Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different.

1. THERMOREGULATION
Presented By,
Miss. Silla Elsa Soji
MSC Nursing

2. Overview
• Humans are homeotherms
• Maintain constant body core temperature
• Heat loss must match heat gain
• Normal core temperature is 37°C
• Above 45°C : May destroy proteins and enzymes and lead to
death .
• Below 34°C : May cause slowed metabolism and arrhythmias.

3. Definition
Thermoregulation is the ability of an organism to
keep its body temperature within certain
boundaries, even when the surrounding temperature
is very different.

4. Core Temperature
• The temperature of the deep tissues of the body— the
―core‖ of the body—remains very constant, within ±
0.6°C
• No single core temperature can be considered normal.
• Range:- 36.5–37.5°C . Core temperature gradually
decreases with age
• Core temperature measurements are used to monitor
intraoperative hypothermia, prevent overheating, and
facilitate detection of malignant hyperthermia

5. Skin Temperature
• The skin temperature, in contrast to the core temperature, rises and
falls with the temperature of the surroundings.
• Body temperature shows circadian rhythm, highest in the afternoon
or in the evening and least at 5:00 A.M in the morning and vary by
0.5 to 1°C.
• In children, body temperature is 0.5°C higher.
• Non-pregnant women in their reproductive phase of life show 0.5°C
higher body temperature in the luteal phase of menstrual cycle.

6. HEAT GAIN AND HEAT
LOSS
Heat is gained by conduction from warm air surrounding the body
by the body’s metabolic activity which generates heat e.g. when
muscle move
1. Extra rate of metabolism caused by muscle activity, including
muscle contractions caused by shivering .
2. Extra metabolism caused by the effect of thyroxine (and, to a
less extent, other hormones, such as growth hormone and
testosterone) on the cells
3. Extra metabolism caused by the effect of epinephrine,
norepinephrine, and sympathetic stimulation on the cells .
4. Extra metabolism caused by increased chemical activity in the
cells themselves, especially when the cell temperature increases .

7. • Heat is lost by conduction and radiation to
cold air (or water) by evaporation of sweat
from the body surface.

8. PATHOPHYSIOLOGY OF NORMAL
THERMOREGULATION
The processing of thermoregulatory information
occurs in three phases:-
i. Afferent thermal sensing
ii. Central regulation
iii. Efferent responses

9. 1. Afferent thermal sensing

10. 2. Central regulation

11. Efferent responses
• Autonomic response: Determined by
the core temperature
• Behavioural alteration: Determined by
the peripheral temperature

12. Thermoregulation In
Paediatrics
• Infants are especially vulnerable to
hypothermia because of the large ratio of
body surface area to weight, the thinness
of the skin, and a limited ability to cope
with cold stress.
• The head comprises of 20% surface area
and shows highest regional heat flux.
hence covering of head is very important

13. Thermoregulation During
Generalanesthesia
Anesthetic- induced normal autonomic
thermoregulatory impairment has a specific
form:
• warm-response thresholds are elevated
slightly
• cold-response thresholds are markedly reduced
• The inter- threshold range is increased from
its normal values near 0.2° C to approximately
2° C to 4° C

14. Adverse Effects Of
Hypothermia:-
1. Wound infection
2. Reversible coagulopathy
3. Prolonged recovery
4. Drug metabolism: Hypothermia
increases the solubility of volatile
anaesthetics
5. Shivering

15. Hyperthermia and Fever
Hyperthermia:- hypothalamic set point is
normal but peripheral mechanisms are
unable to maintain body temperature that
matches the set point. Fever occurs when the
hypothalamic set point is increased by the
action of circulating pyrogenic cytokines,
causing intact peripheral mechanism to
conserve and generate heat until the body
temperature increases to elevated set point.

16. Malignant hyperthermia
• Malignant hyperthermia(MH) is a
pharmacogenetic clinical syndrome
that, in its classic form, occurs during
anaesthesia with a volatile halogenated
alkane such as halothane and/or the
administration of the depolarizing
muscle relaxant succinylcholine.