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Thermoregulation in mildly hypertensive men during beta-adrenergic blockade
L S Pescatello1, G W Mack, C N Leach
1John B. Pierce Foundation Laboratory, Yale University School of Medicine, New Haven, CT 06519.
Medicine and Science in Sports and Exercise
|April 1, 1990
Summary
Nonselective beta-blockers impair thermoregulation in hypertensive men by reducing blood flow and sweating during exercise. This leads to increased body heat storage, highlighting potential risks for this population.
Area of Science:
- Exercise Physiology
- Cardiovascular Pharmacology
- Thermoregulation Research
Background:
- Nonselective beta-blockade (nBB) impairs thermoregulation in normotensive individuals.
- Hypertensive individuals may face similar or exacerbated thermoregulatory challenges during exercise.
Purpose of the Study:
- To investigate the effects of beta-blockade on thermoregulation during exercise in mildly hypertensive men.
- To differentiate the effects of nonselective (nBB) versus cardioselective (sBB) beta-blockade on cutaneous vascular responses.
Main Methods:
- Double-blind, placebo-controlled crossover study involving six mildly hypertensive men.
- Exercise protocol: 30 minutes of cycle ergometry at 60% max O2 uptake in a 22°C environment.
- Pharmacological interventions: propranolol (nBB), metoprolol (sBB), pindolol (nBB), or placebo.
Main Results:
- Beta-blockade (BB) significantly reduced exercise heart rate, systolic blood pressure, and cardiac output.
- Nonselective beta-blockade (nBB) decreased forearm blood flow and sweating responses relative to esophageal temperature.
- nBB increased forearm vascular resistance, indicating cutaneous vasoconstriction, while sBB did not.
Conclusions:
- Nonselective beta-blockade impairs thermoregulatory responses in hypertensive men during exercise.
- The altered cutaneous vascular control during nBB is not mediated by baroreflexes.
- These findings suggest potential thermoregulatory risks associated with nBB in hypertensive patients.