Noninvasive - Kendall cards Flashcards
AANA Standard V states to monitor
-ventilation
Pulse ox consists of
-two light emitting diodes (LEDs)
Pulse oximetry is calculated based on this law
Beer-Lambert
Beer-Lambert law determined that
oxygenated and reduced hemoglobin differ in their absorption of red and infrared light
Oxyhemoglobin (oxygenated) absorbs more
infrared light at 940-990nm wavelength
Deoxyhemoglobin (deoxygenated) absorbs more
red light at 660nm wavelength
Will pulse ox need recalibrated?
NO; LEDs provide monochromatic light, so they emit constant wavelength throughout life and never need recalibration
Noise artifact can arise on a pulse ox when
using electrocautery (saw, drill)
Risks when using pulse oximetry
-thermal injury from the little heat emitted
If finger has poor circulation you can perform a
-finger block with plain local anesthetic or intra-arterial vasodilators to restore circulation & perfusion
If patient is obese you can use this finger for pulse oximetry
little finger
If one extremity is above the other (ex: patient laying on side) pulse oximetry should go
-in the upper extremity
With epidural/spinal block you may have better pulse ox signal with the
toe than finger
Toe pulse ox will be
a slower signal, longer to equilibrate
If patient is in Trendelenburg avoid pulse ox in the
nose
With burn patients, pulse ox can be placed on
cheek
Other pulse ox sites
-palm of hand
Normal saturation decreases as
altitude above sea level increases
When pulse ox is between 90-100% saturation, the paO2 will be
>60 torr
These things will cause the oxyhemoglobin dissociation curve to shift to the left
-hypothermia
What on an a-line represents volume status?
The complete area under the curve
Carboxyhemoglobin exists to varying degrees in these populations
-smokers
Overread spO2 happens with carboxyhemoglobin becuase
it has an absorption spectrum similar to oxyhemoglobin (940-990nm)
What is a late sign of carboxyhemoglobin?
cherry-red appearance
Methemoglobin occurs in
-<1% of humans
Methemoglobin MOA
-binds with oxygen and won’t let that oxygen unload to the tissues
Treatment of methemoglobin
methylene blue; 1mg/kg
Pts with methemoglobinemia that have spO2>85% their pulse ox will read
falsely low
S&S of methemoglobinemia
-brownish-gray cyanosis
Pulse ox in sickle cell anemia
may have questionable accuracy
Fetal hemoglobin
does not affect spO2 readings at low levels
What might cause large decreases in spO2 transiently?
DYES:
What color nail polish could interfere with pulse ox?
-blue
What is the gold standard of ETT placement and verification?
End tidal CO2 measurement
PaCO2 vs EtCO2
PaCO2 will be 4-6mmHg higher
Capnometer
device that performs measurement and displays readings
Capnography
graphic record of CO2 concentration on a screen or paper
Capnograph
machine that generates a waveform and the capnogram is the actual waveform
EtCO2 works by
comparing a control gas sample of CO2 to the gas from the breathing circuit with infrared light of two different wavelengths (2600 and 4300nm)
CO2 samples for EtCO2 are obtained by two methods:
-mainstream (non-diverting)
Mainstream (non-diverting) capnograph
flow through in-line sample where CO2 is measured by passing through adaptor
Sidestream (diverting) analyzer
aspirating analyzer that transports gases through capillary tubing to chamber
On the capnogram, which letter corresponds with end-tidal concentration?
D
Which phase on the capnogram represents inhalation?
Phase IV
What finding on the capnogram greatly increases the chances that the EtCO2 reading is a reliable estimate of the level?
A good alveolar plateau
Slurred upstroke in capnogram indicates
bronchospasm
Plateaus on capnogram all drop is an indication of
hyperventilation
Possible causes of low EtCO2 waveform
-hyperventilation
Possible causes of elevated EtCO2 waveform
-decrease RR
What is the curare cleft on the capnogram waveform an indicator of?
-the patient beginning to breath on their own (muscle relaxants are subsiding)
Depth of the curare cleft is inversely proportional to
the degree of drug activity (paralytic)
Capnogram waveform that starts with a small breath and follows with subsequent breaths getting progressively higher peaks and gradual return to normal waveform indicates
spontaneous respirations
Cardiogenic oscillations of the capnogram waveform is
-mainly artifact
Plateaus starting to slur on the capnogram waveform indicate
progressive obstruction in the airway
Obstructive EtCO2 waveform is classic in
-COPD
Possible causes of obstructive EtCO2 waveform (that is not due to reactive airway condition)
-kinked or occluded artificial airway
How to convert carbon dioxide in volumes % to mmHg
take atmospheric pressure (760 at sea level) and multiply by the %
Possible causes of elevated EtCO2 baseline
*incompetent inspiratory valve
Possible causes of abnormal descending limb of capnogram (D to E)
incompetent inspiratory unidirectional valve
Irregular (wavy) plateau or baseline of capnogram
-leaky or deflated ETT
Sudden drop in EtCO2 to zero causes
-missed intubation
What other things could cause a decrease in EtCO2 from normal to a sudden low value?
-PE
What is the advantage to mass spectrometry?
can monitor nitrogen
Disadvantage to mass spectrometry?
-requires constant suction
Usually monitor CV in two leads
-lead II
Lead II recognizes
P waves easily and detects dysrhythmias
Lead V5 views the
anterior and lateral portions of the LV
Modified V5 lead (MCL) is used to detect
anterior and lateral wall ischemia if only using 3 lead electrodes
Placement of electrodes in modified V5 lead (MCL)
-right arm in right midclavicular line
Systole is
the peak pressure within vasculature
MAP equation
(SBP+ (2*DBP))/3
With manual BP listen for these sounds
Korotokoff
As the BP cuff site becomes more peripheral the
-SBP increases
BP cuff width should be ___ of the circumference of the limb
40-50%
BP cuff should have a length that is ____ of the circumference
80-100%
Too small of a BP cuff leads to
falsely high BPs
Complications of non-invasive BP monitoring
-petechiae
Thoracic bioimpedance technology (Cheetah NICOM) is a non-invasive monitoring of
CO, SV, CI
Cheetah measures
-bioimpedance (resistance within thorax bc fluid level in aorta increases)
Near-Infrared Spectroscopy (NIRS) measures
muscle Hgb O2 sat and muscle hydrogen ion concentration
Continuous non-invasive hemodynamic monitoring
-Clearsight & nexfin
Masimo technology
SpHb tech
Compensatory Reserve Index (CRI) trends
-ciphor ox
Ciphor ox (CRI) would be good for
trauma or larger surgeries
Esophageal doppler technology
-measures descending aortic blood flow (70% of CO)
Peripheral nerve stimulation
-used to determine neuromuscular blockade effect
Why are muscle relaxants (paralytics) used?
To assure the best surgical field/environment
Qualitative peripheral nerve stimulators
-TOF
Quantitative peripheral nerve stimuator
-acceleromyography (AMG)
Accelerometry can detect ___% residual NCM
97%
Most common site of peripheral nerve stimulation
ulnar nerve; stimulating the adductor pollicus muscle
Peripheral nerve stimulation response is greater when which electrode is distal?
negative (black)
Facial nerve simulates which muscle
obicularis oculi muscle
Which drugs are resistant to NMDR?
-facial muscles
Posterior tibial nerve stimulation causes
plantar flexion of the foot and big toe
Peroneal nerve stimulation causes
dorsiflexion of the foot
Full onset of NMB muscle order
adductor pollicis, masseter muscle, and muscles of the foot
Recovery of neuromuscular function is
in reverse order as the onset of blockade with adductor pollicis and foot muscles being last
How does the diaphragm and laryngeal muscles react to sux?
-diaphragm is resistant
Best site to monitor peripheral nerve stimulation for intubation?
facial nerve; orbicularis oculi muscle
Best site to monitor peripheral nerve stimulation for extubation?
ulnar nerve; adductor pollicis
What is the most sensitive clinical assessment test of neuromuscular function?
Head left
Is adequate TV a good indicator of neuromuscular function?
NO
What is the worst evaluation of extubation?
Clinical assessment
Single twitch consists of
single pulse delivered every 1-10 seconds at 0.1-1.0 Hz, lasting 0.1-0.2 seconds
TOF consists of
four twitch stimuli over 2 seconds (0.5 second intervals) at 2Hz
3 twitches = ___blocked
75%
2 twitches = __ blocked
80%
1 twitch = __ blocked
90%
0 twitches = __ blocked
100%
How many twitches do you need before you can start to reverse the patient?
at least one or it will prolong the block!!!
Surgical relaxation generally requires how much blockade?
75-90%
Peripheral nerve stimulation will not produce fade with this muscle relaxant
Sux (depolarizing)
Tetanus is
stimulus delivered at 50-100Hz for 5 seconds
When performing tetanus in a patient on Sux the response will be
depressed but sustained
When performing tetanus in a patient on NDMBs the response will be
depressed and also not sustained (there will be a fade)
What is post-tetanic contraction (PTC)?
it is a single twitch (1Hz) that is given after tetanus
Number of PTCs counted increases as
the depth of the NMB decreases
PTC can be used when
no fade or twitches seen with TOF
Double burst stimulation (DBS) consists of
-a short burst of 3 stimuli at 50Hz, 750ms pause and then the 3 short bursts repeated again
Advantages of double burst stimulation (DBS)
-more sensitive than TOF
Reversal of blockade can be influenced by:
-hypothermia
Sux does not exhibit this with peripheral nerve stimulation
Fade
Awareness monitoring
BIS and PSA 4000
BIS monitoring ranges from
95-100 = awake, no drug effect
BIS is more sensitive to
hypnotic components of anesthetic rather than analgesic/opiate components
BIS should be in this range for general anesthesia
40-60
BIS monitoring is useful with
anesthetic techniques that place patient at increased risk of awareness
Other clinical situation that may lead to awareness under anesthesia
-emergency c-sections
Attempt to maintain UOP >
0.5ml/kg/hr
>50% of heat loss under anesthesia and surgery is through
radiation
Best way to minimize heat loss
-keep room temp>21 C (69.8F)
Most efficient way to rewarm a patient
forced air warming blanket (Bair Hugger)
Esophageal stethoscope allows for
-core temp monitoring
