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Anaesthesia > Clinical Monitoring During Anaesthesia - Pulse Ox, ECG, BP > Flashcards

Clinical Monitoring During Anaesthesia - Pulse Ox, ECG, BP Flashcards

1
Q

What is the normal air PaO2 in mmHg and SpO2%

A
  • PaO2: 100
  • SpO2: 99
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2
Q

What are the expected PaO2 and SpO2 for mild hypoxaemia of any air?

A
  • PaO2: <80
  • SpO2: <95
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3
Q

What are the expected PaO2 and SpO2 for severe hypoxaemia?

A
  • PaO2: <60
  • SpO2: <90 (life-threatening)
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4
Q

SpO2 should always be

A

> /= 95%

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5
Q

The amount of hemoglobin that binds depends on…

A

the partial pressure of oxygen that is free-floating

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6
Q

What is required to detect PaO2?

A

arterial blood gas machine

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7
Q

What colour is visible when there is severe hypoxaemia?

A

Cyanosis

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8
Q

By the time cyanosis is visible to the eye, hypoxaemia is…

A

already very severe
SpO2 is <80

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9
Q

What is the expected mild hypoxaemia PaO2/Pulse Ox number?

A

Mild hypoxaemia:
PaO2 <10.6 kPa (80 mmHg)
SpO2 (Hb saturation) </= 95%

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10
Q

What is the number of PaO2 and SpO2 in severe hypoxaemia?

A

PaO2 < 8kPa (60 mm Hg)
SpO2 </= 90%

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11
Q

What is the number of PaO2 and SpO2 that would produce cyanosis?

A
  • PaO2 < 6.7 kPa (50 mmHg)
  • SpO2 <80%
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12
Q

What are the locations on the body a pulse oximeter can be placed?

A

tongue, lip, nose, ear pinna, foot/toe, Achilles tendon, rectum, vulva, prepuce

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13
Q

What is a plethysmogram?

A

Pulse-volume curve

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14
Q

What does a plethysmogram show?

A

gives information about the strength of both the signal (reliability of the reading) and the pulse

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15
Q

if the pulse of a plethysmogram is weak, the…

A

amplitude of the pulse-volume curve is lose

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16
Q

What are the limitations of pulse oximetry?

A
  • does not give info about efficiency of respiration (ventilation)
  • normal saturation does not guarantee adeq tissue oxygenation
  • does not measure total blood O2 content
  • slow –> SpO2 reading responds to hypoxaemic event or apnoea w/ a delay (about 30 sec-1 min)
  • basic pulse ox cannot differentiate carboxyhaemoglobin or methaemaglobin from oxyhaemaglobin
  • carbon monoxide poisoning leads to falsely high pulse ox reading
  • in methaemoglobin poisoning, the pulse ox will give the reading of approx 85%
  • arrhythmias can affect reading
  • dark pigment or shivering/movement can lead to false readings
  • bright ambient lights can lead to false readings
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17
Q

What are causes of low saturation?

A
  • true hypoxaemia
  • poor contact w/ mm
  • decreased perfusion
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18
Q

What causes a lack of signal on a pulse ox?

A

cardiac arrest
low perfusion
probe fell off

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19
Q

Why do we measure arterial BP?

A
  • best info about tissue perfusion
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20
Q

When is renal autoregulation lost?

A

When SAP < 90 mmHg

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21
Q

When is brain autoregulation lost?

A

if MAP is < 60 or > 160 mmHg

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22
Q

Myocardial perfusion is inadequate if…

A

DAP <40 mmHg

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23
Q

equine myopathy occurs when

A

MAP is <70 mmHg

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24
Q

Mean arterial pressure depends on

A

cardiac output & systemic vascular resistance

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25
MAP =
CO x SVR
26
in an anaesthetised patient, BP measurement should always be performed w/ assessment of
CRT & MM colour
27
During GA, the BP should be maintained at:
SAP > 90 mmHg MAP >60-70 mmHg DAP > DAP 40 mmHg
28
The ideal arterial BP monitor should measure...
systolic, diastolic, and mean arterial BP
29
What are methods of arterial BP monitoring
non-invasive: doppler, oscillometric Invasive: cannula in artery (intra-arterial - gold standard)
30
Doppler flow detectors measure only...
systolic BP
31
Systolic BP in a doppler should be maintained at...
> 90 mmHg
32
For sick P's, what detector is best for monitoring?
doppler
33
Oscillometric BP is
non-invasive, continuous, automatic, portable, and user friendly
34
Oscillometric BP measures...
SAP, DAP, MAP, pulse rate
35
MAP is the most reliable on what machine?
Oscillometric BP machine
36
What are some disadvantages of oscillometric BP?
- may not be useful in very small patients - accuracy depends on cuff width & placement - sometimes fails to read when we need it most
37
What are some limitations of non-invasive BP measurements?
- delay - only reliable as a trend - location of the cuff relative to heart affects reading - take 2-3 readings before making adjustments - size & tightness of cuff affects the reading - over or underestimates extreme values
38
Invasive BP is considered...
the gold standard
39
An invasive BP measures beat-to-beat in real time the...
SAP, DAP, MAP w/ MAP being the most reliable, but all being reliable
40
Blood gas analysis requires...
heparinised arterial blood sample
41
blood gas analysis measures...
pH, PaO2, PaCO2, bicarbonate, etc
42
blood gas analysis is considered the gold standard for...
oxygenation and respiratory function
43
ECG is considered a
non-invasive measure of the electrical activity of the heart
44
ECG does not...
- correlate w/ CO - tell whether heart is beating/contracting or not
45
an ECG is most useful in detecting
cardiac arrhythmias
46
without an ECG, it is not possible to diagnose..
the exact nature of the arrhythmia
47
What are the most common arrhythmias under anaesthesia?
bradycardia, tachycardia, VPCs, AV blocks
48
What are the most common causes of intraoperative arrhythmias that need to be ruled out first?
- too light/deep anaesthesia - insufficient analgesia - hypercapnia - hypoxaemia - hypotension/hypertension - electrolyte imbalance
49
Explain the different segments
- P-wave: atrial depolarisation --> Increased amplitude = RA enlargement --> Increased duration = LA enlargement - P-R segment: AVN conduction, coordinated cardiac filling - QRS complex: ventricular depolarisation --> Q wave: ventricular septum --> R wave: bulk of ventricular myocardium --> S wave: basilar portion --> Increased R wave amplitude = cardiac enlargement --> Decreased amplitude = obesity, masses, cats - T-wave: ventricular repolarisation --> Peaked T waves = hyperkalaemia or normal; limited diagnostic value - ST segment: time from end of ventricular depolarisation to end of repolarisation --> ST elevation/depression = myocardial hypoxia - QT interval: entire ventricular depolarisation and repolarisation --> Prolonged QT interval = risk of arrhythmias
50
What are 6 basic questions that should be asked to help w/ ECG interpretation?
1. What is the HR (slow, normal, fast)? 2. What is the rhythm (regular, regularly irregular, irregular)? 3. Is there a QRS complex for every P wave? 4. Is there a P wave for every QRS complex? 5. Are they consistently & reasonable related? 6. What is the morphology of the QRS complex (narrow & upright or wide & bizarre)?
51
Cardiac output and the patient's haemodynamic stability depends on
HR x SV
52
Bradycardia decreases...
Cardiac output
53
Excessive tachycardia decreases CO & promotes
further arrhythmias
54
in addition to haemodynamic instability, cardiac arrhythmias may lead to...
electronic instability
55
What are life-threatening arrhythmias?
- V-tach (HR >/= 180 dog, >/= 240 cat) - 2nd deg AV block (HR <40 dog, <100 cat) - 2nd deg AV block w/ long pause, followed by an 'escape' rhythm - 3rd degree AV block - missing P-waves due to hyperkalaemia (atrial standstill) - cardiac arrest rhythms: asystole, V-fib, PEA
56
What are the most common peri-anaesthetic bradyarrhythmias?
- sinus bradycardia - AV blocks (1st, 2nd, 3rd) - Atrial standstill
57
What causes sinus bradycardia?
drugs, hypothermia, vagal stimulation, increased ICP
58
What are some causes of AV blocks?
- vagal stimulation, drugs (1st & 2nd blocks)
59
What causes atrial standstill?
Hyperkalaemia
60
What are the most common peri-anaesthetic tachyarrhythmias?
- sinus tachycardia - A-fib - VPCs - V-tach
61
What are causes of sinus tachycardia?
Pain, fear, stress, blood loss, anaemia, drugs (atropine, glycopyrrolate)
62
What causes a-fib?
DCM
63
What causes VPC's/V-tach?
- cardiomyopathy, myocardial hypoxaemia, GDV, haemoabdomen, endocrinological dz, pancreatitis, brain tumours, etc - myocardial oxygenation

Anaesthesia (23 decks)

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