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Dose-response relationship of isoflurane and halothane versus coronary perfusion pressures. Effects on flow
D C Cheng1, J R Moyers, R M Knutson
1Department of Anesthesia, University of Iowa College of Medicine, Iowa City.
Insights
Isoflurane anesthesia better maintains myocardial blood flow in collateral-dependent zones compared to halothane, especially at lower coronary perfusion pressures (CPP). This study highlights isoflurane
Area of Science:
- Cardiovascular Physiology
- Anesthesiology
- Myocardial Perfusion
Background:
- Collateral-dependent (CD) myocardium relies on alternative blood supply pathways.
- Anesthetic agents can influence cardiovascular hemodynamics and regional blood flow.
- Understanding anesthetic effects on CD zones is crucial for managing cardiac patients.
Purpose of the Study:
- To investigate the redistribution of myocardial blood flow in CD zones.
- To compare the effects of isoflurane and halothane anesthesia on myocardial perfusion.
- To assess the impact of varying coronary perfusion pressure (CPP) on blood flow distribution.
Main Methods:
- A swine model with chronically occluded left anterior descending coronary artery was used.
- Piglets were anesthetized with isoflurane or halothane to regulate specific CPP.
- Regional myocardial blood flows were measured using radiolabeled microspheres at varying CPPs (30-55 mmHg).
Main Results:
- Both anesthetics caused proportional decreases in heart rate and blood pressure with decreasing CPP.
- Cardiac output was maintained with isoflurane but decreased with halothane at 30 mmHg CPP.
- Isoflurane sustained significantly higher endocardial blood flow than halothane across CD and normal zones.
Conclusions:
- Isoflurane demonstrates superior ability to maintain myocardial blood flow in CD regions compared to halothane.
- Anesthetic choice significantly impacts myocardial perfusion reserve under reduced CPP.
- Findings suggest isoflurane may be preferable for managing patients with coronary artery disease.
Abstract:
The authors studied the redistribution of myocardial blood flow in a collateral-dependent (CD) zone as a function of coronary perfusion pressure (CPP) during isoflurane and halothane anesthesia. A swine model with CD myocardium distal to a chronically occluded left anterior descending coronary artery was developed and studied. Sixteen piglets were allowed to grow for 8-10 weeks after banding of the left anterior descending coronary artery. They were randomly anesthetized with either isoflurane (n = 8) or halothane (n = 8) as the sole anesthetic, which was used to regulate specific CPP. The resultant regional myocardial blood flows were measured using radiolabeled microspheres. Four randomly allocated CPPs, of 30, 40, 45, and 55 mmHg, were studied in each animal. Four additional collateralized animals were anesthetized with alpha-chloralose, and the same CPPs were obtained using an intravenous adenosine infusion (1-5 microM kg-1) to validate this model. There was a proportional decrease in heart rate and blood pressure in both the isoflurane and and the halothane group with CPP. Cardiac output was significantly decreased in the halothane group at 30 mmHg when compared to 55-mmHg CPP, but it was maintained in the isoflurane group. Systemic vascular resistance was significantly lower in the isoflurane group at 30 and 40 mmHg when compared to 55-mmHg CPP. Both the isoflurane and the halothane group showed a proportional and significant decrease in endo-, mid-, and epicardial blood flows at 30-mmHg CPP when compared to baseline. In both CD and normal perfusion zones, isoflurane consistently sustained a higher endocardial blood flow than halothane (5.7-41.1%).(ABSTRACT TRUNCATED AT 250 WORDS)