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Clinical Anesthesia > Monitoring > Flashcards

Monitoring Flashcards

1
Q

What does anesthesia produce in a patient?

A
  • CNS depression (hypnosis)
  • CV depression (hypotension, +/- bradycardia, arrhythmias)
  • Resp depression (hypoventilation, +/ hypercapnia, hypoxemia)
  • Impairs thermoregulation (hypothermia, +/- hyperthermia)
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2
Q

What are the Big 5 of anesthetic monitoring?

A
  • ECG
  • Blood pressure
  • Pulseoximetry
  • Capnography
  • Temperature
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3
Q

What are the most common causes of perioperative death in small animals?

A

CV or respiratory causes

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4
Q

What should you be monitoring for during each step of the anesthesic process?

A
  • After pre-med: regurg/vomiting, hypoventilation, hypoxemia, arrhythmias
  • During induction: regurg/aspiration, hypoventilation/apnea, arrhythmias, hypotension
  • During maintenance: the Big 5
  • During recovery: airway protection, hypothermia, oxygenation, pain
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5
Q

What are some general considerations to have during the post-operative period?

A
  • Residual resp depression may lead to hypoxemia in animals breathing room air
  • Ability to protect airway against aspiration
  • Analgesics? - animal may be painful
  • Adequate body temp until they are able to thermoregulate normally

47% of anesthesia-related deaths occur in post operative period!!

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6
Q

How do you monitor the CNS in your anesthetic patient?

A

Clinical evaluation of reflexes:

  • Swallowing: important during extubation - patient can protect airway
  • Palpebral: light plane when present, can become fatigued
  • Corneal: presence of reflex is NO indicator of anesthetic depth and may still be present for short time after cardiac arrest
  • Muscular (jaw) tone
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7
Q

Describe the Guedel’s classification scheme for CNS monitoring

A
  • Stage I: Awake
  • Stage II: loss of consciousness, Involuntary movements (central normal pupil, irregular breath-holding, present palpebral, lacrimation, and response to surgical stim)
  • Stage III:
    • LIGHT plane (regular breathing, ventral miotic pupil, present palpebral, lacrimation, response to Surg stim)
    • MEDIUM plane (regular, shallow breathing, ventral miotic pupil, absent palpebral)
    • DEEP plane (jerky breathing, dilated central pupil, present corneal)
  • Stage IV: extreme CNS depression, cardiac arrest
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8
Q

What is the bispectral index (BIS)?

A
  • Combo of several electrical signals from the brain
  • Dimensionless number: indicates patient’s level of consciousness
    • ​ranges from 100 (awake) to 0 (isoelectric EEG)
    • 55 in humans = adequate depth for surgical anesthesia
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9
Q

What is MAP made up of?

A

Stroke volume and SVR

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10
Q

What is cardiac output made up of?

A

HR and SV (preload, afterload [SVR] and contractility)

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11
Q

How is the CV system monitored for anesthesia?

A

Clinically

  • Auscultation
  • Pulse rate/quality
  • CRT

Instrumentally

  • ECG
  • BP
  • Pulse pressure variation
  • Lactate
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12
Q

What is the normal blood pressure in awake animals?

A
  • Systolic: 140-160 mmHg
  • MAP: 95-110 mmHg
  • Diastolic: 80-95 mmgHg
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13
Q

What is the definition of hypotension?

A
  • MAP <65 mmHg
  • Untreated severe/prolonged hypotension => cardiac arrest or blindness or renal failure after recovery
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14
Q

What is the definition of hypertension?

A
  • MAP >140 mmHg or SAP >180 mmHg
  • Increases cardiac after load
  • Can lead to retinopathy, renal DZ, encephalopathy
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15
Q

What does pulse palpation tell you?

A

it’s a subjective estimation of pulse pressure (SAP-DAP); can be high with low pressure associated with vasodilation —> NOT ACCURATE

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16
Q

What are the various methods of measuring BP?

A
  • Non Invasive: Oscillometric, Doppler
  • Invasive (direct): arterial catheter
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17
Q

What value is the most accurate for oscillometric readings?

A

the MAP; SAP and DAP are calculated values

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18
Q

How does the placement and size of the cuff used change the accuracy of the oscillometric BP readings?

A
  • Larger cuff (too loose) = false low pressure
  • Smaller cuff (too tight) = false high pressure
    • ​cuff should be 40-60% circumference of extremity
  • placed above/below heart level = wrong readings
  • arrhythmias might affect readings
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19
Q

What is HDO?

A
  • High definition oscillometric device
    • recognizes artifacts, ultra precise, high sensitive at low amplitudes
    • good for MAP and DAP
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20
Q

Describe how Dopplers work

A
  • Application of piezoelectric ultrasound crystals over artery distal to cuff
  • cuff pressure at which the first audible flow sound is heard approximates SAP
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21
Q

T or F: there is good correlation between the MAP and SAP values calculated by Dopplers and indirect/direct BP methods

A

False; there is poor agreement between the two methods (particularly in small animals)

22
Q

Describe direct blood pressure monitoring

A
  • Gold standard
  • beat to beat measurement (useful when giving vasoactive drugs)
  • Waveform and pulse contour analysis
  • should be positioned at level of R atrium
  • allows for frequent blood sampling
  • measures SAP and DAP and calculated MAP
23
Q

What are the best arteries to use for direct BP monitoring in small animals?

A
  • Dorsal metatarsal (dorsopedal)
  • lingual
  • radial/carpal
  • coccygeal
  • femoral
  • auricular (dogs with large ears)
24
Q

What does damping do to direct BP monitoring?

A
  • It reduces accuracy
  • Overdamping
    • ​results in lower SAP and higher DAP
    • MAP not affected
    • due to long tubes, air bubbles, clots
  • Underdamping
    • ​​results in higher SAP and lower DAP
    • MAP not affected
25
Q

How does direct BP monitoring relate to fluid responsiveness?

A
  • It monitors the ability of the CV system to increase CO when a fluid volume is administered
    • Should have incr in CO in response to bolus of fluids
26
Q

What is an alternative method of direct BP monitoring?

A
  • Improvised method using an aneroid manometer
27
Q

What are the principles of monitoring using capnography?

A
  • Used to assess adequacy of ventilation
  • Estimates PaCO2 by measuring concentration of expired CO2 (ETCO2)
  • Differences b/t PaCO2 and ETCO2 can be d/t dead space (2-5 mmHg)
  • also useful for diagnosis of mechnical problems, airway obstruction, and cardiogenic shock
28
Q

What are the advantages and disadvantages of using side stream capnography?

A

Gas sampled from Y piece

Adv:

  • can sample other gases (anesthetic agents)
  • away from patient
  • inexpensive

Disadv:

  • delayed response
  • eccessive sampling in patients w/ small TV (underestimates ETCO2)
  • need for scavenger
29
Q

What are the advantages and disadvantages of using main stream capnography?

A

Sensor located between ET tube and breathing circuit

Adv:

  • real time measurements, no delay
  • less disposable parts
  • no need for scavenger

Disadv:

  • sensor is heavy and can kink small tubes
  • fragile
  • adds dead space
  • only measures CO2 and O2
30
Q

What does each phase of the capnograph mean?

A
  • Phase I: inspiration
  • Phase II: expiratory upstroke (transition from dead space gas to alveolar gas)
  • Phase III: expiratory plateau (gas coming from alveoli)
    • D point represents ETCO2
    • If there is no plateau —> might not be actual ETCO2
  • Phase IV: inspiratory downstroke
31
Q

What does this capnograph suggest?

A

Low ETCO2

hyperventilation

32
Q

What does this capnograph suggest?

A

High ETCO2

Hypoventilation

33
Q

What does this capnograph suggest?

A

Spontaneous breathing during IPPV

34
Q

What does this capnograph suggest?

A

Cardiac oscillations

35
Q

What does this capnograph suggest?

A

Airway obstruction

progressive increase in alfa angle

36
Q

What does this capnograph suggest?

A

Large leak from the ET tube

Decrease in plateau due to room air contamination

37
Q

What does this capnograph suggest?

A

Rebreathing CO2

exhausted CO2 absorbent

incompetent expiratory valve

38
Q

What does this capnograph suggest?

A

Rebreathing CO2

incompetent inspiratory valve

39
Q

What does this capnograph suggest?

A

Abrupt loss ETCO2

Disconnection

Apnea

40
Q

What does this capnograph suggest?

A

Gradual and significant decrease in ETCO2

Sudden blood pressure drop

Sudden CO drop

Cardiac arrest

PTE

41
Q

What does pulse oximetry tell you?

A
  • Hemoglobin saturation with oxygen
  • normal range =98-99%
    • hypoxemia = <95%
    • severe hypoxemia = <90%
42
Q

What are the downsides of pulse oximetry?

A
  • Cannot measure carboxyhemoglobin
  • Several sources of interference:
    • vasoconstriction, ambient light, electrocautery
43
Q

Pulse ox’s can be placed where?

A
  • Tongue
  • lips
  • vulva
  • prepuce
  • base of tail
  • rectum
44
Q

Describe PaO2

A
  • Measure of the ability of the lungs to move oxygen from the atmosphere to the blood
  • Measured using a blood gas analyzer (requires arterial sample)
  • normal PaO2 at sea level (breathing 21% oxygen) ranges between 80-110 mmHg

Hypoxemia = PaO2 <80 mmHg

Severe hypoxemia = PaO2 <60 mmHg

45
Q

What are the 5 causes of hypoxemia?

A
  1. Low FiO2
  2. Hypoventilation
  3. Ventilation-perfusion mismatch
  4. Diffusion impairment
  5. Shunt
46
Q

What are some important principles in monitoring body temp during anesthesia?

A
  • Body heat is unevenly distributed: core temp is 2-4*C higher than the peripheral
  • General anesthesia inhibits vasoconstriction, allows redistribution of body heat and affects thermoregulatory mechanisms
47
Q

When is the max period of body temperature loss under anesthesia?

A

within the first hour

48
Q

What are the consequences of hypothermia?

A

90-94F

  • Marked CNS depression
  • Little or no anesthetic requirement
  • Atrial arrhythmias
  • 50% reduction on O2 consumption
  • HR and CO reduced by 40%
  • BP reduced by 60%
49
Q

Describe hyperthermia during anesthesia

A
  • Rare during anesthesia
  • Most commonly iatrogenic
  • often large heavy coated animals
  • Opioid associated hyperthermia - most common in cats and ferrets
50
Q

What should you suspect (and aggressively treat) in a patient that is hyperthermic and demonstrates other signs of hypermetabolism (increased ETCO2, metabolic acidosis, hypoxia)?

A

malignant hyperthermia or thyrotoxicosis

Clinical Anesthesia (15 decks)

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