Related Experiment Videos
Effects of halothane and isoflurane on collateral dependent myocardium in chronically instrumented dogs
P F Wouters1, H Van Aken, M A Marcus
1Department of Anesthesiology, Katholieke Universiteit Leuven, Belgium.
Insights
Moderate hypotension with isoflurane (ISO) and halothane (HALO) preserved regional myocardial function in dogs with coronary occlusion. Both anesthetics maintained blood flow distribution, with ISO showing less hemodynamic depression in collateral-dependent areas.
Area of Science:
- Cardiovascular Anesthesiology
- Myocardial Physiology
- Coronary Circulation
Background:
- Chronic coronary artery occlusion leads to collateral-dependent (CD) myocardium.
- Assessing anesthetic effects on regional myocardial function and perfusion is crucial.
- Dipyridamole challenge tests quantify vasodilator reserve in CD myocardium.
Purpose of the Study:
- To investigate the effects of moderate hypotension induced by halothane (HALO) and isoflurane (ISO) on regional myocardial function and perfusion.
- To compare the hemodynamic and functional impacts of HALO and ISO in dogs with chronic coronary occlusion.
Main Methods:
- Dogs with chronic coronary artery occlusion were subjected to controlled hypotension (diastolic arterial pressure of 50 mm Hg) using HALO and ISO.
- Regional myocardial function (systolic wall-thickening fraction) and blood flow were measured in normal (Nl) and CD myocardium.
- Vasodilator reserve was assessed using a dipyridamole challenge test in conscious controls.
Main Results:
- Both HALO and ISO reduced global and regional hemodynamics, with HALO causing more pronounced depression.
- Systolic wall-thickening fraction decreased in both Nl and CD areas under both anesthetics.
- Myocardial blood flow decreased comparably with both agents, but ISO resulted in less reduction in wall-thickening fraction and preserved perfusion better in CD areas.
- Neither anesthetic induced ischemic dysfunction despite hypotension, preserving intercoronary and transmural flow distribution.
Conclusions:
- Moderate hypotensive doses of ISO and HALO preserve regional myocardial function in collateral-dependent myocardium in dogs with single-vessel occlusion and collateral circulation.
- ISO demonstrated a more favorable hemodynamic profile compared to HALO under moderate hypotension.
- Both anesthetics maintained critical blood flow distribution to the myocardium, preventing ischemic dysfunction.
Abstract:
The effects of moderate systemic hypotension with halothane (HALO) and isoflurane (ISO) on regional myocardial function and perfusion were studied in dogs with chronic coronary artery occlusion. Vasodilator reserve in collateral-dependent (CD) myocardium was quantified in conscious animals by using a dipyridamole challenge test. Blood flow was distributed homogeneously to the normal (Nl) and CD myocardium at rest, but subendocardial perfusion increased only in the Nl area after dipyridamole. HALO and ISO were administered at doses that reduced diastolic arterial pressure to 50 mm Hg. End-tidal concentrations were 1.3 +/- 0.2 vol% for HALO (1.5 minimum alveolar anesthetic concentration) and 1.8 +/- 0.2 vol% for ISO (1.4 minimum alveolar anesthetic concentration), respectively. Global and regional hemodynamic depression were more pronounced with HALO. Systolic wall-thickening fraction decreased both in the Nl (-37%) and CD area (-27%). Myocardial blood flow to Nl and CD myocardium decreased to a comparable extent. ISO predominantly decreased systemic vascular resistance and, when compared to HALO, decreased systolic wall-thickening fraction less in both the Nl (-19%) and CD area (-18%). In addition, regional myocardial perfusion to both Nl and CD myocardium remained virtually unaltered from conscious control conditions. Despite reductions of diastolic blood pressure to 50 mm Hg, neither HALO nor ISO induced ischemic dysfunction in myocardium with diminished vasodilator reserve. Both anesthetics preserved intercoronary as well as transmural blood flow distribution. During HALO, myocardial perfusion was less both in Nl and CD myocardium due to a more pronounced metabolic depression. We conclude that moderate hypotensive doses of ISO and HALO preserve regional myocardial function of collateral-dependent myocardium in dogs with single vessel occlusion and enhanced collateral circulation.