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Cardioplegic infusion: the safe limits of pressure and temperature
Insights
Very cold cardioplegic solutions infused at 150 mm Hg and below 8 degrees C did not impair canine myocardium. Higher pressures (150-200 mm Hg) caused significant functional decline, indicating safe limits for myocardial protection.
Area of Science:
- Cardiovascular Surgery
- Cardiothoracic Research
- Myocardial Preservation
Background:
- Coronary artery disease necessitates effective myocardial protection during surgery.
- Cold cardioplegic solutions are used to induce cardiac arrest and hypothermia.
- Optimal infusion pressures and temperatures for cardioplegia are critical to prevent myocardial damage.
Purpose of the Study:
- To investigate the safety of very cold cardioplegic solutions at high infusion pressures.
- To determine if elevated infusion pressures or low temperatures damage normal myocardium.
- To establish safe parameters for cardioplegic infusion in cardiac surgery.
Main Methods:
- Utilized a canine right heart bypass model for controlled hemodynamic conditions.
- Infused a cold crystalloid cardioplegic solution (0-2°C) into coronary arteries.
- Measured regional myocardial function using sonomicrometry during and after cardiac arrest.
- Varied infusion pressures (50-200 mm Hg) and monitored myocardial temperatures (average 9.4°C).
Main Results:
- Infusion pressures up to 150 mm Hg showed no significant impairment in post-arrest myocardial function.
- Pressures between 150-200 mm Hg resulted in a significant decrease in regional myocardial function.
- Myocardial temperatures below 8°C did not correlate with impaired recovery of function when pressures were ≤150 mm Hg.
Conclusions:
- Cardioplegic infusion pressures up to 150 mm Hg and temperatures below 8°C are safe for normal myocardium.
- Higher infusion pressures (150-200 mm Hg) pose a risk of myocardial damage.
- These findings provide critical data for optimizing cardioplegic delivery strategies in cardiac surgery.
Abstract:
In patients with coronary artery disease, infusion of very cold cardioplegic solutions at elevated pressures may facilitate homogeneous cooling and cardioplegia. This study was designed to determine if very high infusion pressures or very low temperatures of the cardioplegic solution damages normal myocardium. In a hemodynamically controlled canine right heart bypass preparation, a crystalloid solution (Plasma-Lyte 148 with 30 mEq/L potassium chloride, 0 degree to 2 degrees C) was infused with separate control of the infusion pressures in the left anterior descending and circumflex arteries. A sonomicrometer measured regional myocardial function in each area. During a 100 minute arrest period, cardioplegic solution was reinfused every 20 minutes and reduced myocardial temperatures to an average of 9.4 degrees +/- 2.2 degrees C. In a comparison of infusion pressures of 50 versus 100 mm Hg and 100 versus 150 mm Hg, postarrest regional myocardial function was unchanged from prearrest. However, in a comparison of infusion pressures of 150 to 200 mm Hg, a significant fall in regional myocardial function was noted with the higher pressures (106% and 64% recovery, respectively, p less than 0.02, n = 6). Excluding the areas perfused at 200 mm Hg, comparison of regions cooled to less than 8 degrees C and to greater than 8 degrees C demonstrated no difference in recovery of regional myocardial function. In this study, elevation of cardioplegic infusion pressures to 150 mm Hg and lowering of myocardial temperatures to less than 8 degrees C caused no impairment of regional myocardial function.