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ANESTHESIA > 25 – Monitoring > Flashcards

25 – Monitoring Flashcards

1
Q

What are the aims of monitoring physiological status?

A
  • Ensure adequate ‘depth’
  • Maintain normal physiology
  • Ensure safety of patient and personnel
  • Legal implications
  • *monitoring decreases odds of death!
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2
Q

What can we monitor?

A
  • Depth of anesthesia (CNS)
  • *Circulation, ventilation, oxygenation: ADEQUATE PERFUSION WITH O2-BLOOD
  • Signs of pain
  • Temperature
  • Neuromuscular function
  • Renal function
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3
Q

What are the 2 methods to measure mean arterial blood pressure?

A
  • Invasive (direct)=GOLD-STANDARD
  • Non-invasive (indirect)
  • *indirect assessment of perfusion
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4
Q

What are the 2 ways to indirectly measure blood pressure?

A
  • Oscillometric method
  • Doppler method (sphygomomanometry)
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5
Q

What are both oscillometric and doppler method based on?

A
  • Occlusion of blood flow to an extremity by inflation of cuff
  • Detection of reappearance of blood flow during deflation
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6
Q

What is the ideal cuff width?

A
  • 30-40% of the circumference of the limb
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7
Q

What happens if the cuff is too wide?

A
  • Underestimation of BP
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8
Q

What happens if the cuff is too narrow?

A
  • Overestimation of BP
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9
Q

Where should the cuff be position?

A
  • Same level as heart
  • *limb or tail
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10
Q

What happens if cuff position is below heart?

A
  • Falsely high
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11
Q

What happens if cuff position is above heart?

A
  • Falsely low
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12
Q

Doppler/sphymomanometry

A
  • PROBE placed over artery distal to cuff
    o Sends ultrasonic signal
    o Reflected by moving structures (RBCs)
    o Changes frequency
    o Converted into an audible signal
  • ENSURE good probe contact with coupling gel
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13
Q

Steps for using a doppler to take a BP reading

A
  1. Inflate cuff until blood flow distal is occluded and doppler sound disappears
  2. Deflate cuff slowly
  3. Pressure at which blood flow recommences (whooshing sound) corresponds to
    a. DOGS and CATS: systolic BP
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14
Q

What are the advantages of a doppler?

A
  • Any size of animal
  • Cold blooded animals
  • *can be used anywhere blood flows!
    o Also used for continuous HR monitoring in exotics and neonates (place over heart)
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15
Q

What are the disadvantages of a doppler?

A
  • Operator experience
  • Labor intensive
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16
Q

Oscillometric method

A
  • Occlusive cuff on limb or tail
  • Cyclically inflates and deflates
  • Sensor detects pressure changes in cuff during its deflation as pulsatile flow returns
  • *mean BP=maximal oscillation amplitude
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17
Q

What are the advantages of oscillometric method?

A
  • Non-invasive
  • Automatic
  • Less labor intensive
  • Can be programmed to take a reading every 1-10mins
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18
Q

What are the disadvantages of oscillometric method?

A
  • Does NOT work well in case of
    o Cardiac arrhythmia, bradycardia, severe hypotension
    o Movement and shivering
    o No continuous HR monitor
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19
Q

What are high definition oscillometric devices (HDO)?

A
  • Used advanced software algorithms to increase accuracy
  • Allows observer to accept/reject measurements
  • *clinical trials
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20
Q

Where is the catheter placed for direct blood pressure monitoring?

A
  • Peripheral artery
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21
Q

Direct BP monitoring

A
  • Continuous measurement
  • Connected to a pressure transducer via noncompliant tubing
  • Transducer must be ‘zeroed’ to ambient air at level of right atrium
  • Allows REPEATED arterial blood sampling
  • *used in large animals (easy to place catheter) and critically ill small animals
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22
Q

Palpation of pulse is NOT the same as BP

A
  • Pulse pressure: difference between systolic and diastolic BP
  • Need a difference of 30mmHg to palpate a strong pulse
  • *no femoral pulses palpable when systolic pressure <60mmHg
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23
Q

Mucous membrane colour and capillary refill time

A
  • Should check on it
  • PINK with CRT less than 2 seconds
  • Blue: cyanosis
  • Pale: anemia or intese vasoconstriction
  • Red: vasodilation: hypercapnia: PaCO2>60mmHg, drugs)
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24
Q

How do you monitor the respiratory system? (ensuring adequate ventilation and oxygenation)

A
  • Capnography
  • Pulse oximetry
25
Q

Pulse oximetry is a Non-invasive continuous measurement of

A
  • Pulse rate
  • SpO2 (oxygen saturation): % of arterial Hb that carriers O2
26
Q

What is the normal value of SpO2?

A
  • 95-100%
27
Q

What are the 2 principles that pulse oximetry is based on?

A
  • Changing volume of tissue bed can be measured by change in light absorption
  • Deoxyhemoglobin and oxyhemoglobin absorb red and infrared light differently
28
Q

Light Emitting Diodes (LEDs) (pulse oximetry)

A
  • Emit light of red and infrared wavelengths alternately (770-1000Hz) through tissue bed
29
Q

Receiver (pulse oximetry)

A
  • Receives signal after it has transversed the tissue bed
  • *ratio of red and infrared light absorption used in an algorithm to determine % saturation of Hb with O2
30
Q

What are the different probes with pulse oximetry?

A
  1. Transmittance: clip onto tongue or other places
  2. Reflectance: rectal or esophagus
    a. Needs to be directed to spinal column (or other bone) so it is reflected back to the transmitter
    b. Ex. when you can’t access the head or if tongue is pigmented
31
Q

What are the commonly used sites for pulse oximetry?

A
  • Tongue
  • Toe web
  • Pinna
  • Prepuce or vulva
32
Q

Pulse oximetry is not a ‘set and forget’ device!

A
  • It squeezes tissues and reduces blood flow
  • Regular repositioning is necessary
33
Q

At what saturation % and PaO2 does hypoxemia occur?

A
  • Less than 90%
  • 60mmHg
  • *late indicator of trouble under GA on 100% O2
34
Q

Poor signal detection with pulse oximetry may be a problem (disadvantages)

A
  • Poor probe positioning
  • Poor perfusion
    o Hypotension or vasoconstriction
  • Arrhythmias, slow HRs
  • Venous congestion (ex.
  • Patient movement, shivery
  • Different forms of hemoglobin
35
Q

Capnometry can measure

A
  • exhaled END-TIDAL CO2
  • Respiratory rate
  • *non-invasive technique to assess adequacy of ventilation
    o Put between ET tube and breathing system
36
Q

End tidal CO2 reflects

A
  • Arterial CO2 (PaCO2)
  • *end tidal CO2 is about 2-5 mmHg less than PaCO2 in small animals
    o Slightly larger gap in large animals
37
Q

What are the 3 factors that determine blood/end-tidal CO2 levels?

A
  • Metabolism: rate of CO2 production by cells
  • Circulation: CO output
  • Alveolar ventilation: if decreases=alveolar CO2 and ET CO2 increases
38
Q

What are the values of normocapnia?

A
  • PaCO2: 35-45mmHg
39
Q

What are the values of hypocapnia?

A
  • PaCO2: less than 35mmHg
40
Q

What are the values of hypercapnia?

A
  • PaCO2: more than 45mmHg
41
Q

Capnometry can provide info about

A
  • Confirmation of intubation
  • Monitoring circuit disconnection
  • ID of airway obstruction
  • Rebreathing
  • Severe circulatory problems
  • *CONTINUOUS MEASUREMENT (slightly delayed)
42
Q

What is the technology of capnography?

A
  • Infrared absorption spectroscopy
  • *mainstream and sidestream sensor
43
Q

What is a side stream sensor: capnography?

A
  • Measuring chamber located in computerized monitor
    o Withdraw gas sample from withing anesthetic breathing system near/at ET tube connector
  • Anesthetic gas should be scavenged or returned to system
  • Low dead-space connecters are available for patients less than 5kg
  • Sampling rate: 50-200mL/min
44
Q

Negatives of sidestream sensor (capnography)

A
  • Sampling tube can be obstructed (moisture, kinked)
    o Water vapor must be removed before entering measuring chamber (water trap/filter)
  • Measurement delay
45
Q

What is a mainstream sensor: capnography?

A
  • Measuring chamber is placed directly between ET tube and breathing system
  • DELICATE: prone to be drooped or broken
    o Prone to moisture damage
  • More accurate results
  • Immediate readings
  • Increase in apparatus dead space
46
Q

Normal wave form

A
  • Square wave form and CONSISTENT
47
Q

What would the capnometry look like if the patient was esophageal intubation?

A
  • No CO2
48
Q

Curare cleft: surgeon notches (notched plateau) REASONS WHY=artifact

A
  • Surgeon leaning/pressing on chest
  • Diaphragmatic activity
    o Animal fights the ventilator
    o Spontaneous ventilation retuning after neuromuscular blockage
49
Q

Cardiogenic oscillations: trouble shooting

A
  • Larger dogs
  • *cardiac movement moves gas in airways
    o ‘ripples at end of exhalation’
50
Q

If see re-breathing of CO2: trouble shooting

A
  • Problem!
  • Tracing does NOT return to zero between breaths
  • Inspired CO2 (normally 0) increases to 5-15mmHg
  • End-tidal CO2 increases
51
Q

What are some reasons for re-breathing CO? **

A
  • Incorrect fresh gas flow (non-rebreathing system)
  • Exhausted soda-lime
  • Malfunction valves
52
Q

Sloping of expiratory trace: ‘shark fin’**

A
  • Partial obstruction of airway: secretions, kinking of ET tube
  • Partial obstruction of lungs: bronchospasm, COPD
53
Q

What happens if you see hypercapnia: high end tidal CO2 (>45mmHg)?

A
  • Hypoventilation
  • Endobronchial intubation
  • Increased CO2 production
    o Malignant hyperthermia, hyperkalemic periodic paralysis
    o Increased metabolic rate
54
Q

What is happening if you see rapidly decreasing end-tidal CO2?

A
  • Impending cardiac arrest, sever hypotension
  • Pulmonary thromboembolism (more common in humans)
  • *anesthetic emergency=CHECK PATIENT!
55
Q

What is happening if you see sudden zero end-tidal CO2: straight line?

A
  • Circuit disconnection
  • Extubation
  • Respiratory arrest (apnea)
  • CO2 sampling line blockage or leak
  • Cardiac arrest
  • *anesthetic emergency: CHECK PATIENT!!
56
Q

ECG

A
  • Continuous monitoring of electrical activity of heart
  • Not reliable for basic monitoring
  • No INFO about mechanical activity: no guarantee heart is actually beating
  • No INFO on CO, BP
  • 3 electrodes (crocodile clips, esophageal)
57
Q

Auscultation: heart and lung sounds

A
  • External
  • Esophageal stethoscope
  • *non-continuous information
58
Q

What is the visual assessment that you can do?

A
  • RR, depth and breathing patterns
  • Chest excursions: visualization and palpation
  • Observation of rebreathing bag

ANESTHESIA (27 decks)

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