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Meded Flashcards 2020 > ABGs > Flashcards

ABGs Flashcards

1
Q

What are the four abnormalities on an ABG?

A

Metabolic acidosis
Metabolic alkalosis
Respiratory acidosis
Respiratory alkalosis

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2
Q

Shortcut for interpreting whether metabolic or respiratory

A

ROME
Resp opposite, metabolic equal
Respiratory- opposite CO2 and pH [eg. high pH=low CO2]
Metabolic- equal CO2 and pH

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3
Q 
SBA One
pH: 7.2
PaCO2: 9.6
PaO2: 9.2
HCO3- : 26
What abnormality is shown?
Metabolic Alkalosis
Respiratory Alkalosis
Metabolic Acidosis
Respiratory Acidosis

Why?
Low ph
High paCO2

A

Respiratory acidosis

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4
Q

Normal ranges for ABGs

A

4.7 < kPa < 6.5
10.5 < kPa< 13.5
22 < mEq/L < 26

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5
Q

What does high Co2 mean?

A

Respiratory acidosis

Or metabolic alkalosis with compensation

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6
Q

What does high bicarb mean?

A

Metabolic alkalosis

Or respiratory acidosis with compensation

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7
Q

How can metabolic acidosis be compensated?

A

Low carbon dioxide

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8
Q

How can metabolic alkalosis be compensated?

A

High carbon dioxide/hyperventilation

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9
Q

How can resp acidosis happen?

A

High carbon dioxide

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10
Q

pH: 7.55
PaCO2: 3.0
PaO2: 13.6
HCO3-: 24

What abnormality is shown?
Metabolic Alkalosis without compensation
Metabolic Alkalosis with compensation
Respiratory Alkalosis without compensation
Respiratory Alkalosis with compensation
A

Respiratory Alkalosis without compensation

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11
Q

How can respiratory alkalosis be compensated?

A

Low bicarbonate/base excess

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12
Q

How can respiratory acidosis be compensated?

A

High bicarbonate

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13
Q

How can respiratory alkalosis happen?

A

Increased resp rate + over breathing= hyperventilation

Low carbon dioxide
Increased pH

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14
Q

How can metabolic acidosis happen?

A

Low bicarbonate

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15
Q

How can metabolic alkalosis happen?

A

High bicarbonate

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16
Q

What is the timeframe of respiratory compensation occurring?

A

Immediate/acute

17
Q

What is the timeframe of metabolic compensation occurring?

A

Chronic= weeks

18
Q

Which of these is a common cause of respiratory alkalosis?

Opiates
Anxiety
COPD
Norovirus 
Atelectasis
A

Anxiety

Causes hyperventilation- blowing off + decrease of carbon dioxide

Breathing into paper bag helps to re breathe in carbon dioxide

NB: panic attacks cause numbness because:
alkalosis causes calcium to bind to albumin in blood
Causes hypocalcaemia and parasthesia

19
Q

What type of pathology in the lung causes respiratory alkalosis?

A

Global
Hyperventilation

[Hyperoxaemia, hypocapnia]

20
Q

What type of pathology in the lung causes respiratory acidosis?

A

Global
Alveolar hypoventilation

hypoxia, hypercapnic

21
Q

pH: 7.5
PaCO2: 6.6
PaO2: 11.0
HCO3-: 28

What abnormality is shown?
Metabolic Alkalosis without compensation
Metabolic Alkalosis with compensation
Respiratory Alkalosis without compensation
Respiratory Alkalosis with compensation

4.7 < kPa < 6.5
10.5 < kPa< 13.5
22 < mEq/L < 26

A

Metabolic Alkalosis with compensation

Can the pH abnormality be explained by the patient’s respiratory status?
If no, it’s opposite= must mean this is compensation

If the carbon dioxide does not explain the clinical picture – you should ask yourself whether the pH derangement can explain the change in carbon dioxide as a mechanism of compensation. You should also look for further proof of a metabolic cause by looking at the bicarbonate/base excess

22
Q

What factors cause metabolic alkalosis?

A

Vomiting [lose hydrochloric acid]
Drugs- for acid reflux- [have bicarbonate in them, which react with and mop up hydrogen ions, leading to decrease in H+ ions]

23
Q

pH: 7.32
PaCO2: 7.1
PaO2: 10.8
HCO3-: 30

What abnormality is shown?
Metabolic Acidosis without compensation
Metabolic Acidosis with compensation
Respiratory Acidosis without compensation
Respiratory Acidosis with compensation

4.7 < kPa < 6.5
10.5 < kPa< 13.5
22 < mEq/L < 26

A

Respiratory Acidosis with compensation

24
Q

pH: 7.21
PaCO2: 3.7
PaO2: 12.9
HCO3-: 15

What abnormality is shown?
Metabolic Acidosis without compensation
Metabolic Acidosis with compensation
Respiratory Acidosis without compensation
Respiratory Acidosis with compensation

4.7 < kPa < 6.5
10.5 < kPa< 13.5
22 < mEq/L < 26

A

Metabolic Acidosis with compensation

Explanation:
If the side with carbon dioxide was the problem, then you would expect the other side to try and compensate as it is in relative excess. Therefore you would expect hydrogen ions to mop up bicarbonate and form carbon dioxide. As a result you would expect the hydrogen ion concentration to drop and an alkalosis.

This would be a respiratory alkalosis. However, the pH in the question is 7.21 meaning an acidosis. The change in carbon dioxide therefore is moving away from the derangement. It is an act of compensation from a healthy set of lungs. Therefore the pH problem must be metabolic in nature.

25
Q

What are the factors causing metabolic acidosis?

A

Diarrhoea [loss of bicarbonate]

Renal tubular acidosis

26
Q

What is an anion gap?

A

An artificial concept for practicality of measuring ions in blood

When measuring ions in blood:
Only sodium and potassium cations are counted,
and only chloride and bicarbonate anions are counted

Sodium + potassium make up most of the cations, but there are quite a few other anions apart from chloride and bicarbonate [eg. ketones, dissociated acids] that we just can’t be bothered to count

Therefore there is a anion gap

All positive and negative ions have equal quantities- because we are electroneutral

27
Q

How do you work out the anion gap?

A

In a e lecture somewhere apparently?
Don’t know if we need to know it
Will add it in when I do the el lecture, sorry lol

28
Q

How do you work out the osmolality from ion concentrations?

A

2 [K+ + Na+] + urea + glucose = osmolality

29
Q

What are the causes of a wide anion gap?

A 
KULT
Ketones [DKA]
Uraemia
Lactate
Toxins- paracetamol, aspirin, anti freeze [ethylene glycol], isoniazid
30
Q

What is a normal anion gap

A

412

Meded Flashcards 2020 (36 decks)

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