Renal Physio 8

Question 1

What is normal acid-base status of the body?

Answer 1

Plasma pH close to 7.4 (range 7.35 – 7.45)
[HCO3-]p close to 25 mmol/l (range 23 – 27)
Arterial PCO2 close to 40 mmHg (range 35 – 45)

Question 2

What is the first barrier to a chnage in acid base balance?

Answer 2

the buffer system

Question 3

When is a person said to be acidotic?

Answer 3

pH <7.5

Question 4

When is a person said to be in alkalosis?

Answer 4

pH >7.5

Question 5

What happens if there is a change in the acid-base balance?

Answer 5

1. Compensation: restore to the pH to 7.4 ASAP

2. Correction - restoration of pH and HCO3 and pCO2 to normal

Question 6

How sare A-B disturbances classified qas?

Answer 6

Respiratory
metabolic

(acidosis and alkalosis in both)

Question 7

What is the immediate buffering of a pH change?

Answer 7

Immediate dilution of the acid or base in ECF

Blood buffers (i.e. Hb, HCO3-. Acidosis would reduce [HCO3-]p)

deoxygentated blood has a higher affinity for H+ ions than Oxygenated blood

replenish the buffer stores as they deplete quickly

Question 8

What regulates the concentration of the bicarbonates in the blood?

Answer 8

Kidney

Question 9

What aregulates the pCO2 in body?

Answer 9

Respiratory system

Question 10

What can be used to measure the pH and PCO2?

Answer 10

blood-gas analyser

Question 11

What is the henderson-hasselbach equation

Answer 11

pH  [HCO3-]

[CO2]

Question 12

Davenport diagram

Answer 12

concentration of bicarbonate - y

pH of plasma - x

Question 13

Causes of repsiratory acidosis

Answer 13

chronic bronchitis

chronic emphysema

airway restriction (bronchial asthma, tumour)

chest injuries
respiratory depression - morphine/ general anesthesia

Question 14

What is respiratory acidosis?

Answer 14

Retention of CO2 by the body

–> increased formation of carbonic acid –> excess of free H+ ions

Question 15

What happens if you have an increased concentration of CO2?

Answer 15

increase in plasma con of H+ and HCO3-

but the pH decreases becuase the HCO3 is formed by the same reaction that causes the acidosis and hence they can’t compensate

Co2 retention drives equilibrium to the right

Question 16

What happens when the reaction moves to the right?

Answer 16

increase in H+ concentration than HCO3- ions

small change in pH leads to a large change in the concentration of H+

Question 17

When is Uncompensated respiratory acidosis is indicated?

Answer 17

pH < 7.35 and PCO2 > 45 mmHg

Question 18

what is the compensation of respiratory acidosis?

Answer 18

nothing much as it is the buffer system that compensates and leads to this situation

Question 19

What drives

Answer 19

increase in H+ ions from the renal tubular cells due as pushed forward by the pCO2

Question 20

What happens to the bicarbonate ion concentration?

Answer 20

further increase it as a result of renal compensation

Question 21

What is the correction for respiratory acidosis?

Answer 21

lowering pCO2 by restoration of the normal ventilation

Question 22

What is respiratory alkalosis?

Answer 22

Excessive removal of CO2 by the body

Question 23

causes of resp alkalosis

Answer 23

low inspired pO2 at high altitudes
hypercentilation
hysterical overbreathing

hypoxia stimulates the peripheral chemoreceptors –> increase ventilation

gets rid of too much carbon dioxide –> decreased pCO2

Question 24

What happens in resp alokalosis to the ions?

Answer 24

drives the reaction towards the left hand side

decrease in H+ and HCO3-

lower than normal pCO2

Question 25

When is Uncompensated respiratory alkalosis indicated

Answer 25

pH > 7.45 and PCO2 < 35 mmHg

Question 26

What is the correction for respiratory alkalosis?

Answer 26

restoration of normal ventilatory

Question 27

what is metabolic acidosis?

Answer 27

excess H+ from any other source other than CO2

Question 28

What is the most common acid base dustrubance?

Answer 28

metabolic acidosis

Question 29

causes of metabolic acidosis?

Answer 29

Ingestion of acids or acid-producing foodstuffs Excessive metabolic production of H+ (e.g. lactic acid during exercise or ketoacidosis - DM) Excessive loss of base from the body (e.g. diarrhoea – loss of HCO3-, as they aren't reabsorbed later on)

Question 30

Uncompensated metabolic acidosis indicated by

Answer 30

pH < 7.35, [HCO3-]p is low HCO3- is tyring to buffer the excess H+ (as the buffer system isnt involved in the process but it will eventually decrease the HCO3- concentration

Question 31

What is the compensation for metabolic acidosis?

Answer 31

as a decrease in plasma pH stimulates the peripheral chemoreceptors to increase ventilation and blow CO2 out drives the buffer system towards the left hand side --> plasma H+ and HCO3 is reduced. HCO3 further decreased - with ventilation and

Question 32

What is the correction for metalbolic acidosis?

Answer 32

kidney is filtering less HCO3 than before H+ secretion continues and produces TA and ammonium ==> to generate more HCO3 (helps to replenish the blood buffer stores) urine --> acid secreted and HCO3 restored additing of more hco3 to bring the plasma conc back to normal

Question 33

What is the metabolci alkalosis?

Answer 33

Less common than metabolic acidosis Excessive loss of H+ from the body

Question 34

Causes of metabolic alkalosis?

Answer 34

Loss of HCl from the stomach (vomiting) Ingestion of alkali or alkali-producing foods (e.g. Ingestion of NaHCO3 as an antacid, though not a problem with modern antacids) ``` Aldosterone hypersecretion (causes stimulation of Na+/H+ exchange at the apical membrane of the tubule; acid secretion) ```

Question 35

Uncompensated metabolic alkalosis indicated by:

Answer 35

pH > 7.45, [HCO3-]p is high

Question 36

What is the compensation for metabolic alkalosis?

Answer 36

respiratory compensation Increased pH slows ventilation (peripheral chemoreceptors) CO2 retained, PCO2 rises drives the qeaction forward, increase H+ secretion, increase the plasma concentration of HCO3 ions (rate of filtration of HCO3 increased as plasma concentration of hco3 increased) can't reabsorb all that hco3 hence excreted in the urine no new TA or NH4+ added by excreting HCO3 in the urine- -->

Question 37

Correction ofr MA?

Answer 37

Filtered HCO3- load is so large compared to normal that not all of the filtered HCO3- is reabsorbed No TA or NH4+ is generated HCO3- is excreted (urine is alkaline) [HCO3-]p falls back towards normal