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Research Applied to Clinical
Practice
by Robert C. Knies, RN MSN CEN
Section Editor
Geriatric Thermoregulation
We have all seen an elderly person wear a sweater on a hot summer day. Thermoregulation is a finely controlled process that maintains the body's core temperature in the range in which most biochemical processes work best (99° to 99.6° F) (Worfolk, 1997). Thermoregulation is affected in 2 ways; endogenous via cardiovascular, respiratory, neuroendocrine, neuromuscular, and gastrointestinal systems, and exogenous via medication and nutrition (Knies, 1996).
Most body heat is generated as a
by-product of metabolism in the core organs and skeletal muscles. As age increases muscle
activity decreases as does the number of functioning cells of the primary organs. By the
age of seventy, 30% of muscle mass is lost, also physical activity is decreased by up to
50 % or more (Solane, 1992). A secondary source of energy production is via
the Sympathetic (autonomic) Nervous System (SANS) with the release of epinephrine
and norepinephrine which increase metabolism. A steady decline in normal metabolism is a
normal occurrence of aging (Guyton, 1991).
While the basic components of homeostasis are intact, the ability to detect changes in external and internal environments and the speed and effectiveness of the response to these changes are often decreased or lost in the very old or debilitated. Thermal, chemical and mechanical receptor density and sensitivity decrease with age. Therefore the elderly have a delayed perception to the cold or hot. Due to this loss of cutaneous receptors or decrease in their sensitivity, the body's temperature control centers (hypothalamus and brain stem) are slow or ineffective in their response to the temperature changes (Sanders, 1996). Also as the skin becomes thinner and subcutaneous fat diminishes, the insulation against cold and the ability to radiate heat off the body, just doesn't occur.
What does this mean to the clinician?
When attempting to compensate or prevent hypothermia, there is no ideal temperature, it is individually patient related. Even in the summer we must assist the elderly in keeping warm. When you are examining a patient or assisting in bathing, only keep the area in which you are working uncovered, then re-cover quickly; a thin sheet is not enough, warm cotton blankets are the ideal.
Watch for signs of chilling, the
human body has a natural drive to keep warm (Worfolk, 1997). So when you
see shivering, remember core energy is being used. When the patient moves into the -fetal-
position or curls up, they are trying to keep warm and using muscular energy to generate
heat. As discussed earlier, these patients may not have this energy to spare.
In hyperthermia, these patient's
hearts are over worked to pump blood to the skin periphery to assist in the body's effort
to release heat via radiant exposure. The extra work of the heart is many times the cause
of death, not heat exposure (Hale, 1997). Also, many elderly -function- in
a state of dehydration and do not have the extra circulating fluid to -sweat off-. So the
heart must pump harder to push blood to the skin, that has decreased, or atherosclerosed
blood vessels in an attempt to release the body heat. (Can you see the cycle?)
When the outside temperature is over
90° F and the humidity is high, the inside of many buildings can reach temperatures of
over 107° F. As was the case in Chicago in 1995 where 733 people died, most from cardiac
overwork than from heat stroke (Hale, 1997). These people need to be in an
area where the air can be circulated via fan or air conditioner, they should also be
encouraged to drink increased amounts of water. But remember, we don't want the ambient
temperature to be too cool, so that we have to worry about hypothermia complications.
Nutrition is an important need in
assisting with the thermal regulation of everyone, more especially the elderly. Many
people presume that a high carbohydrate meal provides a quick heat fix, which it does, but
it uses up metabolic energy and only has a 4% increase in metabolic rate. Whereas a high
protein meal can increase metabolic rate 30% and can last for many hours (Guyton,
1991). Also cold foods should not be served to (potentially thermoregulatory
compromised) patients, especially before bedtime. Our bodies naturally decrease the
internal temperature while asleep, as our metabolic rate decreases and muscle activity
decreases, therefore cold foods at bedtime can further compromise the thermoregulatory
actions.
The research into thermoregulation in the elderly is complex
and growing, it is hoped that these few points have enlightened you and will assist you in
providing better care for our elderly clients and dealing with those who have impaired
thermoregulatory systems.
References:
Guyton, A.C. (1991). Textbook of Medical Physiology 8th ed.
Philadelphia: Saunders.
Hale, B. (1997). Heat stress; the impact on seniors. Pennsylvania State
University College of Health and Human Development News, 10 (3), 3.
Knies, R.C. (1996). Geriatric trauma; What you need to know.
International Journal of Trauma Nursing, 2 (3), 85-91.
Sanders A.B. (1996). Emergency Care of the Elder Person, Saunders ed.
St. Louis: Beverly Cracom Publications.
Sloane, P.D. (1992). Normal aging, in Primary Care Geriatrics Ham, R.J.
& Sloane, P.D. eds, 2nd ed. St. Louis: Mosby.
Worfolk, J. (1997). Keep frail elders warm! Geriatric Nursing, 18 (1),
7-11.
"Research Applied to Clinical Practice: Geriatric Thermoregulation"
[http://ENW.org/Research-GeriTherm.htm]
is a webarticle by Robert C.
Knies, RN MSN CEN [bknies@stevenshealthcare.org]
©Robert C. Knies, RN MSN CEN
presented by Emergency Nursing World !
[http://ENW.org]
Tom Trimble, RN [Tom@ENW.org]
ENW Webmaster
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