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Anesthesia Equipment Exam 2 > Temperature Monitoring > Flashcards

Temperature Monitoring Flashcards

1
Q

Benefits of Warm Patients

A
  • reduced wound infections
  • reduced blood loss
  • reduced cardiac events
  • shortened hospital stays
  • warming recoginzed as a standard of care by Medicare and SCIP
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2
Q

Dominant Thermoregulatory Site in Humans

A
  • hypothalamus
  • thermal input from skin is secondary mechanism that is also important
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3
Q

Processing of Thermal Regulation

A
  1. afferent thermal sensing - many cells in the body are temp sensors
  2. central regulation - set point vs thermoregulatory model
  3. efferent responses - sweating, peripheral cutaneous vasoconstriction, brown fat metabolism

more elaborate mechanisms: shivering, BP, and osmotic control adaptation

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4
Q

Indications for Temp Monitoring

A
  • large volumes of cold fluids administered
  • deliberate cooling/warming of pt
  • pediatrics
  • pts w known temp regulatory problems (MH)
  • major surgical procedures
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5
Q

AANA/ASA Temp Standard

A
  • every pt should have temp monitoring when body temp changes are anticipated, intended, or expected.
  • you can chart “warm blankets applied, pt stats that are comfortable, temp monitoring available” during MAC cases
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6
Q

Thermoregulation During GA

A
  • pts under GA are unable to activate behavioral responses and must rely on autonomic defenses and external temperature management

37 C +/- 0.2 degrees is normothermia

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7
Q

All anesthetics ______ autonomic thermoregulatory control

A

All anesthetics impair autonomic thermoregulatory control

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8
Q

Propofol, Alfentanil, Precedex, Iso, and Des

A
  • increase sweating threshold minimally, if at all
  • these help preserve warm defenses for some time
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9
Q

Propofol, Alfentanil and Precedex

A

produce a significant DECREASE in vasoconstriction and shivering thresholds

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10
Q

Iso and Des

A
  • decrease the cold response threshold only slightly
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11
Q

Thermoregulation During Neuraxial Anesthesia

A
  • Central Temp Control: slightly impaired by neuraxial anesthesia
  • autonomic impairment compounded by an impairment in awareness by the patient that they are becoming hypothermic
  • misperception that since pt awake they are able to regulate their temp… if they are numb, they can’t tell they are cold!
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12
Q

Why is core temp not usually monitored with neuraxial?

A

Because the pt is awake and core temp requires swan ganz or throat temp.

Axilla temp probe often used

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13
Q

4 Etiologies of Shivering During Neuraxial Anesthesia

A
  1. shivering in response to core hypothermia
  2. shivering in normothermic/hyperthermic pts developing a fever
  3. direct stimulation of cold receptors in the neuraxis by the injected LA
  4. non-thermoregulatory muscular activity that resembles thermoregulatory shivering (can let it run its course rather than give demerol 12.5 - 25 mg IV)
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14
Q

US Temp Standards (2002)

A
  1. max contact surface temp shall not exceed 48 C
  2. Average contact surface temp shall not exceed 46 C during normal conditions (max bair hugger temp is 42)
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15
Q

4 Temp Technologies

A
  1. thermistor
  2. thermocouple
  3. liquid crystal
  4. infrared
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16
Q

Thermistor

A
  • composed of metal oxide placed into a wire - Advantages: small size, rapid response size, continuous readings, probes are interchangeable and disposable
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17
Q

Thermocouple

A
  • electrical circuit w 2 metals, one remains at constant temp, other is exposed to area where temp is being measured
  • Advantages: accurate, small size, rapid response time, continuous readings, stability, and probe interchangability
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18
Q

Liquid Crystal

A
  • consists of a flexible adhesive backing w plastic encased in liquid

Advantages: safe, convenient, noninvasive, easy to apply, disposable, inexpensive

Disadvantages: not accurate (subjective and relies on observer interpretation), difficulty w adhesion to skin if wet or oily

19
Q

Infrared

A

electronic instrument, accurate

Tympanic thermometer not useful or available in OR

20
Q

Average Temperature Loss

A
  • 0.5 and 1.5 in the first 30 minutes then 0.5 to 1 degree C per hour afterwards.
  • Usually no more than 2-3 degrees per hour
21
Q

Core Temperature

A
  • deep, vital internal organs
  • uniform: varies between 35.7 and 37.8 C
  • core temp should be monitored when significant changes in temp are expected
22
Q

Periphery

A
  • normal thermoregulatory vasoconstriciton maintains a temp gradient between the core and periphery of 2 to 4 degrees C
  • skin and axillary temps
  • X degrees in the periphery means they are 2-4 degrees higher in the core
23
Q

Pulmonary Artery

A
  • measured via PA cath
  • thought to be the best method to monitor temp
  • not reliable during thoracotomy or cardiopulmonary bypass due to no blood flow through heart and lungs and temp of cardioplegia solution (cold)
24
Q

Esophagus

A
  • temps vary up to 4 degrees depending on location within esophagus (temp probe is curved - insert to curve)
  • probe should be in lower third or fourth of esophagus
25
Q

Nasopharynx

A
  • location close to hypothalamus
  • some studies show correlation w core temp (?)
  • easily accessible during surgery
  • may cause epistaxis
26
Q

Temp Monitoring Graphic

A
27
Q

Methods of Heat Loss

A

radiation > convection > evaporation > conduction

burn pts lose heat via evaporation

28
Q

Each 1 degree C decrease in temp = metabolism decreases by _____

A

7%

so keep burn patients WARM!

29
Q

Skin and Heat Loss

A

skin supports, insulates, and protects against heat loss

30
Q

Radiation

A
  • loss of electromagnetic energy through infrared rays from the warm body to colder objects in the room that do not contact the body.
  • typically accounts for 65-70% of body’s heat loss
31
Q

Convection

A
  • second major heat loss mechanism
  • transfer of heat to an air current
  • determined by temperature gradient between body and air as well as air velocity
  • most of this occurs prior to draping (surgical drapes prevent most convective heat loss during surgery)
32
Q

Conduction

A
  • lost via direct contact between pt and colder objects such as OR table, linens, surgical instruments, skin prep materials, irrigation, and IV fluids
  • heat flow is proportional to the temp difference between the body and the colder object
  • little lost to OR table pad, significant loss to cold prep and irrigation/IV solutions
33
Q

Evaporation

A
  • occur from skin, respiratory tract, open wounds, pneumoperitoneum, or wet towels/drapes that are in direct contact w the patients body
34
Q

High Risk Hypothermia Populations

A
  • geriatrics
  • pediatrics
  • hypothyroid
  • pts w hypothalamic lesions
  • hypothermia is the most common temp related disorder during anesthesia
35
Q

Forced Air Warming Devices AKA Convection Warming Devices

A
  • entrain ambient air through microbial filter
  • air is warmed w thermostat controlled electric heater
  • air is then blown through hose attached to an inflatable pt blanket
36
Q

Advantages to Forced Air Warmers

A
  • safe, simple, effective
  • inexpensive
  • variety of blankets (reusable, disposable)
  • more calories to cost than other warming devices
  • fiberoptic laryngoscopes can be warmed using forced air warming devices
  • OR table can be warmed preoperatively
  • can also be used to cool pts
37
Q

Disadvantages to Forced Air Warmers

A
  • electric power requirements make it unsuitable for field use
  • cumbersome to transfer or set up in CT
  • may need to be removed to expose covered areas
  • most don’t permit concurrent use of multiple blankets without additional units
  • risk of increased infections (debatable)
  • interference w BIS and DOA moitors
38
Q

Controversial Topic Re: Bair Hugger

A
  • some say it spreads germs, blows dust into surgical sites
  • key point: don’t turn on bair hugger until drapes are up!
  • altermative to bair hugger is HotDog Patient Warming System
39
Q

Review of the Literature Re: Temp Monitoring and Perioperative Thermoregulation

A
  • GA > impairment than neuraxial anesthesia
  • prolonged anesthesia = HYPERthermia (cause unknown)
  • hypothermia post cardiac arrest shows little benefit despite trend years ago
40
Q

MH

A
  • Diagnosis made with unexplained signs of pyrexia, or tachycardia, or cyanosis, or rigidity, or failure of masseter muscle to relax (trismus)
  • Defect in sarcoplasmic reticulum of skeletal muscle
  • SR fails to sequester Ca++ and sustained muscle contractions occur w increased metabolism
  • Tx w Dantrolene which acts on SR to decrease the release of Ca++
  • Triggers: sux and halogenated inhaled agents
41
Q

S/S of MH

A
  • elevation of CO2 (earliest sign, it will double or triple)
  • sympathetic hyperactivity manifested as increased HR
  • Trismus (masster muscle spasm) appears in 50% of pts
  • whole body rigidity in 75%
  • cyanosis, unsatble BP, dysrhythmias, hyperkalemia
42
Q

MH Prep

A
  • remove circuit and bellows
  • flush machine w 100% 02 for 30 minutes
  • call work room engineer Steve and he will provide you with “non-triggering machine” with no gas and tape over it
  • no sux in room! TIVA is appropriate
43
Q

MH High Risk Pops

A
  • Duchennes MD
  • Native Americans
  • Peds
  • Kids of parents w MH

Anesthesia Equipment Exam 2 (6 decks)

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