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The safety of intermittent warm blood cardioplegia
1Victoria General Hospital, Dalhousie University, Halifax, Nova Scotia, Canada.
Insights
Intermittent warm blood cardioplegia (WBC) is safe for myocardial protection, comparable to cold blood cardioplegia (CBC) for clamp times under 90 minutes. Longer durations require extra precautions with WBC.
Area of Science:
- Cardiology
- Cardiac Surgery
- Cardiovascular Research
Background:
- Continuous warm blood cardioplegia offers myocardial protection but may require flow interruption for visualization.
- Intermittent warm blood cardioplegia has been suggested as a safe alternative.
Purpose of the Study:
- To compare the safety and efficacy of intermittent warm blood cardioplegia (WBC) versus intermittent cold blood cardioplegia (CBC) for myocardial protection during cardiac surgery.
Main Methods:
- A study involving 76 patients undergoing coronary or valvular surgery, divided into two groups.
- One group received intermittent CBC every 15 minutes; the other received intermittent WBC every 15 minutes.
- Clamp times ranged from 50 to 140 minutes.
Main Results:
- No deaths occurred in either group. Myocardial infarctions were similar (2 in each group).
- Low cardiac output occurred more frequently in the WBC group (13 vs. 7).
- Electrocardiogram (ECG) global ischemic changes were significantly higher in the WBC group (14 vs. 6) for clamp times exceeding 90 minutes (P < 0.001).
Conclusions:
- Intermittent WBC is as safe as intermittent CBC for myocardial protection when aortic clamp time is less than 90 minutes.
- For clamp times longer than 90 minutes, increased precautions are necessary when using intermittent WBC due to higher rates of ECG changes and low cardiac output.
Abstract:
Continuous warm blood cardioplegia is considered to be an effective method for myocardial protection. However, frequently the flow of the cardioplegia needs to be interrupted for better visualization. Intermittent warm blood cardioplegia was reported to be safe by some investigators. To assess the degree of this safety, 76 patients who underwent operations for coronary or valvular disease, or both, were divided into two groups of 38 patients each. The two groups were well matched for age, ejection fraction, number of coronary bypasses and type of valvular procedures. Cold blood cardioplegia (CBC) was used intermittently every 15 min in the first group while the second group received warm blood cardioplegia (WBC) intermittently every 15 min. The clamp time range was 50-140 min. There were no deaths in either group, four myocardial infarctions occurred, two in each group. Low cardiac output occurred in 13 patients of the WBC group and in 7 patients of the CBC group, electrocardiogram (ECG) global ischemic changes were recorded in 14 patients of the WBC group compared to 6 patients of the CBC group. Statistically the results indicate that the techniques are comparable if the clamp time is less than 90 min. However, after 90 min the development of ECG changes and low cardiac output are significantly higher when WBC is used P < 0.001. Therefore, it is concluded that using the WBC intermittently is as safe as CBC when the clamp time is less than 90 min, however extra precautions are needed with longer clamp times.