Acid-base and Blood Gases

Question 1

What happens in an oxygen deficit?

Answer 1

Haemoglobin gives up O
Takes in CO2
HCO3- given up + exchanged for Cl-

Question 2

What happens when its oxygen rich?

Answer 2

Large shunt of O into RBC
High affinity for O
CO2 out = gives up H+
Cl- exchanged for HCO3-

Question 3

What happens if there is an injury in the lungs?

Answer 3

Acute problem = chest can’t respond fast = can’t get rid of gas = RBC becomes saturated

Question 4

What normal metabolic processes are involved in the production of hydrogen?

Answer 4

Digestion of food
Metabolism of drugs
Errors with within metabolism

Question 5

Which organ is responsible for the secretion of hydrogen?

Answer 5

Kidney

Question 6

Why can anaerobic metabolism produce H?

Answer 6

Produces lactate = an acid = H+

Question 7

How is CO2 produced?

Answer 7

Oxidative metabolism

Question 8

How is CO2 excreted?

Answer 8

By ventilation

Question 9

What is the normal pH within the body?

Answer 9

7.35-7.46

Question 10

Describe renal filtration
1. maintain acid-base balance

Answer 10

Na+ + HCO3- filtered in glomerulus
Renal tubule cells secrete H+ in exchange for Na+
CO2 is formed by reaction of H+ + HCO3- + diffuses into tubule cell = impermeable to bicarbonate
CO2 converted back to HCO3- in cell
Na+/HCO3- symporter carries Na+ + HCO3- across membrane

Question 11

What do renal cells do?

Answer 11

Secrete H+ in exchange for Na+

Question 12

Describe renal filtration
2. maintain acid-base balance

Answer 12

Na+/H+ antiport secretes H+
H+ in filtrate combines with filtered HCO3- to form CO2 + H2O
CO2 diffuses into cell + combines with H2O to form H+ + HCO3-
H+ is secreted again + excreted
HCO3- is reabsorbed
Glutamine is metabolised to ammonium ion + HCO3-
NH4+ is secreted + excreted
HCO3- is reabsorbed

Question 13

What are buffering systems in intracellular fluid?

Answer 13

Phosphate buffer system
Protein buffer

Question 14

What are buffering systems in extracellular fluid?

Answer 14

Protein buffer
Carbonic acid-bicarbonate system

Question 15

What is involved in protein buffering system?

Answer 15

Haemoglobin
Amino acid (all proteins)
Plasma protein

Question 16

What is the concentration of H+:
directly proportional to?
inversely proportional to?

Answer 16

[CO2]
[HCO3-]

Question 17

What is the renal system dependent on?

Answer 17

Na+
= no sufficient Na+
= H+ can’t get out

Question 18

What is acidosis?

Answer 18

High [H+] = low pH

Question 19

What is alkalosis?

Answer 19

Low [H+] = high pH

Question 20

What is non-respiratory acidosis caused by?

Answer 20

Increased [H+] = poisons
Decreased excretion = renal failure
Decreased [HCO3-] = diarrhoea

Question 21

What are the reasons for increased [H+]?

Answer 21

Diabetic ketoacidosis = absolute lack of insulin = metabolism of fatty acids

Question 22

What are the reasons for decreased H+ excretion?

Answer 22

Decreased GFR reduces filtration of Na+ = less available to be exchanged with H = H accumulates

Question 23

Describe non-respiratory acidosis

Answer 23

H+ rises = buffered by bicarbonate
Carbonic acid produced + dissociates
Non-respiratory acidosis develops = stimulates respiratory centre to remove CO2 = producing compensatory respiratory alkalosis
= rapid breathing rate

Question 24

How do you treat non-respiratory acidosis?

Answer 24

Removal of underlying problem
BUT renal function must be maintained
Bicarbonate used in patients with pH <7

Question 25

Summary of non-respiratory acidosis

Answer 25

pH decrease H+ increase CO2 decrease = rapid breathing rate HCO3- decrease = bicarbonate used to neutralise H+

Question 26

What are the causes of respiratory acidosis?

Answer 26

Airway obstruction Depression of respiratory centre = drugs + illness Neuromuscular disease Pulmonary disease

Question 27

What happens in acute respiratory acidosis?

Answer 27

pH decreases H+ increases CO2 increases =respiratory system can't function normally HCO3- slight increase = some used to neutralise BUT reaction pushed right

Question 28

What happens in chronic respiratory acidosis?

Answer 28

pH slight decrease/normal H+ slight increase/normal CO2 increase HCO3- increase

Question 29

What is respiratory response to metabolic change?

Answer 29

FAST

Question 30

What is metabolic response to respiratory change?

Answer 30

SLOW

Question 31

How do you treat respiratory acidosis?

Answer 31

Restore O = ventilation + high conc of O = O prime issue = die from hypoxemia 1st

Question 32

What are the causes of non-respiratory alkalosis?

Answer 32

Excess alkali administration Overcorrection of acidosis Loss of free H

Question 33

How is free H lost?

Answer 33

GI loss Mineralocorticoid steroid Diuretic therapy

Question 34

What happens in non-respiratory alkalosis?

Answer 34

pH increases H+ decreases CO2 increases HCO3- increases

Question 35

How do you treat non-respiratory alkalosis?

Answer 35

Normal saline infusion Potassium supplements

Question 36

What causes respiratory alkalosis?

Answer 36

Hypoxia = COPD, altitude Increased drive = infection, respiratory stimulants

Question 37

What happens in acute respiratory alkalosis?

Answer 37

pH increases H+ decrease CO2 decreases HCO3- slight decrease

Question 38

What happens in chronic respiratory alkalosis?

Answer 38

pH slight increase/normal H+ slight decrease/normal CO2 decreases HCO3- decreases

Question 39

What is the treatment for respiratory alkalosis?

Answer 39

Remove underlying cause Hyperventilation = rebreathe CO2 = brown paper bag