Acid-base balance (part 2)

Question 1

only the kindeys can get rid of what?

Answer 1

metabolic acids:

phosphoric, uric, lactic acids and ketones

Question 2

what does kindeys getting rid of acids prevent?

Answer 2

metabolic acidosis

Question 3

in order to maintain acid base balance - what do the kidneys have to do?

Answer 3

1. reabsorb all filtered bicarbonate
2. excrete the daily acid load

Question 4

How does reabsorbtion of filtered bicarbonate occur in kidney?

How much of filtered bicarbonate is reabsorbed?

Answer 4

ALL BICARBONATE REABSORBED

• filtered out in glomerulus
• at proximal convoluted tubule via Na/HCO3- symporter channel: reclamation of 4500 mEq of HCO3- each day. 70 - 90%.
• 10 - 30 % is filtered back at the end of nephron

Question 5

What else does can kidneys do with bicarbonate?

Answer 5

Kidney can produce bicarbonate

• Glutamine -> glucose, HCO3-, NH4+ (excreted out and used to combine with H+ ions to make sure excreted into urine)

Question 6

how does active excretion of H+ work?

Answer 6

Active excretion of H+ happens in the various parts of the distal kidney

- ATP pump of H+ into filtrate of urine

Question 7

when the body is in acidosis, how do we ensure H+ stay out of renal tubule cells?

Answer 7

when the body is acidosis:

@ distal proximal tubule:

H+ get secreted out of renal tubule cell into lumen. BUT want to stay here. SO, use NH4+ and H2PO4 buffes to keep the H+ in the filtrate

Question 8

give a summary of acid elimination

Answer 8

Question 9

what does having two organs that can excrete H+ mean?

Answer 9

means can compensate for each other

if lungs doesnt work as well as should, kidneys will try and help and vice versa

Question 10

what is the Henderson-Hasselbach equation?

what used to find for?

Answer 10

(pKa - a constant. for human plasma = 6.1)

• replace [H2CO3] with partial pressure of C02 (via Henrys Law)

Question 11

what is the Henderson-Hasselbach equation used to find for?

why is it useful?

Answer 11

used to find pH of a buffer solution AND

the ratio of conjugate base to acid of the system

useful:

• links the parameters of pH, conc of HCO3- and partial pressure of CO2
• if one moves, so will the others

Question 12

what are the four things that could go wrong to affect acidity?

Answer 12

• bicarbonate increase
• bicarbonate decrease
• CO2 increase
• CO2 decrease

Question 13

how can you classify acid-base disorders?

Answer 13

- respiratory acid base disorders (abnormal resp function = rise / fall Co2 in ECF)

respiratory acidosis

respiratory alkalosis

- metabolic acid base disorders (generation of organic or fixed acid OR anything affecting conc of HCO3- in ECF)

metabolic acidosis

metabolic alkolosis

Question 14

how can you diagnose acid / base disorder?

Answer 14

1. clinical history
2. physical examination
3. arterial blood gas analysis

Question 15

what do you look for when get results from arterial blood gas? what does each one mean

Answer 15

1. pH low (acidosis) or high (alkalosis)?
2. what is P_aCO2 value? (resp. indicator)
3. what is HCO3- value? (metabolic indicator)

Question 16

what test do you if have a metabolic acidosis?

Answer 16

check anion gap - if greater than 12 then its acidiosis

Question 17

what does each type of the four form of acid-base disturbance means is going on with body?

Answer 17

respiratory acidosis: got CO2 retention - hypoventilation (e.g. from COPD).

respiratory alkalosis: CO2 loss - hyperventilation (e.g anxiety)

metabolic acidosis: gain of acid, loss of base (e.g. diarrhoea, keto-acidosis)

metabolic alkolosis: loss of acid, gain of base (e.g. vomiting, hypokalemia)

Question 18

what compensation do you get for the following?

respiratory acidosis

respiratory alkalosis

metabolic acidosis

metabolic alkolosis

Answer 18

respiratory acidosis: renal compensation

respiratory alkalosis: renal compensation

metabolic acidosis: resp. compensation

metabolic alkolosis: resp. compensation