Disorders of thermoregulation. Fever.

The State Education Institution of Higher Professional Training The First Sechenov Moscow State Medical University

under Ministry of Health of the Russian Federation

Lecture presentation

Professor Pirozhkov S.V.

 Department of Pathophysiology

2014-2015 education year

DISORDERS OF THERMOREGULATION

HYPERTHERMIC STATES HYPOTHERMIC STATES

HYPERTHERMIA

HYPERTHERMIC REACTIONS

FEVER HYPOTHERMIA

► Overheating

► Heat stroke

► Sun stroke

► Malignant hyperthermia

► Supercooling

Types of hypothermia

Core body temperature

Mild 32°-35°С

Moderate 28°-32°С

Severe < 28°C

PATHOLOGICAL COSEQUENCIES OF HYPOTHERMIA

Decrease in body t°

Posterior pituitary

Decreased secretion of vasopressin

Decreased reabsorption of water and

Na+

Dehydration

Decrease in

systemic BP

Haemocon-

centration

Thrombotic diathesis

DIC-syndrome

Inhibition of clotting factors activation

Poor clotting of blood. Significant blood loss in minor trauma.

Fever:

● typical pathological process

● characterized by an increase in body

temperature

● caused by the effect of pyrogenic

substances

● resulting from an increase in the set

point of thermoregulation

PYROGENS

ENDOGENOUS ЕXOGENOUS

Products Products Non-infectious of tissue of hemolysisdecay Infectious

LPS Lipoteichoic (Gram- -bacteria) acids (Gram+ -

bacteria)

SYMPTOMS THAT ACCOMPANY FEVER

● Backache

● Arthralgias

● Anorexia

● Somnolence

● Chills, rigor (profound chill with piloerection)

● Sweats

● Convulsions

● Changes in psychological status:

irritability – delirium – obtundation

PATHOGENESIS OF FEVER

Neuron of the thermoregulation center

cAMP

Centers of the sympathetic n.s.

Spasm of the skin arterioles

Shivering

Brain cortex

Behavioral response

Increase in thermogenesis Preservation of heat

Thyroid gland

Adrenals

STAGES OF FEVER

I. The stage of temperature elevation.

II. The stage of maintenance of increased body temperature.

III. The stage of normalization of body temperature.

TYPES OF FEVER according to the extent of the body temperature

increase (in the arm pit)

Subfebrile < 38°С

Febrile 38°С - 39°С

Pyretic 39°С - 41°С

Hyperpyretic > 41°С

TYPES OF FEVERby the pattern of circadian body temperature fluctuation

Sustained not exceeding 1°С

Remittent 1.5°-2.0°С

Intermittent > 2.0°С

Hectic (septic) 3.0°-5.0°С

Causes of hyperthermia Failure of the heat loss mechanisms under

the condition of high environmental temperature

Great increase in heat production surpassing the capacity of the heat dissipation mechanisms

PATHOGENESIS OF THE SUN/HEAT SHOCK

OVERHEATING OF THE HEAD

ACCRUING ARTERIAL HYPEREMIA INCREASED FILTRATION OF FLUID IN THE BRAIN TISSUE

PROGRESSIVE VENOUS HYPEREMIA

COMPRESSION OF THE BRAIN. INCREASED INTRACRANIAL PRESSURE.

HYPOXIA. ISCHEMIA. INJURY TO THE NERVOUS CENTERS OF THE BRAIN.

DECREASED SYMPATHETIC TONE IN THE PERIPHERAL VESSELS, COLLAPSE

SHOCK

SEVERE POLYORGANIC INSUFFICIENCY, DEATH