Clinical Monitoring II - Exam 1 (Ericksen) Flashcards
(116 cards)
1
Q
Side-stream (diverting) gas analyzer
A
- gas taken away from pts airway to the analyzer
2
Q
Mainstream (non-diverting) gas analyzer
A
- gas is analyzed at the airway
3
Q
Gas Analysis
What is the transit time?
A
- time lag for gas sample to reach analyzer
- not instantaneous
4
Q
Gas analysis
What is the rise time?
A
time taken by the analyzer to react to the change in gas concentration
- ex: ETCO2 fluctuating when pt is getting sleepier - rises and then it levels out
5
Q
Mainstream sampling
Sampling Challenges
A
- Water vapor (condense in airway tubing)
- Secretions & blood - clog ETCO2 sample line
- more interfaces for disconnections w/ mainstream
6
Q
Side-stream Sampling
Sampling Challenges
A
- Kinking of sampling tubing
- water vapor
- failure of sampling pump
- leaks in line
- slow response time
7
Q
Dalton’s Law states that –
A
the total pressure exerted by a mix of gases is equal to the sum of the partial pressures of each gas
8
Q
How are gases expressed?
A
partial pressures (mmHg)
Volumes % (PP/Ptot x 100)
9
Q
What is mass spectrometry?
A
- looking @ how many gas molecules are present in a expired sample
- the concenctration deterimined according to mass/charge ratio
10
Q
What can mass spectrometry tell us?
A
- what portions of the gas are Sevo, O2, Nitrous, etc.
- can calculate 8 diff. gases
11
Q
What is Raman Spectroscopy?
A
- argon laser produces photons that collide w/ gas molecules in a sample
- measured in a spectrum that identifies each gas & concentration
12
Q
What is infrared analysis?
A
the measurement of energy absorbed from narrow band of wavelengths of IR radiation as it passes through a gas sample
13
Q
What does infrared analysis measure?
A
the concentration of gases - they all have a different fingerprint/band length
CO2, nitrous oxide, water, volatile gases
14
Q
What type of infrared analyzer is most common?
A
Non-dispersive (keeps it from going everywhere)
15
Q
Why can infrared analysis not measure O2?
A
O2 does not absorb IR radiation
16
Q
IR analyzer
Less light getting through =
A
higher concentration of the gas being measured
17
Q
IR analyzer
more light getting through to detector =
A
Less concentration of the gas being measured
18
Q
Side-stream analyzers report ________ temperature and ________ ____ dry values.
A
Ambient and Pressure dry
19
Q
analyzers should report results at ____ temperature and pressure ________ values.
A
Body temp & pressure saturated (BTPS)
20
Q
Example - calculating PP of a gas
A
- Ptot - PH2O (FiO2) = PP
- 30% O2 PP =
- 760mmHg - 47mmHg (0.30) = 214mmHg
if she does not say anything about H2O vapor, don’t account for H2O vapor
21
Q
O2 analyzer
What is a fuel cell/galvanic cell?
A
- located in breathing tube (mainstream)
- oxygen battery - measure current produced when O2 diffuses across a membrane
22
Q
Fuel Cell
The current measured by the oxygen battery is proportional to ——?
A
The PP of O2 in the fuel cell
23
Q
O2 analyzers - Paramagnetic
Why is O2 a highly paramagnetic gas?
A
- d/t the magnetic energy of unparied electrons in their outer shell orbits
23
Q
Fuel Cell
Where is it best to monitor the O2 concentration at?
A
In the inspiratory limb - so we know how much O2 the pt is actually getting
24
# O2 analyzers
What does a paramagnetic analyzer detect?
the change in sample line pressure from the attraction of O2 by switched magnetic fields
**signal changes that happen during the switching of magnetic fields correlate w/ O2 concentration**
25
# O2 analyzers
Where is the paramagnetic O2 analyzer mostly used?
In side-stream sampling multi-gas analyzers
26
# O2 analyzers
What is the main advantage of the paramagnetic O2 analyzer over the fuel cell?
* rapid-response, breath-by-breath monitoring
* **informs us w/ every breath what we need to do for the pt**
27
O2 sampling inside the inspiratory limb --
* ensures O2 delivery to pt
* analyzes hypoxic mixtures
28
O2 sampling inside the expiratory limb --
* ensures complete PREOXYGENATION/denitrogenation
* ET O2 > 90% adequate - will never be 1.0 (100%)
29
what does an ET O2 <90% tell us?
The pt has lung comorbidities
30
Low O2 alarm reasons
1. pipeline crossover
2. incorrectly filled tanks
3. failure of proportioning system - nitrous on and only so much can go through
31
Why is a High O2 alarm important?
* important to notify us of high O2 concentration in pts in can be harmful to (free O2 radicals)
-- premature infants
-- pts on chemotherapeutic drugs (bleomycin)
32
Airway pressure monitoring is a key component in measuring ________.
Ventilation
33
T/F: Airway pressure monitoring can only assess mechanical ventilation.
False, it can also assess spontaneous ventilation
34
What can Airway Pressure Monitoring Detect?
1. circuit disconnects
2. ETT occlusions
3. kinking of inspiratory limb
4. fresh gas hose kink/disconnect
5. circuit leak
6. sustained high circuit pressure (collection of H2O vapor, kink)
7. high & low scavenging system pressures
35
What are the 2 types of pressure gauges used for airway pressure monitoring?
Which is highly reliable?
1. Mechanical - highly reliable
* requires monitoring
2. Electronic
* has alarm system integrated
36
What type of Airway Pressure Alarm is required by the AANA/ASA?
Breathing circuit low pressure alarm
37
What is the purpose of the breathing circuit low pressure alarm?
* ID circuit disconnects/leaks
38
# Airway Pressure Monitoring
What should the low pressure limit be set at?
* just below the normal peak airway pressure (20-30cmH2O)
39
Where do 70% of the disconnections of the breathing circuit occur?
At the Y-piece
40
# Airway Pressure Monitoring
What is the sub-atmospheric pressure alarm?
* a negative pressure alarm
* measures and alerts of negative circuit pressure & potential for reverse flow of gases
41
What 3 things can negative airway pressures cause?
1. pulmonary edema
2. atelectasis
3. hypoxia
42
What are 5 causes of the sub-atmospheric pressure alarm going off?
1. active (suction) scavenging system malfunctions
2. pt inspiratory effort against a blocked circuit
3. inadequate FGF
4. suction to misplaced NGT/OGT
5. moisture in CO2 absorbent - prevent suction
43
When is the high-pressure alarm activated? What pt population is it important in?
* activated if airway pressure exceeds a certain limit
* pediatrics
44
Causes of high-pressure alarm activation
1. obstructions
2. reduced compliance
3. coughing/straining
4. kinked ETT
5. endobronchial intubation
45
# Airway pressure monitoring
What triggers the continuous pressure alarms to be activated?
* circuit pressure > 10cmH2O for > 15 seconds
46
Causes of the continuous pressure alarm being activated
* turned off vent, flipped to APL valve & forgot to squeeze bag
* malfunctioning adjustable pressure relief valve
* scavenging system occlusion
* activation of oxygen flush system
* malfunctioning PEEP (comorbidities)
47
# Peripheral nerve monitoring
Supramaximal Stimulation
* reaction of a single muscle fiber to a stimulus follows on all-or-none pattern
48
What are the different sites of nerve stimulation?
1. Ulnar - adductor pollicis muscle **gold standard**
2. Facial nerve - orbicularis oculi & corrugator supercili muscle **where we usually monitor**
3. median nerve
4. posterior tibial nerve
5. common peroneal nerve
49
The diaphragm has a ________ onset than the adductor pollicis. But, recovers ________ than peripheral muscles.
1. shorter
2. faster
50
Does the corrugator supercilii or adductor pollicis reflect NMB of laryngeal & abdominal muscles better?
* Corrugator supercillii
51
What is single twitch stimulation?
What is it used for?
* 1Hz every second - 0.1Hz every 10 seconds
* used in labs to establish an ED95
52
What is TOF and when do we use it?
* 4 supramaximal stimuli every 0.5 seconds
* evaluate the TOF count/fade in muscle response
* **reliable assessment of onset and moderate blockade**
53
What happens w/ TOF and a partial non-depolarizing block (Roc)
* TOFR decreases (fade)
* is inversely proportional to degree of block
54
What happens to TOFR and a partial depolarizing block (succ)
* no fade, ratio is 1.0
* if fade present = phase II block
55
What is Double Burst Stimulation?
* 2-3 short bursts of 50Hz tetanic stimulation separated by 750ms w/ 0.2 ms duration of each square wave impulse in burst
* **DB 3,3 mode**
* **DB 3,2 mode**
56
What is DBS good for?
* detecting fade
* not used in clinical practice
57
What is tetanic stimulation?
non-depolarizers response:
depolarizer response:
* 50Hz for 5 seconds
* non-depolarizers: one strong sustained muscle contraction w/ fade
* depolarizers: strong sustained muscle contraction w/o fade
| * not really used
58
What is post-tetanic stimulation?
* tetanic stimulation (50 Hz for 5 sec)
* followed by 10-15 single twtiches (1Hz after 3 second post-tetanic stimulation)
* 9th twitch - may start to see recovery from non-depolarizer
59
What is the post-tetanic response dependent on?
1. degree of block
2. frequency & duration of tetanic stimulation
3. lengtho f time b/w end of tetanic & first post-tetanic
4. frequency of single twitch stimulation
5. Duration of single twitch stimulation before tetanic stimulation
**Can only perform every 6 min**
60
What situation is post-tetanic stimulation good for monitoring?
1. deep & surgical blockade - if pt is paralyzed very deep
61
Non-depolarizing **intense** blockade
Reversal??
* period of no response (3-6 min after intubating dose of NDMB)
* high dose sugammadex (16mg/kg) reversal
62
Non-depolarizing **deep** blockade
Reversal??
* absence of TOF, presence of at least 1 response to post-tetanic stimulation
* reversal - Neostigmine usually impossible, sugammadex (4mg/kg)
63
Non-depolarizing **moderate** block
Reversal??
* gradual return of 4 responses to TOF
* reversal: Neostigmine after 4/4 responses, Sugammadex (2mg/kg)
64
What happens in a depolarizing phase I block?
* no fade/tetanic stimulation
* no post-tetanic facilitation
* all 4 responses reduced - equal - disappear - come back
65
What happens in a phase II Depolarizing block?
* fade present in TOF and tetanic stimulation
* occurrence of post-tetanic facilitation
66
**clinical tips for NMB & monitoring**
* keep pt warm to prevent delaying nerve conduction
* moderate level block is sufficient for surgery w/ 1-2 responses to TOF
* reverse when all 4 responses to TOF present
* check for NM recovery prior to extubation post-reversal
67
Reliable clinical signs for extubation
1. sustained head lift for 5 sec
2. sustained leg lift for 5 sec
3. sustained handgrip for 5 sec
4. sustained tongue depressor test = can they bite down on the depressor around their ETT?
5. max inspiratory pressure - take deep breath and hold it
68
EEG is a summation of --
excitatory & inhibitory postsynaptic potentials in the cerebral cortex
* 16 channels of info
69
What does an EEG identify?
* consciousness/unconsciousness
* seizures
* stages of sleep/coma
* hypoxemia/ischemia
70
# EEG
Amplitude
* size/voltage of recorded signal
71
# EEG
Frequency
* # of times per second the signal oscillates/crosses the 0-voltage line
72
# EEG
Time
duration of sampling signal
73
Peri-op uses for EEG
1. indentifies inadequate flow to cerebral cortex
2. guides an anesthetic-induced reduction of cerebral metabolism
3. predicts neuro outcome after brain insult
4. Gauges depth of hypnotic state of pts under GA
74
EEG beta waves
> 13Hz
* awake, alert/attentive brain
75
EEG alpha waves
8-13Hz
* eyes closed
* anesthetic effects
76
EEG Theta & Delta Waves
* theta (4-7Hz)
* delta (<4Hz)
* depressed, slower frequency
77
How many channels does a processed EEG use?
What do we use it for?
< 4 channels (2 for each hemisphere)
* delineates unilateral from bilateral changes
-- unilateral: regional ischemia d/t carotid clamping
-- bilateral: depression from anesthetic drug bolus
78
When do we use a BIS monitor?
* cases where there is concern for neuro deficits
* estimates anesthetic depth
* can help prevent intra-op awareness
79
BIS ranges
100:
80:
60:
40:
20:
0:
* 100: Awake - responds to voice
* 80: responds to loud commands, mild prodding
* 60: GA - low chance of recall, no response to verbal
* 40: deep hypnotic state
* 20: burst suppression
* 0: flat line
80
What is the most common type of evoked potentials monitored intra-op?
Sensory-evoked Responses
* electric most common
* can also have auditory, or visual
81
How do sensory evoked potentials work?
* stimulate sensory pathway and record responses along the path to the cerebral cortex
82
# Evoked potentials
Latency
* time measured from application of stimulus to onset/peak of response
83
# Evoked potentials
amplitude
* size/voltage of recorded signal
84
# Evoked potentials
What is one of the most important things for anesthesia?
* let the tech get their baseline tracing while we are pre-oxygenating
85
What are somatosensory evoked potentials (SSEPs)?
* stimulation to peripheral mixed nerves
* responses measured in sensorimotor cortex
86
# SSEPs
short latency vs. long-latency waveforms
* short latency - more commonly recorded intra-op
-- less affected by anesthetics
* long-latency: changed by anesthesia
87
# SSEPs
What things may alter the appearance of SSEPs?
1. induction
2. neuro disease
3. age
88
What are Brainstem Auditory Evoked Potentials (BAEPs)?
1. monitors responses to click stimuli
2. delivered via foam inserts along auditory path from ear to auditory cortex
89
What are Visual Evoked Potentials (VEP)?
* monitors response to flash stimulation of retina
* uses light-emitting diodes in soft plastic goggles through closed eyelids or contacts
* **least common technique intra-op**
90
What are motor evoked potentials?
MEP
* monitors integrity of motor tract along spinal column, peripheral nerves, and innervated muscle
91
What is the most common MEP used?
Transcranial motor evoked potential
* via transcranial electrical stimulation overlying motor cortex
92
# MEPs
What is electromyography?
* monitors responses generated by cranial and peripheral motor nerves
* allows early detection of surgically induced nerve damage & assessment of the level of nerve function intra-op
93
What is the primary thermoregulatory control center?
Hypothalamus
93
What nerve fibers are the heat/warmth receptors?
Unmyelinated C fibers
94
What nerve fibers are the cold receptors?
Alpha & delta fibers
95
Thermoregulatory - threshold:
the temp at which a response will occur
96
Thermoregulatory - Gain:
the intensity of the response
97
Thermoregulatory - Response
* sweating - decreases body temp
* vasodilation - more heat loss
* vasoconstriction - less heat loss
* shivering - increases body temp
98
What 6 things can alter temperature control?
1. anesthesia
2. age
3. menstrual cycle
4. drugs
5. alcohol
6. circadian rhythm
99
# Hypothermia in GA
initial response
* rapid decrease of 0.5-1.0 degree C
* c/b anesthesia induced vasodilation (redistribution of body heat)
* **happens over 30min**
100
# Hypothermia in GA
Slow linear reduction
* 0.3 degree C/hr
* c/b GA reducing metabolic rate by 20-30%
* heat loss exceeds production
* **1-2hrs after anesthesia induction**
101
# Hypothermia in GA
Plateau phase
* thermal steady state
* heat loss = production
* **3-4hrs after anesthesia**
* pt is still losing peripheral heat - but not core (vasoconstriction)
102
# Neuraxial Hypothermia
Central thermoregulatory control is inhibited, which means ---
the threshold (temp) at that triggers peripheral vasoconstriction & shivering is lower
**so more heat is lost**
103
# Neuraxial Hypothermia
What autonomic thermoregulatory defenses are impaired?
1. vasodilation
2. sweating
3. vasoconstriction
4. shivering
104
# Neuraxial Hypothermia
What causes the initial decrease in core temp?
* neuraxial blockade induced vasodilation
105
# Neuraxial Hypothermia
Will there be a plateau in temp?
NO, b/c inhibition of peripheral vasoconstriction
106
# Heat Transfer
Radiation
Heat loss to the environment (30-40%)
**main form of heat loss**
* infants vulnerable b/c low BSA
107
# Heat Transfer
Convection
* loss of heat to air immediately surrounding the body (30%)
* **greater in rooms w/ laminar flow**
108
# Heat Transfer
Evaporation
* loss of heat through vaporization of water from open body cavities & resp. tract
* sweating (DM - blood sugar)
* ex-lap - pack abd w/ soaked gauze to prevent heat loss
109
# Heat Transfer
Conduction
* heat loss d/t direct contact of body tissue or fluids w/ colder material
* ex: skin and OR table, IV fluids
| **electricity conduction - touching**
110
Hypothermia complications (7 things)
1. Coagulopathy
2. increases transfusions (22%) and bleeding (16%)
3. decreases O2 delivery to tissues (vasoconstriction)
4. 3x rate of morbid cardiac outcomes (BP, HR and catecholamine levels increased)
5. shivering (increased O2 demand)
6. decreased drug metabolism - longer DOA NMB
7. post-op thermal discomfort
111
5 benefits of hypothermia
1. protects against cerebral ischemia
2. reduces metabolism (8%/degree C)
3. improved outcomes in cardiac arrest recovery
4. use in neurosurgery when brain ischemia is unexpected
5. more difficult to trigger MH
112
Peri-op temp management (4)
1. airway heating & humidification (peds)
2. warm IV fluids/blood
3. cutaneous warming
-- increase room temp, insulation, hot water mattress
4. forced air warming - prevents loss from radiation (uses convection)
113
4 temp monitoring sites
1. pulmonary artery - gold standard
-- correlates w/ other 3
2. tympanic - approximates hypothalamus temp
3. nasopharyngeal - brain temp (more error, epistaxis)
4. distal esophagus - lower 1/3 - 1/4
114
OR temps
Children: 70 degrees F/21 C
Adults: 65 degrees F/18 C
