acid base 1

Question 1

what defines acidemia

Answer 1

pH < 7.35

Question 2

what defines alkalemia

Answer 2

pH > 7.45

Question 3

difference between acidemia and acidosis

Answer 3

acidemia = state of blood pH
acidosis = pathological processes that change pH

Question 4

define a buffer

Answer 4

Minimises pH changes due to addition or removal of H+ (temporarily)

Question 5

what is Henderson-hasselbach equation

Answer 5

pH = 6.74 + log (HCO3- / pCO2)

is determined by ratio between HCO3- and pCO2 as pKa is constant

Question 6

describe respiratory disturbances

Answer 6

respiratory acidosis

• CO2 retention
• e.g. pCO2 = 9

respiratory alkalosis

• hyperventilation
• e.g. pCO2 = 3

Question 7

describe metabolic disturbances

Answer 7

metabolic acidosis = low bicarbonate

metabolic alkalosis = high bicarbonate

Question 8

name urinary buffers

Answer 8

phosphoric acid

ammonium ions

Question 9

causes of metabolic acidosis

Answer 9

• lactic acidosis
• diabetic ketoacidosis
• renal failure
• renal tubular acidosis
• severe diarrhoea, ilieostomy

Question 10

what is the role of the kidneys in acid-base balance

Answer 10

1. bicarbonate reabsorption
2. ‘new’ bicarbonate generation
3. H+ secretion in distal nephron (distal tubule & CD)
   - via ammonia and phosphate

Question 11

describe the role of acetazolamide

Answer 11

• is a carbonic anhydrase inhibitor
• causes metabolic acidosis
• used to counteract alkalosis due to hyperventilation
• inhibits reabsorption and regeneration of HCO3-

Question 12

what plays a key role in urinary generation (not reabsorption)

Answer 12

urinary buffers

Question 13

describe the role of ammonium in the nephron

Answer 13

1. ammonium generated from glutamine in PT cells and secreted into the lumen (produces 2x HCO3-)
2. most reabsorbed in TAL
3. CD = diffusion trapping

Question 14

describe the response of the kidneys to acidosis

Answer 14

• increased HCO3- & H+ transport along the nephron
• increased ammoniagenesis
• increased availability of urinary buffers
  (=more acid excretion)