Miscellaneous topics Flashcards
What is the BEST method of minimizing intraoperative heat loss?
a. forced air warmer
b. circulating water mattress
c. warm blankets
d. fluid warmer
a. forced air warmer
Hypothermia is defined as a core body temperature less than
36 degrees C
Who has the greatest risk of developing perioperative hypothermia?
patients at extremes of age
What are the four mechanisms of heat transfer?
radiation
convection
evaporation
conduction
What two mechanisms of heat transfer are most significant?
radiation (most)
convection (second most)
Perioperative events contributing to heat loss include
drug-induced vasodilation
impaired shivering
cold operating room
cold OR table
administration of room temperature fluids and cold blood products
core to peripheral temperature redistribution
re-calibration of the hypothalamic set point
After induction of anesthesia, heat loss occurs in three stages:
- heat redistributes from the core (torso) to the periphery (extremities)
- heat transfer to environment exceeds heat production
- heat transfer approximates heat production (new equilibrium)
What is the afferent limb of temperature regulation?
thermoreceptors located in the skin, deep tissue, and spinal cord
What is the control center of temperature regulation?
hypothalamus (preoptic region)
brainstem
What is the efferent response to “too cold” of a body temperature?
vasoconstriction
piloerection
shivering
non-shivering thermogenesis
What is the efferent response to “too hot” of a body temperature?
vasodilation
diaphoresis
What is radiation?
heat follows a temperature gradient and thus, the patient is warmer than the environment so heat is lost through the form of infrared radiation
__________ reduces radiant heat loss.
Covering the patient
What is convection?
it’s the transfer of heat by the movement of matter
____________-increases the amount of heat lost to convection.
Laminar flow
Water can be lost by evaporation from
respiration
wounds
and exposure of internal organs during surgery
What is conduction?
heat is lost when the patient comes into direct contact with a cooler object
What is the least significant source of heat loss in the OR?
conduction
Which temperature monitoring site offers the BEST combination of accuracy and safety over an extended period of time?
a. rectal
b. esophageal
c. tympanic membrane
d. pulmonary artery
b. esophageal
Perioperative hypothermia increases the risk of
morbidity and mortality
Shivering increases oxygen consumption by up to
400-500%
Shivering increases the risk of
myocardial ischemia and infarction
Pharmacologic modalities used to treat postoperative shivering include
meperidine, clonidine, dexmedetomidine
What are times when perioperative hypothermia can improve outcomes?
stroke
cardiopulmonary bypass
aortic cross-clamping
cardiac arrest
cerebral aneurysm clipping
traumatic brain injury
carotid endarterectomy
Esophageal temperature should be measured in the
distal 1/3rd to 1/4th of the esophagus
How far should the esophageal temperature probe be inserted?
38-42 cm past the incisors
Skin temperature ____ with core body temperature
does not correlate
Pharmacologic consequences of perioperative hypothermia include
slowed drug metabolism
increased solubility of volatile agents
prolongs things
Perioperative hypothermia can result in
myocardial ischemia and dysrhythmias
decreased O2 available to tissues
surgical site infection (d/t vasoconstriction & decreased Tissue PO2)
increased blood loss
risk of sickle cell crises
Oxygen consumption is reduced by ________ for every 1 degree C reduction in body temperature
5-7%
Where is the ideal position of a nasopharynx temperature probe?
sensor contacts posterior nasopharyngeal wall posterior to the soft palate
What is the risk of using a rectal temperature?
risk of bowel perforation
What is the risk of bladder temperature?
risk of UTI
-don’t use during GU procedures
What will reduce the accuracy of temperature measurement at the esophagus?
probe positioned in the proximal esophagus
What will reduce the accuracy of temperature measurement at the bladder?
inadequate UOP
What will reduce the accuracy of temperature measurement at the nasopharynx?
leakage of inspiratory gas (if present)
What will reduce the accuracy of temperature measurement at the rectum?
cool blood in lower extremities and insulation by stool
What will reduce the accuracy of temperature measurement in the pulmonary artery?
open chest
Anesthetic considerations for removal of vocal cord papilloma with a carbon dioxide laser include:
a. reducing the FiO2 by adding nitrous oxide
b. applying reflective tape to a red rubber endotracheal tube
c. using amber goggles
d. adding saline instead of air to the cuff of the ETT
d. adding saline instead of air
What are the three ingredients required to produce a fire?
- ignition source
- oxidizer
- fuel
Examples of ignition sources include
electrosurgical cautery
laser
Examples of oxidizers include
oxygen
nitrous oxide
Examples of fuel include
endotracheal tube
drapes
surgical supplies
Immediate steps to take when an airway fire is present include:
- stop ventilation and remove ETT
- stop the flow of all airway gases
- remove other flammable material from the airway
- pour water or saline into the airway
- if the fire isn’t extinguished on the first attempt, use a Co2 fire extinguisher
Steps to take after an airway fire is controlled:
- re-establish ventilation by mask. avoid supplemental O2 or nitrous oxide
- check ETT for damage- fragments may remain in the patient’s airway
- perform bronchoscopy to inspect for airway injury or retained fragments
Laser safety considerations include:
use <30% FiO2
do not use N2O
use a laser resistant ETT. remember all cuffs are vulnerable
fill the cuff with saline
protect the patient’s eyes
What kind of goggles does a CO2 laser require?
Clear goggles
What type of goggles does a Ruby laser require?
Red
What type of goggles does an Argon laser require?
Amber
What type of goggles does a Nd:YAG laser require?
Green goggles
The best way to protect yourself from fine particulates created from tissue vaporization?
a smoke evacuator
high-efficiency masks
Laser light differs from ordinary light because it is:
- monochromatic (a single wavelength)
- coherent (oscillates in the same phase)
- collimated (exists as a narrow parallel beam)
Lasers with short wavelengths absorb __________ water and penetrate____________ into tissue
less; deeper
Which laser has the shortest wavelength?
Argon
Which laser is used for vocal cord and oropharyngeal surgery?
CO2 laser
Which laser is used for tumor debulking?
Nd:YAC
Which laser is used for vascular lesions?
argon
Which laser has the longest wavelength?
CO2
Which laser is used for retinal surgery?
Ruby
