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Surgery I > Anesthetic monitorings > Flashcards

Anesthetic monitorings Flashcards

1
Q

OBJ: Become familiar with the techniques used to monitor anesthetic depth in veterinary patients

A
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2
Q

OBJ: Understand how to use and interpret data form monitors used for:

  • blood pressure
  • Heart rate
  • Cardiac electrophysiologic activity (electrocardiogram)
  • Hemoglobin saturation with O2
  • Ventilatory function and exhaled carbon dioxide
A
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3
Q

What is Anesthetic Monitorings?

A
  • Observational monitoring of the animals responses to:
    • Increases or decreasing delivery of an anesthetic
    • Noxious stimuli
    • Charge in the patient’s body position
  • Recording and responding to information from monitoring equipment
    • ECG
    • Blood pressure monitor
    • Pulse oximeter
    • Capnography
    • Thermometer
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4
Q

Why monitor anesthetic depth?

A
  • Ensure lack of patient awareness, recall, pain and movement
  • Negative effects of anesthetics are associated with increasing depth of anesthesia
    • Hypotension
    • Hypoventilation
    • Decreases in cardiac output
    • Decreases in peripheral perfusion
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5
Q

What are the “stages and Planes’ of anesthesia?

A
  • Refers to Guedel’s classification of stages of anesthesia
    • published 1937
    • Stage 1 - 4
    • Based on older, no longer used anesthetics such as ether
    • NO longer useful
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6
Q

in what ways is Anesthetic depth described?

A
  • “too light”
    • responds to noxious stimuli
      • movement
      • tachypnea
      • increasing heart rate and blood pressure
  • “too deep”
    • no response but undesirable effects of the anesthetic may occur
  • “just right”
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7
Q

How should anesthetic depth be monitored?

A
  • Ongoing moment to moment assessment
    • Changes in depth can be quite subtle
    • No reliable or practical single piece of equipment to assess depth
    • Do not focus on just a single parameter to judge depth of anesthesia
  • Develop observational skills and understand how to respond
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8
Q

What are the subjective measures for judging anesthetic depth?

A
  • Eye position
  • palpebral reflex
  • lacrimation
  • Jaw tone, muscular relaxation
  • character of breathing
  • Patient’s response to position changes
  • patient’s motor response to noxious stimuli
    • first noxious stimuli is often the towel clamp
  • Hemodynamic responses to noxious stimuli
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9
Q

What does the palpebral reflex during isoflurane anesthesia mean?

A
  • Dogs / Cats
    • Present = very light
    • Absent dos not guarantee a surgical plane of anesthesia
  • Horses:
    • slight palpebral reflex often present during surgical planes of anesthesia
  • Cattle / small ruminants
    • may or may not be present
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10
Q

How does one check the palpebral reflex?

A
  • Gently touch medial and lateral canthus
  • Do NOT tap on the eyelid - can elicit a corneal response
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11
Q

What are the positions of the globe and pupil during isoflurane anesthesia?

A
  • Very Light:
    • pupil may still be centrally positioned
    • palpebral reflex present
    • lacrimation present
  • Increasing depth:
    • pupil positioned ventromedially
    • lacrimation markedly decreased
  • Excessive depth:
    • Pupil centrally located
    • NO palpebral
    • little to no lacrimation
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12
Q

How should jaw tone be assessed for anesthetic depth? when is it not useful?

A
  • Reflection of muscle relaxation
  • Open jaw fully 2 times
    • requires both hands
      • one hand stabilizes maxilla
      • one hand moves the mandible
  • Should feel slight resistance when mouth is ½ - ⅔ open
  • Very light = tighter jaw
  • Deep = slack jaw
  • Not useful in very young patients (<8 wks)
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13
Q

What are the objective measurements for depth assessment?

A
  • End-tidal anesthetic agent monitoring
  • End-tidal carbon dioxide tension
    • increased depth, increased hypoventilation
  • Changes in blood pressure in response to noxious stimulus
  • Changes in ventilatory character
    • Thoracic movement
    • Abdominal movement
    • Response to stimulus
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14
Q

What is used to monitor the cardiovascular system during anesthesia?

A
  • Heart rate
  • Blood pressure
  • Mucous membrane color
  • Capillary refill time
  • Limb temperature
  • Pulse oximetry/plethysmography
  • ECG
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15
Q

What technique is used to monitor the heart rate during anesthesia?

A
  • Stethoscope on the thorax
  • Esophageal stethoscope
  • Palpation of peripheral pulse
  • ECG monitor
  • Pulse oximeter reading of the heart rate
  • Doppler peripheral flow signal
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16
Q

What values are normal for heart rate during anesthesia?

A
  • Acceptable rate varies with species and within species
  • Drug influences:
    • alpha 2 agonists
    • Opioids
    • Anticholinergics
    • Body temperature
    • Think in terms of functional rate
  • Anything less than 60 is NOT necessarily bad
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17
Q

What is an esophageal stethoscope?

A
  • Passed through the mouth into the esophagus
  • Balloon tipped end is positioned over the heart
  • Listen and adjust position for where heart sounds are loudest
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18
Q

Where can the peripheral pulse be palpated during anesthesia?

A
  • Dogs / cats
    • lingual, dorsal pedal, femoral, coccygeal, metacarpal, metatarsal
  • Horses:
    • facial, mandibular, auricular, palatine, greater metatarsal
  • Ruminants:
    • Auricular, digital, saphenous, palatine
  • Swine:
    • auricular, femoral, digital
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19
Q

What can the mucous membranes be used to evaluate during anesthesia?

A
  • Gives some indication of peripheral perfusion and Oxygenation
  • Color:
    • pink but not pale
    • Cyanosis difficult to recognize unless very hypoxemic
      • requires 5 grams of desaturated hemoglobin per deciliter of blood to detect cyanosis
    • Pale can represent poor perfusion and/or anemia
  • Capillary refill time:
    • Should occur in less than 2 sec
    • reflection of peripheral blood flow
20
Q

What is a doppler ultrasound for blood pressure?

A
  • Paired piezoelectric ultrasound crystals over an artery
  • Blood pressure cuff proximal to the crystals
  • An ultrasound signal is sent out and back to the crystal and detects flow through an artery
    • crystal detects a change in frequency of the ultrasound when it comes back
    • transforms that information to an audible signal
  • Blood pressure cuff inflated until the sound is gone
  • gradually deflate - when sound occurs that is SYSTOLIC pressure
21
Q

What is the appropriate sized doppler ultrasound cuff? what happens if the cuff size isn’t appropriate?

A
  • Height should be 40-60% of the circumference of the appendage (leg / tail) where the cuff is placed
  • Too small = overestimate pressure
  • Too big = underestimate pressure
22
Q

How does an Oscillometric Blood Pressure Monitor track blood pressure during anesthesia?

A
  • Based on detection of arterial wall movement
    • Machine inflates a cuff to a point where it occludes flow through an artery
    • Deflates cuff
    • Blood starts to flow turbulently through the artery
      • machine detects movement from the blood flow - SYSTOLIC pressure
    • MAgnitude of ocillations increases to a maximum then decreases
      • maximum is MEAN blood pressure
      • as the cuff decreases, flow in vessel becomes laminar and no oscillations are detected - DIASTOLIC pressure
23
Q

What is Direct Blood Pressure Monitoring?

A
  • Catheter placed in peripheral artery
  • A transducer converts the mechanical pressure signal to an electrical signal
  • Digitized and displayed on a monitor
    • Wave form
    • Numbers corresponding to systolic, diastolic, and mean arterial pressure
24
Q

OBJ: Understand the principles of oxygen saturation of hemoglobin and how we monitor this with a pulse oximeter

A
25
Q

OBJ: Know what a capnograph is an how to use it to evaluate a patient’s ventilatory status

A
26
Q

OBJ: know why an ECG would be used during anesthetic monitoring

A
27
Q

OBJ: know the benefits of monitoring temperature during anesthesia

A
28
Q

What is the goal of oxygenation monitoring?

A
  • Ensure an adequate oxygen concentration in the patient’s arterial blood
  • Objective methods of monitoring oxygenation include
    • Arterial blood gas analysis
    • Pulse oximetry
29
Q

What is a Oxygen Hemoglobin Saturation Curve?

A
  • Saturation of hemoglobin (SO2) and partial pressure of oxygen in the blood (PO2) has a relatively linear relationship below a PO2 of about 40mmHg
  • Above a PO2 of about 80 mmHg the curve is relatively flat
    • Saturation changes very little
  • Difference between normoxemia and hypoxemia is only a few saturation points
  • Small changes in SO2 represent large changes in P)2 on the steep part of the curve
30
Q

What does Pulse Oximetry do?

A
  • Measures oxygen saturation of hemoglobin
  • Noninvasive
  • Continuous detection of pulsatile arerial blood in a tissue bed
  • Absorption or reflection of red and infrared light is used to detect % of oyhemoglobin vs deoxyhemoglobin
  • Must detect pulsatile flow
    • Measurement inaccurate or not present with poor peripheral flow
  • Provides a pulse rate
31
Q

What is the cut off for being considered hypoxic?

A

<60 mmHg

32
Q

What are healthy Pulse Oximeter Readings?

A
  • Healthy patients breathing >95% O2
    • saturation should be between 97 - 100%
  • Healthy patient breathing room air
    • saturation should be about 95%
  • patients with low saturation need to be evaluated for causes of hypoxemia
33
Q

What can cause Pulse oximetry artifacts / inaccuracies?

A
  • Motion artifact
  • Ambient light artifact
    • no longer a problem with most
  • Poor peripheral flow
    • hypotension
    • vasoconstriction
  • Electrical interference from cautery
  • Increased carboxyHb or metHb
    • do NOT carry oxygen
    • Can be differentiated by most pulse oximeter
34
Q

What is Capnography?

A
  • Measures and displays CO2 concentration in the expired air
  • End-tidal CO2 reflects partial pressure of CO2 in the alveoli
    • alveolar CO2 will be an accurate estimate of arterial CO2
  • Continuous noninvasive measure of CO2
    • reflects the patient’s ventilatory status
  • Standard of care for monitoring human patients
35
Q

What are the different types of capnographs?

A
  • Sidestream
  • Mainstream
36
Q

What is side stream capnography?

A
  • Aspirate gas through a small tube that is connected to an adaptor between the endotracheal tube and the breathing circuit
  • Rate of gas aspiration varies with the machine
    • Datex-Ohmeda monitors 200ml/min
    • Nellcor microstream 50ml/min
      • Microstream monitors should be used on all small patients
37
Q

What are Mainstream capnographs?

A
  • Infrared light source and infrared detector are in the adaptor that is between the endotracheal tube and the breathing circuit
  • Adaptor between the breathing circuit and ET tube
  • Instantaneous reading with each breath
38
Q

What is the Massimo Emma II?

A
  • Mainstream capnograph
  • Small, portable
  • Designed for short term use
    • confirm ET placement
    • During CPR
  • Adult, pediatric, and neonatal adaptors
  • Used in some veterinary practices as reasonable alternative for capnography because of lower cost
39
Q

Why would a capnograph fail to display a waveform?

A
  • Esophageal intubation
  • Apnea or respiratory arrest
  • Cardiac arrest
  • Disconnected breathing circuit and adaptor from the ET tube
  • Obstructed ET tube
40
Q

Why would the capnograph have high End-tidal CO2 Reading?

A
  • Hypoventilation
    • common during anesthesia with isoflurane or sevoflurane
    • Normal CO2 35 - 45%
  • Rebreathing CO2
    • Faulty breathing circuit
    • Inadequate O2 flow with a nonrebreathing circuit
    • Exhausted CO2 absorbent (soda lime)
    • Excessive dead space between the breathing circuit and the ET tube
    • Rebreathing of CO2 will cause an elevated baseline on the capnograph tracing
      • waveform does NOT return to baseline
41
Q

What are Cardiogenic Oscillations?

A
  • On the capnograph
  • Small, regular sawtooth pattern on the graph
  • Synchronized to heart rate
  • When the heart beats the changes in heart volume causes slight changes in intrathoracic pressure and changes in lung volume
42
Q

What would inadequate sampling of alveolar gas result in? why does it happen?

A
  • Can be a problem with small patients
    • particularly on nonrebreathing circuits
  • Underestimates alveolar CO2
  • Capnograph will still give a value but it will underestimate alveolar CO2
43
Q

What does Rapid Decline in End-tidal CO2 mean?

A
  • CO2 has to get to the lung from pulmonary circulation
  • If there is rapidly declining ET-CO2 you need to be concerned about decreasing cardiac output and cardiac arrest
44
Q

What is a ventilometer?

A
  • Attaches to the expiratory limb of a breathing circuit
  • Measures volume of gas flowing through the tube on expiration
  • Can measure tidal volume and/or minute ventilation
  • Expensive ($1300)
    • secure it to the anesthetic machine so it is not dropped
45
Q

What is an electrocardiogram?

A
  • Measures and displays electrical activity of the heart
  • Continuous ECG necessary for accurate and rapid detection of any dysrhythmias or abnormalities in conduction
  • We place an ECG on all patients prior to induction of anesthesia
    • may not be in a standard lead configuration
    • We are using this to detect dysrhythmia
46
Q

Why is temperature monitoring important during surgery?

A
  • Hypothermia is common in our patients
    • Affects healing
    • Prolongs recovery from anesthesia
    • May induce shivering in recovering which increases oxygen demand
  • Preventing hypothermia is easier than treating hypothermia
  • Overwarming can also occur
    • multiple warm water blankets in use
    • Forced air warming
47
Q

What is a normal capnograph waveform? what are its parts?

A

Surgery I (37 decks)

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