Acid-base abnormality

Question 1

Acid-base abnormality refers to a disruption in the body’s balance of acids and bases, often reflected in an alteration of arterial blood pH. Which of the following is normal for pH of the blood?

1 - 7.50-7.80
2 - 7.35-7.80
3 - 7.35-7.45
4 - 7.15-7.45

Answer 1

3 - 7.35-7.45

• <7.35 = acidosis
• > 7.45 = alkalosis

Question 2

What is the normal range for partial pressure of oxygen (PaO2), which is a measurement of the pressure of oxygen in arterial blood (essentially oxygen dissolved in the blood)?

1 - 10.7 - 13.3kPa
2 - 8.0 - 10.3kPa
3 - 4.7 - 6.0kPa
4 - 10.7 - 11.7kPa

Answer 2

1 - 10.7 - 13.3kPa

Question 3

What is the normal range for partial pressure of oxygen (PaCO2), which is a measurement of the pressure of carbon dioxide in arterial blood (essentially oxygen dissolved in the blood)?

1 - 10.7 - 13.3kPa
2 - 8.0 - 10.3kPa
3 - 4.7 - 6.0kPa
4 - 3.5 - 6.0kPa

Answer 3

3 - 4.7 - 6.0kPa

Question 4

Which of the following is the best indicator of hypoxia and respiratory failure?

1 - PaCO2
2 - bicarbonate
3 - PaO2
4 - lactate

Answer 4

3 - PaO2

Question 5

Which of the following indicates type 1 respiratory failure?

1 - low PaO2 and PaCO2
2 - high PaO2 and low PaCO2
3 - low PaO2 and normal PaCo2
4 - high PaO2 and PaCO2

Answer 5

3 - low PaO2 and normal PaCo2

Question 6

Which of the following indicates type 2 respiratory failure?

1 - low/normal PaO2 and low PaCO2
2 - low PaO2 and high PaCO2
3 - low/normal PaO2 and normal PaCo2
4 - high PaO2 and PaCO2

Answer 6

2 - low PaO2 and high PaCO2

Question 7

pH can be:

• acidotic <7.35
• normal 7.35 - 7.45
• alkalotic >7.45

Then we need to decide if the cause is respiratory or metabolic. Which of the following indicates a respiratory acidosis?

1 - normal pH and high PaCO2
2 - low pH and low PaCO2
3 - low pH and high PaO2
4 - low pH and high PaCO2

Answer 7

4 - low pH and high PaCO2

• CO2 is retained and increases acidity of the blood
• carbonic anhydrase converts the CO2 and H2O into carbonic acid, which increases blood acidity

Question 8

Bicarbonate is produced by the kidney and acts as a buffer to neutralise the acid in the blood. Is the production of bicarbonate a fast or slow process?

Answer 8

• slow process

Therefore changes in bicarbonate in response to acidic pH of the blood is slow to respond

Unable to compensate in acute respiratory acidosis

Question 9

If bicarbonate is raised, which of the following does this typically indicate?

1 - chronic respiratory acidosis
2 - acute respiratory alkalosis
3 - acute respiratory acidosis
4 - chronic respiratory alkalosis

Answer 9

1 - chronic respiratory acidosis

Bodies response to compensate for CO2 retention

Common in COPD

Question 10

Raised bicarbonate is common in COPD to compensate for CO2 retention and respiratory acidosis. But is the kidney able to increase bicarbonate production sufficiently in a COPD exacerbation?

Answer 10

• No

Question 11

Which of the following occurs to cause respiratory alkalosis?

1 - high RR that increases CO2 expiration
2 - high RR that reduces O2 inspiration
3 - low RR that reduces CO2 expiration
4 - bicarbonate loss in the urine

Answer 11

1 - high RR that increases CO2 expiration

Common in:

• hyperventilation syndrome (normal PaO2)
• PE (low PaO2)

Question 12

Which of the following occurs in metabolic acidosis?

1 - low pH and low PaO2
2 - low pH and high PaCO2
3 - low pH and low bicarbonate
4 - low pH and high bicarbonate

Answer 12

3 - low pH and low bicarbonate

Question 13

Which of the following would NOT cause metabolic acidosis?

1 - high lactate (anaerobic respiration)
2 - high ketones (DKA)
3 - vomiting and nausea
4 - high H+ (renal failure, rhabdomyolysis)
5 - diarrhoea and renal failure

Answer 13

3 - vomiting and nausea
Typically leads to metabolic alkalosis

Question 14

Which of the following occurs in metabolic alkalosis?

1 - high pH and low PaO2
2 - high pH and high PaCO2
3 - high pH and low bicarbonate
4 - high pH and high bicarbonate

Answer 14

4 - high pH and high bicarbonate

Question 15

Which of the following would NOT cause metabolic alkalosis?

1 - low H+
2 - high aldosterone
3 - high lactate

Answer 15

3 - high lactate

Question 16

High aldosterone can lead to metabolic alkalosis due to excretion of H+ ions. Which 2 of the following conditions can cause high aldosterone?

1 - lung cancer
2 - conns syndrome
3 - heart failure
4 - COPD

Answer 16

2 - conns syndrome
3 - heart failure

Question 17

High aldosterone can lead to metabolic alkalosis due to excretion of H+ ions. Which 2 of the following medications can cause high aldosterone?

1 - furosemide
2 - bisoprolol
3 - bendroflumethiazide
4 - ramipril

Answer 17

1 - furosemide
3 - bendroflumethiazide

Question 18

What is the normal range for base in the blood?

1 - -4 to +8
2 - 0 to +4
3 - -2 to +2
4 - +2 to +6

Answer 18

3 - -2 to +2 mEq/L

Negative value <-2 = base deficit
- indicates metabolic acidosis

Positive value >+2 = base excess
- indicate metabolic alkalosis

Question 19

Anion gap calculation:

(Na+ add K+) - (Cl- add HCO3-)

Na+ and K+ = cations
Cl- and HCO3- = anions

Answer 19

Normal anion gap:

3 - 11 MEQ/L

Question 20

The anion gap should have equal cations and anions.

This is because the blood in our body is also neutral.

Answer 20

BUT this is not the case because the formula does NOT account for other anions like:

• phosphate
• albumin
• sulphate
• organic acids

Therefore the anion gap is measuring the above anions in the blood

Question 21

If there is a high anion gap, this means that there is something in the unknown anions category that has increased causing a higher than usual anion gap. What of the following may cause this?

1 - lactate
2 - ketoacids
3 - formic acid
4 - oxalic acid
5 - all of the above

Answer 21

5 - all of the above

• lactate = lactate acidosis (Salicylate poisoning or aspirin, and shock
• ketoacids = DKA
• formic acid = methanol poisoning
• oxalic acid = ethylene glycol poisoning

Essentially these are all due to higher organic acids being produced or ingested

Question 22

If there is a normal anion gap, this means that there is something missing in the anions category. What is this typically?

1 - Cl-
2 - organic acids
3 - phosphate
4 - bicarbonate

Answer 22

4 - bicarbonate

Results by an increase in Cl- to compensate

Loss of bicarbonate is most commonly due to diarrhoea and renal tubular acidosis