This document discusses hypothermia and its effects on the body. It begins with definitions of hypothermia and normal body temperature ranges. It then covers the four clinical phases of hypothermia based on core body temperature, from mild hypothermia to severe hypothermia. Risk factors for developing hypothermia and various morphological changes that can occur are described, including fatty changes in organs, gastric mucosal lesions, and hemorrhages. Guidelines for examination focus on organs involved in temperature regulation and death. The document concludes that both external and internal findings can provide diagnostic significance for hypothermia, especially when found in combination.

1. Rijen Shrestha
20-08-2068

2. Introduction
• Definition:
Hypothermia is the condition of the body where the
core temperature of the body is below 35o C
 Indifferent temperature:
Ambient Temperature at which basal metabolic rate
is sufficient to maintain normal body temperature.

3. Dimaio and Dimaio 2001
• Normal body temperature: 98.6° F (37° C) orally
• Newborns and the elderly have temperatures averaging 1° C higher.
• Cyclic changes in body temperature occur with decreases of 0.5° C early
in the morning (approximately 1:00 to 2:00 a.m.) and slight elevations
later in the morning and afternoon.
A Guyton and JE Hall in 2000, and HB Simon in 1993
• Exercise can raise the rectal temperature up to 104° F.
• Rectal temperatures of 39–40° C are common in marathoners after a
race.
Mackowiak et al.
• 98.2° F (36.8° C) is the mean normal oral temperature, with 99.9° F
(37.7° C) the upper limit.
• Maximum temperatures varied with time of day with a low in the early
morning.

4. Epidemiology
Winters as well as during spring or autumn in colder
periods.
Outdoors as well as indoors
• Senile mental deterioration and
immobility in elderly
Risk • Lack of fuel for heating
• Open windows for fresh air
Factors • Intoxication
• New born babies
• Hazardous outdoor activities

5. Factors affecting development of hypothermia:
• Difference in temperatures
• Surface area/Volume ratio
• Children > Adults
• Stored heat
• Medium of transfer

6. 4 clinical phases of hypothermia
Phase 1 Phase 2 Phase 3 Phase 4
36oC – 33oC 33oC – 30oC 30oC – 27oC Below 27oC
Muscular System Drop of muscular Rise of muscular
Shivering
tonus rigidity
Either further
decrease of vital
Heart Tachycardia Sinus bradycardia Bradyrrhythmia functions or
cardiocirculatory
arrest or ventricular
fibrillation or
Rise of resistance due asystolia
Reduced perfusion of Rise of resistance due
Circulation to increased viscosity
body surface to vasoconstriction
of blood
Stimulation of Bradypnoea, apnoic
Central Depression of Cessation of
Ventilation respiration; pause; Decrease of
ventilation breathing. Apnoea
Hyperventilation compliance
Raised vigilance, Disorientation,
Unconsciousness, loss
Nervous system Confusion; Painful apathy; Passing off
of reflex
acra pain
“Excitation” “Exhaustion” “Paralysis” “Vita reducta” –
apparent death

7. Mechanism

8. Guidelines for examination
Examination of organs which contribute to body
temperature
• Thyroid
• Adrenal
Bio-chemical changes due to counter-regulatory
mechanism
• Loss of glycogen in various organs
• Release of catecholamines and excretion in urine
• Fatty changes in organs
Examination of organs responsible for death
• Myocardial damage

9. Guidelines for examination
Examination of freezing tissue and tissue at surface-
core border
• Frost erythema
• Muscle bleeding in core muscles
Other organ damage ( Cold stress)
• Hemorrhagic gastric lesions
• Pancreatic changes
• Hemorrhagic infarcts
• Micro-infarcts

10. Morphological changes
Left shifting of O2-Hb dissociation curve
• Bright red color of blood and lividity
• Blood in left ventricle is bright red
Post-mortem artifacts
• Cutis anserina
• Skull fractures due to freezing of brain
Hemorrhages and erythemas
• Frost erythema
• Hemorrhagic gastric erosions
• Hemorrhagic pancreas
• Hemorrhages into core muscles
• Hemorrhage into synovial fluid

11. Morphological changes
Fatty changes
• Liver
• Heart
• Kidneys
Unspecific changes
• Brain oedema
• Sub-endocardial hemorrhage
• Pneumonia
• Contraction of spleen
Counter-regulation mechanisms
• Vacuolization and loss of glycogen in cells of liver, pancreas, renal
proximal tubules and adrenal cells
• Colloid depletion and activation of thyroid

12. Blood changes
Bright red color of blood
• Non-specific finding
• Mechanism:
Mechanism:
• Left shifting of O2-Hb dissociation curve
Blood in left ventricle appears bright red
• Non-specific finding
• Mechanism:
Mechanism:
• Blood in the left ventricle comes from the lungs where it
was cooled down

13. Skin changes
Skin changes in general hypothermia are
different from those in local hypothermia
• Local Hypothermia
Mechanism:
• Freezing of tissue and obstruction of blood supply to
the tissue
Microscopically:
• Damage of endothelial cells
• Leakage of serum into tissue
• Sludging of red blood cells

14. Three grades of local hypothermia
Dermatitis congelationis erythematosa
• Violaceous discoloration
Dermatitis congelationis bullosa
• Blisters filled with clear or bloody fluid
Dermatitis congelationis gangrenosa
• Bluish discoloration with blister formation and tissue
necrosis

15. Skin Changes in General hypothermia
• Frost-bite like injuries
– Swelling over the nose, ears, hands
• Red or purple skin lesions and violet patches
on knees and elbows or at outside of the hip
joint
Mechanism:
• Capillary damage and leakage of plasma
along with hemoglobin
Frost erythema differs from hemorrhage
due to lack of erythrocytes.

16. Gastric mucosal changes
Wischnewsky in 1895
• Multiple hemorrhagic gastric lesions as a sign indicative of
hypothermia
• Lesions vary from 1 mm to 2 cm in diameter
• Lesion vary from a few to up to 100 in number
• Lesions must not be mistake for true hemorrhagic
erosions
F. Buchner in 1943
• Wischnewsky spots were characterized by necrosis of
mucosa with hematin formation

17. Wischnewsky spots
J Hirvonen and R Elfving in (1974)
Preuß J, Dettmeyer R, Lignitz E, Madea B (2006)
• Mechanism:
• Disturbances of microcirculation (hemoconcentration)
• Tissue amines – histamine and serotonin
JP Sperhake et al in 2004
M Tsokos et al in 2006
• Wischnewsky spots are immunopositive for hemoglobin
• Mechanism
• Circumscribed hemorrhages of the gastric glands phase
• autolysis of RBCs release hemoglobin which is hematinized on
exposure to gastric acid to form blackish-brown spots.

18. Frequency of Wischnewsky spots in studies
Author of study N %
Wischnewsky, 1895 40/44 90.9%
Krjukoff, 1914 44/61 72%
Mant, 1969 37/43 86%
Gillner and Waltz, 1971 22/25 88%
Hirvonen, 1976 10/22 45%
Thrun, 1992 21/23 91.3%
Birchmeyer and Mitchell, 1989 15 60%
Takada et al. 1991 17 88%
Dreβler and Hauck, 1996 29 86%
Kinzinger et al. 1995 30 40%
Mizukami et al. 1999 23 44%
Bonn and Greifswald, 117/145 80.7%

19. Other Gastro-intestinal lesions

20. Pancreatic changes in hypothermia
– Focal or diffuse pancreatitis
– Hemorrhagic pancreatitis
– Patches of fat necrosis over organ surfaces
– Increased serum amylase
– Hemorrhages and focal or diffuse interstitial leucocytic
infiltration
At autopsy,
– Hemorrhages into the pancreas parenchyma as well as
under the mucosa of the pancreatic duct may be seen.
Preuß et al.
24 out of 62 cases of fatal hypothermia (38.7%)
empty vacuoles in the adenoid cells of pancreas

21. Hemorrhage into core muscles
• Dirnhofer and Sigrist (1979)
Hemorrhages into muscles belonging to the core of the body
can be used as a diagnostic criterion of death due to
hypothermia.
Histology
– Vacuolated degeneration of subendothelial layers of the
vascular walls with a lifting of epithelial cells
– Misbalance of reduced perfusion and normal oxygen
requirement causes hypoxic damage of epithelial cells with
resultant raised permeability

22. Lipid accumulation
• Fatty changes in heart, liver, and kidneys have been
described in fatalities due to hypothermia
• Lipid accumulation in epithelial cells of proximal
renal tubules seem to be of high diagnostic
significance
Base of the epithelial cells
strong positive correlation between the
grade of fatty change with the occurrence of
macroscopic signs of hypothermia

23. Grade 0 (x200) fatty degeneration Grade +1 (x200)
of renal tubules
Grade +2 (x200) Grade +3 (x200)

24. Grade 0 Fatty changes of Grade +1
cardiac myocytes
in hypothermia
Grade +2 Grade +3

25. Grade 0 Lipofuscin staining Grade +1
of cardiomyocytes
Grade +2 Grade +3

26. Endocrine glands
Endocrine glands are responsible for the maintenance of normal
body temperature
Morphological findings can be expected only in long-lasting
hypothermia
F Buchner in 1943
• no morphologic changes detected after exposure to cold temperatures for 49 hours
• activation of thyroid observed after long lasting exposure (5–9 days with temperature
drops from 37.5 to 36oC)
morphologic changes:
• lipid depletion of adrenal cortex found after 10 days with core temperatures of 33oC)
not after short exposures of 4–7 h
• depletion of colloid, raise of epithelial cells).

27. Conclusion
External and internal findings are of diagnostic significance
• Not only as the sole finding
• Especially when they are found in combination
• Also true for fatty changes of proximal renal tubules
Pathogenesis of alterations caused by hypothermia
• Hypoxic changes
• Stress
• Disturbances of microcirculation

28. © Rijen Shrestha