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Exercise, dobutamine, and combined atropine, norepinephrine, and epinephrine compared
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 1, 1985
Summary
Comparing exercise and drug infusions in dogs, researchers found similar increases in cardiac output and heart rate. However, total body oxygen consumption and regional blood flow differed significantly across interventions.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
- Pharmacology
Background:
- Understanding how the cardiovascular system responds to different stimuli is crucial for physiological research.
- Exercise and pharmacological agents can significantly impact cardiac function and blood flow distribution.
- Comparing these effects helps elucidate specific physiological mechanisms.
Purpose of the Study:
- To compare the cardiovascular effects of submaximal exercise, dobutamine infusion, and a combination of autonomic drugs in conscious dogs.
- To investigate differences in myocardial oxygen demand, cardiac output, heart rate, and regional blood flow.
- To analyze changes in total body oxygen consumption and vascular resistance under various interventions.
Main Methods:
- Conscious dogs were subjected to three interventions: submaximal exercise, dobutamine infusion, and a combined infusion of atropine, norepinephrine, and epinephrine.
- Cardiovascular parameters including heart rate, blood pressure, cardiac output, and myocardial blood flow were monitored.
- Regional blood flow to various organs and tissues was measured, alongside total body oxygen consumption and arteriovenous oxygen difference.
Main Results:
- All interventions similarly increased myocardial oxygen demand (double product), cardiac output, and heart rate.
- Submaximal exercise uniquely increased total body oxygen consumption and arteriovenous oxygen difference.
- Regional blood flow changes varied, with exercise significantly increasing blood flow to skeletal muscle and the tongue, while the combined drug infusion affected diaphragm and stomach blood flow.
Conclusions:
- While exercise, dobutamine, and combined autonomic drug infusions can elicit similar increases in cardiac output and heart rate, they induce distinct patterns of regional blood flow and oxygen consumption.
- These findings highlight the complex and differential regulation of cardiovascular and regional hemodynamics by various stimuli.
- The study underscores that achieving a similar myocardial oxygen demand does not equate to identical systemic or regional cardiovascular responses.