Temperature Monitoring

Question 1

Benefits of a warm patient

Answer 1

Reduced wound infections, reduced blood loss, reduced cardiac events, shortened hospital stay

Question 2

Physiology of Thermoregulation

Answer 2

Hypothalamus primary, thermal input from skin secondary. Three phases of processing: afferent thermal sensing (cells in body sensing), central regulation (set point system - hypothalamus), & efferent response (sweating, peripheral cutaneous vasoconstriction, brown fat metabolism)

Question 3

Indications for Temperature Monitoring

Answer 3

large volumes of cold fluid, deliberate cooling or warming, pediatric surgery, suspected for MH, major surgical procedures, burn patients

Question 4

How do general anesthetics effect thermoregulation (physiological changes in response to change in temp)?

Answer 4

Increase sweating threshold minimally, actually preserve warm defenses for some time, produce a significant decrease in vasoconstriction & shivering threshold (iso & des decrease cold response only slightly)

Question 5

Neuraxial anesthesia & temperature control

Answer 5

Some autonomic impairment & decreased awareness by patient that they are hypothermic. Skin temp can increase by 4-6 degrees Celsius after a nerve block

Question 6

Shivering etiologies during neuraxial anesthesia

Answer 6

Shivering in response to core hypothermia most common, shivering in normo/hyperthermic who are developing fever, direct stimulation of cold receptors in neuraxis by injected local anesthetic, & nonthermoregulatory muscular activity that resembles thermoregulatory shivering

Question 7

U.S. Standards for temperature

Answer 7

Max contact surface temperature shall not exceed 48 degrees celsius, average contact surface temp shall not exceed 46 degrees celsius during normal conditions (not general anesthesia)

Question 8

Thermistor

Answer 8

Metal oxide in a wire (foley probe). Small, rapid response & continuous readings

Question 9

Thermocouple

Answer 9

Electrical circuit with 2 metals, one constant other exposed to area where temp is measured. Accurate, small, rapid, continuous

Question 10

Liquid Crystal

Answer 10

Flexible adhesive backing with plastic encased liquid crystals on a black background. Safe, convenient, easy.. relies on observer interpretation, difficult adhesion to skin

Question 11

Infrared

Answer 11

Electronic instrument, accurate

Question 12

What does general anesthesia do to temperature (degrees)?

Answer 12

Decreases core body temp by 0.5-1 degree celsius in first 30 minutes, then another 0.5 degrees per hour due to vasodilation/redistribution of body heat from core to periphery. Thermal plateau eventually

Question 13

Core Temp Compartment

Answer 13

Deep, vital internal organs

Question 14

Peripheral Temp Compartment

Answer 14

Varies from core about 2-4 degrees celsius

Question 15

Esophageal temp monitoring

Answer 15

Can vary up to 4 degrees, should be in lower third or fourth of esophagus

Question 16

Pulmonary artery temp monitoring

Answer 16

Most reliable unless during thoracotomy or bypass

Question 17

Nasopharynx temp

Answer 17

Close to hypothalamus, easily accessible but may cause epistaxis

Question 18

Methods of heat loss

Answer 18

Radiation>Convection>Evaporation>Conduction

Question 19

Burn patients & temperature loss

Answer 19

Lose more heat by evaporation/insensible loss.. each 1 degree decrease in temp = metabolism decrease of 7%

Question 20

High risk populations & temperature monitoring

Answer 20

Geriatric, pediatric, hypothyroid, hypothalamic lesions, burns

Question 21

Forced air warming devices

Answer 21

warmed Ambient air through microbial filter.. safe, disposable, can be used to cool but need electrical power, cumbersome, may need to be removed occasionally

Question 22

Malignant Hyperthermia signs

Answer 22

**Sudden unexplained doubling or tripling of end tidal CO2) despite adequate tidal volume, purple baralyme, dysrhythmias, mottling, Unexplained signs of pyrexia, or tachycardia, or cyanosis, or rigidity, or trismus (failure of masseter muscle relaxation), unstable BP, hyperkalemia

Question 23

Malignant hyperthermia physiology

Answer 23

Defect of RyRy receptor, SR of skeletal muscle fails to sequester calcium, sustained muscle contractions with increased metabolism

Question 24

Agents that trigger MH

Answer 24

Succinylcholine, volatile anesthetics

Question 25

Treatment of MH

Answer 25

Dantrolene- acts on SR to decrease release of Calcium

Question 26

Which drugs increase sweating threshold minimally

Answer 26

Prop, alfentanil, precedex, iso & des