Endocrine - Temperature managment Flashcards
Homeothermic means we actively maintain our body termperature in a tight range usually between
36.5 to 37.3
Skin may be __ to __ degrees celsius lower than core body temperature
3 to 4
The axilla is usually __ degrees celsius lower than core body temperature
1 degree
Nasopharynx reflects _____ temp
brain
External Auditory Meatus reflects _____ temp but there is risk of TM rupture
Brain
Hypothermia
core body temperature is less than 36 Celsius
Hyperthermia
rise in core body temperature >38 degrees celsius
Normothermia
core body temperature 37 degrees +/- 1 degree
Ambient temperature
temperature of the surroundings
**What regulates the body temperature
the anterior hypothalmus / preoptic nuclei mediates temperature regulation
Set point temperature
Body attempts to maintain a ceratin temperature
**Hypothermia consequenees are extensive and _______ with degree of hypothermia
worsen
**Vascular consequences of hypothermia
vasoconstriction, hypoperfusion of tissues, pulse oximetry difficult
**Cardiac consequences of hypothermia
shivering increases oxygen consumption up to 300%, increased myocardial ischemia, increased cardiac morbidity, increased arrhythmias, Osborne of J wave (ST elevation), VF occurs @ 22-23 degrees Celsius, defib not successful below 30 degrees celsius, should resuscitate until rewarmed
**Pulmonary consequences of hypothermia
PVR increases, ventilatory drive is depressed, C02 levels in blood decrease
**Renal consequence of hypothermia
Cold diuresis, decreased plasma volume
**Hepatic consequnce of hypothermia
Hepatic blood flow is decreased
Will hypothermic patient be a slow wake-up?
SLOW
Hypothermia results in ______ drug metabolism and elimination
reduced
**For every degree celsius drop in temperature, MAC decreases ___ to ____%, meaning more gas has to come off before the patient will wake up
5 to 7%
Hypothermia results directly in a diminished state of ________ and NMBs will be _______ in cold patients
consciousness / prolonged
Hypothermic patients = _________ infections
increased
Hypothermic patients have decreased peripheral perfusion, decreased cutaneous perfusion which results in _____ penetration of antibiotics to these areas. In addition there is decreased phagocytic activity and impairment in neutrophil function
less
Prospective study of colorectal patients kept normothermic highlights
sutures removed 1 day earlier, 1/3 less infections, discharged from hospital 2.6 days earlier than nontreated group
The peripheral compartment consists of
limbs, skin, subQ tissue AND has 1/3 of the body’s heat content
The core compartment consists of what?
major thoracic and abdominal organs and brain AND holds 2/3 of the body’s heat content
Cord body temperature is maintained within a narrow temperature range of?
36.6 - 37.4
Peripheral body temperature varies widely from __ to ____ degrees celsius
0 to 40
The difference between core and peripheral body temperatures is maintained by __________
vasoconstriction
______ _______ from the body core to the skin provides heat transfer
blood flow
The degree of heat conduction to the skin is controlled by the degree of _______ in the skin
vasoconstriction
Vasoconstriction is controlled by the _____
SNS
_______ production is the principal byproduct of metabolism
heat
Heat production is increased by
exercise, shivering, non-shivering thermogenesis, hypermetabolic states (sepsis, thyroid storm), medications or hypothalmic lesioins
Normal basal heat production would incerase a patients temp by ____ per hour if they werer completely insulated from heat loss
1.2 degree ceslsius
**Shivering can increase heat production by ____%
300%
Under normal conditions body heat is preserved by tonic _______ _____
peripheral vasoconstriction
**Radiation heat loss
Loss of heat to cool surroundings via electromagnetic energy, major method of heat loss to environment, accounts for 60% of heat loss, determined by temp difference between patient and environment, also affected by exposed body surface area
**Convection heat loss
wind chill, layer of air next to skin moves and carries heat away from body, can account for 25% of heat loss in OR’s with forced airflow, degree depends on body surface area exposed and airflow
Evaporation heat loss
loss of heat with skin prep solutions and in major surgeries with open abdominal cavities, normal respiration of inspired gases can account for evaporative losses, inspired gases are usually dry and moderately cool increasing heat loss
Conduction heat loss
transfer of heat between adjacent surfaces (OR table), contributes <5% of heat loss, affected by temperature
Anesthesia (both general and regional) _______ peripheral vasconstriction
inhibit
In the first hour after induction of anesthesia there is a __ to ___ decreased in the core temp because of peripheral _______
1-1.5 degrees celsius / vasodilation
Basic Metabolic Rate decreases ___ to _____% with general anesthesia decreasing heat production in the next 2-3 hrs
20-40%
Initial heat losses slow as most significant and slow with ________ time
anesthetic
Regional anesthesia (spinal or epidural) produce similar patterns of heat loss because of ________
vasodilation
One unit of refrigerated blood or one liter of room temp crystalloid decrease core body temp by ____ degree celsius
0.25 degree celsius
Cutaneous heat loss is proportional is proportional to exposed body surface area and accounts for ___% of heat loss
90%
General anesthesia promotes vasodilation, decreases metabolic rate/heat production, and decrease hypothalmic responsiveness to ________
hypothermia
Do NMBs prevent shivering?
Yes
Heat loss becomes more pronounced with ___ and ______ patients
elderly and neonates
Basic metabolic rate decreases approximately __% per year beyond age 30
1
**Elderly and neonatal patients have diminished _____ _____ functioning which results in less vasoconstrictive heat conserving mechanisms
autonomic neural
**Neonates have ____ surface area to mass resulting in more rapid ___ ____ to the environment
increased / heat loss
Preoperative prevention of hypothermia
warm environment, insulate patient with blanket, actively warm so that peripheral body temp is warm, avoid sweating
Intraoperative prevention and treatment of hypothermia
warm the OR, inuslate patient, forced warming, circulating water mattress, HME, cover exposed areas, used warm IVF, field irrigation with warm fluids, use low flow circuits, heating lamps for neonates, CPB warming
Postoperative prevention and management of hypothermia
forced air warming, treatment of postop shivering
**Post op shivering occurs in up to ___% of unwarmed patients after general anesthesia
40%
**Causes dramatic increases in oxygen consumption and catecholamine release
shivering
post-op shivering is associated with __ times increase in myocardial events
3 times
Post op shivering is induced by cooling of preooptic region of _______ which causes the involuntary, oscillatory muscular activity to increase heat production
hypothalmus
Treatment of postoperative shivering
prevention is preferable, demerol is the most commonly used agent for post operative shivering
Demerol is the most commonly used agent for post operative shivering because….
effective, partially mediated by kappa opiod receptors, decreases shivering threshold twice as much as vasoconstriction
Hyperthermia is relatively _______ in OR
uncommon
Causes of Hyperthermia that should be ruled out
MH, sepsis/infection, thyrotoxicosis, pheocromocytoma, hypothalmic lesion, trauma, anoxia, neuroleptic malignant syndrome, transfusion reactions, medications
With infection/sepsis - during bacteremia, pyogens cause release of _______ ______, increasing set point for temperature in the hypothalmus. This leads to heat conservation (vasconstriction) and increased heat production (shivering)
interleukin one
**Malignant hyperthermia initially manifests as a _______ state with tachycardia, hypercapnia, muscle rigidity, tachyarrhythmias, metabolic acidosis. Treatment includes discontinuing triggering agents, administering dantrolene, active cooling, adequate hydration, and supportive care
hypercatabolic
Hyperthermia treatment
Preop: Acetaminophen Intraop: cooling the OR, forced air cooling, cooled IVF, field irrigation with cold fluids, NG or Bladder irrigation with cooled fluids Postop: forced air cooling
