Week 6: Anesthesia Monitoring Flashcards
The purpose of monitoring
- Assist with data collection regarding patient’s physiologic status.
- Guide the administration of the anesthetic
-Enhance situational awareness
-Extend the senses
-Not a substitute for a qualified provider.
Standard I
Qualified anesthesia personnel shall be present in the room throughout the conduct of all general, regional, and monitored anesthesia care (MAC).
** the ASA and AANA standards for basic anesthetic monitoring.
Standard II
During all anesthetics, the patient’s:
- oxygenation, -
- ventilation,
- circulation, and
- temperature shall be continually evaluated.
** the ASA and AANA standards for basic anesthetic monitoring.
purpose of oxygenation monitoring
To ensure adequate oxygen concentration in the inspired gas and the blood during all anesthetics.
Methods to ensure oxygenation.
Inspired gas:
- Oxygen analyzer with LOW concentration limit alarm.
Blood oxygenation:
- Pulse oximeter with pitch and threshold alarm.
- Adequate visual inspection.
Purpose of monitoring ventilation
To ensure adequate ventilation throughout anesthetic
Oxygen concentration in the blood is objectively measured by a blood gas/ lab. That is the saturation of arterial blood gas, the ___________.
SaO2
FiO2 monitoring can be waived under certain circumstances – T/F?
True
** it is a monitor it is not YOU. Monitors themselves are not the providers.
As AANA stardard of care, BP cycles intervals should occur under _______ or less. What are the common options?
<5 minutes.
Options 2.5, 3, 5
Methods of ensuring adequate ventilation:
- Auscultation, reservoir bag, chest excursion .
- Quantitative measure of expired gas and capnography.
- Ability to detect disconnection from ventilator.
How to ensure adequate circulatory function during all anesthetics?
- EKG and HR,
- BP ( cycles cannot exceed <5 minutes)
- palpation of a pulse
- Auscultation of heart sounds.
- monitoring of a tracing of intra-aterial pressure.
- ultrasound peripheral pulse monitoring.
- pulse oximetry (also monitors HR)
The skin temperature monitor adjusts quickly but it only monitors the area where you place it at. T/F
False; not quick enough.
To aid in the maintenance of appropriate body temperature during all anesthetics when clinically significant changes in body temperature are intended, anticipated or suspected.
4 methods to achieve this:
Temperature monitoring.
- skin (least accurate)
- nasal
- esophageal
- pulmonary artery catheter (GOLD STANDARD)
Form of human error occurring when a practitioner is desensitized to alarms or alerts.
Alarm Fatigue
** deaths have been attributed to alarm fatigue.
AANA Practice ________ indicates that alarm limit parameters and audible warning systems should be used,
Standard V
** the ideal monitoring device should elicit the minimal number of false alarms.
Four Stages of Oxygen Transport
- Lungs **
- Arterial blood **
- Tissue
- Venous blood
How can you check lungs O2 (inspired/expired gas)?
- noninvasive:
noninvasive:
- FIO2 meter (fuel cell, polarographic, paramagnetic).
- Mass spectrometer
- Raman spectrometer
- Magnetoacoustic
** no invasive way
How can you check arterial blood O2?
- noninvasive:
-invasive:
noninvasive:
- pulse oximeter
invasive:
-intraarterial optode
-clarke electrode
How can you check tissue O2?
- noninvasive:
-invasive:
noninvasive:
- transcutaneous PO2
- niroscope
- cerebral oximeter
- skin color
invasive:
- organ surface PO2 (ex. liver, brain)
- intramuscular fiberoptic
How can you check venous blood O2?
-invasive:
Fiberoptic pulmonary artery oximeter (SvO2)
** no non-invasive way.
Oxygen Analyzers (FiO2 meters) goal:
Goal is to detect hypoxia or hyperoxia
Oxygen Analyzers (FiO2 meters) - what does it monitor?
Monitors the fraction of inspired oxygen (FiO2) -controlled by CRNA.
where is Oxygen Analyzers (FiO2 meters) placed?
Placed in the inspiratory arm to ensure oxygen going to the patient
Fuel (_______) cell
Polarographic (_______) electrode.
Both are what type of analysis ?
Galvanic;
Clark
Electrochemical analysis
3 main methods of Oxygen Analyzers (FiO2 meters):
Electrochemical analysis
- Fuel (Galvanic) cell
- Polarographic (Clark) electrode.
- Paramagnetic analysis (Pauling).
This electrochemical analysis must be calibrated:
Fuel (Galvanic) cell.
Why can’t these be used to ensure oxygenation?
-Fail-safe valve
-Second-stage O2 pressure regulator
-O2 pipeline supply
because they all belong to the intermediate system.
Low O2 concentration alarms given hypoxic mixtures due to:
- Pipeline crossover
- Incorrectly filled storage tanks
- Failure of the proportioning system
High O2 audible and visual concentration alarms are used:
- Used with neonates
- On the inspiratory limb of the breathing system.
- Used to monitor inspired and end-expired oxygen.
- Preoxygenation and end-tidal oxygen greater than 90%, airway fire (<30%).
Fuel (Galvanic) Cell Oxygen Analyzer
Fundamentally an oxygen battery. (Oxygen is the fuel)
**It must be calibrated daily.
** The components may need intermittent replacement.
Fuel (Galvanic) Cell Oxygen Analyze is a breath by breath analysis. T/F
False - it is a metric of AVERAGE O2 in the inspiratory limb
where is Fuel (Galvanic) Cell Oxygen Analyzer placed?
Usually located in the inspired limb of the anesthesia circuit.
Fuel (Galvanic) Cell Oxygen Analyzer takes how long to respond?
Is slow (~30 sec) to respond
Fuel (Galvanic) Cell Oxygen Analyzer includes a ________ concentration alarm.
low O2
In a fuel (Galvanic) cell oxygen analyzer, ____________ compensation is required for accurate measurement. It also creates its own _________ potential.
Temperature;
Polarizing
Describe how the Fuel (Galvanic) Cell Oxygen Analyzer works:
Oxygen in the gas sample permeates a membrane and enters a ___________.
An electrical potential is established between a noble metal (e.g., gold, platinum) ______ and _______ (e.g., lead, zinc).
The measured _________ between the electrodes is proportional to the oxygen _______(PO2) of the gas sample.
KOH solution;
Cathode; & Anode
voltage; tension
how does the Polarographic (Clark) Electrode work?
Oxygen diffused via a membrane and electrolytes to the cathode and a similar reaction occurs like the fuel cell.
The current is proportional to the number of oxygen molecules surrounding the electrode.
The main difference between the Polarographic (Clark) electrode and the fuel cell is that it requires an:
EXTERNAL polarizing potential (a battery)
What is the name of the relationship between flow, pressure and resistance?
Ohm’s Law
Ohm’s Law and what does each letter mean?
I = V/R
I is current (flow) in amperes;
V is voltage (pressure) in volts;
R is resistance in ohms.
Molecular oxygen has two electrons in unpaired orbits, it is:
paramagnetic
** the result of an unpaired electron having a magnetic dipole moment
This electrochemical analysis must be calibrated:
Fuel (Galvanic) cell.
to 21%
When a sample and a reference O2 streams are passed through a magnetic field, the difference in concentrations creates a _______.
This is seen in what O2 analyzer?
pressure differential
Paramagnetic O2 analyzer.
What are the advantages of a paramagnetic O2 analyzer? (4)
- There are no replaceable parts.
- It is self calibrating.
- Fast response time
- Permits continuous breath by breath monitoring of FiO2.
In a Paramagnetic O2 Analyzer
Increasing oxygen tension creates an increased ___________.
A pressure wave is generated and sensed,
Then converted to an electrical signal proportional to PO2 and displayed as ________.
magnetic tension;
Volume %
Adequate FiO2 does not equal Adequate SaO2 (T/F)
True.
Pulse Oximetry measures:
Measures pulse rate and oxygen saturation of hemoglobin (SpO2)
** not the same as SpO2
SpO2 (%) is related to oxygen tension (mmHg); specifically the:
Hemoglobin Dissociation Curve
Pulse Oximetry is affected by (2):
hypothermia and hypoperfusion
Pulse oximetry is noninvasive, easy to use, and risk-free (T/F)
F - ALMOST risk free.
Pulse oximetry works on what pulsation?
Arterial pulsation ONLY.
Pulse Oximetry Premises
- The color of the blood is a function of _________.
- The change in color results from the optical properties of Hb and its interaction with O2.
- The ratio of oxyhemoglobin (HbO2) to hemoglobin (Hb) can be determined by absorption ______________.
O2 saturation;
spectrophotometry
Under what assumption does the pulse oximeter work on? and why is this assumption incorrect?
That Hemoglobin is either bound to O2 or it is not bound to O2.
** it is incorrect because there are other species of Hgb but the pulse ox cannot detect them.
PaO2
Partial pressure of oxygen in arterial blood
SaO2
Fractional saturation of HbO2 in arterial blood
(how much O2 bound in the blood).
SpO2
Functional saturation of HbO2 (approximation of SaO2 measured by pulse oximetry).
CaO2 equation:
(1.34 ∙ Hb ∙ SaO2/100) + (0.003 ∙ PaO2)
what is CaO2? and what are the two parts to its measurement?
Content of arterial O2
- How much oxygen is bound to hemoglobin.
- How much oxygen is dissolved in blood (not bound.)
Hemoglobin normal values: M/F
Males: 14-20 g/dl
Females: 12-15 g/dl
**g/dl means “grams of Hb per 100 ml of blood
Oxyhemoglobin Dissociation Curve shows:
Shows SaO2 (%) as a function of oxygen tension (mmHg)
(measure the pressure of arterial oxygen)
Sigmoid shape on the oxygen dissociation curve models the
greater unloading rate of oxygen to the peripheral tissues (where the PaO2 is low).
What does left shift on Oxyhemoglobin Dissociation Curve represent?
greater affinity of Hb to O2
(Lift it and Leave it attached)
What does right shift on Oxyhemoglobin Dissociation Curve represent?
represents reduced affinity of Hb to O2
(Release it and Reject it)
in Oxyhemoglobin Dissociation Curve neither of the shift are good nor bad (T/F)
T
Oxyhemoglobin Dissociation Curve
Left shift causes:
Causes:
- Low temp
- Low DPG
- Low CO2
- High pH (alkalosis)
Additional causes:
- Carboxyhemoglobin (COHb)
- Methemoglobin (MetHb)
- Fetal Hemoglobin (Why?)
Oxyhemoglobin Dissociation Curve
Right shift causes:
Caused by Increased:
- High Temp
- High DPG
- Exercise (metabolism)
- High CO2
- Low PH
CO2
Acidity (lower pH)
2,3-bisphosphoglycerate (BPG)
Exercise (Metabolism)
Temperature
CADET! Right
Hemoglobin lovesss _______ more than it loves O2.
Carbon monoxide
** this creates a situation where it won’t let O2 go away.
** you cannot use regular SpO2 when this happens.
What effect is this?
What O2 does to CO2
Higher O2 concentrations promote _______ of CO2
Lower O2 concentrations promote ________ of CO2
Haldane effect (Left pull)
unloading;
loading
What effect?
What CO2/H+ do to O2
Higher CO2/H+ concentrations promote ________ of O2
Lower CO2 and H+ concentrations promote ______ of O2
Bohr effect (Right pull)
unloading;
loading
The Physics of Pulse Oximetry
- Provides a noninvasive estimate of SaO2 via physical properties of Hb.
- Analyzes red and near infrared light absorbed through living tissue.
-The photodiodes turn on/off several hundred hertz (times/second) to record flow during pulsatile and nonpulsatile blood flow
Lambert’s law
The amount of light that gets absorbed by the pulse Ox is directly proportional to how long it has to travel.
Less distance to travel through (diameter of artery) = less light will be absorbed.
(More light passes thru)
More absorbed= less light passing thru.
Absorption based on length.
Beer’s Law
The amount of light that gets absorbed by the pulse Ox is directly proportional to concentration of red blood cells.
More concentration = More light absorbed
(Less light passing thru).
Absorption based on concentration.
Lambert-Beer Law (Light Absorbance)
The law relates solute concentration and distance traveled to the intensity of the light transmitted through a solution
uses measurement of attenuation to determine concentrations of various solutes in clear solutions
Spectrophotometry
Assumptions Behind Pulse Oximetry Measurement
- The two and only two light absorbers in human blood are Hb and HbO2.
- All pulsations in light absorbance are caused by fluctuations in the local volume of ARTERIAL blood.
- One empirical, experimental calibration curve (the relationship between the ratio R and SpO2) is valid for the entire human race.
Assumptions Behind Pulse Oximetry Measurement
- The two and only two light absorbers in human blood are Hb and HbO2.
- All pulsations in light absorbance are caused by fluctuations in the local volume of ARTERIAL blood.
- One empirical, experimental calibration curve (the relationship between the ratio R and SpO2) is valid for the entire human race.
Pulse ox detects how much hemoglobin has absorbed red light and how much has absorbed infrared light. Hb species absorbs red and infrared light differently.
HbO2 (oxyhemoglobin) absorbs more _______ light than Hb
Hb (deoxyhemoglobin) absorbs more ________ light than HbO2
infrared;
red
** once it measures those two light assertions it spits out a percentage.
Pulse oximeter performs a __________ analysis to differentiate the pulsatile arterial signal from the non-pulsatile.
plethysmograph
This pulse ox site performs better in conditions of poor perfusion
Ear
** not Mik’s because is clogged haha jk friend <3 - just keep swimming! you got this!
This pulse ox site responds more rapidly to saturation changes than extremity
Nose
Finger pulse ox considerations:
Poor perfusion/vasoconstricted
Nail polish?
Do not place on index finger during recovery ( corneal lesion )
Place on the opposite arm of the BP cuff
The toe pulse ox has a delay in detection of hypoxemia _____ minutes.
Better for what population?
1-2 ;
Neonates/pediatrics
Ways to Improve the SpO2 Signal
Warm the extremity
Protecting the extremity from ambient light
Administering an arterial dilator
Not too tight nor too loose
Not placed properly (on hand or check the cable)
Someone leaning on the pulse ox
in Carboxyhemoglobin (COHb), pulse oximeter interprets the COHb as if it is composed of _______. Given a falsely _______ oxygen saturation.
deoxyhemoglobin (Hb);
high
** it messes up the ratio throughout different scales
** reasons why you cannot measure with regular spo2
in Methemoglobin (MetHb), Iron center is oxidized to ferric +3 state (how is this different from normal?)
Normal is FERROUS +2 state
What is the issue wit Methemoglobin (MetHb) and pulse ox?
The 1:1 absorption ratio is read as 85%
- Messes up the ratios in a steady way
**Falsely underestimates and overestimates SpO2
Pulse Ox limitations
Low blood flow conditions
Movement artifacts
Varying Light Absorbance
Low blood flow conditions :
- hypotension
- hypothermia (causing peripheral vasoconstriction)
- high-dose vasopressors
- cardiopulmonary bypass
Movement artifacts:
- Light anesthesia/ no paralysis
- surgical interference (bobie)
- neuromuscular twitch causing motion artifact
- shivering
Varying Light Absorbance:
- methemoglobinemia
- carboxyhemoglobinemia
- methylene blue/indigo carmine
- nail polish
- ambient light
which Dyes can affect pulse ox reading?
Indigo Carmine
Methylene Blue
Indocyanine Green
__________ dye messes up your pulse ox for 30 seconds and it goes back to normal.
Methylene Blue
Pulse Oximeter Plethysmograph provides:
- Provides a measurement of heart rate
- Crude estimation of blood pressure (dampened wave form in severe hypotension).
- Estimate intravascular volume status and volume responsiveness
Pulse Oximetry as a Tool.
Poor indicator of adequate ventilation
±2% accuracy for SpO2 > ______%
±3% accuracy for _____% < SpO2 < _____%
SpO2 < ________% has no reported accuracy values
70%;
50%—–70%
50%
Movement of gases between the environment and the alveoli
Ventilation
Ventilation can be assessed qualitative by:
- Accomplished with visual inspection of chest rise and fall,
- Condensation of airway water vapor in the endotracheal tube or mask during expiration.
- auscultation
- Cyclic filling and emptying of the reservoir bag or ventilator bellows
- Respiratory rate, pattern and depth
We can adjust our ventilation based on 2 main things
- Volume delivered and respiratory rate.
ways of determining adequacy of ventilation (3)
Airway pressures,
Tidal volume
Capnography (EtCO2) - goldstandard
There are two types of gas sampling systems:
Which one is the one most commonly used?
- Diverting (Sidestream) ** most common
-Non-dirverting (mainstream)
How does a diverting (sidestream) - gas sampling system work?
Extracts gas from the sampling tubing attached near the patient end of the circuit and pumps it to the monitor,
Traps are used to avoid water and particulate contamination
If water droplets enter the tube in a diverting system it can:
increase resistance in the tubing, affecting accuracy
***Accuracy is lower with long tubing and small breaths (neonates)
Diverting (Sidestream) is continually sampling gas for analysis of _______ ml/min
150-200
**High flow will entrain fresh gas flow into the sampling line
Non-diverting (Mainstream) are mainly seen in the
Mapleson systems.
Non-diverting (Mainstream)
Measures gas by a sensor located in the gas stream
Special airway adapter between the breathing circuit and ETT
Advantages:
Fast response time-breath by breath
No scavenging necessary because gas is not removed from the system
Disadvantages:
Greater risk of interference by condensation and secretions
Facial burns with old monitors
Difficult to use in unusual positions
(he doesn’t really care for this one.
Diverting (Sidestream) gas sampling; advantages and disadvantages:
Advantages:
- Automatic calibration
- Minimal increase in dead space
- Can measure several gases
- The sampling port can be used to administer bronchodilators - albuterol (causes other issues).
Disadvantages:
- Leaks, kinking and clogging
- Scavenging system needed
- There is some delay
- Variable difference between the arterial and EtCO2 levels
- Rapid breathing
Which gas sample line has a time lag for the gas samples to reach the analyzer (transit time) and a Rise Time for the analyzer to react to the change in gas concentration = Total response time.
Diverting (Sidestream) gas sampling
Other gases are analyzed the same way as O2. (T/F)
False- O2 has its own analyzers (electrochemical; paramagnetic etc).
Gas Analysis Technology:
Contemporary respiratory multiple gas analyzers use some form of ______________ to measure carbon dioxide, nitrous oxide, and the potent inhaled anesthetic agents.
Infrared (IR) spectroscopy
** Most common today is Infrared Absorption Analysis or Spectrophotometry (IRAS)
Other types of Gas Analysis technology:
Piezoelectric absorption
Mass Spectrometry and Raman Spectroscopy
pressure applied to a piezoelectric material will generate a voltage.
Older and not really in use.
Infrared (IR) spectroscopy analyzers CANNOT measure ___________.
elemental molecules (O2, N2…)
** because they are nonpolar, symmetrical : so it doesn’t have dipole moment changes.
measure partial pressure of exhaled gas but give us a concentration
Infrared (IR) Analysis
** Measurement of energy absorbed from a narrow band of wavelengths of IR radiation as it passes through a gas sample
Infrared (IR) Analyzers two types
Dispersive and Non-dispersive
The infrared (IR) analysis has different wavelengths between ________ and ________ ( each agent absorbs a different wavelength of IR radiation, each with a “signature fingerprint”).
0.40 mcirometers and 40 micrometers.
The infrared (IR) analysis measures concentrations of CO2, N2O, and inhaled anesthetics since they are (3).
asymmetric,
polyatomic,
polar
**They absorb IR energy when their atoms rotate or vibrate asymmetrically
** Results in a change in DIPOLE moment (charge distribution) within the molecule
Non-Dispersive IR Analyzer has how many beams?
A single beam:
** all gases get thrown into a single beam and then give a reading
infrared (IR) analyzer advantages:
- Can measure multiple gases
*** CO2, N2O and all IA (inhaled anesthetics) - Can detect a mixture of agents
- Can be incorporated into the anesthesia machine
- Quick response time
- Short warm up time
- Convenience- periodic calibration
infrared (IR) analyzer disadvantages:
- Cannot measure O2 and N2 (why do you think?)
- Since O2 is not absorbed by IR radiation it can interfere with CO2 readings
- Interference with water vapor
- It absorbs light
- Can be inaccurate with high respiratory rates (stacking)
SINGLE OPTICAL FILTER, PRISM , or diffraction to separate the component wavelengths for each agent
After passing through the gas sample, the radiation emitted by an IR source is separated, or dispersed, into the component wavelengths and arranged sequentially.
Dispersive IR analyzers
Multiple narrow-band optical filters
Radiation from the IR source is filtered to allow passage of only the specific wavelength bands, for which the gases of interest have distinct absorption peaks
Nondispersive IR analyzers
*IR analyzers used clinically are predominantly of the nondispersive type
- he said this one is a single beam.
Carbon dioxide analysis can be broken down into 2 components:
Capnometry: the numbers
Capnography: the curves/shape
this measurement is the gold standard of ETT placement and verification
End tidal CO2
EtCO2 level is usually lower than PaCO2 by ________ mmHg
2-5
** because of dead space
Arterial CO2 (PaCO2) - normal values
ETCO2 - normal values
PaCO2: 35- 45 mmHg
ETCO2: 30 - 43 mmHg ( he said he normally “wants it at 35 - goo number to remember).
Capnogram Phases
Phase 0
Phase I
Phase II
Phase III
Phase IV ** not always present
Capnogram
Phase 0 is the inspiration segment (once the patient starts to breath there should be a dramatic drop to zero), almost zero CO2. What happens if it’s above zero and what could be the causes?
**if above zero= rebreathing)
Issues: incompetent expiratory unidirectional valve, exhausted CO2 absorber, channeling, gas calibration issues, rapid RR and small tidal volumes in children
Capnogram
Phase I is:
Beginning of expiration: expelling of CO2-free gas and exhalation of anatomic dead space, 1/3 Vt)
** remember there is a lag time in curve until the machine detects CO2
Capnogram
Phase II is:
Expiratory upstroke:
Should be steep
Slanted if exhaled gas is partially obstructed (kinked tube, COPD, bronchospasm)
Capnogram
Phase III is:
Exhalation continues, slight increased upstroke (why?))
** in healthy patients it becomes steady once it reaches peak - CO2 from lungs has been exhaled completely - (when you drop a breath in patient’s lungs the flows are not completely steady) - flows slow down overtime - CO2 still escapes little by little - which is why you see a tiny slant.
(He said this - hope it makes sense)
Capnogram
Phase IV is:
not always present. It’s the terminal upswing, after alveolar plateau.
** it occurs when the alveolus sort of contracts at the very end and expels CO2 a little bit more - most likely won’t be seen. Won’t affect anesthetics.
In the capnogram phases; a very steep phase III usually means:
Obstruction
** COPD
Capnogram Alpha Angles
Separated by :
Changes correlate with:
Angle is greater than 90 degrees with:
phase II and III
emptying the alveoli and V/Q mismatch
V/Q mismatch (Obstruction, main stem intubation, COPD etc)
Capnogram Beta Angles
Where is it:
Normally how many degrees:
Represents the :
Increases in Beta angle mean:
Downstroke that follows phase III
90 degrees
Inspiratory phase
Malfunctioning inspiratory unidirectional valve, rebreathing, low tidal volumes with rapid respiratory rate.
The ETCO2 monitoring will give you a number at the very end of phase ____.
Phase 3
Analyzing CO2 Waveform
Height
Higher = increasing CO2
Shape
Frequency
More frequent = increased RR
Rhythm
Baseline
Should return each time to zero
If not: Recalibrate, rebreathing CO2, retaining CO2 Change absorber, check expiratory valve
Factors that may increase ETCO2:
increases in metabolic rate:
- hyperthermia
- sepsis
- malignant hyperthermia
- shivering
- hyperthyroidism
changes in CO2 elimination:
- hypoventilation
- rebreathing
Factors that may decrease ETCO2
Decreases in metabolic rate:
- hypothermia
- hypothyroidism
changes in CO2 elimination:
- hyperventilation
- hypoperfusion
-pulmonary embolism
Things that happen with Hypocarbia:
- Respiratory alkalosis
- Decreased CBF
-Decreased pulmonary vascular resistance - Potassium from serum to intracellular
