Acid-Base and Blood Gasses

Question 1

with less CO2 partial pressure what happens to ventilation rate?

Answer 1

decreases

Question 2

what metabolic processes produce significant amounts of hydrogen?

Answer 2

1. digestion of foods
2. metabolism of drugs
3. errors within metabolism

Question 3

what organ is responsible for excreting hydrogen ions through the urine?

Answer 3

the kidneys

Question 4

What two energy substrates produce hydrogen ions when oxidised incompletely?

Answer 4

lactic acid and the metabolism of fats (triacylglycerols)

Question 5

what metabolic reaction uses up hydrogen ions?

Answer 5

oxidative metabolism of ketones

Question 6

how is carbon dioxide produced?

Answer 6

as a product of oxidative metabolism

Question 7

how is CO2 excreted?

Answer 7

by ventilation (expired air)

Question 8

What equation shows how CO2 contributes to H+ production?

Answer 8

CO2+H2O H2CO3

Question 9

what is normal body extracellular fluid pH maintained between?

Answer 9

7.35-7.46

Question 10

what is the equation of the body’s buffering system?

Answer 10

H+ + HCO3 H2CO3

Question 11

how does renal filtration of Na+ and HCO3- work?

Answer 11

1. Na+ and HCO3- are filtered in the glomerulus
2. renal tubule cells secrete H+ in exchange for Na+.
3. CO2 is formed by the reaction of HCO3-with H+ and diffuses into the tubule.
4. CO2 coverted back into HCO3 in the renal tubule cell.
5. Na+/HCO3- symporter carry Na+ and HCO3- across basal membrane of tubule cell

Question 12

what two things are secreted and excreted from the kidneys after filtration?

Answer 12

NH4+ and H+

Question 13

what is metabolized to release NH4+ and HCO3- in the kidneys?

Answer 13

glutamine

Question 14

how does the phosphate buffer system work in the renal tubule?

Answer 14

1. H2O and CO2 combine to form H2CO3.
2. H2CO3 breaks down into HCO3- nd H+
3. H+ leaves the renal tubule and enters the tubular lumen
4. it binds to HPO4(2-) in the lumen to form H2PO4-
5. as H+ leaves, Na+ enters the cell
6. Na+ leaves via ATPase transporter which pumps K+ in at the same time.

Question 15

how does the protein buffer system work?

Answer 15

(at the tissues)
1. CO2 and H2O form HCO3- and H+ which binds with Hb from HbO2 dissociating into O2 and Hb.
2. HCO3- leaves the red blood cell and Cl- enters.
3. CO2 and Hb combine to form HbCO2
(then the reverse of all the reactions take place at the lungs-slide 13 for more details)

Question 16

how does the carbonic acid-bicarbonate buffer system work?

Answer 16

1. Na+ - H+ antiport secretes H+
2. H+ combines with HCO3- forming CO2 and H2O
3. CO2 diffuses into the cell and combines with H2O forming HCO- and H+
4. H+ is secreted and excreted
5. HCO3- is reabsorbed
6. glutamine is metabolised into ammonium ions and HCO3-
7. NH4+ is secreted and excreted
8. HCO3- is reabsorbed

Question 17

two buffer systems that occur in the intracellular fluid (ICF)

Answer 17

1. phosphate buffer system

2. protein buffer systems

Question 18

two buffer systems that occur in the ECF?

Answer 18

1. carbonic acid-bicarbonate buffer system.

2. protein buffer systems

Question 19

What are the three types of protein buffer systems?

Answer 19

1. haemoglobin buffer systems (RBCs)
2. amino acid buffers (all proteins)
3. Plasma protein buffers

Question 20

what equation links [H+], PCO2 and [HCO3-]?

Answer 20

[H+] = k (PCO2/[HCO3-])

Question 21

how do you calculate anion gap?

Answer 21

(Na+K) - (Cl+HCO3)

Question 22

what is acidosis and alkadosis?

Answer 22

acidosis - high H+ conc

alkalosis - low H+ conc

Question 23

four components that influence non-respiratory acidosis?

Answer 23

1. H+ generation
2. Buffering
3. Compensation
4. Correction

Question 24

what causes non-respiratory acidosis?

Answer 24

1. increased [H+]
2. Decreased excretion
3. Decreased [HCO3-]

Question 25

what causes increased H+ concentration?

Answer 25

1. diabetic ketoacidosis due to lack of insulin so fatty acids are metabolised. Excess glucose causes dehydration 2. aspirin poisoning causes acidosis as well.

Question 26

how does decreased excretion of H+ cause acidosis?

Answer 26

1. decreased GFR reduces sodium ion filtration, hence less H+ can be excreted as less Na+ to exchange with. So H+ ions accumulate. 2. decreased GFR also means reduced phosphates hence mechanism for H+ ion clearance is compromised.

Question 27

what happens when H+ concentration rises?

Answer 27

1. it is buffered by the bicarbonate whose conc falls as it makes carbonic acid (H2CO3). 2. carbonic acid dissociates producing carbon dioxide which is lost on expiration. 3. non-respiratory acidosis develops 4. respiratory centre is stimulated causing hyperventilation to remove more CO2 5. producing a compensatory alkalosis

Question 28

how is non-respiratory acidosis treated?

Answer 28

1. removal of the underlying problem. | 2. bicarbonates used with care in patients with pH <7

Question 29

what causes respiratory acidosis?

Answer 29

1. airway obstruction 2. depression of respiratory centre 3. neuromuscular disease 4. Pulmonary disease 5. Extra pulmonary thoracic disease

Question 30

what are all respiratory acidosis characterised by?

Answer 30

increase in PCO2

Question 31

although H+ concentration increases in respiratory acidosis, why does the pH still fall?

Answer 31

because the HCO3- conc increases also which would then neutralise the H+

Question 32

what is hypoxemia?

Answer 32

low oxygen levels

Question 33

what is hypercapnia?

Answer 33

high CO2 levels

Question 34

what is non-respiratory alkalosis?

Answer 34

an increase in bicarbonate levels

Question 35

what causes non-respiratory alkalosis?

Answer 35

1. excess alkali administration | 2. loss of free hydrogen

Question 36

what happens during respiratory alkalosis?

Answer 36

PCO2 increases in order to increase H+ concentration.

Question 37

how do we manage respiratory alkalosis?

Answer 37

- infusion of normal saline solution | - taking potassium supplements

Question 38

what is respiratory alkalosis?

Answer 38

a decrease in PCO2 levels

Question 39

what causes respiratory alkalosis?

Answer 39

1. hypoxia - increased CO2 loss | 2. increased drive: infections, hyperventilation, cerebral malignancy etc.

Question 40

how is respiratory alkalosis treated?

Answer 40

1. remove underlying cause | 2. if hyperventilation in the cause, re-breathe CO2 in