Temperature Monitoring Flashcards
(43 cards)
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
2
Q
Dominant Thermoregulatory Site in Humans
A
- hypothalamus
- thermal input from skin is secondary mechanism that is also important
3
Q
Processing of Thermal Regulation
A
- afferent thermal sensing - many cells in the body are temp sensors
- central regulation - set point vs thermoregulatory model
- efferent responses - sweating, peripheral cutaneous vasoconstriction, brown fat metabolism
more elaborate mechanisms: shivering, BP, and osmotic control adaptation
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
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
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
7
Q
All anesthetics ______ autonomic thermoregulatory control
A
All anesthetics impair autonomic thermoregulatory control
8
Q
Propofol, Alfentanil, Precedex, Iso, and Des
A
- increase sweating threshold minimally, if at all
- these help preserve warm defenses for some time
9
Q
Propofol, Alfentanil and Precedex
A
produce a significant DECREASE in vasoconstriction and shivering thresholds
10
Q
Iso and Des
A
- decrease the cold response threshold only slightly
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!
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
13
Q
4 Etiologies of Shivering During Neuraxial Anesthesia
A
- shivering in response to core hypothermia
- shivering in normothermic/hyperthermic pts developing a fever
- direct stimulation of cold receptors in the neuraxis by the injected LA
- non-thermoregulatory muscular activity that resembles thermoregulatory shivering (can let it run its course rather than give demerol 12.5 - 25 mg IV)
14
Q
US Temp Standards (2002)
A
- max contact surface temp shall not exceed 48 C
- Average contact surface temp shall not exceed 46 C during normal conditions (max bair hugger temp is 42)
15
Q
4 Temp Technologies
A
- thermistor
- thermocouple
- liquid crystal
- infrared
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
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
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
Nasopharynx
- location close to hypothalamus
- some studies show correlation w core temp (?)
- easily accessible during surgery
- may cause epistaxis
26
Temp Monitoring Graphic
27
Methods of Heat Loss
radiation \> convection \> evaporation \> conduction
burn pts lose heat via evaporation
28
Each 1 degree C decrease in temp = metabolism decreases by \_\_\_\_\_
7%
so keep burn patients WARM!
29
Skin and Heat Loss
skin supports, insulates, and protects against heat loss
30
Radiation
- 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
Convection
- 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
Conduction
- 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
Evaporation
- occur from skin, respiratory tract, open wounds, pneumoperitoneum, or wet towels/drapes that are in direct contact w the patients body
34
High Risk Hypothermia Populations
- geriatrics
- pediatrics
- hypothyroid
- pts w hypothalamic lesions
- *hypothermia is the most common temp related disorder during anesthesia*
35
Forced Air Warming Devices AKA _Convection_ Warming Devices
- 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
Advantages to Forced Air Warmers
- 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
Disadvantages to Forced Air Warmers
- 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
Controversial Topic Re: Bair Hugger
- 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
Review of the Literature Re: Temp Monitoring and Perioperative Thermoregulation
- GA \> impairment than neuraxial anesthesia
- prolonged anesthesia = **HYPERthermia** (cause unknown)
- hypothermia post cardiac arrest shows little benefit despite trend years ago
40
MH
- 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
S/S of MH
- 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
MH Prep
- 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
MH High Risk Pops
- Duchennes MD
- Native Americans
- Peds
- Kids of parents w MH
