 200, 300, and 500 ml/min in randomized order.
Main Results:
- Low flow rates (≤100 ml/min) resulted in high lactate production and low coronary venous pH.
- Flow rates of 200 ml/min or higher minimized lactate production and maintained physiologic pH.
- Flows of 300 ml/min or higher did not offer additional metabolic benefits.
Conclusions:
- Warm retrograde cardioplegia should be delivered at a minimum of 200 ml/min.
- Higher flow rates beyond 200 ml/min do not provide further advantages.
- Optimized flow rates are essential for improved patient outcomes in cardiac surgery.