ABG’s Flashcards

1
Q

When should an ABG be done?

A

•The acutely unwell patient, including:
• Respiratory distress
• Sepsis
• Low GCS
• Seizure
• Head/neck injury

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2
Q

How to do an ABG?

A

• Confirm patient details
• Confirm current oxygen therapy
• Ensure correct PPE
• Allen’s test
• Position patient appropriately – access to radial artery, wrist extended with hand at 45 degrees
• Palpate the radial artery
• Insert needle with the bevel facing upwards at 45 degrees – if in the artery, the syringe will self-fill
• Remove needle, cover with gauze, apply firm pressure for 3 minutes

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3
Q

Normal ranges when looking at an ABG

A

pH 7.35 – 7.45
pCO2 4.5-6.0
pO2 11 – 14
Bicarbonate (HCO3-) 22-28
Base Excess -2 - 2

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4
Q

ABG interpretation

A

pH
Low - acidosis
High PCO2 respiratory acidosis
Low HCO3- metabolic acidosis

High pH- alkilosis
Low PCO2 respiratory alkalosis
High HCO3 - metabolic alkalosis

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5
Q

Type 1 respiratory failure

A

Low oxygen (hypoxia)

Causes could be:
Pneumonia
PE
ILD

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6
Q

Type 2 respiratory failure

A

High carbon dioxide
Sometimes low oxygen also

Causes could be:
Opioids
COPD
Coma

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7
Q

ABG taken on RA
pH= 7.27
PaO2= 7.6kPa
PaCO2= 7.7 kPa
Bicarbonate= 26.5mmol/L
Base Excess= +1.0
SATs= 89%

A

Respiratory acidosis
As low ph and high co2
Type 2 reps failure could be as a result of COPD

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8
Q

ABG taken on RA
pH= 7.59
PaO2= 11.3kPa
PaCO2= 5.4 kPa
Bicarbonate= 35.6mmol/L
Base Excess= +7.1
SATs= 97%

A

Metabolic alkalosis
As pH is high and so is bicarb

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9
Q

ABG taken on RA
pH= 7.61
PaO2= 15.8kPa
PaCO2= 2.3 kPa
Bicarbonate= 23.1mmol/L
Base Excess= -1.5
SATs= 99.6%

A

Respiratory alkalosis
High pH and low CO2

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10
Q

ABG taken on RA
pH= 7.14
PaO2= 14.6kPa
PaCO2= 2.7 kPa
Bicarbonate= 12.4mmol/L
Base Excess= -7.6
SATs= 99%

A

Metabolic acidosis

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11
Q

ABG taken on RA
pH= 7.36
PaO2= 7.7kPa
PaCO2= 7.9 kPa
Bicarbonate= 38.1mmol/L
Base Excess= +6.7
SATs= 90%

A

Respiratory acidosis with full compensation
As pH is normal
Type 2 compensated reps failure

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12
Q

ABG taken on 35% venturi mask
pH= 7.24
PaO2= 11.7kPa
PaCO2= 8.2 kPa
Bicarbonate= 36.3mmol/L
Base Excess= +6.5
SATs= 96%

A

Respiratory acidosis with partial compensation
As pH is low, CO2 is high
Partial as bicarb has increased but pH hasn’t gone back to normal

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13
Q

ABG taken on RA
pH= 7.14
PaO2= 7.6kPa
PaCO2= 7.7 kPa
Bicarbonate= 12.4mmol/L
Base Excess= -7.6
SATs= 86%

A

Mixed respiratory and metabolic acidosis
Eg type 2 COPD resp failure with sepsis

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14
Q

Normal anion gap range

A

12-16mmol/L= Normal (including Potassium)
• 8-12mmol/L= Normal (without Potassium)

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15
Q

Potential causes for raised anion gap and normal anion gap

A

• Raised Anion Gap: Ketoacidosis, AKI, Lactic Acidosis, Ethylene glycol, Aspirin, Methanol
• Normal Anion Gap (ie. bicarbonate loss):Vomiting, Renal tubular acidosis

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16
Q

ABG taken on RA
pH= 7.14
PaO2= 14.6kPa
PaCO2= 2.7 kPa
Bicarbonate= 12.3mmol/L
Base Excess= -7.6
SATs= 99%
Na= 140 mmol/L
K= 4.3 mmol/L
Cl= 100 mmol/L
What is the anion gap?

A

32
(140+4.3)-(12.3+100) = 32

17
Q

Causes of metabolic acidosis

A

Metabolic Acidosis
• Diabetic Ketoacidosis
• Diarrhoea
• Renal failure
• Shock
• Aspirin Overdose
• Sepsis

18
Q

Causes of metabolic alkalosis

A

Generally not too worrying
Metabolic Alkalosis
• Loss of Gastric Secretions • Overuse of Antacids
• Diuretics

19
Q

Causes of respiratory acidosis

A

Respiratory Acidosis
• Hypoventilation
• COPD
• Airway Obstruction
• Drug overdose – e.. Opioids
• Chest Trauma
• Neuromuscular Disease
• Pulmonary Oedema

20
Q

Causes of respiratory alkalosis

A

Respiratory Alkalosis
• Hyperventilation
• Hypoxia
• Anxiety
• High Altitude
• Pregnancy
• Fever

21
Q

A 36 year old woman presents with right-sided pleuritic chest pain. Her observations are normal. She is not requiring any oxygen. Her D-Dimer is negative.

pH 7.51
pCO2 2.3
pO2 25.1
Bicarb 25
Base Excess 1

A

Respiratory alkalosis
Causes: hyperventilating from panic attack

22
Q

25 year old lady with asthma presents with SOB and wheeze.
What would you want to know?

RR= 28/min; PEFR= 47% predicted
On examination chest= widespread wheeze, speaking full sentences Obs= stable otherwise

ABG on 2L NC:
pH= 7.49
PaO2= 14.6kPa
PaCO2= 3.1 kPa
Bicarbonate= 27.4mmol/L
Base Excess= +1.7
SATs= 99%

30 minutes later, she feels worse and appears more drowsy.
ABG taken on 2L NC
pH= 7.41
PaO2= 8.4kPa
PaCO2= 5.7kPa
Bicarbonate= 26mmol/L
Base Excess= +0.1
SATs= 89%
What is happening? Are you worried about this patient?

A

Respiratory alkalosis
30mins later- type 1 resp failure, very worried as approaching T2 ( contact ICU)

23
Q

6 week old baby with vomiting after feeding has the following capillary blood gas
pH= 7.53
pO2= 12.4kPa
pCO2= 5.8kPa
Bicarbonate= 34mmol/L
BE= +4.1
SATs= 95%, RA

A

Metabolic alkalosis as throwing up a lot of stomach acid

24
Q

19 year old male with abdominal pain, vomiting
Observations: BP= 70/40, P= 130bpm,T= 36.5, RR= 28, SATs= 99%, RA
What are the possible causes? What would you want to know?
pH= 7.21
pCO2= 3.0kPa
pO2= 14.3kPa
Bicarbonate= 9.9mmol/L
BE= -8.4
SATs 99%
Glucose= 29.4 mmol/L

A

Metabolic acidosis
DKA

25
Q

Cardiac Arrest of 50 year of female- PEA
ROSC after 2 cycles (4 minutes)
Intubated and ventilated

pH= 7.05
PaO2= 28.6kPa
PaCO2= 4.1 kPa
Bicarbonate= 11.4mmol/L
Base Excess= -8.4
SATs= 100%

A

Metabolic acidosis

26
Q

25 year old lady presents is being treated for sepsis of unknown source.
Has suddenly deteriorated, complains of weakness and hands and legs feel strange.
RR= 30/min, P= 130bpm; BP= 100/70;T= 39.0degreesC, SATs= 99% on 15L non-rebreather
ABG (on 15L non-rebreather)

pH= 7.59
PaO2= 28.3kPa
PaCO2= 2.1 kPa
Bicarbonate= 17.9mmol/L
Base Excess= -3.9
SATs= 100%

A

Respiratory alkalosis with partial metabolic compensation

27
Q

35 year old man found on the street unresponsive.
Obs- RR= 8/min; SATs= 97% (8L FM); P= 70bpm; BP= 95/70;T= 35.7degreesC
Lots of arm wounds
ABG on 8L O2 via FM
pH= 7.31
PaO2= 12.5kPa
PaCO2= 7.0 kPa
Bicarbonate= 24.3mmol/L
Base Excess= 0.0
SATs= 98%

A

Respiratory acidosis from opioid use