Monitoring Flashcards
AANA monitoring standard
9
Oxygenation monitoring standards
Clinical observation
Pulse oximetry; continuous
ABG’s as indicated
Ventilation monitoring standards
Auscultation after placement
Chest excursion; rise and fall
ETCO2; MAC case(salter canula)
Pressure monitors as indicated
Monitor RR every 5 minutes
CV monitoring standards
Electrocardiogram
Auscultation as needed
BP and HR every 5 minutes
Thermoregulation monitoring standards
When clinically significant changes in body temp are anticipated or suspected
Peds, elderly
Cases more than 20 min.
Neuromuscular monitoring standards
When neuromuscular blocking agents are administered
Chart q15 min
Chart when administering nm blocker
Chart when redosed
Causes of L shift on oxygb curves
Alkalosis
hypocarbia
hypothermia
decreased COhB
Fetal Hb
L shift = higger affinity for O2
Causes of R shift on oxyhb dissociation curve
acidosis
hypercarbia
hyperthermia
increased 2,3 dpg
Beer-Lambert
Law of absorption
Relates the transmission of light through a solution to the concentration of the solute in the solution
Light absorption must be measured at wavelengths that are proportional to the number of solutes
More concentrated solution absorbs _____ light than a less concentrated solution
more
Pulse ox low concetration
low absorption
Pulse ox high concnetration
high absorption
Pulse ox shorter light path length
Less absorbed = more through the other side
Pulse ox more light path length
more absorption
Co-oximetry
looks at all 4 wave lengths
Gold standard if oximetry is inaccurate
co-oximetry
Red wavelengths of light
660
Infrared wavelengths of light
940 nm
Deoxyhemoglobin (deO2Hb) absorbs more______ light than oxyhb
Red
Oxyhemoglobin (O2Hb) absorbs more——- light than deoxygb
infrared
Pulse ox operating principles
Ratio of AC (alternating current) and DC (direct current) light absorption
AC: Pulsatile expansion of the artery increases length of light path which Increases absorbency
DC looks at non pulsatile
Pulsatile component divided by non-pulsatile component for each wavelength
(AC(660)/DC(660))/ AC(940)/DC(940)
What Absorbs as much light in the 660 nm range as oxyhemoglobin does
carboxyhb
Falsely elevates SpO2
Each 1% increase of COHb will increase SpO2 by …..
1%
Many smokers have >6% COHb
Venous blood pulsations does what to the pulse ox?
Detection of venous O2Hb sat, results in reduction of presumed arterial SpO2
Disadvantages of Pulse ox
Inaccuracy with dyes
Inaccuracy with different hemoglobin
Poor function with poor perfusion
Delayed hypoxic event detection
What finger to not put pulse ox on
index finger
Pulse ox placement for epidural block
Toes may be more reliable with epidural blocks because of dilation
Pulse ox sites that are less affected by vasoconstriction, reflects desaturation quicker
Tongue, Cheek, Forehead
Phases of Korotkoff sounds that measure BP
Phase I: the most turbulent/audible (SBP)
Phase II: softer and longer sounds
Phase III: crisper and louder sounds
Phase IV: softer and muffled sounds
Phase V: sounds disappear (DBP)
Map equation
map = SBP + (2x DBP) / 3
ideal bp Cuff bladder
40% of arm circumference
80% of length of upper arm
Centered over an artery
Automatic Non-invasive bp Techniques
Based on oscillometry
The maximal amplitude of oscillations = MAP
SBP and DBP calculated from algorithm
SBP – the least agreement with invasive BP
BP Cuff too large
Low bp
BP cuff too small
High bp
Atherosclerosis, edema, obesity, and chronic HTN produces what bp read out?
Low SBP and high DBP
BP average deviations
Average difference must be < +/- 5 mm Hg
Deviations up to 20 mm Hg are “acceptable”
When to use BP with caution…..
Severe coagulopathies
Peripheral neuropathies; use side with less neuopathies
Arterial/venous insufficiency
Recent thrombolytic therapy
Examiner compresses radial and ulnar arteries
Examiner compresses radial and ulnar arteries
Examiner releases ulnar artery
Color of palm should return in seconds
Severely reduced collateral flow > 10 seconds
Art line procedure
insert needle
pass guidwire through needle
remove needle
insert catheter over guidewire
Art line Transfixion Technique
Front and back walls are punctured intentionally
Needle removed
Catheter withdrawn until pulsatile blood flow appears and then advanced
Level and zeroing for artline
Zeroing; References pressures against atmospheric air;
Leveling; Aortic root; midaxillary line
Art line wave forms
1: systolic upstroke
2: systolic peak pressure
3: systolic decline
4: dicrotic notch- aortic valve closing
5: diastolic runoff
6: end-diastolic pressure
BP measured at 2 and 6
systolic waveform happens after the R wave
looking at blood flow and stiffness of arteries and distance from the heart and harmonic resonance along the vascular tree
Impedance
As pressure wave moves TO periphery:
Arterial upstroke steeper
Systolic peak higher (PP wider)
Dicrotic notch later
End-diastolic pressure lower
How are arterial waveforms made?
Summation of sine waves
Fundamental wave + harmonic wave = typical pressure wave
how many harmonic waves are required for most arterial pressure waveforms
6-10
analysis of the summation of multiple sine waves
Fourier analysis
mathmatical recreation of the pressure wave that’s transmitted.
Underdamped art wave
Systolic pressure elevated
Too many Oscilations
Shouldn’t have more than 2 or greater than 1/3 of the previous oscillation
Overdamped art wave form
Systolic pressure decreased
Absent dicrotic notch
Loss of detail
Falsely narrowed pulse pressure, MAP accurate
What contributes to Pressure Gradient Changes with bp?
Age: lack of distensibility (wider pulse pressure)
Atherosclerosis
Peripheral vascular resistance changes
Septic shock - femoral artery pressure can exceed radial artery pressure by 50mmhg
Hypothermia; constriction/ dilation
Cyclic arterial BP variations d/t respiratory-induced changes in intra-thoracic pressure
Pressure Wave Form Analysis
have to be;
Positive pressure ventilation (PPV)
closed chest and stomach
Lung volume change
PPV Effects on Pressure; inspiration
During inspiratory phase
⬆️ in intra-thoracic pressure, simultaneously ⬇️ LV afterload
⬆️ in total lung volume
Displaces pulmonary venous blood into left side of the heart…. ⬆️ LV preload
⬆️ LV preload and ⬇️ LV afterload….
⬆️ LV stroke volume, CO, and systemic arterial pressure
Increasing intra-thoracic pressure… ⬇️ systemic venous return and RV preload
⬆️ RV afterload by ⬆️ PVR
RV stroke volume drops during early phase of inspiration
PPV effect on pressure; expiratory phase
Decreased RV stroke volume… travels through pulmonary vascular bed to enter the left heart
⬇️ Reduced LV filling, ⬇️ LV stroke volume, and ⬇️ systemic arterial BP
Cycle of increasing and decreasing SV and systemic arterial BP in response to end-expiratory pressure
Systolic Pressure Variation (SPV)
Normal SPV
Mechanically ventilated patients, normal SPV = 7 - 10 mm Hg
Normal ΔUp = 2 – 4 mm Hg
Normal ΔDown = 5 – 6 mm Hg
Increased SPV =
Volume responsive or have residual preload reserve
Possible early indicator of hypovolemia
Critically ill - dramatic increase SPV (ΔDown component)
Utilizes maximum and minimum pulse pressures over entire respiratory cycle
Pulse pressure variation
Maximal difference in arterial pulse pressure
Divided by average of maximum and minimum pulse pressures
Normal and abnormal PPV
Normal <13 – 17%
>13 - 17% = Positive response to volume expansion
When to give volume for PPV
> 13% = gets volume
<9% = do not get volume
Computer analysis of arterial pulse pressure waveform
Correlates resistance and compliance based on age, gender
Computes SV
Stroke Volume Variation (SVV)
SVV formula
SVV = (SV max – SV min) / SV mean
Normal SVV
Normal: 10 - 13%
>10 - 13% = Positive response to volume expansion
What makes a SVVV reading accurate
mech vent w/ VT 8-10 ml/kg
PEEP > 5mmhg
NSR
Normal Intra abd pressure
closed chest
What is a side stream or diverting analyzer
Gas must be brought to the analyzer
what is a Mainstream or non-diverting analyzer
The analyzer brought to the gas in the airway
A fuel cell oxygen analyzer is an example of what gas sampling system?
mainstream or non-diverting analyzer
Rise time
time taken by the analyzer to react to the change in gas concentration
faster with non diverting = shorter rise time
longer with side stream
Side-stream responses is dependent on
dependent on sampling tubing inner diameter, length, and gas sampling rate
Normal gas sampling rate
200ml/min - 250 ml/min
Adding tubing does what to the gas sampling response time
longer transit time
longer rise time
narrower tubing= takes longer for gas to be removed from the system
wider tubing= more gas is sucked
Transit time
time lag for the gas sample to reach the analyzer
will be short in mainstream or non diverting
Dalton’s Law
The total pressure exerted by a mixture of gases is equal to the sum of the partial pressures exerted by each gas in the mixture
atm pressure
760 mmhg
Mass Spectrometry
Breath by breath basis to ID 8 gasses.
Abundance of ions at specific mass/charge ratios is determined and r/t the fractional composition of the gas mixture
Concentration determined according to mass/charge ratio
Infrared Analysis
Measurement of energy absorbed from narrow band of wavelengths of IR radiation as it passes through a gas sample
Measures the concentrations of gases
Infrared measures;
Measures CO2, nitrous oxide, water, and volatile anesthetic gases
O2 does not absorb IR radiation (use fuel cell)
Strong absorption of IR light occurs at …..
specific wavelengths for each gas (ex: CO2 at 4.3 microns)
IR light is transmitted through a gas sample over a range of frequencies, then is filtered via ….. for infrared analysis
a narrow-band pass filter
Amount of IR light that reaches the detector is inversely related …..
concentration of the gas being measured
Less light going through = high concentration
Saturated H2O vapor
47 mmhg
Oxygen battery that measures the current produced when oxygen diffuses across a membrane
Fuel or Galvanic Cell
short life span
slow rsp time
Best to monitor O2 concentration in the …. with an fuel oxygen analyzer
inspiratory limb
Paramagnetic oxygen analyzers
Detects the change in sample line pressure resulting from the attraction of oxygen by switched magnetic fields
Signal changes during switching correlates with O2 concentration
use with side stream
faster; breath by breath / rapid response
Oxygen sampling in the inspiratory line
Ensures oxygen delivery
Analyzes hypoxic mixtures
Oxygen sampling inside the expiratory limb
Sampling inside the expiratory limb
Ensure complete pre-oxygenation “denitrogenation”
ET O2 above 90% adequate. lower = something is wrong
causes of High O2 alarm = toxic
Premature infants
Patients on chemotherapeutic drug (ex: bleomycin)
Patients on Bleomycin may have what hemodynamic change
High O2 alarm
Cause of low O2 alarms
Pipeline crossover; If line plugged in wrong
Incorrectly filled tanks
Failure of a proportioning system; Nitrous and oygen turn on at the same time.
Airway Pressure Monitoring detects
Detects circuit disconnections, ETT occlusions, kinking in the inspiratory limb, fresh gas hose kink or disconnection, circuit leaks, sustained high circuit pressure, and high and low scavenging system pressures
airway pressure alarm Required by AANA/ASA standards
Breathing circuit low pressure alarm
What airway pressure monitor requires no power, is always on and have a high reliability
Mechanical pressure gauges
Primary purpose of the breathing circuit low pressure alarm
Primary purpose is identification of circuit disconnection or leaks
Does not detect some partial disconnections
May not detect misconnections or obstructions (70% at Y piece)
Breathing circuit Low-pressure limit should be set just below the normal_______
Peak airway pressure
Measure and alerts negative circuit pressure and potential for reverse flow of gas
Sub atmospheric pressure alarm (subambient alarm)
Normal peak airway pressure
18-20 mmhg
Negative pressures can cause …..
cause pulmonary edema, atelectasis, and hypoxia
Causes of Sub atmospheric pressure alarm (subambient alarm)
Active (suction) scavenging system malfunctions (high vacuum pressure)
Pt inspiratory effort against a blocked circuit
Inadequate fresh gas flow - low flow
Suction to misplaced NGT/OGT
Moisture in CO2 absorbent
Activated if the pressure exceeds a certain limit
High-pressure alarms
User-adjustable or automated
Valuable in pediatrics
Causes of high-pressure alarms
obstructions, reduced compliance, coughing/straining, kinked ETT, endobronchial intubation
Triggered with circuit pressure exceeding 10 cm H2O for >15 seconds
Continuing pressure alarms
Fresh gas continues to enter the circuit but cannot leave
Causes of continuing pressure alarms
malfunctioning adjustable pressure relief valve, scavenging system occlusion, activation of oxygen flush system, malfunctioning PEEP
types of PNM
Electrical and magnetic
Electrical nerve stimulation most commonly used
The reaction of single muscle fiber to a stimulus follows an all-or-none pattern
supramaximal stimulation
The response of the whole muscle depends on how many muscle fibers are activated
Gold standard for PNM
Ulnar nerve-adductor pollicis muscle easily accessible
Lowest risk of direct muscle stimulation
most resistant to depolarizing and nondepolarizing NMBDs….
Diaphragm
Shorter onset than adductor pollicis, recovers quicker than peripheral muscles
can be accessed when arms are unavailable …..
Facial nerve-orbicularis oculi (7; close eye) and facial nerve-corrugator supercilii muscle- (eyebrow wrinkle)
What reflects extent of neuromuscular block of laryngeal adductor and abdominal muscles better
Corrugator supercilii > adductor pollicis
Hz for single twitch
1.0 Hz (every second) to 0.1 Hz (every 10 seconds)
Reference value mandatory prior to NMBD
TOF stimuli
Four supramaximal stimuli every 0.5 seconds – evaluate TOF count or fade in the muscle response
TOF ratio – 4th response/1st response
Partial nondepolarizing block - TOF ratio
decreases (fade) and is inversely proportional to degree of block
Partial depolarizing block - TOF
No fade, ratio is 1.0
If fade, phase II block developed
Double Burst Stimulation htz
2 short bursts of 50 Hz tetanic stimulation separated by 750 ms w/ 0.2 ms duration of each square wave impulse in the burst
DBS3,3 mode
3 impulses in each of the 2 bursts
DBS3,2 mode
1st burst has 3 impulses and 2nd has 2 impulses
Tetanic Stimulation
Tetanic stimulation given at 50 Hz for 5 seconds
Tetanic stim with non depol
one strong sustained muscle contraction with fade after stimulation
tetanic stim with depol
strong sustained muscle contraction w/o fade
Phase II block – fade occurs
Post-tetanic Stimulation composition
tetanic stimulation (50 Hz for 5 sec) followed by 10 to 15 single twitches (1 Hz after 3 sec post tetanic stimulation)
Perform every 6 minutes
Deep and surgical blockade assessment
Post-tetanic stim dependent on
Degree of blockade
Frequency and duration of tetanic stimulation
Length of time between the end of tetanic stimulation and first post-tetanic stimulus
Frequency of the single-twitch stimulation
Duration of single-twitch stimulation before tetanic stimulation
intense non depol blockade and treatment
period of no response, 3 – 6 minutes after intubating dose of non-depolarizing NMBD
Neostigmine reversal impossible; high dose of sugammadex (16 mg/kg) for reversal
Deep non depol blockade and treatment
absence of TOF but presence of at least one response to post-tetanic count stimulation
Neostigmine reversal usually impossible; dose of sugammadex (4 mg/kg) for reversal
Suggammadex side effects
asystole / bradycardia
moderate non depol blockade and treatment
gradual return of the 4 responses to TOF stimulation appears
Neostigmine reversal after 4/4 TOF; dose of sugammadex (2 mg/kg) for reversal
Depolarizing Blockade- phase 1
No fade or tetanic stimulation; no post-tetanic facilitation occurs
All 4 responses are reduced, yet equal and then all disappear simultaneously in TOF (ratio is 1.0)
Normal plasma cholinesterase activity
Depolarizing Blockade- phase 2
Fade present in response to TOF and tetanic stimulation; occurrence of post-tetanic facilitation
Response is similar to non-depolarizing blockade
Abnormal plasma cholinesterase activity
Keep pt warm to prevent ….
delaying nerve conduction
level of blockade is sufficient for surgery
moderate ; 1 or two responses on TOF
Reverse blockade when ….
all 4 responses present to TOF
Reliable clinical signs for nm recovery prior to extubation port reversal
Sustained head lift for 5 sec
Sustained leg lift for 5 sec
Sustained handgrip for 5 sec
Sustained ‘tongue depressor test’
Maximum inspiratory pressure
Summation of excitatory and inhibitory post-synaptic potentials in the cerebral cortex
EEG monitoring
EEG Electrodes placed so that surface anatomy relates to….
cortical regions
Uses at least 16 channels of information
EEG identifies
Consciousness, unconsciousness, seizure activity, stages of sleep, and coma
Inadequate oxygen delivery to the brain (hypoxemia or ischemia)
EEG Amplitude
size or voltage of recorded signal
EEG frequency
number of times per second the signal oscillates or crosses the 0-voltage line
EEG time
duration of the sampling of the signal
EEG peri-op uses
Identifies inadequate blood flow to cerebral cortex
Guides an anesthetic-induced reduction of cerebral metabolism
Used to predict neurologic outcome after a brain insult
Gauges the depth of the hypnotic state of patients under GA
EEG Beta waves
Beta (> 13 Hz): Awake
Alert attentive brain
EEG alpha waves
Alpha (8 - 13 Hz): Eyes closed
Anesthetic effects
EEG theta waves
Theta (4 - 7 Hz)
EEG delta waves
(< 4Hz):
Depressed eeg waves
Theta and delta
deep anesthesia
What Contains artifact along with desired EEG signal
Processed EEG/ BIS
Uses < 4 channels of information
2 channels per hemisphere
Bis necessary to display….
activity of both hemispheres
Delineates unilateral from bilateral changes
Not an adequate number of studies comparing EEG (gold standard) vs processed EEG
BIS 100
awake - resonds to normal voice
BIS 80
response to loud commands or mild prodding/shaking
BIS 60
general anesthesia
low probabilty of explicit recall
unresponsive to verbal stimulus
BIS 40
deep hypnotic state
BIS 20
Burst suppression
BIS 0
Flat line EEG
Most common type of evoked potentials monitored intra-op
Sensory-Evoked Responses (SER)
Sensory-Evoked Responses is….
Electric CNS responses to electric, auditory, or visual stimuli
Sensory system stimulus with responses recorded at various sites along the sensory pathway to the cerebral cortex
Cortical or subcortical
SER are described in terms of…..
latency and amplitude
Need baseline reading
SER latency
time measured from the application of the stimulus to the onset or peak of the response
SER amplitude
size or voltage of recorded signal
Monitor the responses to stimulation of peripheral mixed nerves (contain motor and sensory nerves) to the sensorimotor cortex ….
Somatosensory-Evoked Potentials
SSEP resonses consist of….
short-latency and long-latency waveforms
Short-latency SSEPs are most commonly recorded intra-op; less influenced by changes in anesthetic drug levels
Things that may alter appearance of SSEPs
Induction, neurological disease or age, and use of different recording electrode locations
Monitors the responses to click stimuli that are delivered via foam ear inserts along the auditory pathway from the ear to the auditory cortex……
Brainstem Auditory-Evoked Potentials (BAEPS)
Monitors the responses to flash stimulation of the retina using light-emitting diodes embedded in soft plastic goggles through closed eyelids or contact lenses
Visual-Evoked Potentials (VEPS)
Most common MEP
Transcranial motor-evoked potentials
Monitors stimuli along the motor tract via transcranial electrical stimulation overlying the motor cortex….
Transcranial motor-evoked potentials
Monitors the responses generated by cranial and peripheral motor nerves to allow early detection of surgically induced nerve damage and assessment of the level of nerve function intra-op
Electromyography
Assesses the integrity of cranial or peripheral nerves at risk during surgery
Monitoring the integrity of the motor tracts along the spinal column, peripheral nerves, and innervated muscle
Motor-Evoked Potentials
Primary thermoregulatory control center is the ….
hypothalamus
heat and warmth receptors
Unmyelinated C fibers
cold receptors
A-delta fibers
Thermoregulatory response characterized by:
Threshold – temperature at which a response will occur
Gain – the intensity of the response
Response – sweating, vasodilation, vasoconstriction, and shivering
Temperature control varies based on….
Vary by anesthesia, age, menstrual cycle, drugs, alcohol, and circadian rhythm
Hypothermia in GA
Initially: rapid decrease of approx. 0.5 to 1.5°C
-occurs over 30 min
Slow linear reduction: approx. 0.3°C per hour
- GA decreases metabolic rate by 20-30% lasts 1-2 hours after anesthesia
Plateau phase
-Thermal steady state, Heat loss equals heat production, Occurs 3-4 hours after anesthesia, Vasoconstriction prevents loss of heat from core, but peripheral heat continues to be lost
Hypothermia does not cause much thermal discomfort in…
neuraxial anesthesia
Pts do not complain of feeling cold
no plateau d/t inhibition of peripheral vasoconstriction
Central thermoregulatory control is inhibited by….
neuraxial anesthesia
Decreases the thresholds that trigger peripheral vasoconstriction and shivering
heat loss to the environment, approx. 40% of heat loss in pt
Radiation
BSA exposed to environment
Infants: high BSA/body mass ratio makes them vulnerable
loss of heat to air immediately surrounding the body, approx. 30%
Convection
Clothing or drapes decrease heat loss
Greater in rooms with laminar air flow
latent heat of vaporization of water from open body cavities and respiratory tract, approx. 8-10%
Evaporation
Sweating is main pathway
heat loss due to direct contact of body tissues or fluids with a colder material, negligible
Conduction
Ex: contact between skin and OR table; intravascular compartment and an infusion of cold fluid
Coagulopathy Hypothermia Complications by…
Impairs platelet aggregation and activity of enzymes involved in coagulation cascade
Hypothermia Complications
Increases need for transfusion by 22%; blood loss by 16%
Decreases oxygen delivery to tissues
3x the incidence of morbid cardiac outcomes
Shivering
Decreased drug metabolism (inc duration of nmb)
Post-op thermal discomfort
Meds to reduce shivering
demerol, meperidine, clonidine, dexmetadomidine, ketamine
Benefits of Hypothermia
Protective against cerebral ischemia
Reduces metabolism… 8% per degree Celsius
Improved outcome during recovery from cardiac arrest
Neurosurgery when brain tissue ischemia is expected
More difficult to trigger MH
Peri-Op Temperature Management
airway heating and humidification
warm IV fluid and blood
Cutaneous warming
forced air warming
Forced air warming prevents heat los from….
radiation
Uses convection to transfer heat to pt
Gold standard temp monitoring
Pulmonary artery
Correlates well with tympanic membrane, distal esophageal, and nasopharyngeal temperatures
Morbind cardiac outcomes associated with hypothermia
Increased BP, HR, and plasma catecholamine levels
Tympanic membrane temperature approximates temp at the….
Hypothalamus
Placement risks perforation
Nasopharyngeal temperature reflects…..
Reflects brain temperature, more prone to error
Risk of epistaxis
Placement of esophageal temp probe
Placement in distal esophagus, lower 1/3 to ¼ of esophagus
Single blanket reduces loss by…
30%
Doesn’t increase body temperature
surgeries with increased room temp
liver transplants, major trauma, pediatrics
Oxyhemoglobin (O2Hb) absorbs more infrared light than …….
deoxyhemoglobin
Art line procedure
insert needle
pass guidwire through needle
remove needle
insert catheter over guidewire
Art line Transfixion Technique
Front and back walls are punctured intentionally
Needle removed
Catheter withdrawn until pulsatile blood flow appears and then advanced
how many harmonic waves are required for most arterial pressure waveforms
6-10
Computer analysis of arterial pulse pressure waveform
Correlates resistance and compliance based on age, gender
Computes SV
Stroke Volume Variation (SVV)
A fuel cell oxygen analyzer is an example of what gas sampling system?
mainstream or non-diverting analyzer
