Miscellaneous Monitors Flashcards
febrile definition
> 38 degrees C
hypothermia defintion
<36 degrees C
room temp
23 degrees C
what is the recommended room temperature for the OR
between 20-24 degrees C
what are the 6 temperature monitoring sites?
blood (swan) esophageal rectal nasal bladder skin/ axillary
which temp monitoring location is the best estimate of core temp?
swan ganz
which temp monitoring site is the most consistently reliable estimate of core body temp
esophageal
when is the esophageal temp probe less reliable?
open chest cases
when would the rectal temp probe be less reliable?
if rectum isnt clear
What is a good temp probe choice during open heart surgery?
nasal bc the chest is open so esophageal will not be accurate
what does the accuracy of the bladder temp probe rely on?
urine output being normal
what are the 4 causes of intraop temp loss?
IV fluids
vasodilation
blood products
volatile agents
how much does 1 unit of blood or 1 L of crystalloids decrease the mean body temp by?
0.25 degrees C
how does vasodilation cause temp loss?
redistributes heat from warm central compartments to cooler peripheral tissues
how dose the volatile agents cause temp loss?
interferes with hypothalamic thermoregulation
what blood products are stored at cool temps and should be given through a blood warmer?
PRBC
cryo
FFP
what blood product is not given through a fluid warmer?
platelets
4 adverse cardiovascular effects of hypothermia
platelet dysfunction/bleeding
decreased SV
bradycardia/arrhythmia
increased blood viscosity
for every 1 degree C drop in body temp the cerebral blood flow decreases how much?
5-7%
what is the adverse neurologic effect of hypothermia
increased cerebral vascular resistance
decreased cerebral blood flow
adverse renal effects of hypothermia
decreased GFR
impaired renal tubular function
adverse respiratory effects of hypothermia
respiratory depression
left shift of the HbO2 dissociation curve
adverse metabolic effects of hypothermia
decreased drug metabolism & delayed emergence
decreased wound healing
shivering
how much does shivering increase oxygen consumption?
five fold
what pts should we be extremely concerned with shivering?
pts with CAD
When is shivering more likely? 3
lower intraop temp
longer surgery
higher volatile agent
what are the two treatments for shivering?
warm the pt
demerol 25mg
4 types of heat loss in the OR (in order of most heat loss to least, with %)
radiation 60%
evaporation 20%
convection 15%
conduction 5%
radiation definition
losing heat to the colder temp of atmosphere (requires no contact)
60%
evaporation definition
body loses heat through the loss of water
(when the body is opened up)
20%
convection definition
air flow over exposed surfaces
(moving air currents in OR)
15%
conduction definition
transfer of heat between adjacent surfaces
(laying on the cold metal table)
5%
2 purposes of an esophageal stethoscope
measure temp
listen to heart and lung sounds
precordial stethoscope function, where is it popular?
constant heart/lung sounds
popular in peds
BIS monitor reading 65-85 indicates?
sedation
BIS monitor reading 40-65 indicates?
general anesthesia
BIS monitor reading <40 indicates?
too deeply anesthetized
what drug can actually increase the BIS number?
ketamine
What is a BIS monitor?
bispectral index monitor that uses EEG to monitor awareness
3 common situations for the BIS monitor
paralyzed pt
pt undergoing TIVA that are paralyzed
sick pts that require less anesthesia
Are sick pts always able to mount a sufficient sympathetic response to alert anesthetist of light anesthesia?
NO, this is why BIS should be used on these pts, may not be HTN and tachy
when are the two exceptions of when we cannot trust vital signs to monitor awareness?
beta blockers were not given
pts arent healthy enough to mount normal sympathetic response
should an anesthetist need a BIS monitor if the patient is not paralyzed?
if a patient is deep enough to not move, they should be deep enough to not have awareness
probably no BIS
what is urine output an indicator of?
adequate cardiac output and renal perfusion
what is the common goal for urine output?
> 0.5-1.0 mL/kg/hr
What is a TEE?
transesophageal echocardiography: ultrasound of cardiac structures with probe resting in the esophagus posterior to heart
what can a TEE estimate?
EF
CO
patency of heart valves (stenosis/regurg)
PAP
What is the best monitor for diagnosing venous air embolism?
TEE
Evoked potentials definition
monitor nerves that are close to the surgical site
monitor waves are warn if nerve is ischemic or damaged
evoked potentials method 2
1 nerve is electrically stimulated and produce waveform
2 ischemic/damaged nerve abnormal wave
evoked potential wave amplitude
height of the wave
evoked potential wave latency
time from the onset of the wave to the peak of the response
effect of nerve damage and ischemia on waves
decreased amplitude and increased latency
when can the surgeon be lad to believe that ischemia is present when it is not?
when our anesthetics also cause a decrease in amplitude and increase in latency
how can an anesthetist intervene if the amplitude decreases or latency increases?
increase the patients BP
which two drugs increase amplitude?
ketamine
etomidate
which two drugs cause no change to latency?
nitrous oxide
versed
what effect do opiods have on amplitude and latency?
minimal effect
which drugs have the greatest effect on SSEPs?
volatile agents and nitrous oxide
4 types of evoked potentials?
somatosensory evoked potentials (SSEPs)
motor evoked potentials (MEPs)
brainstem auditory evoked potentials (BAEPs)
visual evoked potentials (VEPs)
which type of evoked potential can you not use a muscle relaxant?
motor evoked potentials
what do SSEPs monitor?
the integrity of sensory nerves
peripheral nerve stimulated and travel through dorsal nerve roots
Can you use a muscle relaxant during SSEP?
yes
What do MEPs monitor?
integrity of motor nerve
where do the motor nerves travel through in spinal cord?
anterior and lateral pathways
are MEPs or SSEPs more sensitive to volatile agents?
MEPs
what do BAEPs monitor?
integrity of the vestibulocochlear (CN7) and brainstem
uses earphones
which evoked potential is least affected by anesthetics?
BAEPs
what do VEPs monitor?
the integrity of the optic nerve
when are VEPs used?
during pituitary tumor resection
What EP is most effected by anesthetics?
VEPs
3 steps to anesthetic management with EPs
<0.5 MAC
keep anesthetic level constant
avoid muscle relaxant if MEPs
what are the two supplements for the volatile agent on cases with EPs?
propofol drip narcotic drip (remi)
does bolused or infused propofol have a larger effect on EPs?
bolused propofol
