Death due toHypothermia

Rijen Shrestha20-08-2068

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.

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.

Epidemiology

• Senile mental deterioration and immobility in elderly

• Lack of fuel for heating• Open windows for fresh air• Intoxication• New born babies• Hazardous outdoor activities

Risk Factors

Winters as well as during spring or autumn in colder periods.Outdoors as well as indoors

Factors affecting development of

hypothermia:•Difference in temperatures•Surface area/Volume ratio•Children > Adults•Stored heat•Medium of transfer

Muscular System

Heart

Circulation

Ventilation

Nervous system

4 clinical phases of hypothermia

Mechanism

Disturbances of

microcirculation

Changes of rheology

Cold stress Hypoxidosis

Guidelines for examinationExamination 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

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

Guidelines for examination

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

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

Morphological changes

Blood changes

Bright red color of blood

• Non-specific finding• Mechanism:• Left shifting of O2-Hb dissociation curve

Blood in left ventricle appears bright red

• Non-specific finding• Mechanism:• Blood in the left ventricle comes from the lungs where it was cooled down

Mechanism:

Mechanism:

Skin changesSkin changes in general hypothermia are different from those in local hypothermia

• Local HypothermiaMechanism:• Freezing of tissue and obstruction of blood supply to

the tissueMicroscopically:• Damage of endothelial cells• Leakage of serum into tissue• Sludging of red blood cells

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

Three grades of local hypothermia

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 jointMechanism: • Capillary damage and leakage of plasma

along with hemoglobinFrost erythema differs from hemorrhage

due to lack of erythrocytes.

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

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 2004M 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.

Frequency of Wischnewsky spots in studiesAuthor 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%

Other Gastro-intestinal lesions

Ulceration of colon as well as hemorrhagic infarcts of the colon may be present

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

infiltrationAt 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

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

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 cellsstrong positive correlation between the grade of fatty change with the occurrence of macroscopic signs of hypothermia

fatty degeneration of renal tubules

Grade 0 (x200)

Grade +2 (x200)

Grade +1 (x200)

Grade +3 (x200)

Fatty changes of cardiac myocytes in hypothermia

Grade 0 Grade +1

Grade +2 Grade +3

Lipofuscin staining of cardiomyocytes

Grade 0 Grade +1

Grade +2 Grade +3

Endocrine glands

Endocrine glands are responsible for the maintenance of normal body temperature• 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)• lipid depletion of adrenal cortex found after 10 days with core temperatures of 33oC)

not after short exposures of 4–7 hMorphological findings can be expected only in long-lasting hypothermia

• depletion of colloid, raise of epithelial cells).

F Buchner in 1943

morphologic changes:

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

© Rijen Shrestha