INTRODUCTION HOMEOTHERMIC ANIMALS POIKILOTHERMIC ANIMALS BODY TEMPERATURE Normal Body Temperatures VARIATIONS OF BODY TEMPERATURE Pathological Variations HEAT GAIN OR HEAT PRODUCTIONIN THE BODY HEAT LOSS FROM THE BODY Regulation of Body Temperature Hypothalamus has two centers which regulate the body temperature: Applied

1. Metabolism and
Temperature Regulation
Body Temperature Regulation

2. INTRODUCTION
• Living organisms are classified into two groups,
• Depending upon the maintenance (regulation) of body
temperature:
1. Homeothermic animals
2. Poikilothermic animals.

3. HOMEOTHERMIC ANIMALS
• This type of animals body temperature is maintained at a
constant level,
• irrespective of the environmental temperature.
• Birds and mammals including man belong to this category.
• They are also called warm blooded animals.

4. POIKILOTHERMIC ANIMALS
• This animals body temperature is not constant.
• It varies according to the environmental temperature.
• Amphibians and reptiles are the poikilothermic
animals.
• These animals are also called coldblooded animals.

5. BODY TEMPERATURE
• Body temperature can be measured by placing the clinical
thermometer in different parts of the body such as:
1. Mouth (oral temperature)
2. Axilla (axillary temperature)
3. Rectum (rectal temperature)
4. Over the skin (surface temperature).

6. Normal Body Temperatures
Body Core Temperature and Skin
Temperature
a. Deep tissues temperature remains
very constant (within a 0.6 ̊C)
b. Skin temperature rises and falls with
the temperature
of the surroundings
c. Range of core temperatures is 36-
37.5 ̊C and 97-99.5 F

7. NORMAL BODY TEMPERATURE
• Normal body temperature in human is 37°C (98.6°F),
• when measured by placing the clinical thermometer in
the mouth (oral temperature).
• It varies between 35.8°C and 37.3°C (96.4°F and
99.1°F).

8. TEMPERATURE AT DIFFERENT PARTS
OF THE BODY
• Axillary temperature is 0.3°C to 0.6°C (0.5°F to 1°F)
lower than the oral temperature.
• The rectal temperature is 0.3°C to 0.6°C (0.5°F to
1°F) higher
• The superficial temperature (skin or surface
temperature) varies between 29.5°C and 33.9°C
(85.1°F and 93°F). than oral temperature.

9. • Body Temperature is Controlled by Balancing Heat
Production and Heat Loss
a. Heat production- principal by-product of metabolism;
factors affecting the rate of heat production
1) Basal metabolic rate of the cells
2) Muscle activity
3) Thyroxine effects
4) Effects of the sympathetic nervous system
5) Increased activities of cells
6) Digestion, absorption, and food storage (thermogenic
effect of food

10. VARIATIONS OF BODY
TEMPERATURE
Physiological Variations
1. Age
2. Sex
3. Diurnal variation
4. After meals
5. Exercise
6. Sleep
7. Emotion
8. Menstrual cycle

11. Pathological Variations
•hyperthermia or fever & hypothermia

12. HEAT GAIN OR HEAT PRODUCTION
IN THE BODY
1. Metabolic Activities
2. Muscular Activity
3. Role of Hormones
• Thyroxine and adrenaline increase the heat production by accelerating the metabolic
activities.
4. Radiation of Heat from the Environment
5. Shivering
6. Brown Fat Tissue
its one of the two types of adipose tissues, the other being white
adipose tissue. It produces enormous body heat, particularly in infants.

13. HEAT LOSS FROM THE BODY
•Conduction
•Radiation
•Convection
•Evaporation – Insensible Perspiration
•Panting

14. • Body Temperature is Controlled by Balancing Heat
Production and Heat Loss
b. Heat Loss- determined by two factors (1) how rapidly
it can be conducted to the skin, and (2) how rapidly it
can be transferred from the skin to the surroundings.
c. Insulator system of the body-skin, subcutaneous tissues,
and fat; fat conducts heat 1/3 as readily as other tissues
d. Blood flow to the skin from the body core provides heat
transfer

15. • Body Temperature is Controlled by Balancing Heat
Production and Heat Loss
Fig. 73.2 Skin circulation

16. • Body Temperature is Controlled by Balancing Heat
Production and Heat Loss
Fig. 73.3 Effect of changes in the environmental temperature on heat conductance
from the body core to the skin surface

17. Cont…..
e. Heat conduction in the skin is controlled
by the sympathetic nervous system; controlled
by vasoconstriction

18. • Basic Physics of How Heat is Lost from the Skin Surface
a. Radiation-loss in the form of infrared heat rays
b. Conduction-conduction of heat from the body is self-
limiting unless the heated air moves away from the skin;
accounts for only about 3% of heat loss
c. Convection-removal of heat by convection air currents;
heat must first be conducted to the air before convection
can occur

19. Normal Body Temperatures
• Basic Physics of How Heat is Lost from the Skin Surface
Fig. 73.4 Mechanisms of heat loss from the body

20. • Basic Physics of How Heat is Lost from the Skin Surface
d. Cooling effect of wind-at low velocities is about
proportional to the square root of the wind velocity
e. Conduction and convection of heat from a person
suspended in water-rate is much greater than heat loss
in air
f. Evaporation-when the temperature of the surroundings
becomes greater than that of the skin, instead of losing
heat, the body gains heat. The only means of removing
heat, then, is through evaporation

21. • Sweating and Its Regulation by the ANS
a. Stimulation of the anterior hypothalamic-preoptic area
in the brain either electrically or by excess heat causes
sweating
b. Mechanism-sweat gland is a tubular structure consisting
of (1) deep subdermal coiled portion that secretes the
sweat, and (2) duct portion that passes outward through
the epidermis

22. Normal Body Temperatures
• Sweating and Its Regulation by the ANS
Fig. 73.5 Sweat gland innervated by
an Ach secreting sympathetic
nerve

23. Sweating:
Two types of sweat glands
1)Apocrine glands:
Develop from hair follicles.
Found in the axilla & around nipples & in
females in labia majora & mons pubis.
Stimulated by epinephrine (non thermal sweating).
Atropine does not inhibit this secretion.

24. 2)Eccrine glands
Densest on the palm & soles
Next dense on the head
Much less dense on the trunk & extremities.
They are supplied by cholinergic fibers present
in sympathetic nerves & secrete dilute solution
containing sodium chloride, urea & lactic acid.

25. • Sweating and Its Regulation by the ANS
c. Acclimatization of the sweating mechanism to heat-
increased secretion of aldosterone

27. Regulationof Body Temperature

28. Hypothalamus has two centers which
regulate the body temperature:
1. Heat loss center
2. Heat gain center.

29. HEAT LOSS CENTER
• Its situated in preoptic nucleus of anterior hypothalamus.
• Neurons in preoptic nucleus are heat sensitive nerve cells,
which are called thermoreceptors
• Stimulation of preoptic nucleus
• Causes vasodilatation cutaneous and sweating.
• Removal or lesion of this nucleus increases the body
temperature.

30. HEAT GAIN CENTER
• Heat gain or heat production center.
• It is situated in posterior hypothalamic nucleus.
• Stimulation of posterior hypothalamic nucleus causes
shivering.
• The removal or lesion of this nucleus leads to fall in
body temperature.

31. • Role of the Hypothalamus- temperature of the body
is regulated almost entirely by nervous feedback
mechanisms, and almost all of these operate
temperature regulating centers located in the
hypothalamus
• Detection of Temperature by Receptors in the Skin and
Deep Body Tissues

37. • Fever- body temperature above the normal range
a. Resetting the hypothalamic temperature
regulating center in febrile diseases-effect of
pyrogens
b. Mechanism of pyrogens-release of cytokines,
especially interleukin I which may or may not
cause the release of prostaglandin E-1

38. Benefits of fever:
Many organisms grow best within a
relatively narrow temperature range.
Increase in temperature inhibit
bacterial growth.
Antibody production is increased
when the body temperature is
increased.
Slows down growth of some tumors.

42. Acclimatization to heat:
•Person exposed to heat for several hours
•everyday will develop increased tolerance to hot & humid
conditions in
•1-3 wks.
•Two fold increase in the maximum rate
•Of sweating.
•Increase plasma volume
•decrease loss of salt in the sweat & urine almost to none.
•Last two effects are because of increased aldosterone
Secretion.

43. Applied

44. Hypothermia…

45. Definition
• Core body temperature less than 35oC
• Mild: 34-36oC
• Moderate: 30-34oC
• Severe: < 30oC

46. Causes…
• Decreased heat production
• Endocrine, insufficient fuel, neuromuscular inactivity
• Increased heat loss
• Accidental/immersion hypothermia, vasodilatation, skin disorders,
iatrogenic
• Impaired thermoregulation
• Central (metabolic, drugs, CNS)
• Peripheral (spinal cord injury, neuropathy, diabetes, neuromuscular
disorders)

47. Predisposing Factors
TABLE 19-1 Risk Factors for Hypothermia
Age extremes
Elderly
Neonates
Outdoor exposure
Occupational
Sports-related
Inadequate clothing
Drugs and intoxicants
Ethanol
Phenothiazines
Barbiturates
Anesthetics
Neuromuscular
blockers
Others
Endocrine-related
Hypoglycemia
Hypothyroidism
Adrenal insufficiency
Hypopituitarism
Neurologic-related
Stroke
Hypothalamic disorders
Parkinson's disease
Spinal cord injury
Multisystem
Malnutrition
Sepsis
Shock
Hepatic or renal failure
Burns and exfoliative dermatologic disorders
Immobility or debilitation

48. Signs and Symptoms
TABLE 110-2. Clinical Manifestations of Hypothermia
System Mild Hypothermia Moderate Hypothermia Severe Hypothermia
CNS Confusion, slurred
speech, impaired
judgment, amnesia
Lethargy, hallucinations,
loss of pupillary reflex,
EEG abnormalities
Loss of
cerebrovascular
regulation, decline
in EEG activity,
coma, loss of
ocular reflex
CVS Tachycardia, increased
cardiac output and
systemic vascular
resistance
Progressive bradycardia
(unresponsive to
atropine), decreased
cardiac output and BP,
atrial and ventricular
arrhythmias, J (Osborn)
wave on ECG
Decline in BP and
cardiac output,
ventricular
fibrillation (<
28°C) and asystole
(< 20°C)
Respiratory Tachypnea,
bronchorrhea
Hypoventilation (decreased
rate and tidal volume),
decreased oxygen
consumption and CO2
production, loss of
cough reflex
Pulmonary edema,
apnea

49. Signs and Symptoms, cont’d
TABLE 110-2. Clinical Manifestations of Hypothermia, cont’d
System Mild Hypothermia Moderate hypothermia Severe Hypothermia
Renal Cold diuresis Cold diuresis Decreased renal perfusion
and GFR, oliguria
Hematologic Increased hematocrit and
decreased platelet,
white blood cell
count, coagulopathy,
and DIC
GI Ileus, pancreatitis, gastric
stress ulcers, hepatic
dysfunction
Metabolic
endocrine
Increased metabolic rate,
hyperglycemia
Decreased metabolic rate,
hyper- or hypoglycemia
Musculoskeletal Increased shivering Decreased shivering (< 32°C,
90°F), muscle rigidity
Patient appears dead,
"pseudo-rigor
mortis"

50. History
• Often from bystanders/medics
• Circumstances surrounding exposure
• Where, submersion, ambient temperature?
• Length of exposure
• Mental status changes
• Any predisposing illness – acute/chronic?
• Alcohol/drugs?

51. Physical Exam
• Vitals…
• Temperature – want a core temperature
• Where do we take it?
• Signs of other injuries?
• Can you find the cause of hypothermia?
• Any focal findings?

52. Diagnositics
• ECG!!!
• Will depend on the clinical scenario
• Any signs of trauma? May need imaging…
• Are you able to take a history?
• Past medical history?
• Labs for all:
• CBC, electrolytes, glucose, renal function, toxicology, coags, ABGs, cultures

53. Interventions
• Airway: need for intubation?
• Breathing: spontaneous respiration?
• Warmed humidified oxygen – either through an ETT, or via mask
• Circulation: pulse? BP?
• Large IVs – warmed IV fluids
• Arrhythmias – when do we treat?
• CPR?

54. Interventions, cont’d
• Disability
• Glucoscan, narcan, thiamine
• C-spine immobilization prn
• Exposure
• Undress, assess for trauma
• Recover quickly

55. Rewarming
TABLE 192-3 Rewarming Techniques
Passive rewarming:
Removal from cold environment
Insulation, Warm blankets
Active external rewarming:
Warm water immersion
Heating blankets set at 40°C
Radiant heat
Forced air
Active core rewarming at 40°C:
Inhalation rewarming
Heated IV fluids
GI tract lavage
Bladder lavage
Peritoneal lavage
Pleural lavage
Extracorporeal rewarming

56. Active Rewarming
• When?
• Cardiovascular instability
• Temp less than 32C
• Concominant illnesses
• Extremes of age
• Failure of passive rewarming
• Active external or Internal?

57. Rewarming - Extracorporeal
TABLE 19-3 Options for Extracorporeal Rewarming
Extracorporeal Rewarming
(ECR) Technique Considerations
Venovenous (VV) Circuit — CV catheter to CV or peripheral catheter
No oxygenator/circulatory support
Flow rates 150-400 mL/min
ROR 2°-3°C/h
Hemodialysis (HD) Circuit — single-or dual-vessel cannulation
Stabilizes electrolyte or toxicologic abnormalities
Exchange cycle volumes 200-500 mL/min
ROR 2°-3°C/h
Continuous arteriovenous rewarming
(CAVR)
Circuit — percutaneous 8.5 Fr femoral catheters
Requires BP 60 mmHg systolic
No perfusionist/pump/anticoagulation
Flow rates 225-375 mL/min
ROR 3°-4°C/h
Cardiopulmonary bypass (CPB) Circuit — full circulatory support with pump and oxygenator
Perfusate-temperature gradient (5°-10°C)
Flow rates 2-7 L/min (ave. 3-4)
ROR up to 9.5°C/h
Note: BP, blood pressure; CV, central venous; ROR, rate of rewarming.

58. Hyperthermia…

59. Definition
• Core body temperature > 38oC
• Spectrum of heat-related illnesses
• Heat cramps
• Heat exhaustion
• Heat stroke

60. Causes
• Increased heat load
• Heat absorption from environment
• Heat stroke (exertional, classic)
• Metabolic heat
• Diminished heat dissipation
• Obesity, anhidrosis, drugs
• Sepsis

61. Predisposing Factors…
TABLE 111-1. Predisposing Factors for Heat Stroke
Increased Heat Production Decreased Heat Loss
Environmental heat stress Environmental heat stress
Exertion Cardiac disease
Fever Peripheral vascular disease
Hypothalamic dysfunction Dehydration
Drugs (sympathomimetics) Anticholinergic drugs
Hyperthyroidism Obesity
Skin disease
Ethanol
β Blockers

62. Causes of Hyperthermia…
TABLE 16-1 Causes of Hyperthermia Syndromes
HEAT STROKE
Exertional: Exercise in higher-than-normal heat and/or humidity
Nonexertional: Anticholinergics, including antihistamines; antiparkinsonian drugs; diuretics;
phenothiazines
DRUG-INDUCED HYPERTHERMIA
Amphetamines, cocaine, phencyclidine (PCP), methylenedioxymethamphetamine (MDMA;
"ecstasy"), lysergic acid diethylamide (LSD), salicylates, lithium, anticholinergics,
sympathomimetics
NEUROLEPTIC MALIGNANT SYNDROME
Phenothiazines; butyrophenones, including haloperidol and bromperidol; fluoxetine; loxapine;
tricyclic dibenzodiazepines; metoclopramide; domperidone; thiothixene; molindone;
withdrawal of dopaminergic agents
SEROTONIN SYNDROME
Selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), tricyclic
antidepressants
MALIGNANT HYPERTHERMIA
Inhalational anesthetics, succinylcholine
ENDOCRINOPATHY
Thyrotoxicosis, pheochromocytoma
CENTRAL NERVOUS SYSTEM DAMAGE
Cerebral hemorrhage, status epilepticus, hypothalamic injury

63. Differential Diagnosis
TABLE 193-1 Differential Diagnosis of Heatstroke
Drug toxicity: anticholinergic toxicity, stimulant toxicity (phencyclidine,
cocaine,
amphetamines, ephedrine), salicylate toxicity
Drug withdrawal syndrome: ethanol withdrawal
Serotonin syndrome
Neuroleptic malignant syndrome
Generalized infections: bacterial sepsis, malaria, typhoid fever, tetanus
Central nervous system infections: meningitis, encephalitis, brain abscess
Endocrine derangements: diabetic ketoacidosis, thyroid storm
Neurologic: status epilepticus, cerebral hemorrhage

64. Signs and Symptoms
• Heat cramps
• Cramps in big muscles – spasms
• Normal temperature, mentation
• Caused by dilutional hyponatremia (hypotonic fluid replacement)

65. Signs and Symptoms, cont’d
• Heat exhaustion
• Weakness, dizziness, headache, syncope
• Nausea, vomiting
• Temperature 39-41.1oC
• Normal mentation
• Profuse sweating

66. Signs and Symptoms, cont’d
• Heat Stroke
• Mortality of 10-20% with current treatment
• Coma, seizures, confusion
• No sweating
• Temperature >41.1oC
• Classic triad: hyperpyrexia, CNS dysfunction, anhidrosis
• Classic vs. Exertional

67. History
• Circumstances (as per hypothermia)
• Exertion?
• Fluids?
• Past medical history – any acute or chronic illnesses that may worsen
situation
• Trauma?

68. Physical Examination
• Temperature
• Where do we take it? And how?
• Vitals!
• Look for complications or other causes of the patients symptoms

69. Diagnostics
• ECG
• Imaging guided by history
• CBC, electrolytes, renal function, LFTs, Ca, Mg, PO4, coags
• Urine – myoglobin
• Pan-cultures

70. Poor prognostic factors
• Temperature > 41.1oC
• Coma
• Rhabdomyolysis
• Renal Failure
• Hypotension

71. Treatment
• ABC’s!!!
• Cooling
• Remove to cool environment!
• Correct fluid and electrolyte imbalances

72. Treatment
TABLE 193-2 Comparison of Cooling Techniques
Technique Advantages Disadvantages
Evaporative Simple, Readily available
Noninvasive
Easy patient access
Relatively effective
Shivering
Difficult to maintain monitoring electrodes in
position
Immersion Noninvasive
Relatively effective
Shivering, Cumbersome
Poorly tolerated
Logistically difficult to access
Difficult to maintain monitoring
Ice packing Noninvasive
Readily available
Shivering
Poorly tolerated
Strategic ice packs Noninvasive
Readily available
Combined with other
techniques
Shivering
Poorly tolerated
Medium efficiency
Cold gastric lavage Generally available Invasive
Labor intensive
Potential for water intoxication
May require airway protection
Limited human experience
Cold peritoneal lavage Theoretically beneficial Invasive
Limited human experience

73. Complications of Heat Stroke
TABLE 193-3 Complications of Heatstroke
Initial Delayed
Vital signs Hypotension
Hypothermia overshoot
Hyperthermic rebound
Muscular Shivering
Rhabdomyolysis
Neurologic Delirium
Seizures
Coma
Cerebral edema
Cardiac Heart failure
Pulmonary Pulmonary edema Acute respiratory distress syndrome
Renal Oliguria Renal failure
Gastrointestinal Diarrhea Hepatic necrosis
Mucosal gastrointestinal hemorrhage
Metabolic Hypokalemia
Hypernatremia
Hyperkalemia
Hypocalcemia
Hyperuricemia
Hematologic Thrombocytopenia
Disseminated intravascular
coagulation

74. Reference
•Textbook of Practical Physiology
•A.K. Jain
•C.L. Ghai
•G.K.Pal
•Textbook of Medical Physiology
By Guyton & Hall

76. THANK YOU . . .