Basic Intraoperative Monitoring Flashcards
(119 cards)
1
Q
Which standard states that the CRNA must monitor the patient’s physiologic condition as appropriate for the type of anesthesia and specific patient needs?
A
Standard V
2
Q
What are the 5 components of monitoring stated in Standard V?
A
Monitor ventilation continuously
Monitor cardiovascular status continuously
Monitor body temperature continuously
Monitor neuromuscular function continuously
Monitor and assess patient positioning
3
Q
When did the AANA create standards of monitoring for the CRNA?
A
1974
4
Q
What does vigilance mean in anesthesia?
A
a state of clinical awareness whereby dangerous conditions are anticipated or recognized and promptly corrected
5
Q
What is the most important monitor in anesthesia?
A
the vigilant anesthetist
6
Q
What is the fundamental goal of ventilation and oxygenation?
A
avoidance of hypoxia
7
Q
How can we determine if the patient has optimal oxygenation?
A
Oxygen analyzer Pulse oximetry Skin color Color of blood ABG (when indicated)
8
Q
Where does the oxygen analyzer work?
A
Measures inspired gas on the inspiratory limb of the circuit, determines if pipeline is truly O2
9
Q
When does the oxygen analyzer alarm?
A
Should alarm of concentration <30%
10
Q
At what oxygen percentages do you calibrate the oxygen analyzer?
A
21% and 100%
11
Q
Is the oxygen analyzer required for any general anesthetic?
A
Yes
12
Q
What is the O2 percentage on the O2 analyzer useful for calculating?
A
PaO2
Alveolar gas equation: PAO2 = FiO2 x (BP - 47) - PaO2
13
Q
What type of sensor is the oxygen analyzer and how does it work?
A
- electrochemical
- has cathode and anode embedded in electrolyte gel separated from gas by O2-permeable membrane
- O2 reacts with electrodes and generates electrical signal proportional to O2 pressure (mmHg) in sample gas
14
Q
Which component of oxygenation monitoring provides early warning of hypoxia?
A
pulse oximetry
15
Q
How does the pulse oximeter work?
A
- measures arterial oxygen saturation combining principles of oximetry and plethysmography (pulsatile measurement)
- requires pulsatile arterial bed
- continuous measurement of pulse rate and oxygen saturation of peripheral hemoglobin (SpO2)
- produces SpO2 measurement by changes in light absorption during arterial pulsations
16
Q
Which law applies to pulse oximetry?
A
Beer-Lambert Law of spectrophotometry, oxygenated and reduced Hgb differ in their absorption of red and infrared light; comparison of absorbances of these wavelengths enables oximeter to calculate O2 saturation (ratio of infrared and red transmitted to a photodetector)
17
Q
At what wavelength does HgbO2 (saturated Hgb) absorb infrared light?
A
960 nm
18
Q
At what wavelength does Hgb (unsaturated) absorb red light?
A
660 nm
19
Q
What are factors that can affect the accuracy of the pulse oximeter?
A
- high intensity light
- patient movement
- electrocautery
- peripheral vasoconstriction
- hypothermia
- cardiopulmonary bypass (no pulsatile bed)
- presence of other Hgbs (COHgb or MetHgb)
- IV injected dyes (dec. with methylene blue)
- Hgb < 5 (will not register)
20
Q
What is the rule of thumb for estimating PaO2 from pulse oximeter percentages?
A
PaO2 30 = SaO2 60
PaO2 60 = SaO2 90
PaO2 40 = SaO2 75
(30 is 60…60 is 90…45 is 75)
21
Q
What are different ways to monitor ventilation?
A
- Continuous auscultation
- Observation of chest excursion
- End-tidal capnography
- Spirometry
22
Q
What is the purpose of the precordial stethoscope?
A
Easily detect changes in breath sounds or heart sounds; ability to quickly detect airway/circuit disconnect, endobronchial intubation, and anesthetic depth (increased heart rate or contractility means decreased anesthetic depth)
23
Q
Where do you listen with the precordial stethoscope?
A
suprasternal notch or apex of left lung
24
Q
What is the purpose of the esophageal stethoscope?
A
Allows better quality heart and breath sounds with incorporated temperature probe
25
What must a patient have in order to use an esophageal stethoscope?
ETT
26
Where is correct placement of the esophageal stethoscope?
distal 1/3 of esophagus
27
What are some of the primary principles of capnography?
- confirms ETT placement
- Confirms adequate ventilation
- average adult produces 250 mL CO2/min that changes with patient's condition, anesthetic depth, and temperature
28
How does capnography work?
Uses sidestream sampling (most common) and aspirates airway gas and pumps it through measuring device
29
What are the sampling flow rates of capnography?
50-250 mL/min
30
What are some limitations of capnography?
- H2O condensation can contaminate the system and falsely increase readings
- lag time between sample aspiration and reading
31
What is the normal PACO2 - PaCO2 gradient?
2-10 mmHg
32
What are some causes for an abnormal PACO2 - PaCO2 gradient?
- gas sampling errors
- prolonged expiratory phase
- VQ mismatch
- airway obstruction
- embolic states
- COPD
- hypoperfusion
33
What does phase 1 of the capnograph correspond to?
- inspiration
| - at baseline (should be 0 unless rebreathing) and indicates anatomic/apparatus dead space devoid of CO2
34
When would the baseline be elevated on capnography?
- CO2 absorbent exhausted
- Expiratory valve incompetent/missing
- Bain circuit
35
What does phase 2 of the capnograph correspond to?
- early exhalation, steep upstroke
| - mixing of dead-space with alveolar gas
36
What does a prolonged upstroke of phase 2 indicate on a capnograph?
- mechanical obstruction, kinked ETT
| - slow emptying of lungs due to COPD or bronchospasm
37
What does phase 3 of the capnograph correspond to?
- horizontal plateau with mild upslope
- CO2 rich alveolar air
- steepness is function of expiratory resistance (COPD or bronchospasm)
38
What does phase 4 of the capnograph correspond to?
Steep decline, inspiration of fresh gas, return to baseline
39
What is the purpose of the anesthetic gas analysis?
Measures volatile agents
40
How does the anesthetic gas analysis work?
Obtains sample with sidestream sampling, uses mass spectrometry to ionize gas sample by electron beam and pass it through magnetic field; ions are then identified by own unique trajectory across magnetic field
41
What are different alarms on the ventilator that alert you to inadequate ventilation?
- tidal volume (integrated spirometry)
- airway pressure (in-circuit pressure gauge, peak inspiratory pressure, sustained elevated pressure)
- disconnect alarm (low airway pressure)
42
How can you monitor adequate circulation/cardiovascular status?
- BP
- HR
- EKG
- heart sounds
43
What abnormalities can an EKG detect?
- cardiac dysrhythmias
- conduction abnormalities
- MI / ST depression
- electrolyte changes
- pacemaker function/malfunction
44
What lead do we typically monitor in a three lead EKG?
Lead II
45
What is a disadvantage of monitoring a three-electrode EKG?
limited in detection of MI
46
What leads does a five electrode EKG monitor?
Six standard limb leads (I, II, III, aVR, aVL, aVF) and one precordial lead (usually V5)
47
What are some advantages of using a five electrode EKG monitor?
- Better in detecting myocardial ischemia
| - Allows better differential diagnosis of atrial and ventricular dysrhythmias
48
What are the 2 most commonly used EKG leads?
Lead II and V5
49
Why is lead II a commonly monitored lead?
- Yields max P wave voltages
- Superior detection of atrial dysrhythmias
- Detects inferior wall ischemia/ST depression
50
Why is lead V5 a commonly monitored lead?
- 5th ICS/anterior axillary line
| - Allows detection of anterior and lateral wall ischemia
51
What are some advantages of automated indirect blood pressure monitoring (NIBPM)?
- easy and accurate
- versatile in children and obese
- may be used on calf or thigh
52
How does noninvasive arterial blood pressure monitoring work?
Is oscillometric device that uses air pump (microprocessor) to inflate cuff and then deflation valve opens to sample oscillations
53
What can cause errors in oscillometric blood pressure monitoring?
- surgeon leaning on cuff
- inappropriate cuff size (small cuff --> high reading; large cuff --> low reading)
- shivering/excessive motion
- atherosclerosis and HTN (systolic low; diastolic high compared with invasive arterial pressure)
54
What are some indications for invasive arterial BP monitoring?
- any patient requiring BP measurement more frequently than minute to minute
- critically ill
- anticipated rapid blood loss
- major procedures (cardiopulmonary bypass, aortic cross-clamping, intracranial surgery, carotid sinus manipulation)
- frequent ABG sampling
55
Where are possible sites for arterial lines?
- radial artery (most common)
- ulnar artery (not often used, could compromise circulation in hand, technically more difficult)
- brachial artery (complications may risk limb, predisposed to kinking/location)
- femoral artery (prone to pseudoaneurysm and atheroma formation)
- dorsalis pedis (may have distorted waveform)
- axillary artery (potential for plexus/nerve damage from hematoma or traumatic cannulation)
56
What are some indications for CVP monitoring?
- fluid management of hypovolemia and shock
- infusion of caustic drugs
- aspiration of air emboli
- insertion of pacing leads
- TPN
- venous access in patients with poor peripheral veins
57
Where are possible sites for CVP monitoring?
- internal jugular (right preferred)
- subclavian
- external jugular
- antecubital (requires special kit with long catheter)
58
What are some indications for a PA cath?
- poor LV function (EF < 2L/min)
- valvular heart disease
- recent MI
- ARDS
- massive trauma
- major vascular surgery
- evaluate response to fluid administration, vasopressors, vasodilators, inotropes
59
What are some factors affecting temperature?
```
Ambient room temperature
Scope and length of surgery
Hypothalamic depression
Intraoperative fluid replacement (not warming fluids)
Vigiliance in maintaining core temp
```
60
What are the 4 mechanisms of heat loss?
Convection, conduction, radiation, evaporation
61
What is radiation heat loss?
heat radiated from patient into room
62
What is convection heat loss?
Heat loss due to air velocity over patient
63
What is conduction heat loss?
Heat lost by contact with OR table
64
What is evaporative heat loss?
heat loss due to dry inspired gases
65
What is hypothermia?
Environmental heat loss outpaces metabolic heat production
66
Who is at greatest risk for hypothermia?
elderly, burn patients, neonates, and patients with spinal cord injuries
67
What are some adverse effects of hypothermia?
Delay awakening or cause shivering that increases body's O2 need by 400%
68
At what temperature would you consider the patient hypothermic?
<36 degrees Celsius
69
What is mild hypothermia and what can it cause?
Mild: 33-36 degrees celsius (reduced enzyme function and coagulopathy)
70
What is moderate hypothermia and what can it cause?
Moderate:
71
Is hyperthermia usually seen under anesthesia?
No, and it is a late sign of malignant hyperthermia
72
What are some other causes of hyperthermia under anesthesia besides malignant hyperthermia?
- Endogenous pyrogens
- Thyrotoxicosis or pheochromocytoma (increased metabolic rate)
- Anticholinergic blockade of sweating
- Excessive environmental warming
73
Where are some monitoring sites for temperature?
- Esophagus (lower 1/3) accurately reflects body temperature
- Nasopharynx
- Rectum
- Bladder (integrated into Foley)
- Tympanic membrane (risk of perforation)
- Blood (PA cath)
- Skin
74
What are some superficial warming modalities?
- Forced air warmer (Bair hugger; most effective because decreases radiant and convective heat loss; decreases postoperative shivering and PACU stay)
- Warming blanket (minimally effective; Arctic sun water circulating)
- Radiant heat unit (no role in OR; no impact on mean body temp)
- Heated liquids (iv bags or bottles on patient; very dangerous and can cause burns)
75
What are some core warming modalities?
- IV fluid warmers
- Gastric lavage (warms body core but impractical to perform during surgery)
- Peritoneal irrigation (encourage use of warm irrigation during intraabdominal procedures)
76
What are some passive warming modalities?
- Increase ambient temperature (has greatest effect on maintaining body heat; if >24 degrees Celsius most adults remain normothermic without requiring other measures)
- Insulation (extremities and head)
- Heat and moisture exchanger ("artificial nose"; retains moisture)
- Coaxial breathing circuit ("King" circuit; warms and humidifies inspiratory gases)
77
What is a peripheral nerve stimulator?
monitors status of neuromuscular junction when using NM blocking drugs
delivers electrical stimulation to a peripheral motor nerve mechanically evoking a response
permits titration of drug to optimal effect
quantifies recovery from NMB
78
What is the onset sequence of a NMB drug?
```
Eyes
Extremities
Chest
Abdominal muscles
Diaphragm
```
79
Where are the monitoring sites for a PNS?
Ulnar nerve
Facial nerve
Posterior tibial nerve
Peroneal nerve
80
What muscle does the ulnar nerve innervate?
Adductor pollis
81
Where are electrodes placed to innervate ulnar nerve?
placed at wrist or elbow with the negative (depolarizing) mode placed distally
82
If monitoring ulnar nerve, what is it not an accurate reflection of?
degree of diaphragm or airway muscles (muscles are less sensitive to NMB)
could have adductor pollis paralysis but still have coughing, breathing, and vocal cord movement
83
Where does the facial nerve lie?
Within the parotid gland, if doing excision of that gland should not use NMB
84
Where do you place the electrodes to monitor the facial nerve?
infront of tragus of ear and below; avoid direct muscle stimulation
85
What is the facial nerve a better indicator of?
NM blockade of diaphragm and airway; better to use facial nerve for induction
86
What muscle does the facial nerve innervate?
orbicularis oculi
87
Where do you place the electrodes to monitor the posterior tibial nerve and what do you see when nerve is innervated?
behind medial malleolus of tibia; plantar flexion
88
Where do you place the electrodes to monitor the peroneal nerve?
lateral aspect of knee with response of dorsiflexion of the foot
89
What are the patterns of stimulation for a PNS?
```
Single 0.5-1 second twitch (0.5-1 Hz)
TOF ratio
Tetanic stimulation
Post-tetanic stimulation
Double-burst stimulation
```
90
What is single twitch stimulation?
Single pulse delivered every 10 secs; increasing block results in diminished response
91
What is TOF stimulation?
most common
4 repetitive stimuli
ratio of responses to 1st and 4th twitches are sensitive indicator of ND relaxation
92
What are the T4:T1 ratios and what do they mean?
Loss of 4th twitch = 75% of receptors blocked
Loss of 3rd twitch = 80% of receptors blocked
Loss of 2nd twitch = 90% of receptors blocked
93
How many receptors need to be blocked for clinical relaxation?
75-95% blocked
94
What type of NMBD would you see fade on a TOF?
non-depolarizers
95
What is tetanic stimulation?
Tetany at 50-100 Hz
5 seconds at 50 Hz evoked tension approximates tension developed during maximal voluntary effort
Sustained response occurs when TOF >70%
96
When is post-tetanic count used?
when all twitches are suppressed
97
What is post-tetanic count?
applies tetanus at 50 Hz for 5 seconds, waits 3 seconds then applies single twitches every second up to 20
98
What is the relation between number of twitches and depth of block with post-tetanic count?
inversely related, less anesthetic means more twitches present
99
What is double burst stimulation?
less painful than tetany
| 3 short 50 Hz impulses followed by 750 msec then another 3 bursts
100
When is double burst stimulation more helpful than TOF?
more sensitive for visual evaluation of fade
101
What modes on the PNS are used during induction?
single twitch
| TOF
102
What modes on the PNS are used during maintenance?
TOF
| post-tetanic count
103
What modes on the PNS are used during emergence?
TOF
| double-burst stimulation
104
Which nerves do you monitor for onset and recovery of NM monitoring?
onset - facial
| recovery - ulnar
105
How long will reversal take with 1 out of 4 twitches?
30 minutes
106
How long will reversal take with 2-3 out of 4 twitches?
10-12 minutes with long-acting relaxants, 4-5 minutes after intermediate relaxants
107
How long will it take to recover with 4 out of 4 twitches?
Within 5 mins of Neostigmine, 2-3 mins of edrophonium
108
What is the bispectral index score (BIS)?
used to assess depth of anesthesia
109
Is BIS monitoring required or optional?
optional, not currently under standard of care
110
What are some advantages of using BIS monitoring?
- Reduced risk of awareness
- Better management of responses to surgical stimulation
- Faster wake up (controversial)
- More cost effective use of anesthetics
111
What is the BIS range and what does it mean?
EEG signal with index ranging from 0-100
0 = isoelectric EEG
100 = awake CNS
112
What does a BIS of 80-100 mean?
responds to normal voice
113
What does a BIS of 60-80 mean?
Can respond to loud commands or mild shaking
114
What does a BIS of 40-60 mean?
*General anesthesia
| low probability of explicit recall and unresponsive to verbal stimulus
115
What does a BIS of 20-40 mean?
Deep hypnotic state
116
What does a BIS of 0-20 mean?
Burst suppression or flat line EEG
117
What affects BIS readings?
```
electro-cautery
EMG
pacer spikes
EKG signal
patient movement
```
118
What numbers on EEG monitoring are associated with recall?
no absolute or guarantees, but research indicates that levels >70 have increased risk of recall
119
What are routine monitors?
```
NIBP
stethoscope
EKG
pulse ox
O2 analyzer
EtCO2
Et agent
```
