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Effect of systemic vasodilators on internal mammary artery flow. Implications for postoperative treatment after
M B Izzat1, R R West, C Ragoonanan
1Department of Cardiac Surgery, University of Bristol, United Kingdom.
Insights
Enoximone and sodium nitroprusside effectively increase internal mammary artery free flow, preventing potentially fatal postoperative spasms after myocardial revascularization surgery.
Area of Science:
- Cardiovascular Surgery
- Pharmacology
- Anesthesiology
Background:
- Postoperative spasm of the internal mammary artery graft is a significant cause of morbidity and mortality following myocardial revascularization.
- The efficacy of systemic vasodilators in preventing or treating internal mammary artery spasm has not been previously investigated clinically.
Purpose of the Study:
- To investigate the effect of five systemic agents on internal mammary artery (IMA) free flow in patients undergoing myocardial revascularization.
- To determine which agents are most effective in increasing IMA free flow and potentially preventing spasm.
Main Methods:
- A study involving 50 patients who received the left internal mammary artery for myocardial revascularization.
- Free flow of the harvested IMA was measured before and after systemic infusion of normal saline, dobutamine, glyceryl trinitrate, sodium nitroprusside, or enoximone.
- Hemodynamic conditions were controlled throughout the measurements.
Main Results:
- Enoximone demonstrated the greatest increase in IMA free flow (94% +/- 24%), followed by sodium nitroprusside (78% +/- 37%).
- Both enoximone and sodium nitroprusside showed significantly greater increases in flow compared to normal saline and dobutamine.
- Glyceryl trinitrate also significantly increased flow compared to normal saline and dobutamine.
Conclusions:
- Systemic enoximone and sodium nitroprusside are recommended for preventing and treating postoperative internal mammary artery spasm.
- These agents effectively increase IMA free flow, addressing a critical concern in myocardial revascularization.
Abstract:
Postoperative spasm of the internal mammary artery graft can cause morbidity and mortality after myocardial revascularization. To our knowledge, the ability of systemic vasodilators to overcome internal mammary artery spasm has not been studied clinically. In 50 patients in whom the left internal mammary artery was used for myocardial revascularization, we have investigated the effect of five agents on internal mammary artery free flow: normal saline, dobutamine, glyceryl trinitrate, sodium nitroprusside, and enoximone, a phosphodiesterase III inhibitor. After the internal mammary artery was harvested, free flow was measured under controlled hemodynamic conditions before any pharmacologic intervention (flow 1) and a mean of 18.5 +/- 3 (standard deviation) minutes after a systemic infusion of one of the five agents was begun (flow 2). The increase in free flow expressed as a percentage of initial flow was greater for enoximone (94% +/- 24%) than for normal saline (18% +/- 11%), dobutamine (40% +/- 27%), and glyceryl trinitrate (52% +/- 36%) (all three p < 0.01). The increase in flow for sodium nitroprusside (78% +/- 37%) was greater than for normal saline and dobutamine (both p < 0.05). We therefore recommend the systemic use of enoximone and sodium nitroprusside, in rank order, to prevent and treat postoperative spasm of the internal mammary artery.