Acid-base balance

Question 1

What is being regulated in acid-base balance?

Answer 1

The hydrogen ion concentration [H+]

Question 2

How does the body get rid of H+?

Answer 2

Most, or all, of the H+ is excreted in urine

Question 3

What do hydrogen ions react with to form carbonic acid?

Answer 3

Bicarbonate

H+ + HCO3- –> H2CO3

Question 4

What is carbonic acid removed as?

Answer 4

Carbon dioxide and water

Question 5

What are the 2 acid-base problems that can arise in the body?

Answer 5

1. Too much H+

2. Too much CO2

Question 6

Explain compensation

Answer 6

The body will try and restore the concentrations back to normal by compensation. If there is too much H+ the body will blow off CO2. If there is too much CO2 the kidney will excrete more H+.

Question 7

Define acidaemia

Answer 7

Increased [H+]

pH < 7.35

Question 8

Define alkalaemia

Answer 8

Decreased [H+]

pH > 7.45

Question 9

Define acidosis

Answer 9

The process tending to cause increased [H+]

Question 10

Define alkalosis

Answer 10

The process tending to cause decreased [H+]

Question 11

What is the primary change if it is respiratory?

Answer 11

The primary change is in the pCO2

Question 12

What is the primary change if it is metabolic?

Answer 12

The primary change is in the HCO3-

Question 13

Define respiratory acidosis

Answer 13

Increased [H+] due to an increased pCO2

Question 14

Define respiratory alkalosis

Answer 14

Decreased [H+] due to a decreased pCO2

Question 15

Define metabolic acidosis

Answer 15

Increased [H+] due to decreased HCO3-

Question 16

Define metabolic alkalosis

Answer 16

Decreased [H+] due to increased HCO3-

Question 17

What is the primary problem in metabolic acidosis and how is it compensated for?

Answer 17

Too much H+

Respiratory compensation - CO2 is blown off (reduces the pCO2)

Question 18

What is the primary problem in respiratory acidosis and how is it compensated for?

Answer 18

Too much CO2

Metabolic compensation - excrete more H+

Question 19

What are the 4 arterial blood gases?

Answer 19

H+, pCO2, HCO3-, pO2

Question 20

Give 3 causes of respiratory acidosis

Answer 20

Choking
Bronchopneumonia
COPD

Question 21

Give 3 causes of respiratory alkalosis

Answer 21

Hysterical over breathing
Mechanical over-ventilation
Raised intracranial pressure – potentially impact on the respiratory centre in the brain

Question 22

Give 3 causes of metabolic acidosis

Answer 22

Impaired H+ excretion
Increased H+ production or ingestion
Loss of HCO3-

Question 23

Give 3 causes of metabolic alkalosis

Answer 23

Loss of H+ in vomit
Alkali ingestion
Potassium deficiency

Question 24

What is the equation for oxygen delivery?

Answer 24

DO2 = CO x [(1.3 x Hb x SaO2) + 0.003 x PaO2]

cardiac output x arterial oxygen concentration

Question 25

What are 4 causes of tissues hypoxia?

Answer 25

Anaemic hypoxia Perfusional hypoxia Toxic hypoxia Hypoxaemic hypoxia

Question 26

What is FiO2?

Answer 26

FiO2 is the fraction of inspired oxygen. In other words, what percentage of the air being inspired is oxygen.

Question 27

What range of saturation should you keep a patient with a chronic condition?

Answer 27

SaO2 88-92%

Question 28

What range of saturation should most patients be kept in?

Answer 28

SaO2 94-98%

Question 29

Give 4 buffers for H+ in the body

Answer 29

Haemoglobin Bicarbonate Potassium Ammonium

Question 30

What is the clinical term for uncompensated respiratory acidosis?

Answer 30

Acute Type II respiratory failure

Question 31

What is the clinical term for compensated respiratory acidosis?

Answer 31

Chronic Type II respiratory failure

Question 32

What is the clinical term for decompensated respiratory acidosis?

Answer 32

Acute on chronic respiratory acidosis

Question 33

What is the anion gap?

Answer 33

The difference between the positively charged (cations) and the negatively charged (anions) in serum, plasma or urine. Values show the number of extra positive things.

Question 34

How is the anion gap calculated?

Answer 34

Calculated by subtracting the serum concentration of chloride and bicarbonate (anions) from the concentration of sodium and potassium (cations) -Na+ + K+ = Cl- + HCO3-

Question 35

What does a higher than normal anion gap show?

Answer 35

Metabolic acidosis

Question 36

What are the causes of a high anion gap?

Answer 36

AMUDPILES | Alcohol, methanol, uraemia, DKA, paraquat, infection, lactic acid, ethylene glycol and salicylates

Question 37

What is base excess?

Answer 37

The amount of strong acid required to bring the pH back to 7.4, when CO2 is corrected to 5.3 (normal BE is between 2 and -2)

Question 38

What is base excess used to diagnose?

Answer 38

Metabolic acidosis and alkalosis BE > +2 = metabolic alkalosis BE < -2 = metabolic acidosis