Basic Intraoperative Monitoring Flashcards
1
Q
What does early intervention lead to?
A
Improved outcomes
2
Q
What does the data collected by the anesthetic provider reflect?
A
Physiologic homeostasis
Response to therapeutic interventions
Proper functioning of anesthetic equipment
3
Q
What year did the AANA produce standards of care that CRNAs should adhere to?
A
1974 which it has evolved and revised over time
4
Q
What year did Harvard produce guidelines for anesthesiologists?
A
1986, ASA closely mirrors those produced by the AANA
5
Q
What year did the AANA revise the standards to include the scope of practice as well?
A
1983
6
Q
What standard determines how a patient should be monitored by an anesthesia provider?
A
Standard V, monitor the patient’s physiologic condition as appropriate for the type of anesthesia and specific patient needs
7
Q
What are the five monitors required by Standard V?
A
Monitor ventilation continuously
Monitor cardiovascular status continuously
Monitor body temperature continuously
Monitor neuromuscular function continuously
Monitor and assess patient positioning
8
Q
What two factors are the basis of safe anesthetic care?
A
Continous clinical observation and vigilance
9
Q
A state of clinical awareness whereby dangerous conditions are anticipated or recognized and promptly corrected
A
Vigilance in Anesthesia
10
Q
What is the anesthetic provider continually monitoring?
A
Patient’s medical status
Effects of anesthesia
Effects of surgical intervention
11
Q
What is the most important monitor?
A
The vigilant anesthetist
12
Q
What are the AANA standard for monitoring?
A
Oxygenation/ventilation Circulation Body temperature Neuromuscular function Qualified Anesthetist Present
13
Q
How should oxygenation be measured?
A
Clinical observation, pulse oximetry and if indicated arterial blood gas analysis
14
Q
How should we verify intubation of the trachea?
A
Auscultation, chest excursion and confirmation of carbon dioxide in the expired gas
15
Q
What should be used to measure ventilation?
A
Continuous monitoring of end tidal CO2 during controlled or assisted ventilation. Spirometry and ventilatory pressure monitors as indicated
16
Q
What is the fundamental goal of the anesthetic provider?
A
Avoidance of hypoxia (airway, airway airway)
17
Q
What should the anesthetic provider be assessing for adequate oxygenation?
A
Oxygen analyzer Pulse oximetry Skin color Color of blood ABG (when indicated)
18
Q
What measures the pipeline gas to ensure O2 is truly being administered?
A
Oxygen analyzer
19
Q
Where is the O2 analyzer located?
A
Inspiratory limb
20
Q
When will the O2 analyzer notify the provider of low O2 concentrations?
A
< 30% low concentration alarm
21
Q
What two values should the O2 analyzer be calibrated to every day with the AGM check?
A
Room air and 100%
22
Q
What is the Alveolar gas equations?
A
PAO2 = FiO2 x (Pb-47) - PaCO2
23
Q
In the alveolar gas equation, if you do not have PaCO2 what value can be substituted?
A
End tidal CO2 can be substituted
24
Q
What type of sensor is the O2 analyzer?
A
Electrochemical sensor
25
What is the structure of the electrochemical sensor of the O2 analyzer?
Cathode and anode embedded in electrolyte gel separated from gas by an oxygen permeable membrane
26
How does the electrochemical sensor in the O2 analyzer function?
O2 reacts with electrodes, generates electrical signal proportional to O2 pressure (mmHg) in sample gas
27
What is the standard of care for continuous non-invasive monitoring of oxygenation?
Pulse oximetry
28
What is a late sign of hypoxemia?
Cyanosis
29
When was the pulse oximeter introduced to anesthetic practice?
1987
30
What two principles are combined to explain the use of a pulse oximeter?
Oximetry & plethysmography
31
What is required in order to use a pulse oximeter?
Pulsatile arterial bed, a blood pressure must be present
32
What does plethysmography measure?
pulsatile measurement
33
What are some common sites to place a pulse oximeter?
Finger, toe, ear lobe, bridge of nose, palm and foot (especially in children)
34
What is the pulse oximeter continuously measuring?
Measurement of pulse rate and oxygen saturation of peripheral hemoglobin (SpO2)
35
What law dictate how a pulse oximeter works?
Lambert-Beer law of spectrophotometry
36
At what wavelength does HbO2 absorb light?
960nm (more infrared)
37
What does the Lambert-Beer Law of spectrophotometry measure?
Oxygenated and reduced Hgb differ in their absorption of red and infrared light
38
What is being compared in order to calculate an accurate SpO2 reading?
Comparison of absorbances of the wavelengths enables oximeter to calculate O2 saturation (ratio of infrared and red transmitted to a photodetector)
39
At what wavelength does reduced Hgb absorb more light?
660nm (more red)
40
What is the primary mechanism of action of the pulse oximeter?
Therefore, the basis of oximetry is change in light absorption during arterial pulsations
41
What does a patient's Hgb have to be in order for a pulse oximeter to be functional?
>5
42
What IV medication causes a large decrease in SpO2 while using a pulse oximeter?
Methylene blue
43
What are two other types of hemoglobins that could affect the pulse oximeter?
COHb (falsely increased)
| MetHb (could be increased or decreased)
44
What is the correlation between SpO2 and PaO2?
40 50 60 PaO2
| 70 80 90 SpO2
45
Where should the precordial stethoscope be placed?
Suprasternal notch or apex left lung
46
What is the purpose of the precordial stethoscope?
Easily detects changes in breathe sounds or heart sounds
Circuit disconnect
Endobronchial intubation
47
What can be heard on the precordial stethoscope as anesthesia lightens?
Louder heart sounds from increased rate and contractility
48
What population can only use an esophageal stethoscope?
Limited to intubated patients
49
Where should the esophageal stethoscope be placed?
Distal 1/3 of esophagus
50
What are the advantage of an esophageal stethoscope compared to a precordial stethoscope?
Better quality heart and breath sounds and incorporates a temperature probe
51
How much CO2 does the average adult produce?
250mL CO2/min
52
What changes can affect a patient's CO2 production?
Patient's condition
Anesthetic depth (deeper decreases metabolism)
Temperature (colder decreases CO2 production)
53
What is the purpose of Capnography?
Confirms ETT placement
| Confirms adequate ventilation
54
What is the most common type of capnography and how does it work?
Sidestream sampling, airway gas aspirated and pumped to measuring device
55
What are the sampling flow rate?
50-250mL/min pulled from circuit (be aware in peds patients)
56
What are some limitations to sidestream capnography?
H2O condensation can contaminate the system and falsely elevate readings
Lag time between sample aspiration and reading
57
How might an attached capnography affects a machine check?
May fail a machine check if sidestream sampling line attached, specifically the pressure check
58
What could a problem be if CO2 is detected on inspiration?
Incompetent inspiratory valve
59
What is the normal PACO2-PaCO2 gradient?
2-10mmHg
60
What does phase I on a capnograph represent?
Corresponds to inspiration, anatomic/apparatus dead space devoid of CO2
61
What should the phase I level be at?
Should be zero unless rebreathing
62
What would cause baseline elevation on a capnograph?
CO2 absorbant exhausted
Expiratory valve missing/incompetent
Bain circuit
63
What does phase II of a capnograph represent?
Early exhalation/steep upstroke, mixing of dead space with alveolar gas
64
What would cause a prolonged upstroke of phase II on a capnograph?
```
Mechanical obstruction (kinked ETT)
Slow emptying of lungs (COPD and bronchospasm)
```
65
What does phase III on the capnograph represent?
CO2 rich alveolar air, horizontal with mild upslope
66
Why would phase III on a capnograph be steep?
Steepness is a function of expiratory resistance
COPD
Bronchospasm
67
What does phase IV on a capnograph represent?
Inspiration of fresh gas, return to baseline (near 0)
68
What might a low plateau on a capnogram represent?
Excessive ventilation
Low CO2 production
Diminished CO2
Significant dead space
69
What might a high plateau on a capnogram represent?
Hypoventilation
| High CO2 production (MH)
70
What might a flat plateau with wide dips represent on a capnogram?
Less TV are superimposed on normal or mechanically timed exhalations, common when NMBA begin to wear off
71
What might small dips at the end of a flat plateau that is synchronous with the heart represent on a capnogram?
Cardiac oscillations from hypovolemia
72
What type of technology does an anesthetic gas analyzer utilize?
Mass spectrometry
73
How does mass spectrometry work?
Gas sample is ionized by electron beam and passed through a magnetic field, ions then identified by own unique trajectory across magnetic field
74
What airway pressures are measure by the ventilator?
In-circuit pressure gauge
Peak inspiratory pressure
Sustained elevated pressure
75
What alarm on the ventilator would notify the provider that there has been a disconnect somewhere in the circuit?
Low airway pressure
76
What is the circulation guideline regarding standard V in the AANA monitoring guidelines?
Monitor cardiovascular status continuously via EKG and hear sounds. Record BP and heart rate at least every 5 minutes
77
What could continuous EKG monitoring detect during anesthesia?
```
Cardiac dysrhythmias
Conduction abnormalities
Myocardial ischemia/ ST depression
Electrolyte changes
Pacemaker function/malfunction
```
78
What lead is typically monitored in a three electrode approach?
Lead II
79
What leads are typically monitored in a five electrode approach?
Six standard limb leads (I,II, III, aVR, aVL and aVF) and one precordial lead (usually V5)
80
Why would we use five electrodes versus three electrodes?
Better at detecting myocardial ischemia
| Allows better differential diagnosis of atrial and ventricular dysrhythmias
81
What are the two most commonly used leads monitored?
Lead II and V5
82
What does lead II specifically monitor?
Yields max P wave voltages
Superior detection of atrial dysrhythmias
Detects inferior wall ischemia/ST depression
83
What does V5 specifically monitor?
5th ICS/anterior axillary line
| Detection of anterior and lateral wall ischemia
84
What is the appropriate size of a blood pressure cuff?
The width must be 20% greater than the mean diameter of extremity
85
How can blood pressure cuff size affect the reading?
Too narrow increases pressure
| Too wide decreases pressure
86
What is the standard way to measure arterial blood pressure?
Korotkoff sounds
87
What is the most commonly used method to measure blood pressure during anesthesia?
Automated indirect NIBPM
88
What are the advantages to using a NIBPM?
Easy and accurate
Versatile in children and obese
May be used on thigh or calf
oscillometry
89
How does a oscillometric device work?
Air pumping inflates cuff --> microprocessor
| Opens deflation valve --> oscillations sampled
90
At what measurement does oscillometric devices become less reliable?
When BP falls below 70
91
What is a major benefit to using oscillometric devices intraoperatively?
Their use has reduced the incidence of undetected HoTN intraoperatively
92
What type of errors can occur with the use of oscillometric BP devices?
Surgeon leaning on cuff
Inappropriate cuff size
Shivering/excessive movement
Atherosclerosis and HTN
93
What are some indications for invasive arterial BP monitoring?
Patient requiring BP more often than minute to minute
Critically ill
Anticipated rapid blood loss
Major procedures (cardiac, intracranial, carotid sinus)
Frequent ABGs
94
Where is the most common site for arterial line placement?
Radial artery
95
Why isn't the ulnar artery typically used?
More difficult and more tortuous
96
Why isn't the brachial artery a good choice for an arterial line?
Complications may risk limb and its predisposed to kinking
97
What arterial line location will more than likely cause a distorted wave form?
Dorsalis pedis
98
Why isn't the axillary artery a desirable location for an arterial line?
Potential for plexus/nerve damage from hematoma or traumatic cannulation
99
What are some indication for central line placement?
Fluid management of hypovolemia and shock
Infusion of caustic drugs
Aspiration of air emboli
Insertion of pacing leads
TPN
Venous access in patient with poor peripheral veins
100
What side is preferred for internal jugular line placement?
Right side
101
Why isn't an external jugular line ideal?
More difficult to place leading to complications
102
What are some comorbidities that may require a pulmonary artery catheter?
```
Valvular heart disease
Recent MI
ARDS
Massive trauma
Major vascular surgery
```
103
Why has the pulmonary artery catheter lost favor?
TEE less invasive
104
What does standard V of AANA monitoring guidelines require of body temperature monitoring?
Monitor body temperature continuously on ALL pediatric patients receiving general anesthesia and when indicated on all other patients
105
What factors affect body temperature?
Ambient room temperature
Scope and length of surgery (abdominal surgeries)
Hypothalamic depression
Intraoperative fluid replacement
106
What are the four mechanisms of heat loss in the OR?
Evaporation
Convection
Conduction
Radiation
107
How much does body temperature decrease when one liter of crystalloid is given at room temperature?
70kg patient's temp is decreased by 0.4C for every liter of fluid given at room temperature
108
What mechanism looses the most heat in the OR?
Radiation about 40%
109
What type of heat loss occurs because of air velocity, OR air exchanges?
Convection about 30% heat loss
110
What type of heat loss occurs because of contact with OR table and can be prevented with the use of blankets?
Conduction
111
What type of heat loss occurs because of dry inspired gases?
Evaporation
112
What structure maintains body temperature within a tight range?
Hypothalamus
113
How does phase I affect thermoregulation?
Convective loss
| Vasodilation causes redistribution of blood and temperature
114
How does phase II affect thermoregulation?
Altered perception of dermatomes in areas anesthetized
115
What can be done to prevent the convective losses that occurs in stage I of anesthesia?
Pre warm the patient for 30 minutes with warming blanket
116
When does hypothermia occur?
When environmental heat loss outpaces metabolic heat production
117
How much can anesthesia decrease body temperature?
1-4°C
118
How does hypothermia affect wake up and oxygen demand?
May delay awakening
| Can cause shivering which can increase O2 needs by 400%
119
What patient populations are at the greatest risk for hypothermia?
Elderly
Burn patients
Neonates
Patients with spinal cord injuries
120
What is considered hypothermia?
Temperature < 36°C
121
What is considered mild hypothermia and what type of effects does it have on the body?
Mild 33-36°C
Reduced enzyme function
Coagulopathy
122
What is considered moderate hypothermia and what type of effects does it have on the body?
Moderate < 32°C
| Fibrillatory threshold
123
When does hyperthermia occur during anesthesia?
```
Rarely develops
LATE sign of MH
Endogenous pyrogens
Thyrotoxicosis
Anticholinergic blockade
Excessive environmental warming
```
124
Where is the proper location for esophageal temperature monitoring?
Lower 1/3 of esophagus
125
What mode of temperature monitoring is rarely used due to effect of perforation?
Tympanic membrane
126
What are some superficial methods of warming patients?
Forced air warmer --> Most effective
Warming blanket
Radiant heat unit --> no role in OR doesn't effect mean body temperature
Heated liquids --> burns
127
What methods of warming are used for warming the core of the patient?
IVF warmers (Hotline)
Gastric lavage
Peritoneal irrigation
128
What are some passive warming modalities?
Ambient temperature
Insulation
Heat and moisture exchanger (artificial nose)
Coaxial breathing circuit --> modified baine circuit
129
At what ambient temperature of the OR will most adults remain normothermic?
>24°C
130
What does Standard V of the AANA monitoring guidelines state regarding neuromuscular function?
Monitor neuromuscular function and status when neuromuscular blocking agents are administered
131
What do we use to monitor neuromuscular function?
Peripheral nerve stimulator, monitors the status of neuromuscular junction when using NMBAs
132
How does a peripheral nerve stimulator work and what are its functions?
Delivers electrical stimulation to a peripheral motor nerve mechanically evoking a response
Permits titration of drug to optimal effect
Quantifies recovery from NMBA
133
What occurs if a peripheral nerve stimulator is placed on a sensory nerve?
It will not evoke a response
134
In what order does the onset sequence of NMBA affect the body?
```
Eyes
Extremities
Chest
Abdominal muscles
Diaphragm
```
135
What is the first muscle to recover from NMBA and why?
The diaphragm is extremely rich with nicotinic receptors, it is the first muscle to recover function (will see a small cleft in the end tidal pleth)
136
What sites can be used to monitor neuromuscular blockade?
Ulnar nerve
Facial nerve
Posterior tibial nerve
Peroneal nerve
137
What does the ulnar nerve innervate and where should the electrodes be placed?
Adductor pollicis muscle, electrodes can be placed at the wrist or the elbow
138
How should the electrodes be placed on the nerve?
Negative (depolarizing) placed distally
139
Why isn't the ulnar nerve an accurate reflection of degree of block of the diaphragm or airway muscles?
These muscles are less sensitive to ND block
| Adductor policies still paralyzed but can have coughing, breathing and vocal cord movement
140
Where should the electrodes be placed when monitoring the facial nerve?
In front of the tragus of the ear and below while avoiding direct muscle stimulation
141
What muscle is contracting when we stimulate the facial nerve?
Orbicularis oculi, can feel twitches by placing hand over the eye brow
142
What gland does the facial nerve innervate?
Parotid gland
143
What nerve is the best indicator of ND blockade of the diaphragm and airway muscles?
Facial nerve
144
Where should you place the electrodes for posterior tibial nerve stimulation?
Place electrodes behind medial malleolus of tibia
145
What movements should result from posterior tibial nerve stimulation?
Plantar flexion
146
Where should yo place the electrodes for peroneal nerve stimulation?
Place electrodes on the lateral aspect of the knee
147
What movements should result from peroneal nerve stimulation?
Dorsiflexion of the foot
148
What are the five types of peripheral nerve stimulation?
```
Single twitch
Train of four
Tetanic stimulation
Post-tetanic stimulation
Double burst stimulation
```
149
Define what occurs during a single twitch stimulation.
Single pulse delivered every 10 seconds, increasing block results in diminished response
150
What is the most commonly used nerve stimulating setting in anesthesia?
Train of four
151
Define what occurs during train of four stimulation.
Four repetitive stimuli, ratio of responses to 1st and 4th twitches are sensitive indicator of ND relaxation
152
How many receptors are block with each loss of twitch?
Loss of 4th twitch = 75% receptors blocked
Loss of 3rd twitch = 80% receptor blocked
Loss of 2nd twitch = 90% receptors blocked
153
What is considered clinical relaxation?
75-95% block
154
What will you see on a TOF with a non-depolarizing NMBA?
Fade with each twitch
155
What other scenario might you see the same results in theTOF as non-depolarizing NMBA?
Phase II block from Succs
156
What will you see on a TOF with a depolarizing NMBA?
Same height just diminishes over time
157
Define what occurs during tetanic stimulation?
Tetany at 50-100Hz, five seconds at 50 Hz evoked tension approximates tension developed during maximal voluntary effort
158
What occurs with tetanic stimulation in the presence of ND relaxants?
Fade occurs
159
When will a sustained response occur in tetanic stimulation?
When TOF > 70%
160
What type of peripheral nerve stimulation is useful when all twitches are suppressed?
Post-tetanic count
161
Define what occurs in Post-tetanic count?
Apply tetanus at 50 Hz for 5 seconds, wait 3 seconds, apply single twitches every second up to 20
162
What does the number of twitches tell you when using post-tetanic count?
The number of twitches is inversely related to the depth of block
163
Define what occurs in double burst stimulation.
There are three short 50 Hz impulses followed by 750 sec by another 3 bursts
164
Why might you use double burst stimulation over train of four for monitoring twitches?
More sensitive that TOF for visual evaluation of fade
165
What two methods of peripheral nerve stimulation are appropriate to use during induction of anesthesia?
Single twitch
| Train of four
166
What two methods of peripheral nerve stimulation are appropriate to use during maintenance of anesthesia?
Train of four
| Post tetanic count
167
What two methods of peripheral nerve stimulation are appropriate to use during emergence of anesthesia?
Train of four
| Double burst stimulation
168
What do the NM monitoring guidelines state for which nerve to monitor during induction and emergence?
Monitor facial nerve for onset and ulnar nerve for recovery
169
How long might recovery take if you only have 1/4 twitches?
As long as 30 minutes
170
How long might recovery take if you only have 2-3 twitches?
Reversal may take 10-12 minutes following long acting relaxants and 4-5 minutes after intermediate
171
How long might recovery take if you only have 4/4 twitches?
Adequate recovery within 5 minutes of neostigmine and 2-3 minutes with edrophonium
172
What is the Bispectral index score tool utilized for during anesthesia?
Used to assess depth of anesthesia, however, not currently standard of care
173
What are some reported advantage of BIS monitoring?
Reduced risk of awareness
Better management of responses to surgical stimulation
Faster wake up (controversial)
Most cost effective use of anesthetics
174
What does the BIS measure?
EEG signal with index ranging from 0-100
0 = isoelectric
100 = awake CNS
175
What things in the OR can effect the reading of the BIS monitor?
```
Electro-cautery
EMG
Pacer spikes
EKG signal
Patient movement
```
176
What BIS number is associated with increased risk of recall?
>70
177
What BIS number is the level suggested for anesthesia?
40-60
