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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
Q

MAP =

A

CO x SVR

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26
Q

in an anaesthetised patient, BP measurement should always be performed w/ assessment of

A

CRT & MM colour

27
Q

During GA, the BP should be maintained at:

A

SAP > 90 mmHg
MAP >60-70 mmHg
DAP > DAP 40 mmHg

28
Q

The ideal arterial BP monitor should measure…

A

systolic, diastolic, and mean arterial BP

29
Q

What are methods of arterial BP monitoring

A

non-invasive: doppler, oscillometric
Invasive: cannula in artery (intra-arterial - gold standard)

30
Q

Doppler flow detectors measure only…

A

systolic BP

31
Q

Systolic BP in a doppler should be maintained at…

A

> 90 mmHg

32
Q

For sick P’s, what detector is best for monitoring?

A

doppler

33
Q

Oscillometric BP is

A

non-invasive, continuous, automatic, portable, and user friendly

34
Q

Oscillometric BP measures…

A

SAP, DAP, MAP, pulse rate

35
Q

MAP is the most reliable on what machine?

A

Oscillometric BP machine

36
Q

What are some disadvantages of oscillometric BP?

A
  • may not be useful in very small patients
  • accuracy depends on cuff width & placement
  • sometimes fails to read when we need it most
37
Q

What are some limitations of non-invasive BP measurements?

A
  • 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
Q

Invasive BP is considered…

A

the gold standard

39
Q

An invasive BP measures beat-to-beat in real time the…

A

SAP, DAP, MAP w/ MAP being the most reliable, but all being reliable

40
Q

Blood gas analysis requires…

A

heparinised arterial blood sample

41
Q

blood gas analysis measures…

A

pH, PaO2, PaCO2, bicarbonate, etc

42
Q

blood gas analysis is considered the gold standard for…

A

oxygenation and respiratory function

43
Q

ECG is considered a

A

non-invasive measure of the electrical activity of the heart

44
Q

ECG does not…

A
  • correlate w/ CO
  • tell whether heart is beating/contracting or not
45
Q

an ECG is most useful in detecting

A

cardiac arrhythmias

46
Q

without an ECG, it is not possible to diagnose..

A

the exact nature of the arrhythmia

47
Q

What are the most common arrhythmias under anaesthesia?

A

bradycardia, tachycardia, VPCs, AV blocks

48
Q

What are the most common causes of intraoperative arrhythmias that need to be ruled out first?

A
  • too light anaesthesia
  • too deep anaesthesia
  • insufficient analgesia
  • hypercapnia
  • hypoxaemia
  • hypotension
  • hypertension
  • electrolyte imbalance
49
Q

Explain the different segments

A
  • 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
Q

What are 6 basic questions that should be asked to help w/ ECG interpretation?

A
  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
Q

Cardiac output and the patient’s haemodynamic stability depends on

A

HR x SV

52
Q

Bradycardia decreases…

A

Cardiac output

53
Q

Excessive tachycardia decreases CO & promotes

A

further arrhythmias

54
Q

in addition to haemodynamic instability, cardiac arrhythmias may lead to…

A

electronic instability

55
Q

What are life-threatening arrhythmias?

A
  • 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
Q

What are the most common peri-anaesthetic bradyarrhythmias?

A
  • sinus bradycardia
  • AV blocks (1st, 2nd, 3rd)
  • Atrial standstill
57
Q

What causes sinus bradycardia?

A

drugs, hypothermia, vagal stimulation, increased ICP

58
Q

What are some causes of AV blocks?

A
  • vagal stimulation, drugs (1st & 2nd blocks)
59
Q

What causes atrial standstill?

A

Hyperkalaemia

60
Q

What are the most common peri-anaesthetic tachyarrhythmias?

A
  • sinus tachycardia
  • A-fib
  • VPCs
  • V-tach
61
Q

What are causes of sinus tachycardia?

A

Pain, fear, stress, blood loss, anaemia, drugs (atropine, glycopyrrolate)

62
Q

What causes a-fib?

A

DCM

63
Q

What causes VPC’s/V-tach?

A
  • cardiomyopathy, myocardial hypoxaemia, GDV, haemoabdomen, endocrinological dz, pancreatitis, brain tumours, etc
  • myocardial oxygenation

Anaesthesia (24 decks)

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