6. INTRODUCTION
6.7 Hypothermia
DEFINITION OF HYPOTHERMIA Hypothermia refers to the cooling of the body beyond the normal temperature
range. In prac ce, a limit of 36°C is normally accepted. Below this value, organ func on begins to deteriorate.
Temperatures between 36°C to around 33°C are considered mildly hypothermic. The body reacts with ther-
moregulatory mechanisms such as shivering and vasoconstric on. In addi on, symptoms such as increased heart
rate (tachycardia), increased respiratory rate (tachypnoea), coordina on disturbances (ataxia), apathy, and a re-
duc on in circula ng blood volume (hypovolaemia) appear. Moderate hypothermia, or temperatures between
32 and 28°C, cause respiratory depression (hypoven la on) slow pulse (bradycardia), decreased blood pressure
(hypotension), reflex suppression (hyporeflexia), enlarged pupils and an ever-increasing loss of consciousness.
Shivering ceases. At even lower temperatures (severe hypothermia) the human organism reacts with circulatory
and respiratory collapse.
6.8 Fever or hyperthermia
The terms fever and hyperthermia both describe a state in which core body temperature is increased above
normal limits. While fever is considered to be a regulated physiological reac on, hyperthermia occurs when the
body’s thermoregulatory mechanisms are pushed beyond their limits. Depending on the defini on, tempera-
tures higher than 37.5°C are considered to be higher than normal.
Fever is a reac on of the human organism to both infec ous and non-infec ous challenges. In intensive care
pa ents, infec ons are the most common cause of fever. These are usually in the form of pneumonia and sep-
sis. Aside from infec ons, non-infec ous, inflammatory reac ons can also lead to fever. These can be brought
about by myocardial infarc on, pulmonary embolism and tumours. It is rare that non-infec ous reac ons are
sufficient to increase temperatures above 38.9°C. Excep ons include pa ents with fever reac ons to pharmaceu-
cals of blood transfusions. Cerebral damage can cause fever of up to 40°C. Structured differen al diagnos cs
are necessary in order to avoid inappropriate pharmaceu cal therapy.
6.8.1 The consequences of fever
Fever is a core func on within the unspecific immune response. An increase in temperature ac vates T-lymphocytes,
neutrophils and macrophages and s mulates the produc on of an bodies and cytokines, thereby modula ng
the immune system. Simultaneously, the growth of many microbial pathogens which thrive at normal tempera-
tures is inhibited. Very high temperatures, above 41°C, can lead to the derangement of the coagula on system
and disturb enzyme func on. Hallucina ons and confusion can also occur. In addi on, hyperthermia causes an
increase in cardiac output, increasing oxygen consump on and fluid losses.
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