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Principles > Anesthesia Monitoring > Flashcards

Anesthesia Monitoring Flashcards

1
Q

Standard 9

A

Monitoring and alarms

  • ventilation (etco2 and spo2)
  • cv status
  • thermoregulation
  • neuromuscular function (NMBs)
  • patient positioning
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2
Q

What must you do if you omit a standard monitor

A

DOCUMENT

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3
Q

standard 11

A

Transfer of care

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4
Q

How do we monitor oxygenation

A 
O2 analyzer
Pulse ox
Skin color
Color of blood
ABG
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5
Q

O2 analyzer

A

Measures fio2 of inspired gas on the Inspirators limb

Low concentration alarm = <30%

Required for any general anesthetic

Electrochemical sensor - cathode and annode embedded in electrolyte gel, separated from oxygen gas by O2 permeable membrane
- O2 reacts with electrodes, generates electrical signal proportional to O2 pressure in sample gas in mmHg

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6
Q

PAO2 calculation

A

PAO2 = FiO2 * (Pb-47) - PaCO2

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7
Q

pulse ox

A

Standard of care to provide early warning sign of hypoxemia

Measures arterial o2 sat (oximetry and plethysmography)

Requires pulsatile arterial bed (finger, toe, earlobe, nose, palm and foot in kids)

Gives continuous measurement of pulse rate and oxygen saturation of peripheral Hgb

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8
Q

What law deals with pulse ox

A

Beer-lambert law of spetrophotometry

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9
Q

Wavelength of oxygenated hgb

A

960nm

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10
Q

Wavelength of deoxygenated hgb

A

660nm

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11
Q

How does pulse ox calculate spo2

A

Ratio of infrared (oxyhgb) to red (deoxyhgb)

Basis of oximetry is change in light absorption during arterial pulsations

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12
Q

What affects accuracy of pulse ox

A 
High intensity light
Patient movement
Electrocautery
Peripheral vasoconstriction
Hypothermia
Cardiopulmonary bypass
Presence of other hemoglobins
- COHb - false pos
-MetHb - false neg or pos
IV injected dyes (methylene blue decreases spo2)
Hgb <5 will not register
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13
Q

Pleth variability index (PVI)

A

Indication of pulse strength at indicator site

Useful in measuring goal-directed fluid therapy and fluid responsiveness

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14
Q

Oxyhgb dissociation curve

A

PaO2 30 is SpO2 60
PaO2 60 is SpO2 90
PaO2 40 is SpO2 75

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15
Q

Hypoxia definition

A

O2 sat < 90

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16
Q

Precordial stethescope

A

Easily detects change in heart lung sounds

  • Used to detect circuit disconnection
  • Rapid changes in anesthetic depth

Held in place with double sided tape

Placed in suprasternal notch or apex of left lung

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17
Q

Esophageal stethescope

A

Soft plastic catheter placed into these distal 1/3 of the esophagus through mouth or nose to monitor heart and breath sounds and temp

Only use on intubated patients

Contraindicated in patients with esophageal varices

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18
Q

Respiratory gas analysis

A

Allows measurement of VA

Most commonly a non-dispersive infrared method (side stream sampling, gas absorbs infrared energy at specific wavelengths, complex algorithm and microprocessor)

50-250ml/min is the rate of processing

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19
Q

Capnography

A

Confirms ETT placement and adequate ventilation

Most often side-stream sampling
-airway gas aspirated and pumped into device at sampling flow rates of 50-250 ml/min

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20
Q

What is the normal adult CO2 production and what makes it change

A

250 ml CO2/min

Patients condition
Anesthetic depth
Temperature

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21
Q

What are the limitations of capnography

A

H2O condensation can contaminate system and falsely elevate readings
There is a lag time between sample aspiration and reading

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22
Q

Et CO2 is less than alveolar CO2 and that’s less than Pa CO2

A

This is a fact i just wanted to remember

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23
Q

PACO2 -PaCO2 gradient

A

Normal = 2-10

Abnormal can be due to

  • gas sampling error
  • prolonged expiratory phase
  • V/q mismatch
  • airway obstruction
  • embolic states
  • COPD
  • Hypoperfusion
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24
Q

Capnograph

A

1 - inspiration (baseline) - should be NO CO2
2 - early exhalation - rapid rise with steep upstroke - dead space mixed with alveolar gas
3 - CO2 rich alveolar air (horizontal portion/mild upslope)
4 - return to baseline (inspiration of fresh gas)

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25
Q

Why would phase 1 (baseline) of your capnograph be elevated

A

CO2 absorbant exhausted
Expiratory valve missing/incompetent
Bain circuit

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26
Q

Why would there be a prolonged upstroke during phase 2 of your capnograph

A 
Mechanical obstruction (kinked ETT)
Slow emptying of lungs (COPD, bronchospasm)
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27
Q

What is the steepness of phase 3 of your capnograph a function of?

A

Expiratory resistance

COPD, bronchospasm

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28
Q

Capnograph with a notch in phase 3

A

Caused by inadequate NMB as diaphragm responds with patients attempt to breathe

“Curare cleft”

Or caused by surgeon pressing on abdomen

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29
Q

If your capnograph fails to return to baseline, what does that mean

A

You are rebreathing CO2

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30
Q

Slow rise of phase 2 of capnograph

A

Some sort of expiratory obstruction

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31
Q

what Monitors are on an mechanical vent

A

Tidal volume
Airway pressure
Disconnect alarm

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32
Q

What leads do you typically monitor in your EKG to best show myocardial ischemia

A

2 and V5

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33
Q

Why would you choose a 5 lead over a 3 lead ekg system

A

The 5 lead system is better at detecting myocardial ischemia and allows a better differential diagnosis of atrial and ventricular dysrhythmias

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34
Q

Lead 2

A

Yields max p wave voltages
Superior detection of atrial dysrhythmias
Detects inferior wall ischemia/ST depression

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35
Q

V5

A

5th ICS/anterior axillary line

Detection of anterior and lateral wall ischemia

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36
Q

BP Cuff width

A

20% greater than mean diameter of the extremity

- too narrow = artificially high pressure

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37
Q

Oscillometric device

A

Air pump inflates cuff - linked to microprocessor - opens deflation valve - oscillations sampled

Non invasive

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38
Q

Errors for oscillometric BP

A 
Surgeon leans on cuff
Inappropriate size
- too big = low reading
- too small = high reading
Shivering or excessive motion
Atherosclerosis and HTN
- systolic low
- Diastolic high
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39
Q

A-line when to use

A

Used when you need continuous BP monitoring, critically ill patients, if you are anticipating blood loss, for major procedures, or if you need frequent ABGs

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40
Q

What are the most common IABP sites

A

Radial (most common), ulnar (more tortuous), brachial (predisposed to kinking), femoral (prone to pseudoaneurysm and atheroma formation), DP (distorted waveform), axillary (potential for plexus nerve damage from hematoma or traumatic cannulation)

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41
Q

CVP indications

A

Fluid management of hypovolemia and shock
Infusion of caustic drugs
Aspiration of air emboli
Insertion of pacing leads
TPN
Venous access in patients with bad peripheral veins

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42
Q

Where do you place CVP

A

Right IJ (preferred - straight to heart)
Subclavian
EJ
AC (special kit with long catheter)

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43
Q

PA catheterization indications

A

Poor LV function, evaluate response to fluids, pressors/dilators, inotropes, valvular heart disease, recent MI, ARDS, trauma, vascular surgery

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44
Q

In a 70 kg patient, a liter of crystalloid at room temp will lower body temp by

A

0.4 degrees celcius

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45
Q

In a 70 kg patient a unit of RBC will lower body temp

A

0.2 degrees C

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46
Q

What method of heat lost is most prevalent in the OR

A

Radiation

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47
Q

Convection

A

Heat loss due to air velocity (fan)

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48
Q

Conduction

A

Heat loss due to contact of two objects

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49
Q

Evaporation

A

Heat loss due to sweat evaporating off skin

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50
Q

Unintentional hypothermia

A

Phase 1 - steep drop in core temp during first hour
Phase 2 - slower decline during the next 3-4 hours
Phase 3 - steady state equilibrium

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51
Q

What part of brain normally maintains core body temp and what is that range called

A

Hypothalamus

“Interthreshold range”

52
Q

Do anesthetics inhibit thermoregulation?

A

Yes they inhibit central thermal regulation by interfering wiht hypothalmic function

Dose-dependent

53
Q

isoflurane produces a dose dependent decrease in vasoconstrictor threshold

A

At a rate of 3 degrees celcius for each percent of isoflurane

54
Q

Spinal/regional epidural causes phase 1 hypothermia d/t

A

Vasodilation and internal redistribution of heat

55
Q

Spinal regional anesthesia causes unintentional hypothermia in phase ii d/t

A

Regulatory impairment that allows continued loss d/t altered perception of temp d/t blocked dermatomes

56
Q

How long should you prewarm patients and why

A

30 minutes

Because it decreases the central peripheral temperature gradient

57
Q

Hypothermia ranges

A

<36

Mild = 33-36

Moderate = 32

58
Q

At what temp do you start to see reduced enzyme function

A

36 degrees

59
Q

At what temp do you start to see coagulopathy issues

A

36

60
Q

At what temp is the fibrillatory threshold

A

32

61
Q

why is surgery a problem that causes hypothermia

A

Environmental heat loss outpaces metabolic heat production

Anesthesia impairs normal response

62
Q

What are anesthesia considerations of hypothermia

A

May delay awakening or cause shivering (this increases myocardial o2 consumption)

63
Q

Which patients are at greatest risk for hypothermia

A

Elderly
Burn
Neonates
Patients with spinal cord injuries

64
Q

Causes of intraop hyperthemia

A 
Malignant hyperthermia
Endogenous pyrogens
Thyrotoxicosis or pheo d/t increased met rate
Anticholinergic blockade of sweating
Excessive environmental warming
65
Q

Monitoring site for temps

A

Esophagus (lower 1/3) - best indicator of trend of heat gained/loss
Nasopharynx
Rectum
Bladder (pretty accurate)
Tympanic
Blood (PA catch) - great choice
Skin - not that accurate but good for monitoring trends

66
Q

Bair hugger

A

Forced air warmer - most effective
Decreased radiant and convective losses
Decreased post op shivering and PACU stay

Concern for post op infection rates?

67
Q

Warming blanket

A

Circulates water - minimally effective

68
Q

Radiant heat unit

A

Not ok for OR, not impact on mean body temp

69
Q

Heated liquids

A

Very dangerous because it can cause burns

70
Q

IV fluid warmers

A

Core modality

Warmed liquid transfer of heat
Delivers fluids at the highest temp of any tech

Not as effective in shorter cases

71
Q

Gastric lavage

A

Warms body core

Impractical intraop

72
Q

Peritoneal irrigation

A

Encourage use of warm irrigation during intra-abdominal procedures

73
Q

Ambient temp

A

Hugely important

Ambient temp >24C, most adults remain normothermic without needing other measures

74
Q

Insulation

A

Passive warming where you cover extremities and head

75
Q

Heat and moisture exchanger

A

Passive warming in circuit “artificial nose” - retains moisture and heat from patient

76
Q

Coaxial breathing circuit

A

Warms and humidifies Inspiratory gases

“King circuit”

77
Q

Why do we monitor neuromuscular blockade

A

Assess depth of blockade and degree of recovery

78
Q

Peripheral nerve stimulator

A

Monitors effect of NM blocking agents on NM junction

  • know and compare to baseline
  • quantify by feel

Delivers electrical stimulation to a peripheral motor nerve which evokes a mechanical response

Titration of drug to optimal

Quantifies recovery from NMB

79
Q

Monitoring sites for a peripheral nerve stimulator

A

Ulnar nerve - adductor pollicis stimulation
Facial - orbicularis occuli
Posterior tibial nerve
Peroneal nerve

Place electrodes over nerves to avoid direct muscle stimulation

80
Q

Ulnar nerve

A

Innervates adductor pollicis muscle - abducts thumb
Black (neg) at crease of wrist and red lead 1-2 cm proximal to black electrode
Most common monitoring site

81
Q

Is the ulnar nerve an accurate reflection of degree of block

A

The adductor pollicis muscle is more sensitive to ND block than diaphragm or airway muscles, so you may be paralyzed there but still have coughing/breathing/vocal cord movement

82
Q

Which nerve has the least chance of muscle stimulation via electrode placement for TOF

A

Ulnar nerve

83
Q

Facial nerve

A

Lies within the parotid gland

Place electrodes in front of Tragus of ear and below (negative over nerve)

Orbicularis oculi - closes eyelid
Corrugated supercili - furrows brow

84
Q

Which nerve site for PNS is the better indicators of ND blockade of diaphragm and airway than peripheral muscles

A

Facial nerve

85
Q

Posterior tibial nerve

A

Place electrode behind medial malleolus of tibia and results in plantar flexion

Black - 2 cm poster to MM of foot
Red - 2 cm above MM of foot

86
Q

What does the flexor hallucinations brevis muscle do

A

This is the sole of the foot and it flexes the big toe

87
Q

Peroneal nerve

A

Electrodes on lateral aspect of knee that elicits Dorsiflexion of foot

88
Q

Single twitch

A

Single pulse delivered every 10 seconds
0.1Hz (stimulus every 10 seconds)

Increasing block results in diminished response

Twitch height will be depressed only when 75% of ach receptors are blocked and will disappear with 90% blocked

89
Q

Train of four

A

4 repetitive stimuli - twitches progressively fade as relaxation increases

Ratio of 1st to 4th twitches are sensitive indicator of ND relaxation

90
Q

TOF - lose 4th twitch =

A

75% receptors blocked

91
Q

TOF - lose 3rd twitch =

A

80% receptors blocked

92
Q

TOF - lose 2nd twitch =

A

90% receptors blocked

93
Q

How many receptors are required to be blocked to be considered clinical relaxation

A

75-90% blocked

94
Q

0 twitches on TOF =

A

90-98% receptors blocked

95
Q

TOF ratio

A

Amplitude of 4th twitch divided by amplitude of 1st twitch

Partial ND block - ratio decreases (inversely proportional to degree of block)

Partial depolarizing blockade - amplitude of every twitch decreases, but ratio remains 1

96
Q

Tetanic stimulation

A

Tetany at 50-100Hz

5 sec @50Hz evoked tension approximates tension developed during max voluntary effort

ND = fade occurs

97
Q

How many receptors are blocked when you get a sustained response to tetanic stimulation

A

70%

98
Q

disadvantage to tetanic stimulation

A

Painful - don’t use when awake

99
Q

Post tetanic count

A

Useful when all twitches suppressed during TOF

Apply tetanus at 50Hz for 5 seconds
Wait 3 seconds
Apply single twitches every second up to 20
**number of twitches is inversely related to depth of block

If your goal is to keep them profoundly blocked, the goal is 0

100
Q

Double burst stimulation

A

Less painful than tetany

3 short 50 Hz in pulses followed by 750ms followed by another 3 bursts

More sensitive than TOF for visual evaluation of fade

DBS3,3

101
Q

What patterns of stimulation do you use during induction

A

Single twitch

TOF

102
Q

Which stimulation pattern do you use during maintenance

A

TOF and post-tetanic count

103
Q

What stimulation pattern do you use during emergence

A

TOF and double burst stimulation

104
Q

When giving a NMB drug, which is most sensitive? Aka what is paralyzed first

A

Eyes (extraocular)

105
Q

What muscle recovers quickest from blockade

A

Diaphragm and vocal cords

106
Q

What site should you monitor for onset

A

Facial

107
Q

What site should you monitor for recovery

A

Ulnar

108
Q

TOF 1/4 twitches = how long to recovery?

A

30 minutes

109
Q

TOF 2-3 twitches = how long until reversal

A

10-12 minutes following long acting relaxants and 4-5 minutes after immediate relaxants

110
Q

4/4 twitches time to recovery?

A

5 minutes with neostigmine and 2-3 minutes with edrophonium

111
Q

Why does hypothermia limit interpretation of evoked responses?

A

It increases skin impedance

112
Q

Most reliable clinical signs of recovery

A

Sustained head lift x 5 sec
Sustained leg lift X 5 sec
Sustained hand grip x 5 sec
Max inspiratory pressure 40-50 cm H2O or >

113
Q

Quantitative nerve monitoring

A

Device that quantifies degree of NM blockade

More reliable accurate and objective

114
Q

Acceleromyography

A

Piezoelectric sensor measures muscle acceleration (voltage generated on contraction)

Change in muscle length without change in tension

It is not essential that sites that are being monitored remain mobile

Used primarily in research

115
Q

Electromyography

A

Muscle action potential recorded, electrical activity proportional to force of contraction

116
Q

Kinemyography

A

Quantifies muscle movement with motion sensor strip containing piezoelectric sensors

117
Q

Mechanomyography

A

Detects contraction force, converts to electrical signal, signal amplitude reflects contraction strength

118
Q

Phonomyography

A

Muscle contraction produces low-frequency sounds, calculates muscle response

119
Q

bispectral index score

A

Used to assess the depth of anesthesia (optional)

This is good for

  • reduced risk of awareness
  • better management of responses to surgical stimulation
  • faster wake up (controversial)
  • more cost effective use of anesthetics
120
Q

BIS scoring

A 
100= awake
>70 = greater recall risk
40-60 = general anesthesia
0 = isoelectric EEG
121
Q

BIS readings are affected by

A 
Electrocautery
EMG
Pacer Spikes
EKG signal
Patient movement
122
Q

What indicates that BIS score is accurate

A

SQI high and EMG low

123
Q

Cerebral oximetry

A

Assess cerebral O2 sat using near infrared spectrophotometry

Noninvasive

Detects decreases in CBF in relation to CMRO2

Difference in transmitted and received light determines regional oxygen saturation

Light source adheres to patient forehead, light transmits through tissue and cranium

Allow for transmission and absorption of light by hemoglobin to determine saturation

124
Q

What would decrease cerebral oximetry reading?

A

Drop in BP
Partial pressure of CO2 in arterial blood
Regional blood volume
Hgb concentration

125
Q

Goal of cerebral oximetry (number)

A

Keep within 75% of baseline reading

A greater than 20% reduction from baseline is correlated with regional and global ischemia

Principles (11 decks)

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