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Principles of Monitoring & Fluid balance > Basic Intraoperative Monitoring > Flashcards

Basic Intraoperative Monitoring Flashcards

1
Q

What does early intervention lead to?

A

Improved outcomes

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2
Q

What does the data collected by the anesthetic provider reflect?

A

Physiologic homeostasis
Response to therapeutic interventions
Proper functioning of anesthetic equipment

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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

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4
Q

What year did Harvard produce guidelines for anesthesiologists?

A

1986, ASA closely mirrors those produced by the AANA

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5
Q

What year did the AANA revise the standards to include the scope of practice as well?

A

1983

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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

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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

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8
Q

What two factors are the basis of safe anesthetic care?

A

Continous clinical observation and vigilance

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9
Q

A state of clinical awareness whereby dangerous conditions are anticipated or recognized and promptly corrected

A

Vigilance in Anesthesia

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10
Q

What is the anesthetic provider continually monitoring?

A

Patient’s medical status
Effects of anesthesia
Effects of surgical intervention

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11
Q

What is the most important monitor?

A

The vigilant anesthetist

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12
Q

What are the AANA standard for monitoring?

A 
Oxygenation/ventilation
Circulation
Body temperature
Neuromuscular function
Qualified Anesthetist Present
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13
Q

How should oxygenation be measured?

A

Clinical observation, pulse oximetry and if indicated arterial blood gas analysis

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14
Q

How should we verify intubation of the trachea?

A

Auscultation, chest excursion and confirmation of carbon dioxide in the expired gas

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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

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16
Q

What is the fundamental goal of the anesthetic provider?

A

Avoidance of hypoxia (airway, airway airway)

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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)
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18
Q

What measures the pipeline gas to ensure O2 is truly being administered?

A

Oxygen analyzer

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19
Q

Where is the O2 analyzer located?

A

Inspiratory limb

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20
Q

When will the O2 analyzer notify the provider of low O2 concentrations?

A

< 30% low concentration alarm

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21
Q

What two values should the O2 analyzer be calibrated to every day with the AGM check?

A

Room air and 100%

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22
Q

What is the Alveolar gas equations?

A

PAO2 = FiO2 x (Pb-47) - PaCO2

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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

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24
Q

What type of sensor is the O2 analyzer?

A

Electrochemical sensor

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25
Q

What is the structure of the electrochemical sensor of the O2 analyzer?

A

Cathode and anode embedded in electrolyte gel separated from gas by an oxygen permeable membrane

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26
Q

How does the electrochemical sensor in the O2 analyzer function?

A

O2 reacts with electrodes, generates electrical signal proportional to O2 pressure (mmHg) in sample gas

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27
Q

What is the standard of care for continuous non-invasive monitoring of oxygenation?

A

Pulse oximetry

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28
Q

What is a late sign of hypoxemia?

A

Cyanosis

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29
Q

When was the pulse oximeter introduced to anesthetic practice?

A

1987

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30
Q

What two principles are combined to explain the use of a pulse oximeter?

A

Oximetry & plethysmography

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31
Q

What is required in order to use a pulse oximeter?

A

Pulsatile arterial bed, a blood pressure must be present

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32
Q

What does plethysmography measure?

A

pulsatile measurement

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33
Q

What are some common sites to place a pulse oximeter?

A

Finger, toe, ear lobe, bridge of nose, palm and foot (especially in children)

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34
Q

What is the pulse oximeter continuously measuring?

A

Measurement of pulse rate and oxygen saturation of peripheral hemoglobin (SpO2)

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35
Q

What law dictate how a pulse oximeter works?

A

Lambert-Beer law of spectrophotometry

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36
Q

At what wavelength does HbO2 absorb light?

A

960nm (more infrared)

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37
Q

What does the Lambert-Beer Law of spectrophotometry measure?

A

Oxygenated and reduced Hgb differ in their absorption of red and infrared light

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38
Q

What is being compared in order to calculate an accurate SpO2 reading?

A

Comparison of absorbances of the wavelengths enables oximeter to calculate O2 saturation (ratio of infrared and red transmitted to a photodetector)

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39
Q

At what wavelength does reduced Hgb absorb more light?

A

660nm (more red)

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40
Q

What is the primary mechanism of action of the pulse oximeter?

A

Therefore, the basis of oximetry is change in light absorption during arterial pulsations

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41
Q

What does a patient’s Hgb have to be in order for a pulse oximeter to be functional?

A

> 5

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42
Q

What IV medication causes a large decrease in SpO2 while using a pulse oximeter?

A

Methylene blue

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43
Q

What are two other types of hemoglobins that could affect the pulse oximeter?

A

COHb (falsely increased)

MetHb (could be increased or decreased)

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44
Q

What is the correlation between SpO2 and PaO2?

A

40 50 60 PaO2

70 80 90 SpO2

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45
Q

Where should the precordial stethoscope be placed?

A

Suprasternal notch or apex left lung

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46
Q

What is the purpose of the precordial stethoscope?

A

Easily detects changes in breathe sounds or heart sounds
Circuit disconnect
Endobronchial intubation

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47
Q

What can be heard on the precordial stethoscope as anesthesia lightens?

A

Louder heart sounds from increased rate and contractility

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48
Q

What population can only use an esophageal stethoscope?

A

Limited to intubated patients

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49
Q

Where should the esophageal stethoscope be placed?

A

Distal 1/3 of esophagus

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50
Q

What are the advantage of an esophageal stethoscope compared to a precordial stethoscope?

A

Better quality heart and breath sounds and incorporates a temperature probe

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51
Q

How much CO2 does the average adult produce?

A

250mL CO2/min

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52
Q

What changes can affect a patient’s CO2 production?

A

Patient’s condition
Anesthetic depth (deeper decreases metabolism)
Temperature (colder decreases CO2 production)

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53
Q

What is the purpose of Capnography?

A

Confirms ETT placement

Confirms adequate ventilation

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54
Q

What is the most common type of capnography and how does it work?

A

Sidestream sampling, airway gas aspirated and pumped to measuring device

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55
Q

What are the sampling flow rate?

A

50-250mL/min pulled from circuit (be aware in peds patients)

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56
Q

What are some limitations to sidestream capnography?

A

H2O condensation can contaminate the system and falsely elevate readings
Lag time between sample aspiration and reading

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57
Q

How might an attached capnography affects a machine check?

A

May fail a machine check if sidestream sampling line attached, specifically the pressure check

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58
Q

What could a problem be if CO2 is detected on inspiration?

A

Incompetent inspiratory valve

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59
Q

What is the normal PACO2-PaCO2 gradient?

A

2-10mmHg

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60
Q

What does phase I on a capnograph represent?

A

Corresponds to inspiration, anatomic/apparatus dead space devoid of CO2

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61
Q

What should the phase I level be at?

A

Should be zero unless rebreathing

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62
Q

What would cause baseline elevation on a capnograph?

A

CO2 absorbant exhausted
Expiratory valve missing/incompetent
Bain circuit

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63
Q

What does phase II of a capnograph represent?

A

Early exhalation/steep upstroke, mixing of dead space with alveolar gas

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64
Q

What would cause a prolonged upstroke of phase II on a capnograph?

A 
Mechanical obstruction (kinked ETT)
Slow emptying of lungs (COPD and bronchospasm)
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65
Q

What does phase III on the capnograph represent?

A

CO2 rich alveolar air, horizontal with mild upslope

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66
Q

Why would phase III on a capnograph be steep?

A

Steepness is a function of expiratory resistance
COPD
Bronchospasm

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67
Q

What does phase IV on a capnograph represent?

A

Inspiration of fresh gas, return to baseline (near 0)

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68
Q

What might a low plateau on a capnogram represent?

A

Excessive ventilation
Low CO2 production
Diminished CO2
Significant dead space

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69
Q

What might a high plateau on a capnogram represent?

A

Hypoventilation

High CO2 production (MH)

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70
Q

What might a flat plateau with wide dips represent on a capnogram?

A

Less TV are superimposed on normal or mechanically timed exhalations, common when NMBA begin to wear off

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71
Q

What might small dips at the end of a flat plateau that is synchronous with the heart represent on a capnogram?

A

Cardiac oscillations from hypovolemia

72
Q

What type of technology does an anesthetic gas analyzer utilize?

A

Mass spectrometry

73
Q

How does mass spectrometry work?

A

Gas sample is ionized by electron beam and passed through a magnetic field, ions then identified by own unique trajectory across magnetic field

74
Q

What airway pressures are measure by the ventilator?

A

In-circuit pressure gauge
Peak inspiratory pressure
Sustained elevated pressure

75
Q

What alarm on the ventilator would notify the provider that there has been a disconnect somewhere in the circuit?

A

Low airway pressure

76
Q

What is the circulation guideline regarding standard V in the AANA monitoring guidelines?

A

Monitor cardiovascular status continuously via EKG and hear sounds. Record BP and heart rate at least every 5 minutes

77
Q

What could continuous EKG monitoring detect during anesthesia?

A 
Cardiac dysrhythmias
Conduction abnormalities
Myocardial ischemia/ ST depression
Electrolyte changes
Pacemaker function/malfunction
78
Q

What lead is typically monitored in a three electrode approach?

A

Lead II

79
Q

What leads are typically monitored in a five electrode approach?

A

Six standard limb leads (I,II, III, aVR, aVL and aVF) and one precordial lead (usually V5)

80
Q

Why would we use five electrodes versus three electrodes?

A

Better at detecting myocardial ischemia

Allows better differential diagnosis of atrial and ventricular dysrhythmias

81
Q

What are the two most commonly used leads monitored?

A

Lead II and V5

82
Q

What does lead II specifically monitor?

A

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

83
Q

What does V5 specifically monitor?

A

5th ICS/anterior axillary line

Detection of anterior and lateral wall ischemia

84
Q

What is the appropriate size of a blood pressure cuff?

A

The width must be 20% greater than the mean diameter of extremity

85
Q

How can blood pressure cuff size affect the reading?

A

Too narrow increases pressure

Too wide decreases pressure

86
Q

What is the standard way to measure arterial blood pressure?

A

Korotkoff sounds

87
Q

What is the most commonly used method to measure blood pressure during anesthesia?

A

Automated indirect NIBPM

88
Q

What are the advantages to using a NIBPM?

A

Easy and accurate
Versatile in children and obese
May be used on thigh or calf
oscillometry

89
Q

How does a oscillometric device work?

A

Air pumping inflates cuff –> microprocessor

Opens deflation valve –> oscillations sampled

90
Q

At what measurement does oscillometric devices become less reliable?

A

When BP falls below 70

91
Q

What is a major benefit to using oscillometric devices intraoperatively?

A

Their use has reduced the incidence of undetected HoTN intraoperatively

92
Q

What type of errors can occur with the use of oscillometric BP devices?

A

Surgeon leaning on cuff
Inappropriate cuff size
Shivering/excessive movement
Atherosclerosis and HTN

93
Q

What are some indications for invasive arterial BP monitoring?

A

Patient requiring BP more often than minute to minute
Critically ill
Anticipated rapid blood loss
Major procedures (cardiac, intracranial, carotid sinus)
Frequent ABGs

94
Q

Where is the most common site for arterial line placement?

A

Radial artery

95
Q

Why isn’t the ulnar artery typically used?

A

More difficult and more tortuous

96
Q

Why isn’t the brachial artery a good choice for an arterial line?

A

Complications may risk limb and its predisposed to kinking

97
Q

What arterial line location will more than likely cause a distorted wave form?

A

Dorsalis pedis

98
Q

Why isn’t the axillary artery a desirable location for an arterial line?

A

Potential for plexus/nerve damage from hematoma or traumatic cannulation

99
Q

What are some indication for central line placement?

A

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
Q

What side is preferred for internal jugular line placement?

A

Right side

101
Q

Why isn’t an external jugular line ideal?

A

More difficult to place leading to complications

102
Q

What are some comorbidities that may require a pulmonary artery catheter?

A 
Valvular heart disease
Recent MI
ARDS
Massive trauma
Major vascular surgery
103
Q

Why has the pulmonary artery catheter lost favor?

A

TEE less invasive

104
Q

What does standard V of AANA monitoring guidelines require of body temperature monitoring?

A

Monitor body temperature continuously on ALL pediatric patients receiving general anesthesia and when indicated on all other patients

105
Q

What factors affect body temperature?

A

Ambient room temperature
Scope and length of surgery (abdominal surgeries)
Hypothalamic depression
Intraoperative fluid replacement

106
Q

What are the four mechanisms of heat loss in the OR?

A

Evaporation
Convection
Conduction
Radiation

107
Q

How much does body temperature decrease when one liter of crystalloid is given at room temperature?

A

70kg patient’s temp is decreased by 0.4C for every liter of fluid given at room temperature

108
Q

What mechanism looses the most heat in the OR?

A

Radiation about 40%

109
Q

What type of heat loss occurs because of air velocity, OR air exchanges?

A

Convection about 30% heat loss

110
Q

What type of heat loss occurs because of contact with OR table and can be prevented with the use of blankets?

A

Conduction

111
Q

What type of heat loss occurs because of dry inspired gases?

A

Evaporation

112
Q

What structure maintains body temperature within a tight range?

A

Hypothalamus

113
Q

How does phase I affect thermoregulation?

A

Convective loss

Vasodilation causes redistribution of blood and temperature

114
Q

How does phase II affect thermoregulation?

A

Altered perception of dermatomes in areas anesthetized

115
Q

What can be done to prevent the convective losses that occurs in stage I of anesthesia?

A

Pre warm the patient for 30 minutes with warming blanket

116
Q

When does hypothermia occur?

A

When environmental heat loss outpaces metabolic heat production

117
Q

How much can anesthesia decrease body temperature?

A

1-4°C

118
Q

How does hypothermia affect wake up and oxygen demand?

A

May delay awakening

Can cause shivering which can increase O2 needs by 400%

119
Q

What patient populations are at the greatest risk for hypothermia?

A

Elderly
Burn patients
Neonates
Patients with spinal cord injuries

120
Q

What is considered hypothermia?

A

Temperature < 36°C

121
Q

What is considered mild hypothermia and what type of effects does it have on the body?

A

Mild 33-36°C
Reduced enzyme function
Coagulopathy

122
Q

What is considered moderate hypothermia and what type of effects does it have on the body?

A

Moderate < 32°C

Fibrillatory threshold

123
Q

When does hyperthermia occur during anesthesia?

A 
Rarely develops
LATE sign of MH
Endogenous pyrogens
Thyrotoxicosis
Anticholinergic blockade
Excessive environmental warming
124
Q

Where is the proper location for esophageal temperature monitoring?

A

Lower 1/3 of esophagus

125
Q

What mode of temperature monitoring is rarely used due to effect of perforation?

A

Tympanic membrane

126
Q

What are some superficial methods of warming patients?

A

Forced air warmer –> Most effective
Warming blanket
Radiant heat unit –> no role in OR doesn’t effect mean body temperature
Heated liquids –> burns

127
Q

What methods of warming are used for warming the core of the patient?

A

IVF warmers (Hotline)
Gastric lavage
Peritoneal irrigation

128
Q

What are some passive warming modalities?

A

Ambient temperature
Insulation
Heat and moisture exchanger (artificial nose)
Coaxial breathing circuit –> modified baine circuit

129
Q

At what ambient temperature of the OR will most adults remain normothermic?

A

> 24°C

130
Q

What does Standard V of the AANA monitoring guidelines state regarding neuromuscular function?

A

Monitor neuromuscular function and status when neuromuscular blocking agents are administered

131
Q

What do we use to monitor neuromuscular function?

A

Peripheral nerve stimulator, monitors the status of neuromuscular junction when using NMBAs

132
Q

How does a peripheral nerve stimulator work and what are its functions?

A

Delivers electrical stimulation to a peripheral motor nerve mechanically evoking a response
Permits titration of drug to optimal effect
Quantifies recovery from NMBA

133
Q

What occurs if a peripheral nerve stimulator is placed on a sensory nerve?

A

It will not evoke a response

134
Q

In what order does the onset sequence of NMBA affect the body?

A 
Eyes
Extremities
Chest
Abdominal muscles
Diaphragm
135
Q

What is the first muscle to recover from NMBA and why?

A

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
Q

What sites can be used to monitor neuromuscular blockade?

A

Ulnar nerve
Facial nerve
Posterior tibial nerve
Peroneal nerve

137
Q

What does the ulnar nerve innervate and where should the electrodes be placed?

A

Adductor pollicis muscle, electrodes can be placed at the wrist or the elbow

138
Q

How should the electrodes be placed on the nerve?

A

Negative (depolarizing) placed distally

139
Q

Why isn’t the ulnar nerve an accurate reflection of degree of block of the diaphragm or airway muscles?

A

These muscles are less sensitive to ND block

Adductor policies still paralyzed but can have coughing, breathing and vocal cord movement

140
Q

Where should the electrodes be placed when monitoring the facial nerve?

A

In front of the tragus of the ear and below while avoiding direct muscle stimulation

141
Q

What muscle is contracting when we stimulate the facial nerve?

A

Orbicularis oculi, can feel twitches by placing hand over the eye brow

142
Q

What gland does the facial nerve innervate?

A

Parotid gland

143
Q

What nerve is the best indicator of ND blockade of the diaphragm and airway muscles?

A

Facial nerve

144
Q

Where should you place the electrodes for posterior tibial nerve stimulation?

A

Place electrodes behind medial malleolus of tibia

145
Q

What movements should result from posterior tibial nerve stimulation?

A

Plantar flexion

146
Q

Where should yo place the electrodes for peroneal nerve stimulation?

A

Place electrodes on the lateral aspect of the knee

147
Q

What movements should result from peroneal nerve stimulation?

A

Dorsiflexion of the foot

148
Q

What are the five types of peripheral nerve stimulation?

A 
Single twitch
Train of four
Tetanic stimulation
Post-tetanic stimulation
Double burst stimulation
149
Q

Define what occurs during a single twitch stimulation.

A

Single pulse delivered every 10 seconds, increasing block results in diminished response

150
Q

What is the most commonly used nerve stimulating setting in anesthesia?

A

Train of four

151
Q

Define what occurs during train of four stimulation.

A

Four repetitive stimuli, ratio of responses to 1st and 4th twitches are sensitive indicator of ND relaxation

152
Q

How many receptors are block with each loss of twitch?

A

Loss of 4th twitch = 75% receptors blocked
Loss of 3rd twitch = 80% receptor blocked
Loss of 2nd twitch = 90% receptors blocked

153
Q

What is considered clinical relaxation?

A

75-95% block

154
Q

What will you see on a TOF with a non-depolarizing NMBA?

A

Fade with each twitch

155
Q

What other scenario might you see the same results in theTOF as non-depolarizing NMBA?

A

Phase II block from Succs

156
Q

What will you see on a TOF with a depolarizing NMBA?

A

Same height just diminishes over time

157
Q

Define what occurs during tetanic stimulation?

A

Tetany at 50-100Hz, five seconds at 50 Hz evoked tension approximates tension developed during maximal voluntary effort

158
Q

What occurs with tetanic stimulation in the presence of ND relaxants?

A

Fade occurs

159
Q

When will a sustained response occur in tetanic stimulation?

A

When TOF > 70%

160
Q

What type of peripheral nerve stimulation is useful when all twitches are suppressed?

A

Post-tetanic count

161
Q

Define what occurs in Post-tetanic count?

A

Apply tetanus at 50 Hz for 5 seconds, wait 3 seconds, apply single twitches every second up to 20

162
Q

What does the number of twitches tell you when using post-tetanic count?

A

The number of twitches is inversely related to the depth of block

163
Q

Define what occurs in double burst stimulation.

A

There are three short 50 Hz impulses followed by 750 sec by another 3 bursts

164
Q

Why might you use double burst stimulation over train of four for monitoring twitches?

A

More sensitive that TOF for visual evaluation of fade

165
Q

What two methods of peripheral nerve stimulation are appropriate to use during induction of anesthesia?

A

Single twitch

Train of four

166
Q

What two methods of peripheral nerve stimulation are appropriate to use during maintenance of anesthesia?

A

Train of four

Post tetanic count

167
Q

What two methods of peripheral nerve stimulation are appropriate to use during emergence of anesthesia?

A

Train of four

Double burst stimulation

168
Q

What do the NM monitoring guidelines state for which nerve to monitor during induction and emergence?

A

Monitor facial nerve for onset and ulnar nerve for recovery

169
Q

How long might recovery take if you only have 1/4 twitches?

A

As long as 30 minutes

170
Q

How long might recovery take if you only have 2-3 twitches?

A

Reversal may take 10-12 minutes following long acting relaxants and 4-5 minutes after intermediate

171
Q

How long might recovery take if you only have 4/4 twitches?

A

Adequate recovery within 5 minutes of neostigmine and 2-3 minutes with edrophonium

172
Q

What is the Bispectral index score tool utilized for during anesthesia?

A

Used to assess depth of anesthesia, however, not currently standard of care

173
Q

What are some reported advantage of BIS monitoring?

A

Reduced risk of awareness
Better management of responses to surgical stimulation
Faster wake up (controversial)
Most cost effective use of anesthetics

174
Q

What does the BIS measure?

A

EEG signal with index ranging from 0-100
0 = isoelectric
100 = awake CNS

175
Q

What things in the OR can effect the reading of the BIS monitor?

A 
Electro-cautery
EMG
Pacer spikes
EKG signal
Patient movement
176
Q

What BIS number is associated with increased risk of recall?

A

> 70

177
Q

What BIS number is the level suggested for anesthesia?

A

40-60

Principles of Monitoring & Fluid balance (3 decks)

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