Lecture 9-Acid Base Balance

Question 1

What is the normal range of plasma pH?

Answer 1

7.35-7.45

Question 2

How does alkalaemia lower free calcium?

Answer 2

By causing Ca2+ to move out of solution and bind to proteins -> increases neuronal excitability

Question 3

What happens if pH > 7.45?

Answer 3

Paraesthesia and tetany

Question 4

How can acidaemia cause arrhythmias?

Answer 4

Increases plasma [K+]

Question 5

How does the PCT of the kidney make HCO3-?

Answer 5

From AA, by putting NH4+ into urine:

• Glutamine -> alpha-ketoglutarate
• Produces HCO3- and NH4+

Question 6

How does the DCR of the kidney make HCO3-?

Answer 6

From CO2 and H20 - H+ is buffered by phosphate and NH3 in urine

Question 7

How do the DCT and CD secrete H+?

Answer 7

Actively, by H+ ATPase

Question 8

How is H+ buffered in urine?

Answer 8

By ammonia and phosphate to produce NH4+ and H2PO4- which are excreted

Question 9

How does acidosis lead to hyperkalaemia?

Answer 9

K+ moves out of cells because of the excess H+ in the cells so less K+ excretion from the distal nephron

Question 10

How does alkalosis lead to hypokalaemia?

Answer 10

K+ moves into cells -> more K+ excretion in distal nephron

Question 11

True or false: hypokalaemia can lead to metabolic alkalosis and hyperkalaemia can lead to metabolic acidosis

Answer 11

TRUE

Question 12

What is anion gap?

Answer 12

Difference between measured cations and anions

Question 13

When is the anion gap increased?

Answer 13

When HCO3- is replaced by other anions

Question 14

True or false: in renal causes of acidosis, anion gap is unchanged

Answer 14

TRUE

Question 15

Which conditions can lead to respiratory acidosis?

Answer 15

• type 2 respiratory failure (low pO2 and high pCO2): severe COPD, asthma, drug overdose
• chronic conditions

Question 16

Which conditions can lead to respiratory alkalosis?

Answer 16

• hyperventilation

- type 1 respiratory failure

Question 17

Which conditions can lead to metabolic acidosis?

Answer 17

• if anion gap is increased: keto-acidosis in diabetes, lactic acidosis, uraemic acidosis (renal failure)
• if normal anion gap: renal tubular acidosis, severe persistent diarrhoea

Question 18

What is type 1 renal tubular acidosis?

Answer 18

Can’t pump out H+

Question 19

What is type 2 renal tubular acidosis?

Answer 19

Problems with HCO3- reabsorption

Question 20

Which conditions can lead to metabolic alkalosis?

Answer 20

• severe prolonged vomiting

- loop and thiazide diuretics (loss of K+)