This study will test the hypothesis that the drugs propranolol and metoprolol will result in greater increases in core body temperature during 3 hours of extreme heat exposure in older adults.
Older individuals are more likely to die or become ill during heat waves. During the 1995 Chicago heat wave, there was 35% increase in hospital admissions for individuals older than 65 years of age. Moreover, adults over the age of 65 have a heat-related death rate that is more than double any other age group. Therefore, with an increasing elderly population that is expected to rise by 60% (to 78 million) by 2035, the causes of this excess mortality must be understood to better protect the ageing United States population. It is notable that selective and non-selective beta blocker drugs are commonly prescribed to older individuals with cardiovascular diseases. In younger individuals exposed to a heat stress, beta blocker administration reduced whole-body sweat rate and skin blood flow responses resulting in greater increases in core body temperature. Notably, nothing is known regarding the effects of beta blockers on thermoregulatory responses during heat exposure in older individuals. This project will evaluate core body temperature responses to selective and non-selective beta blocker drugs during simulated heat wave exposure in older individuals.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
22
Subjects will spend 3-hours in a heat chamber at 41°C and 40% humidity.
IEEM Texas Health Presbyterian Hospital Dallas
Dallas, Texas, United States
RECRUITINGInternal temperature
The change in internal temperature to the 3-hour heat exposure will be measured.
Time frame: Continuously throughout the 3-hour heat exposure.
Whole body sweat rate
Whole body sweat rate will be measured via changes in pre/post nude body mass.
Time frame: Nude body mass will be measured before and after the 3-hour heat exposure.
Heart rate
Heart rate will be measured via electrocardiogram.
Time frame: Continuously throughout the 3-hour heat exposure.
Arterial blood pressure
Systolic and diastolic arterial blood pressures will be measured via a brachial blood pressure cuff.
Time frame: Continuously throughout the 3-hour heat exposure.
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