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44 Cards in this Set
- Front
- Back
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Why is temperature monitoring important?
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Allows detection of hypothermia & hyperthermia
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AANA Standard of Care regarding temp monitoring.
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Temperature should be monitored during general anesthetics > 30 min & any pediatric (<12 y/o) anesthetic
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What effect can mild hypothermia have on pts?
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Triple incidence of cardiac complications & surgical wound infections
Significantly incr surgical blood loss |
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What are the conversions for Celsius to Fahrenheit & vice versa?
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(C X 1.8) + 32 = F
(F-32) X 0.55 = C |
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What is the core zone?
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trunk & head (protected by outer layer)
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What is the peripheral zone?
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-Superficial (skin & subcutaneous tissues)
-Intermediate (skeletal muscle) |
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What is Total Body Heat (TBH)?
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-combination of zone temps (core & peripherial)
-Maintenance of TBH is more important than individual temps |
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How does the body responds to cold exposure?
2 ways |
-increasing heat production
-reducing Heat loss (Behavioral changes; decr metabolic rate; vasoconstrict peripheral vessels) |
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What is shivering thermogenesis?
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-Involves skeletal muscles, particularly those of locomotion (arms & legs)
-Can incr heat production by 500% -Indirectly controlled by catecholamines |
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What is nonshivering thermogenesis?
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-Major Target Organs -Brown Adipose Fat & Skeletal Muscle
-Brown adipose fat has more mitochondria than white -Makes them capable of more metabolic activity (d/t more fat vacuoles) -incr source of energy supply nearby |
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Where is brown fat located in infants & importance?
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-scapulae, axilla, around neck, & along vertebral axis
-primary source of thermogenic tissue -can double their heat production |
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Where is brown fat located in adults?
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concentrated around neck & kidneys
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What are the 4 major types of heat loss?
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Convection.
Radiation. Conduction. Evaporation. |
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What is convection & example?
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When objects of different temperatures come in contact with a fluid (water & air are fluids)
-e.g. wind, circulating fluid warmers, & operating room ventilation |
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What is radiation & example?
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an exchange of heat from warmer to cooler objects without any physical contact between objects (Highest loss of heat in OR ~40%)
e.g. heat from pts body into a cold OR |
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What is conduction & example?
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Net energy transfer is from warmer object to cooler object (requires direct contact)
-e.g. heat being lost from pts body into the OR table |
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What is evaporation & example?
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insensible loss from evaporation from skin & lungs (1/2 is from resp loss)
-e.g. open abdominal surgery or ETT to vent |
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What is the prevalence of hyperthermia in OR?
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-Rare in OR in absence of malignant hyperthermia
-Monitoring temp can detect over warming -cutaneous vasodilation & diaphoresis |
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How does anesthesia contribute to heat loss in OR?
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-initial loss may be attributed to prepping & draping
-loss d/t intubation & colder anesthesia gases -redistribution of body heat from core to periphery with anesthesia-induced vasodilation |
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Describe the MOA for the pattern of heat that occurs in the surgical patient
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Phase I. decrease in core temp of 1-2ºC in first hour
Phase II. a more gradual loss of core temp (~ 0.3º C/hour) Phase III. After 4 hrs of anesthesia temperature levels (loss = heat generation) |
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What are some CV (ECG) changes seen in hypothermic pt?
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increased PR, QRS, & QT intervals
ST may be inverted, T waves become diphasic then inverted Develop extra deflection called “J wave” in precordial leads increased incidence of myocardial ischemia mild hypothermia (34-36ºC) can cause a cold induced hypertension in elderly |
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How does hypothermia effect wound healing?
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decreases wound healing.
increased infection. increases protein wasting. impairs neutrophil function |
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What is considered Normo-temperature?
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36-37.5 deg C
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What is considered Mild Hypothermia?
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34-36 deg C
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How does hypothermia increase the incident of Myocardial Ischemia?
(overall) |
by causing cold induced hypertension
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What is the mechanism behind cold induced hypertension?
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In an attempt to warm the hypothalamus, the SNS triggers the release of Norepi(vasoc & HTN & augment cardiac irritability)
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What leads show the J wave best?
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J waves are best seen in the Inferior and Lateral precordial leads.
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Name EKG changes that occur as a result of hypothermia
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J wave
Prolonged PR Prolonged QRS Prolonged QT interval ST may inc or dec T waves become biphasic and invert |
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What is a J wave?
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extra deflection at the end of the QRS complex.
aka Camel Hump or Osbourn Waves resolves with normothermia |
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How does hypothermia decrease wound healing?
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Hypothermia decreases 02 supply to the wound by vasoconstriction...... lack of 02 impairs neutrophil function
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How does hypothermia impact fibrinolytic activity?
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-Fibrinolytic Activity remains the same
-d dimer is normal note: HYPERthermia greatly increases fib. activity |
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What effect does hypothermia have on blood loss?
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Increases blood loss!
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By what mechanisms does Blood Loss increase due to Hypothermia?
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Relative Thromboctopenia
(fluid shifts occur and platlets are sequestered in the spleen) Platlet function is decreased by reduced tromboxane A2 release |
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Recall reasons why infants are at higher risk for hypothermia.
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BSA to weight is greater.
Thin layer of subcutaneous tissue. More transcutaneous evaporation. Larger minute volume. |
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Recall reasons why elderly are at higher risk for hypothermia.
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decreased ability to regulate temperature (difficulty increasing metabolism -> half that of a younger adult)
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Name 3 non-central way to monitor temp.
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-Axillary
-Rectal -Skin |
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Name advantage & disadvantage to axillary temp monitoring.
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Adv - easy to place; close to axillary/brachial artery; can correlate to core temp if arm adducted completely
Disadv - Slower to reflect changes in core; dependent on blood flow & environmental temperatures |
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Name advantage & disadvantage of rectal temp monitoring.
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Adv - Easy to access
Disadv - does not correlate well with core temp |
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What are some passive methods of treating & preventing heat loss during surgery?
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-Ambient temperature (most effective -> 24C adult & 32-35C infant)
-Insulation (blanket->will decr loss by 30%) -Heat & moisture exchanger (artificial nose-1hr minimum required) -Wrapping head or arms with plastic to surgical towel |
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What are active methods of treating & preventing heat loss during surgery?
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1. Core warming (heated humidifiers, gastric lavage, peritoneal irrigation, IV fluid warmers), Forced air warmer (Bair hugger-most freq method used), Warming blanket, Radiant Heat Unit, Extracorporeal Heat Exchanger (Heart transp)
2. Superficial warming (warming blanket, radiant heat unit, forced air warmer, heated liquids against skin) |
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Name the ways to monitor temperature (ranked in order) from nearest to core outward.
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1st - Pulmonary artery (Swan)
2nd - Esophageal (can be inaccurate if influenced by respiratory gases) 3rd - Tympanic (not very accurate if not performed properly) 4th - Nasopharyngeal (can be inaccurate if influenced by respiratory gases) 5th - Bladder (if pt has a high urine output) |
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Recall the effects of hypothermia on the renal system
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-hypokalemia (minimal)
-shunting of blood from kidneys -decreased filtration rate (ARF) -decreased urine output -Decreased ETCO2 (Sodium bicarb admin to increase paCO2) |
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Recall the effects of hypothermia on the Resp system.
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-lost protective warmth humidification of upper respiratory (nose)
-decreased respirations -decreased ETCO2 -decreased MAC |
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Recall the effects of hypothermia on the Neuro system.
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slower recovery from anesthesia.
increased irritability. slower reaction times. |
