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[Effect of catecholamine on reperfused myocardium following hypothermic global ischemia]
Insights
Catecholamines like epinephrine and dobutamine improve hemodynamics but do not protect the heart after hypothermic global ischemia. High-dose epinephrine worsens myocardial damage during reperfusion.
Area of Science:
- Cardiology
- Biochemistry
- Cell Biology
Context:
- Hypothermic global ischemia is a critical condition affecting the heart during cardiac surgery.
- Reperfusion injury can occur after restoring blood flow, leading to further myocardial damage.
- Understanding the effects of catecholamines during reperfusion is vital for improving patient outcomes.
Purpose:
- To evaluate the impact of epinephrine and dobutamine on myocardial function and structure post-hypothermic global ischemia.
- To assess hemodynamic, biochemical, and ultrastructural changes in the reperfused myocardium.
- To determine if catecholamines mitigate or exacerbate ischemia-reperfusion injury.
Summary:
- Dogs underwent 60 minutes of hypothermic global ischemia followed by 60 minutes of reperfusion with saline (control), low-dose epinephrine, high-dose epinephrine, or dobutamine.
- Hemodynamic parameters improved with catecholamine infusion, but tissue calcium content increased, particularly with high-dose epinephrine.
- Adenosine triphosphate (ATP) levels remained low, and myocardial ultrastructure, especially mitochondria, showed damage, with high-dose epinephrine causing the most significant injury.
Impact:
- Catecholamines enhance hemodynamics but do not prevent ATP depletion or ultrastructural damage in the reperfused myocardium.
- High-dose epinephrine can accentuate ischemic damage, highlighting the need for careful dosage during reperfusion.
- These findings suggest that current catecholamine strategies may not be optimal for protecting the myocardium against ischemia-reperfusion injury.
Abstract:
This study was aimed to evaluate the effect of catecholamine on the myocardium reperfused after hypothermic global ischemia, by changes of hemodynamics, biochemistry and ultrastructure. Under cardiopulmonary bypass (CPB) at flow rate 80 ml/kg/min., the aorta was clamped for 60 min. at 28 degrees C of myocardial temperature and reperfused for 60 min. in 26 mongrel dogs. They were divided into 4 groups by infusion of physical saline solution (control), epinephrine 1 microgram/kg/min. (group 1), epinephrine 0.1 microgram/kg/min. (group 2) and dobutamine 5 micrograms/kg/min. (group 3) during reperfusion. The hemodynamic parameters and myocardial isoenzyme (m-AST, MB-CPK) of coronary sinus venous blood were measured before CPB, 30 and 60 min. after declamp. The myocardial adenosine triphosphate (ATP), creatine phosphate (CP), water content, tissue Ca content and fine structure with score of mitochondrial membrane and cristae were examined in epicardium and endocardium at the end of experiment. Hemodynamic parameters after declamp were higher in group 1, 2 and 3 than control (p less than 0.05). The water content and tissue Ca content in group 1 were higher than control. The ATP of endocardium was lowest but CP was no significant difference among four groups. The mitochondrial score in group 1 was lower than control. These data suggest that epinephrine and dobutamine increase hemodynamics and tissue Ca content on the reperfused myocardium following 60 min. of hypothermic global ischemia, but they do not improve depletion of ATP and disruption of myocardial ultrastructure. High dose of epinephrine accentuates ischemic damage of reperfused myocardium after hypothermic global ischemia.