Thermoregulation and pyrexia Flashcards
Conscious intelligence range =
35-40 degrees
Usual core temp
37 degrees
Diurnal variation
Temp reaches lowest point just fore wake and highest 12 hrs after
Ex of intersex variation of temp
Females have +0.5 degrees during ovulation
Ways to measure temperature:
- Mecury thermometer
- Ear
- Oesophagus
- Rectal
- Electrical skin probe
Disadvantages of mecury thermometer
- not quick
- food and drink can effect
- difficult for children
Ear thermometers measure the..
Typanic membrane
Thermistor and rectal thermometers are used when
Patient is asleep (ICU)
Thermoreceptors are mainly found:
- Skin (peripheral)
- GI tract
- Great veins
- Hypothalamus (central)
What kind of fibres are thermoreceptors?
Alpha delta
C
Thermoreceptor fibers are:
- Slower
- Smaller diameter
Fibres of thermoreceptors are the same as…
pain
Coordinator of thermoregulation
Anterior hypothalamus
Hypothalamus coordinates the
Set point
Methods of heat production:
- Metabolic
- Voluntary
- Shivering
- Brown fat
- Vasoconstriction
- Neuroendocrine
Enzymatic processes in the body are
Exothermic
Voluntary actions to reduce heat loss are important in which groups of patients
Young people
Dementia etc.
Why is shivering not a good method for certain patients?
Metabolically expensive. O2 consumption can increase.
White fat =
Metabolically inert
Brown fat has lots of
Mitochondria
Where is brown fat found
Infants: Scapula, clavical, around main organs
Paradoxical increased flow with prolonged cold exposure:
Cold –> vasoconstriction –> ischemia –> inflammatory products –> vasodilation –> more heat lost
Neuroendocrine method of increasing heat:
- Increase catecholamines to increase metabolic activity
Catecholamines ex:
Dopamine, adrenaline, noradrenaline
Hyperthyroidism and temperature =
Not much increased temp unless grossly hyper
Hypothyrodisim and temperature =
Not uncommon for this to make a patient hypothermic
Methods of direct heat loss
- Conduction/convection
- Radiation
- Evaporation
Definition of hypothermia:
Core of <35 degrees
Severe hypothermia:
<28 degrees
Causes of hypothermia
- behavioural
- hypothyroid
- dermatological
Clinical features common to hypothermia and hyperthermia
Coma
Confusion
CV collapse
Clinical features of hypothermia:
Confusion
Coma
CV collapse
Increased change of arrthymias
why is the chance of arrthymia increased with hypothermia
Catecholamine surge
J wave:
Junctional wave on QRS complex. Hypothyroidism
What causes J wave?
Abnormal cardiac replarisation because of low temp
Management of hypothermia:
- ABC
- Silver blanket
- Controlled warming: hot air blankets, cardiac bypass
Definition of hyperthermia:
> 38 degrees
Life-threatening hyperthermia:
40 degrees +
Causes of hyperthermia:
Extertional
Situational
Drugs
Pyrexia
Clinical features of hyperthermia:
Confusion
Coma
CV collapse
Seizures
Pyrexia is due to =
Altered set point
What causes ‘chills’
Altered set point. Temp is high but body reacts to increase temp (shivering, goosebumps, vasoconstriction)
Causes of PUO
Infection Blood transfusion of pyrogens Inflammation Malignancy Hypothalamic insults = bleed, inflammation
PUO =
Pyrexia of unknown origin
Major pyrogenic cytokines:
IL-1,IL-6, TNF, IFN
Pyrogenic cytokines act to increase
Prostaglandins
What acts on the hypothalamus to alter set point?
Prostaglandins
Treatment of pyrexia:
Paracetamol NSAIDs Aspirin Cooling packs/ice Exposure Fan CPB (cardiopulmonary bypass)
