Alterations in Body Temperature (Pyrexia) (complete) Flashcards
What is a fever?
- elevation in body temperature exceeds normal variations in response to a pyrogen
– pyrogens: bacteria, viruses, MI, malignancies - one of the most prominent manifestations of the acute inflammatory response
- aka hyperpyrexia
What is the normal body temperature?
97-99.5 F (36-37.5C)
- varies about 0.5 degrees throughout day
Different in every person, diurnal variations
- is a dynamic process
What are the diurnal variations of body temperatures?
- lowest temperature in the early morning
- highest temperature in the late afternoon/evening
What is the role of the hypothalamus?
Thermoregulatory center in the hypothalamus regulates body temperature (thermostatic set point)
Helps to balance heat production and heat loss
How does the hypothalamus help to balance heat production and heat loss (other body experiences)?
To cool body:
- sweat glands excrete sweat
- blood vessels dilate
- heat loss through radiation and conduction
To heat body:
- erector muscles constrict, traps air (goosebumps)
- shivering: increases metabolic rate, increasing temp
- blood vessels constrict: decreases blood flow to conserve heat
What is the thermostatic set point
keeps the core temperature at a normal level (either raises or lowers)
Hypothalamus and core temperature; effects of extreme temperature
When core temp is greater than 105.8F or less than 93.2F
- the ability to regulate temperature is impaired
- hypothalamus is no longer in control
Can lead to increased risk of denaturalization of brain cells, leading to cell death, and death
What is heat production?
Derived from metabolic activity in the muscles and liver
SNS neurotransmitters play a role (epinephrine and norepinephrine)
- released when an increase in body temp is needed
- heat production rather than energy generation
- often feel weak and tired due to the amount of energy being used
What does shivering do?
leads to increased heat production by increasing metabolic rate
side note: non-shivering heat production by the liver can increase core temperature
What are goosebumps and what do they do?
contraction of the pilomotor muscles of skin reduce the surface area for heat loss
- surface insulation
What does exercise/exertion do to body temperature?
Increases it
Causes of heat production
- work/exercise
- heat stroke (overwhelms body, impairs organs)
- drug-induced
- malignant hyperthermia
- neuroleptic malignant syndrome
- CNS damage (can’t regulate temp especially if hypothalamus is impacted)
What are the 5 processes through which heat loss occurs?
- radiation (most common)
- conduction
- convection
- evaporation (sweat)
- respiration (insensible)
What is radiation heat loss?
- transfer of heat from one place to another
What is conduction heat loss?
Requires direct contact
Ex: cool cloth, ice pack
What is convection heat loss?
Requires fluid flow, such as air or water
Ex. fan
What is the febrile response?
During fever, thermostatic set point is reset at a higher level
- caused by a cytokine-induced disruption of the set point in the hypothalamus (inflammatory response)
- cytokines –> arachidonic acids –> prostaglandins –> increased set point
- set point rises, existing body temp is sensed as too cool
– heat production will occur until new set point reached
- once pyrogens decreased or antipyretic given: set point will reset downward
– process of heat loss occurs
What are the stages of fever?
- prodrome
- chill
- defervescence (fever breaks)
What occurs in the prodrome stage of fever?
non-specific complaints (aches, pains, etc)
What occurs in the chill stage of fever?
- shivering, which causes the core temperature to rise
- complaints of “freezing to death”
- vasodilation causes red flushed skin once set point has been reached
What occurs during the defervescence stage of fever?
- complains of burning up
- diaphoresis
- fever breaks
Associated symptoms of a fever
- heart rate: should go up but does not have to happen
– because of SNS kicking in and NE and E - myalgias (b/c prostaglandins)
- fatigue
- joint pain
- respirations increase (trying to blow off heat)
- dehydration:
– sweating and increase vapor loss through rapid breathing - chills come with pyrogens which enter the system
- headache: from vasodilation of cerebral vessels
- decreased perfusion causes delirium, confusion, agitation
symptoms come from increased need for metabolic rate increased, increase oxygen and use of body proteins as a resource
What is heat stroke?
- type of hyperthermia
- person so overheated that heat regulating ability of hypothalamus fails
- leading cause of death in athletes
– seen with those with no fans or air conditioning
Treatment for heat stroke?
- cool the person
- antipyretics do not work
What is malignant hyperthermia?
- is a rare hereditary disorder
- related to exposure to anesthetics and muscle relaxants
– need to ask about problems with anesthesia before surgery - causes a rapid increase in intracellular calcium levels
– leads to muscle rigidity, acidosis, CV instability - hypermetabolic state
- temperature increases 1-2 degrees within 5 minutes
– can go higher to like 104-105 F
Can be fatal
Treatment for malignant hyperthermia?
Ice, ice baby
dantrolene
What is done in the management of a fever?
- determine cause
- monitor CBS with differential (WBC)
- monitor CMP (electrolytes, kidney function, glucose)
- assess VS (HR and RR had increased, BP can go up or down depending on cause of fever)
- fix external environment
– if severe: cooling blankets
– be careful with baths because can cause shivering - hydration is crucial
- medication
– acetaminophen
– ibuprofen
– ASA
– reset the temperature control point
How does tylenol, ibuprofen, ASA lower fever?
- synthesis of prostaglandin E2 depends on cyclooxygenase (pathway for prostaglandins)
– basis for COX is arachidonic acid released from cell membrance
– release is rate-limiting step in synthesis of PGE2 - inhibitors of COX (1 or 2) are potent antipyretics
- if process blocked at arachidonic acid level: prostaglandins are not released
What is hypothermia?
- profound loss of body heat for a prolonged period
- body temperature less than 95F (35C)
- prolonged vasoconstriction and shivering become ineffective
– lack of blood flow and oxygen: ischemia, frostbite - loss of thermoregulatory ability
- considered a medical emergency
What happens when temperature drops less than 87.8F?
- neurologic signs (confusion, stupor, lethargy, etc)
- arrhythmias (J wave, A-Fib, etc)
the lower the temp, more symptoms related to neuro
Fever in children
- very common
- may or may not have symptoms to indicate the cause of fever
- can rebound quickly
- can have febrile seizures (not on there, but relating this to peds)
Older adults and fever
- not unusual for a sick older adult to NOT have a fever or to be very sick with small elevation
– may present with confusion
– change in mental status - *temperature of 99 may be concerning
– change in baseline
– need to evaluate - confusion and other symptoms may indicate illness
A 73 y.o. patient asks the nurse, “Why is my body temperature only 99.2°F, if I have this serious infection?” Which is the nurse’s best response?
“Body temperature in an older adult is not a reliable indicator of the seriousness of an illness.”
Rationale:
Body temperature may not be a valid indication of serious illness in an older adult. The older adult may have an infection and exhibit only a temperature elevation. Other symptoms, such as confusion and restlessness, may be present.
The ED nurse is assessing a patient who fell into a cold lake. Which assessment finding indicates that the Patient’s body is attempting to regulate its temperature?
cold hands, shivering
Rationale:
When the skin is chilled, the body attempts to regulate temperature by vasoconstriction of blood vessels. This could be why the Patient’s hands are cold. The body also shivers to
increase heat production. The body does not regulate temperature through sleep, thirst, or by sweating.
