I&M I: Lecture 7 - Temp Monitoring Flashcards
(26 cards)
Why do we care about temperature in the OR?
Patient safety
ASA standard monitor
Differential diagnoses and warning of major pt events
ASA Temp
Note: difference between continual vs continuous
Hypothermia Bad?
Mild hypothermia can lead to:
Cardiac complications
Increased bleeding
Decrease clotting
Wound infection
Delayed wound healing
Delayed wakeup
Drug metabolism effects
Shivering
Increased O2 demands
MI or respiratory insufficiency
Hypo not hyperthermia can cause increase would infection
Normothermic Pts Are Happy Pts
Age extremes have poor thermoregulation
Use multiple methods to keep these pts warm:
Bair Hugger
Fluid Warmer
Warm ambient OR temp
Warm towels over exposed parts
Plastic
Babies especially, they cannot regulate their body temperatures. They increase their metabolism of brown fat to retain heat (LOOK INTO MORE!!!)
Most patients lose heat through radiation (WHAT IS THE PERCENTAGE AND WHAT ARE THE OTHER WAYS???)
Hyperthermia
Pts can present with thyroid storm, malignant neuroleptic syndrome, MH, or other events ⇧ temp
Monitoring temp can aid in DD
Many intraoperative conditions present with similar s/s
Hypercarbia
Tachypnea in SV pt
⇧ ETCO2 (one of the first signs in MH)
⇧ temp
HTN
Why are you so sweaty?
Hyperthermia
Hypoglycemia
Hyperthyroid/Graves Disease
Use that probe if:
Large volumes of cold IV fluids or blood products administered
Deliberate hyper- or hypothermia (WHEN IS THIS DONE FOR BOTH???)
Pediatric surgery
Pts with known thermoregulatory issues
Known hypothermic or feverish pts
Major surgical procedures
Trauma
Suspected or known MH history
Thermistor
Metal oxide fused into a rod or bead or sintered into a wire
Sinter: heat compacted, powdered metal until it fuses into a strong, uniform piece of metal
Source current and receiver to measure current
Resistance is converted to temperature reading
As temp decreases, resistance increases
As temp increases, resistance decreases
Probes are inexpensive, interchangeable, and disposable
Rapid response time, continuous readings, sensitive to small ∆T
Thermocouple
Electrical circuit with 2 unlike metals welded together at the ends
1 metal remains constant temp
2nd metal exposed to temp measurement site
Voltage difference produced, measured, converted to temp reading
Accurate, small, rapid response time, continuous readings, interchangeable probes, inexpensive, disposable
Platinum Wire
Small diameter platinum wire equilibrates rapidly to changing temp
Electrical resistance of platinum wire changes ~linearly with ∆T
Accurate, continuous readings, and can be interchangeable
Liquid Crystal
Anisotropic behavior (optically active)
Organic compounds transform from solid to liquid with ∆T
Between solid and liquid states = liquid crystal
Crystals scatter light in iridescent colors
Flexible black strip covered in crystals, encapsulated in plastic
Safe, convenient, cheap, disposable, user-friendly, continuous readings, no need for power source/circuitry
Subjective readings, cannot translate readings to EMR, adhesive allergies, problems sticking, low precision
Infrared
Measures infrared radiation from small surface area
Otoscope style has 2 modes of temp display:
Unadjusted, calibration mode: actual temperature
Site equivalent mode: offset estimates temperature
Scanning style: scan on forehead, behind ear, neck
Rapid readings, pts tolerate well
Intermittent measurements, inconvenient in OR, inaccuracy potential (ear canal shape, improper depth, obstructions)
Common in PACU, they want 36C otherwise have to perform warming techniques
Core vs. Peripheral
Core
Deep, vital internal organs
Uniform
35.7-37.8 normal range
Periphery (shell)
Skin, axilla, peripheral tissue that surrounds core
Variable
Vasoconstriction can affect readings
2-4∘C difference b/n shell and core
Where to monitor?
Different body parts can vary in temp at any given time
Consider:
Tissue heat production
Circulation
Insulation
External influences on the site
Bair hugger
Tourniquet
Surgical exposure
Purpose of measurement
Surgery length
Surgical site
Anesthesia technique
Equipment
Accuracy, speed, access, pt tolerance, cost
Please do not try to put a nasal temp prop in an awake or sedated patient (MAC)… you will use a peripheral site.
Pulmonary Artery
Swan-Ganz catheter with thermistor detects core body temp
Unreliable during CPB or thoracotomies
Esophagus
Temps can vary up to 4∘C
Measure at lower 3rd or 4th of esophagus
Unreliable in thoracic surgery
Esophageal stethoscope
Ideal placement 12-18cm distal to max heart sounds
If placement higher, ⇩ temp vs core
If lower, ⇧ temp vs core
Respiratory gases can affect readings
Airway humidification ⇧
Avoid in facial, oral, airway, or esophagus surgery
Avoid in pts with esophageal disorders, LINX, gastric bypass, etc.
Avoid in awake pts
Considered core body temperature
Nasopharynx
Place sensor with contact on posterior NP wall posterior to soft palate
Easily accessed
Not affected by inspired gases (unless ett leaks) and gastric suctioning
Avoid in awake pts
Possible epistaxis
Considered core body temperature
Urinary Bladder
Indwelling catheter with thermistor or thermocouple near pt end
Correlates to NP, PA, and esophageal sensors
Slight lag with rapid heating/cooling
With lots of fluid movement/urine will actually give you a decreased temperature as compared to the core temperature
Avoid in any cystoscopy/prostate cases
Considered core body temperature
Rectum
2 modes
Dwell: continuous temp display
Takes 2-3 mins to display
Monitor: predictive mode
Estimates temp based on temp rise curve
Takes 30 seconds to display
Insert at least 8-10 cm in adults, 3 cm in children
Prolonged lag time
Bowel perf risk, heat-producing flora increase reading, fecal insulation
Considered core body temperature
Tympanic Membrane
Contact
Insert thermistor or thermocouple probe into ext auditory canal
Must contact tympanic membrane
Pt will hear rubbing of wire easily if correctly placed
Risks: tympanic membrane perf, trauma, oozing, external otitis
Infrared
Otoscope-like probe measures tympanic membrane and ear canal
Some devices give offsets to account for difference between ear and core temps
Wide variability, user-error, ambient temp influence
Rapid reading, awake pts tolerate well, reduced X-contamination risk, easy-access to ear canal
Skin
Probes:
Liquid crystal
Flat disc
Tip of lead-containing thermocouple or thermistor
Locations:
Forehead
Axillary
Back, chest, anterior abdominal wall
Fingers, toes
2-4∘C < core temp… but helpful for you knowing where the temperature is going with your temp control measures
Easily accessible
Poor core temp estimate, affected by ambient temp, ∆ cardiac output
May use to evaluate block quality (vasodilation = increased temp)
Peripheral thermo monitoring
Axilla
Thermocouple or thermistor probe over axillary artery, adduct arm
Easy measurement, pt tolerability, and accessible site
Inaccurate in adults, more accurate in children and infants
Readings affected by external contact, skin perfusion, environmental exposure, improper placement
Peripheral temp monitoring
Mouth
Sublingual temp probe, like elementary school
Easily accessed and tolerated by awake pts
Inaccurate if pt has tachypnea or is a mouth-breather
Trachea
Temp sensor in ett cuff
Unclear accuracy/effectiveness (though probably inaccurate due to the air that is used from machine is generally cool air)
