Miscellaneous Monitors Flashcards
febrile temperature
> 38 degrees
hypothermia temperature
<36 degrees
room temperature
23 degrees
the recommended operating room temperature
between 68-75 degrees (20-24 Celsius)
- helps to inhibit bacterial growth
- certain patients (infants, children, burn patients) require a warmer environment for the purpose of preventing hypothermia
what is the best estimate of core temperature
Blood (from the pulmonary artery catheter)
-not practical in most cases because most patients do not have a swan Ganz catheter
what is the most consistently reliable estimate of core body temperature during general anesthesia
esophageal (distal esophagus)
-less reliable in open chest cases and in cardiac bypass
when is rectal temperature not reliable?
when the rectum is not clear
-feces can blunt temperature measurement
temperature monitoring site that isn’t as accurate as esophageal temperature but a good choice for open heart surgery
nasal
reliable estimate of core temperature only when urine output is not low
bladder
- if urine output is low, becomes less reliable
not accurate reflections of core body temperature
skin and axillary
list 4 etiologies of intraoperative temperature loss
- IV fluids
- vasodilation
- blood products
- volatile agent
one unit of refrigerated blood or 1 L of crystalloid solution administered at room temperature each decreases mean body temperature by _____
0.25 degrees Celsius
intraoperative temperature loss from vasodilation can be caused by?
spinal/epidural anesthesia
- similar degrees of hypothermia as general anesthesia
- redistributes heat from warm central compartments (abdomen/thorax) to cooler peripheral tissues (arms/legs)
these blood products are stored in cooler temperatures to preserve shelf life and should be given through a blood warmer and used with IV tubing that has a filter
Packed red blood cells (PRBC)
cryoprecipitate
fresh frozen plasma
type of blood products that are stored at room temperature and should NOT be given through a fluid warmer
platelets
how does volatile agent cause intraoperative temperature loss
interferes with hypothalamic thermoregulation
4 adverse cardiovascular effects of hypothermia
- platelet dysfunction and bleeding
- decreased stroke volume
- bradycardia/ arrhythmias
- increased blood viscosity
hypothermia causes (increased/decreased) stroke volume
decreased
hypothermia causes (tachycardia/ bradycardia)
bradycardia
hypothermia causes (increased/ decreased) blood viscosity
increased
hypothermia causes a (increase/decrease) in cerebral vascular resistance and a (increase/decrease) in cerebral blood flow
increase
decrease
in hypothermia, for every 1 degree Celsius drop in temperature, cerebral blood flow decreases ____-____%
5-7%
hypothermia causes a (increased/decreased) GFR and (impaired/increased) renal tubular function
decreased
impaired
hypothermia causes a (increase/decrease) in respiration
decrease
hypothermia causes a (left/right) shift of the HbO2 dissociation curve
left shift
hypothermia causes (increased/decreased) drug metabolism and (rapid/delayed) emergence from anesthesia
decreased
delayed
hypothermia causes (increased/decreased) wound healing
decreased
hypothermia causes (shivering/non-shivering) metabolic effect
shivering
shivering (increases/decreases) oxygen consumption by ____ fold
increases
5
in which patients is shivering particularly concerning for?
patients with coronary artery disease
list 3 circumstances that shivering is more likely with
- lower intraoperative temperature
- longer surgeries
- higher concentrations of volatile agent
2 treatments for shivering
- warming the patient
2. demerol 25 mg IV
list the 4 types of heat loss in the operating room in order from greatest to least
- radiation
- evaporation
- convection
- conduction
type of heat loss that is described as losing heat to the colder temperature of the atmosphere
radiation
-does not require contact
radiation accounts for _____% of heat loss in the operating room
60
type of heat loss where the body loses heat through the loss of water
evaporation
-sweating, and in surgery when the body is opened up
evaporation accounts for _____% of heat loss in the OR
20
type of heat loss when air flows over exposed surfaces
convection
-moving air currents with operating room circulation
convection accounts for _____% of heat loss in the OR
15
type of heat loss that involves the transfer of heat between adjacent surfaces
conduction
-laying on a cold metal table or immersing yourself in cold water
conduction accounts for _____% of heat loss in the OR
5
2 purposes to an esophageal stethescope
- measure temperature
2. listen to heart and lung sounds
2 reasons to use a precordial stethescope
- constant heart/lung sounds
2. popular in pediatrics
this monitor uses EEG to monitor awareness during anesthesia
BIS (bispectral index monitor)
on the BIS monitor a reading of ____ to _____ indicates sedation
65-85
on the BIS monitor, a reading of ____ to ____ indicates general anesthesia
40-65
on the BIS monitor, a reading of ____ indicates that the patient is too deeply anesthetized
<40
what drug can actually increase the BIS number
ketamine
list 3 common situations in which we would use the BIS monitor
- paralyzed patients
- patients undergoing TIVA who are paralyzed
- anesthetists do not monitor “end tidal” propofol to gauge awareness like MAC values - sick patients that require less anesthesia
- may not be able to mount a sufficient sympathetic response to alert the anesthetist of light anesthesia
the 2 exceptions when we cannot use vital signs to monitor awareness ( need to use BIS)
- when beta blockers have been given
2. when patients aren’t healthy enough to mount a normal sympathetic response
it is (easier/harder) to prevent awareness than it is to prevent movement
easier
-if a patient is deep enough to not move, they should be deep enough to not have awareness
should an anesthetist need a BIS monitor if the patient is not paralyzed?
no
______ output is an indicator of adequate cardiac output and renal perfusion
urine
a common goal for urine output is > _____- ____mL/kg/hr
0.5-1
an ultrasound of cardiac structures with the probe resting in the esophagus posterior to the heart
TEE (Transesophageal Echocardiography)
4 things a TEE can estimate
- ejection fraction
- cardiac output
- patency of heart valves (stenosis vs. regurge)
- pulmonary artery pressure
the best monitor for diagnosing a venous air embolism
TEE
monitors nerves that are close to the surgical site and the technician monitors waves and can alert the surgeon when the nerve is ischemic or damaged
evoked potentials
what is the method of evoked potentials
- the nerve is electrically stimulated, which produces a waveform
- ischemic or damaged nerves produce abnormal waves
what are the two parts with evoked potential waves the technician looks at
- amplitude
- height of the wave - latency
- time from the onset of the wave to the peak of the response
nerve damage and ischemia cause a (increased/decreased) amplitude and (increased/decreased) latency of the wave
decreased
increased
anesthetics display the (same/different) waveform of an ischemic nerve
same
3 things that can effect evoked potential readings
- ischemia
- lack of perfusion
- hypotension
what can an anesthetist do to intervene when the wave amplitude decreases or latency increases in evoked potentials
increase the patient’s blood pressure
which 2 anesthetics have the greatest effects on somatosensory evoked potentials (SSEP)
volatile agents and nitrous oxide
which anesthetics result in better signal quality of evoked potential waves
use of intravenous agents
which 2 anesthetics decrease amplitude and increase latency of evoked potential waves (mimic nerve damage)
propofol and volatile agents
what effect does versed have on evoked potential waves
- decreases amplitude
2. does NOT change latency
what effect does ketamine and etomidate have on evoked potential waves
- increases latency
2. INCREASE amplitude
what effects does nitrous oxide have on evoked potential waves
- decreases amplitude
2. does NOT change latency
what effect do opioids have on evoked potential waves
minimal effect
list the 4 types of evoked potentials
- somatosensory evoked potentials (SSEP)
- motor evoked potentials (MEP)
- brainstem auditory evoked potentials (BAEPs)
- visual evoked potentials (VEPs)
type of evoked potential that are used to monitor the integrity of sensory nerves
somatosensory evoked potentials
-peripheral nerve is stimulated which travels through the dorsal nerve roots of the spinal cord
class of drugs that do not affect somatosensory evoked potentials and can be dosed when SSEP are used
muscle relaxants
type of evoked potential that are used to monitor the integrity of a motor nerve
motor evoked potentials
somatosensory evoked potentials stimulate which nerves and where do they travel?
-peripheral nerve is stimulated which travels through the dorsal nerve roots of the spinal cord
motor evoked potentials stimulate which nerves and where do they travel?
motor nerves and they travel through the anterior and lateral pathways of the spinal cord
motor evoked potentials are (more/less) sensitive to volatile agents than SSEPs are
more
which drug class should not be administered when MEPs are used?
muscle relaxants
which evoked potentials measure the integrity of the vestibulocochlear nerve (VIII) and even the brainstem
brainstem auditory evoked potentials
-an audible click is delivered to the tympanic membrane through earphones
which evoked potentials are the LEAST affected by anesthetics
brainstem auditory evoked potentials
which evoked potentials measure the integrity of the optic nerve and can be used during pituitary tumor resection
visual evoked potentials
which evoked potentials are MOST affected by anesthetics?
visual evoked potentials
anesthetic management with evoked potentials:
use _____ MAC volatile agent
<0.5
anesthetic management with evoked potentials:
what are two agents we can supplement volatile agent with?
- propofol drip
- less effect on evoked potentials when infused, great effect on evoked potentials when bolused - narcotic drips
- sufentanil, remifentanil
anesthetic management with evoked potentials:
Keep anesthetic level as ______as possible
constant
anesthetic management with evoked potentials:
avoid ______ ______ if MEPs are being used
muscle relaxants
